Tracheal Intubation

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Chapter 4

Tracheal Intubation

Robert F. Reardon, John W. McGill and Joseph E. Clinton

Intubation is often the pivotal procedure in the emergency management of critically ill patients. There are several new devices that can improve the likelihood of successful intubation, but it is important to understand that intubation is just one aspect of airway management. The primary objective of airway management is to maintain adequate oxygenation. Intubation allows oxygenation once it is completed, but not during the procedure.¹ A comprehensive approach, such as the algorithm described in Chapter 3, is crucial (see Fig. 3-15).² In the emergency setting it is important to use intubation techniques that have a high likelihood of success, critically recognizing when a given approach has failed and quickly moving to a different technique.

This chapter describes nearly every possible means of tracheal intubation, with emphasis on widely used techniques. The most common means of intubation in the emergency setting is rapid-sequence intubation (RSI), but this approach must be considered very carefully.³ If a difficult intubation is anticipated, awake intubation may be preferred. With good topical anesthesia, nearly any intubating technique can be used for awake intubation, although flexible fiberoptic devices are commonly used. Because many difficult airways cannot be predicted, it is essential to have a well-defined backup plan and appropriate resources. The intubating laryngeal mask airway (LMA Fastrach) is an ideal backup device for failed RSI because it provides ventilation and oxygenation and facilitates tracheal intubation in a high percentage of patients with failed RSI.²

General Approach to Emergency Intubation

Preplanning is the key to successful emergency airway management. Providers should follow a clear, preconceived, practiced airway algorithm that uses readily available and familiar equipment and techniques. When encountering a difficult airway, it is more important to be comfortable with a few well-proven devices and techniques than to try new or unfamiliar devices.2,4 It is important to know when to abandon one approach and move on to the next. No single approach is mandated. The best technique is the one chosen by the clinician at the bedside based on one’s individual experience and expertise and the specific clinical scenario.

A critical aspect of preparation is making sure that all essential equipment required to perform the airway maneuvers is immediately available and within easy access. This may be accomplished by wall-mounting essential equipment in the emergency department (ED) resuscitation room.⁵ Alternatively, equipment can be placed in dedicated adult and pediatric airway carts or tackle boxes in an open, organized, and labeled manner, and the carts and boxes checked regularly and stocked (Fig. 4-1).⁶ Essential equipment that is seldom used but is potentially lifesaving should be clearly identified and placed in an easily accessible location such as a dedicated difficult airway cart. The importance of this concept cannot be overstated. Technical expertise cannot substitute for the lack of essential equipment. In airway management, failure has ominous consequences. Mental, physical, and equipment preparation maximizes the chance of success.

Figure 4-1 A, Adult airway cart. Equipment and materials are visible, labeled, and accessible. B, Labeling is especially important because it lets you know what is missing. (Concept of Dr. Ernest Ruiz, Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis.)

Airway Anatomy

An understanding of airway anatomy and its terminology is requisite for any discussion of airway management procedures (Fig. 4-2). The following terms are used frequently in this chapter:

Figure 4-2 A, Anatomy of the upper airway. B, View of the larynx, epiglottis, and vocal cords seen with a laryngoscope. (A, Netter illustration used with permission of Elsevier, Inc. All rights reserved.)

Pharynx: the upper part of the throat posterior to the nasal cavity, mouth, and larynx

1. Nasopharynx: base of the skull to the soft palate

2. Oropharynx: soft palate to the epiglottis

3. Hypopharynx: epiglottis to the cricoid ring (posteriorly), including the piriform sinus/recess/fossa

Piriform sinus/recess/fossa: the pockets on both sides of the laryngeal inlet separated from the larynx by the aryepiglottic folds

Larynx: the anterior structures of the throat (commonly called the voice box) from the tip of the epiglottis to the inferior border of the cricoid cartilage, including the laryngeal inlet

Laryngeal inlet: the opening to the larynx bounded anterosuperiorly by the epiglottis, laterally by the aryepiglottic folds, and posteriorly by the arytenoid cartilage

Arytenoid/posterior cartilage: the posterior aspect of the laryngeal inlet separating the glottis (anterior) from the esophagus (posterior)

1. Corniculate cartilage: the medial portion of the arytenoid/posterior cartilage

2. Cuneiform cartilage: the lateral prominence of the arytenoid/posterior cartilage

3. Interarytenoid notch: the notch between the posterior cartilage

Glottis: the vocal apparatus, including the true and false cords and the glottic opening

Vallecula: the space between the base of the tongue and the epiglottis

Hyoepiglottic ligament: anterior midline ligament connecting the epiglottis to the hyoid bone

Preparation

Intubation is best accomplished with two operators, one to perform the intubation and the other to handle equipment, help with positioning, observe the monitor, and keep track of time. Unfortunately, the ideal scenario and adequate time for preparation are not always available to the clinician, who has to make calculated adjustments based on the situation at hand. Before intubating, it is preferable to take the following steps in chronologic order: (1) attach the necessary monitoring devices and administer oxygen, (2) establish intravenous access, (3) draw up essential medications and label them if time permits, (4) confirm that the intubation equipment is available and functioning, (5) reassess oxygenation and maximize preoxygenation, (6) position the patient correctly, and (7) make sure that all team members are aware of the primary procedural approach and the most likely backup plan. In the haste of the moment, it is a common error to forget to preoxygenate or to position the patient optimally. Simple omissions, such as failing to restrain the patient’s hands or remove the patient’s dentures or misplacing the suction tip, can seriously hamper the success of the procedure. One suggested preintubation checklist is presented in Box 4-1. In addition, be sure to use universal precautions by wearing gloves, a gown, and eye and mouth protection.

Box 4-1 Suggested Preintubation Checklist

1. Ask an assistant to monitor O₂ saturation and vital signs and to remind the intubator how much time has elapsed without ventilation.

2. Be sure that an intravenous infusion is running properly. Administer oxygen to the patient.

3. Draw up the necessary drugs (e.g., lidocaine, paralyzing agent, induction agent).

4. Attach the bag-valve-mask device to an oxygen source (rate of 15 L/min).

5. Insert a stylet into the tracheal tube and have a “straight to cuff” shape with a 35-degree distal bend.

6. Check the integrity of the balloon and cuff on the tracheal tube.

7. Have tape, twill tape, or a commercial tube stabilizer available.

8. Check the laryngoscope light source. Have a second light source, a selection of blades, and additional endotracheal (ET) tubes available.

9. Turn on the oral suction device and place it so that it is immediately available near the clinician’s right hand. Prepare the catheter suction for postintubation use.

10. Place a syringe, to inflate the ET tube balloon, on the bed to the right of the patient’s head.

11. If the patient is not pharmacologically paralyzed, restrain the hands.

12. Remove the patient’s dentures (delay this action until immediately before intubation if the patient is undergoing bag-mask ventilation).

13. Position the patient in the sniffing position (conditions permitting). Facilitate this by placing a towel under the patient’s occiput to raise it 10 cm. Obese patients usually require significantly more elevation of the occiput.

14. Have waveform capnography on and ready to connect immediately after intubation or an aspiration device for detection of the esophagus if capnography is not available.

Preoxygenation

Preoxygenation is one the most important aspects of emergency airway management. Preoxygenation before RSI provides much more time for intubation before desaturation occurs and thus significantly increases the chance for successful intubation on the first attempt. Failure to preoxygenate before RSI is often a critical factor when a straightforward emergency airway becomes an unexpected airway problem. Preoxygenate by providing the maximal fraction of inspired oxygen (Fio₂) with a non-rebreather mask for 3 to 5 minutes before intubation. Alternatively, give eight vital capacity breaths from a maximal Fio₂ system, such as a non-rebreather mask or a bag-valve-mask device, if there is not enough time for standard preoxygenation.⁷ When using a bag-valve-mask device for preoxygenation it is important for the exhalation port to have a one-way valve so that room air is not drawn into the mask when the patient inhales.

The purpose of preoxygenation is not solely to maximize oxygen saturation, but also to wash out nitrogen from the patient’s lungs and replace it with oxygen. This provides the maximum safe apneic time during RSI. Those at greatest risk for rapid desaturation include obese, pregnant, critically ill, and pediatric patients, and they will benefit the most from appropriate preoxygenation. Most studies addressing preoxygenation have been conducted under ideal conditions on relatively healthy individuals. It is far more challenging to effectively preoxygenate critically ill patients.⁸

Morbidly obese patients are best preoxygenated in a 25-degree head-up position because significantly higher oxygen tension can be achieved with this position.⁹ Patients who are hypoxic despite maximal oxygen delivery have been shown to benefit from 3 minutes of noninvasive positive pressure ventilation (NPPV) with 100% O₂ just before intubation.^10,11

Sometimes patients who will benefit the most from preoxygenation are uncooperative with a face mask because of delirium from hypoxia, hypercapnia, or other factors. These patients may benefit from delayed-sequence intubation: careful sedation without suppression of respirations, and oxygenation with a face mask or NPPV for 2 to 3 minutes before administration of a paralytic agent.¹¹ Ketamine (1 to 1.5 mg/kg by slow intravenous push) has been suggested for this technique. Delayed-sequence intubation is a commonsense way to deal with a difficult problem, but it has not been well studied and providers using this method should be ready for hypoventilation or apnea.

Another method to delay desaturation during RSI is nasopharyngeal oxygen insufflation during apnea. Many studies have shown that providing oxygen therapy during apnea is much more beneficial than previously considered.12–15 During apnea, oxygen continues to be absorbed through the alveoli, and thus air with a low oxygen concentration remains in the lower airways. Supplying oxygen to the nasopharynx during apnea allows air with a higher oxygen concentration to passively replenish oxygen in the alveoli. In two studies of patients undergoing RSI, nasopharyngeal oxygen insufflation significantly delayed desaturation after the onset of apnea in both normal and morbidly obese patients.^12,15 In these studies, nasopharyngeal oxygen insufflation was accomplished by inserting a 10-Fr catheter into the nasopharynx to a distance equal to that from the mouth to the tragus of the ear and delivering oxygen at a flow rate of 5 L/min when apnea occurred.¹² Using a standard nasal cannula with a nasopharyngeal airway is simpler and would probably provide the same benefit. It is important to keep the upper airway open with a jaw thrust or artificial airway for this technique to be most beneficial.

Assessing for a Difficult Airway

When trying to predict whether there will be difficulty during emergency intubation, it is important to understand that most of the literature on prediction of difficult laryngoscopy does not apply very well in the emergency setting. A study by Levitan and colleagues in 2004 showed that two thirds of patients who were intubated in their ED via RSI could not be assessed with the most common difficult airway prediction tests (Mallampati scoring, measurement of thyromental distance, and neck mobility testing) because of altered mental status or cervical spine immobilization.¹⁶ Even in the best circumstances, only about half of cases of difficult laryngoscopy can be predicted.¹⁷ Many factors such as Mallampati scoring and measurement of thyromental distance have not been found to accurately predict difficult laryngoscopy, especially in the emergency setting.^16–19 Only obvious anatomic and pathologic abnormalities and a history of difficult intubation are accurate predictors of difficult laryngoscopy.¹⁶ The American Society of Anesthesiology Difficult Airway Guidelines state that “in patients with no gross upper airway pathology or anatomic anomaly, there is insufficient published evidence to evaluate the effect of a physical examination on predicting the presence of a difficult airway.”²⁰ This does not mean that emergency providers should ignore factors that are known to be associated with difficult laryngoscopy, but these must be placed in perspective.

No examination finding alone can predict difficult laryngoscopy, but a combination of multiple factors makes difficulty more likely. The classic predictors of difficult intubation include a history of previous difficult intubation, prominent upper incisors, limited ability to extend at the atlanto-occipital joint,²¹ poor visibility of pharyngeal structures when the patient extends the tongue (Mallampati classification or the tongue-pharyngeal ratio) (Fig. 4-3A),²² limited ability to open the mouth (suggested by a space less than three fingerbreadths between the upper and lower incisors),²³ short thyromental distance (<6 cm from the thyroid notch to the chin with the neck in extension) (Fig. 4-3B),²⁴ and a limited direct laryngoscopic view of the laryngeal inlet (Fig. 4-4).²³ A relatively new test is the upper lip bite test, which has been shown in some studies to be more accurate and specific than older tests.^25–27 It is essentially a test of anterior mandibular mobility, and the less mobility, the more difficult it is to intubate the patient. Upper lip bite criteria are as follows: class I, the lower incisors can bite the upper lip above the vermillion line; class II, the lower incisors can bite the upper lip below the vermillion line; and class III, the lower incisors cannot bite the upper lip.²⁵ Interestingly, a 2008 study by Tremblay and associates identified factors predictive of difficult GlideScope intubation, which included a high Cormack-Lehane grade during direct laryngoscopy, short thyromental distance, and high upper lip bite test score.²⁸

Figure 4-3 A, The Mallampati classification predicts intubation difficulty based on the visibility of intraoral structures. Classes III and IV predict difficult intubation. B, A short thyromental distance (less than 6 cm or 3 fingerbreadths) when the head is extended predicts difficult intubation. (A, From Kryger MH. Sleep breathing disorders: examination of the patient with suspected sleep apnea. In: Kryger MH, ed: Kryger Atlas of Clinical Sleep Medicine. Philadelphia: Elsevier; 2010.)

Figure 4-4 Cormack and Lehane grading of laryngeal views during laryngoscopy. A, Grade I. Most of the glottis is visible. B, Grade II. The posterior aspect of the glottis is visible. C, Grade 3. Only the epiglottis is seen; no part of the laryngeal inlet is visible. D, Grade IV. The epiglottis is not visible. Patients with grades I and II are usually easy to intubate with direct laryngoscopy, whereas those with grades III and IV are often difficult; the ability to see the arytenoid cartilage is the important difference.

As noted earlier, many of these predictors cannot be assessed in the emergency setting.¹⁶ Fortunately, some of the key predictors are apparent simply by observing the external appearance of the patient’s head and neck. Patients with neck tumors, thermal or chemical burns, traumatic injuries involving the face and anterior aspect of the neck, angioedema, infection of pharyngeal and laryngeal soft tissues, or previous operations in or around the airway suggest a difficult intubation because distorted anatomy or secretions may compromise visualization of the vocal cords. Facial or skull fractures may further limit airway options by precluding nasotracheal (NT) intubation. Patients with ankylosing arthritis or developmental abnormalities such as a hypoplastic mandible or the large tongue of Down’s syndrome are difficult to intubate because neck rigidity and problems of tongue displacement can obscure visualization of the glottis.

Besides these obvious congenital and pathologic conditions, the presence of a short, thick neck is one of the more common predictors of a difficult airway. Such individuals are easily identifiable by observing the head and neck in profile. Obesity alone may not be an independent predictor of difficult intubation, but obese patients with large-circumference necks are likely to be difficult to intubate.²⁹ Facial hair can complicate a difficult airway by rendering bag-mask ventilation ineffective because of the lack of a good mask seal. One patient type that does not immediately stand out as a difficult intubation—but can be surprisingly so—is a patient with an unusually long mandibulohyoid distance (the thyroid prominence appearing low in the neck) and a short mandibular ramus.³⁰ Visualization of the larynx is difficult because of the distance to the larynx and the relative hypopharyngeal location of the tongue.

Knowledge of the poor performance of difficult airway predictors should not make emergency providers more cavalier about using RSI; it should create more concern. The solution is not to avoid RSI, because lack of paralysis makes every intubation more difficult. Instead, it is essential to appreciate the critical importance of having a clear backup plan when intubation with RSI fails.16,31 This situation mandates the need for a preconceived algorithm that uses proven rescue techniques applicable to a broad range of clinical scenarios, such as the bougie (flexible intubating stylet) and the LMA Fastrach.² The value of the bougie is indisputable, and it is clear that using the LMA Fastrach after failed RSI has decreased the frequency of failed airways and the need for surgical intervention.^2,4,32–38 Finally, if RSI is the “go to” method for emergency intubation, providers must be prepared to perform a surgical airway when laryngoscopy, bag-mask ventilation, and backup devices fail.^2,39

Direct Laryngoscopy

Review Box 4-1 Direct laryngoscopy: indications, contraindications, complications, and equipment.

Despite the proliferation of approaches and devices designed to secure a definitive airway, direct laryngoscopy remains the mainstay of tracheal intubation. The equipment is simple and the approach direct. Visual confirmation of the tube going through the vocal cords is usually possible.

Indications and Contraindications

Direct laryngoscopy is indicated in any clinical situation in which a definitive emergency airway is necessary, including routine and difficult airways. Relative contraindications to direct laryngoscopy include limited mouth opening, upper airway distortion or swelling, severe kyphosis, or copious blood or secretions.

Equipment

Laryngoscope

There are two basic blade designs for direct laryngoscopy, curved (Macintosh) and straight (Miller) (Fig. 4-5). Each comes in various adult and pediatric blade sizes. Slight variations in laryngoscopic technique follow from the choice of blade design, and it is often a matter of personal preference. The tip of the straight blade goes under the epiglottis and lifts it directly, whereas the curved blade fits into the vallecula and indirectly lifts the epiglottis via engagement of the hyoepiglottic ligament to expose the larynx.

Figure 4-5 Macintosh (A) and Miller (B) laryngoscope blades.

Each blade type has advantages and disadvantages. The straight blade is often a better choice in pediatric patients, in patients with an anterior larynx or a long floppy epiglottis, and in individuals whose larynx is fixed by scar tissue. It is less effective, however, in patients with prominent upper teeth, and it is more likely to damage dentition. Use of the straight blade is also more often associated with laryngospasm because it stimulates the superior laryngeal nerve, which innervates the undersurface of the epiglottis. A straight blade may inadvertently be advanced into the esophagus and initially reveal unfamiliar anatomy until it is withdrawn. The blade has a lightbulb at the tip, which may slightly hamper vision. The wider, curved blades are helpful in keeping the tongue retracted from the field of vision and allowing more room for passing the tube through the oropharynx, and they are generally preferred for uncomplicated adult intubations. Aside from patient considerations, some clinicians prefer the curved blade because they find that it requires less forearm strength than the straight blade does.

The illumination provided by the laryngoscope can make a big difference in the ability to visualize the laryngeal inlet. The importance of these factors is underappreciated, as demonstrated by Levitan ⁴⁰ in a survey of the Macintosh blades used in 17 Philadelphia EDs. It was found that only 24% of all blades provided the brightness necessary for fine inspection. This finding was largely explained by the fact that the majority of EDs used the A-Mac (American) as opposed to the clearly superior brightness design of the G-Mac (German) or the intermediate brightness of the E-Mac (English).

Tracheal Tubes

The standard adult endotracheal (ET) tube measures approximately 30 cm in length. Tube size is typically printed prominently on the tube and is based on the internal diameter (ID) and measured in millimeters. The range is 2.0 to 10.0 mm in increments of 0.5 mm. The outer tube diameter is 2 to 4 mm larger than the internal diameter.⁴¹ Tubes are also imprinted with a scale in centimeters that indicates the distance from a tube’s distal tip.

Adult men can generally accept a 7.5- to 9.0-mm orotracheal tube, whereas women can usually be intubated with a 7.0- to 8.0-mm tube. Larger tubes are theoretically desirable because airway resistance increases as tube size decreases, but in practice, a 7.5-mm tube is adequate for almost all patients. In emergency intubations, particularly if a difficult intubation is anticipated, many clinicians choose a smaller tube and change to a larger tube later if necessary. Though generally an acceptable practice, this should be avoided in burn patients because swelling may prohibit subsequent tube placement. For nasal intubation, a slightly smaller (by 0.5 to 1.0 mm) tube may be easier to advance through the nasal passages.

Correct tube size is important in the pediatric population. It is especially important when using an uncuffed tube because a good seal is needed between the ET tube and the upper part of the trachea (Table 4-1). Since tube size is based on the ID, a cuffed tube should generally be a half size (0.5 mm) smaller than an uncuffed tube. The smaller ID of an appropriately sized, small cuffed tube could theoretically make it more prone to plugging from secretions. Cuffed tubes are available down as small as 3-mm ID, although indications for these tubes in neonates and infants are rare. A cuffed tube is used in children with decreased lung compliance who may require prolonged mechanical ventilation. In a child, the smallest airway diameter is at the cricoid ring rather than at the vocal cords, as in adults. Hence, a tube may pass the cords but go no farther. If this should occur, the next smaller size tube should be passed.

TABLE 4-1

Tracheal Tube Sizes for Average Patients *

^*A slightly smaller size may be required for nasotracheal intubation.

Modified from Applebaum EL, Bruce DL, eds. Tracheal Intubation. Philadelphia: Saunders; 1976.

In children 2 years or older, the following formula is a highly accurate method for determining correct uncuffed and cuffed ET tube size:

For most clinical situations, using the width of the nail of the little (fifth) finger as a guide is sufficiently accurate and has been shown to be more precise than finger diameter (Fig. 4-6).⁴² A standard tracheal tube uses a high-volume, low-pressure cuff to avoid pressure necrosis the tracheal lining. A clinical test for determining correct cuff inflation is to slowly inject air until no air leak is audible while the patient is receiving bag-tube ventilation. This usually occurs with 5 to 8 mL of air if the proper size tracheal tube has been selected. Many clinicians use the tension of the pilot balloon as a guide to cuff inflation. Slight compressibility with gentle external pressure indicates adequate inflation for most clinical situations. For long-term use, cuff pressure should be measured and maintained at 20 to 25 mm Hg. Capillary blood flow is compromised in the tracheal mucosa when cuff pressure exceeds 30 mm Hg. In emergency situations, the balloon may simply be inflated with 10 mL of air and adjusted when the patient’s condition has stabilized.

Figure 4-6 Pediatric endotracheal (ET) tube size estimation using the fingernail width of the little finger. In children, a cuffed or uncuffed ET tube may be used. If an uncuffed ET tube is used for emergency intubation, it is reasonable to select a tube 3.5 mm in internal diameter (ID) for infants up to 1 year of age and a 4.0-mm-ID tube for patients between 1 and 2 years of age. If a cuffed tube is used for emergency intubation of an infant younger than 1 year, it is reasonable to select a 3.0-mm-ID tube. For children between 1 and 2 years of age, it is reasonable to use a cuffed ET tube with an ID of 3.5 mm After age 2, ET tube size can be estimated by the following formulas: estimated size of an uncuffed ET tube in millimeters = [4 + age]/4 and estimated size of a cuffed tube in millimeters = [3 + age]/4.

Interest in design of the tip of the tracheal tube has grown as the Seldinger technique is increasingly being applied to intubation. When a tracheal tube is passed over a smaller-caliber introducer (Seldinger technique), regardless of whether it is a tracheal tube introducer or a fiberoptic scope, there is a reasonable chance that the tube will get hung up on the laryngeal soft tissue.⁴³ A tracheal tube that has been designed to overcome this problem has a bevel oriented posteriorly and a flexible tip that decreases the distance between the tube and whatever it is being passed over (Fig. 4-7).

Figure 4-7 Comparison of the standard tracheal tube tip with the Parker Flex-Tip Tracheal Tube. Note: When a standard tube is inserted in the normal fashion, the bevel is oriented vertically and toward the patient’s left. The Parker tube tip bevel faces posteriorly and may avoid getting caught on laryngeal structures. The flexible tip of the Parker tube also provides a closer fit on an introducer.

Check the ET tube cuff for leaks by inflating the pilot balloon before attempting intubation. Prepare the tube for placement by passing a malleable stylet down the tube to increase its stiffness and enhance control of the tip of the tube. Do not extend the stylet beyond the eyelet of the tube. Bend the tube and stylet to create a “straight-to-cuff” shape with a 35-degree distal bend. Lubricate the tip and cuff of the tube with viscous lidocaine or a water-soluble gel.

Optimal Patient Positioning for Direct Laryngoscopy

The sniffing position, with the head extended on the neck and the neck flexed relative to the torso, has traditionally been considered the best head position for direct laryngoscopy.44,45 This position aligns the oral, pharyngeal, and laryngeal axes (Fig. 4-8A–C). Horton and colleagues described the ideal sniffing position for normal patients as neck flexion of 35 degrees and atlanto-occipital extension such that the plane of the face is −15 degrees to the horizontal position (Fig. 4-8C).⁴⁶ In supine patients, neck flexion is achieved by head elevation. Depending on the size and shape of the patient, the amount of head elevation may differ significantly, and the end point should be horizontal alignment of the external auditory meatus with the sternum.^44,47–49 In normal-size adults it is usually possible to achieve the sniffing position with 7 to 10 cm of head elevation.^50,51 Morbidly obese patients require much more head elevation to achieve the proper sniffing position. In these patients, aligning the external auditory meatus with the sternum requires elevation of the head and neck, as well as the upper part of the back (Fig. 4-8D).^3,48,49,52 This can be accomplished by building a ramp of towels and pillows under the upper torso, head, and neck or by using a Troop Elevation Pillow (Mercury Medical, Clearwater, FL) or similar device (see Fig. 3-2).^3,48,49,52 Alternatively, elevating the head to a 25-degree backup position may achieve the same purpose.⁵³

Figure 4-8 Head positioning for tracheal intubation. A, Neutral position. B, Head elevated. C, “Sniffing” position with a flexed neck and extended head. Note that flexing the neck while extending the head lines up the various axes and allows direct laryngoscopy. D, Morbidly obese patients are best intubated in a ramped position with elevation of the upper part of the back, neck, and head; the ideal position aligns the external auditory canal and the sternum.

Two studies have shown that elevating the head (flexing the neck) beyond the sniffing position often improves visualization of the glottis.48,54 Because the amount of head elevation needed for optimal laryngoscopy varies depending on individual patient anatomy, it is important to make laryngoscopy a dynamic procedure. This is best accomplished by putting your right hand behind the patient’s head to lift, flex, and extend the head as needed to bring the glottis into view.⁵⁵ Optimal positioning of the head and neck is not possible in trauma patients who require in-line stabilization of the cervical spine. This is one of the aspects that makes trauma airways so challenging and makes other maneuvers, such as external laryngeal manipulation, even more important in these patients.⁵⁵

Procedure and Technique of Direct Laryngoscopy

Adults

Place the patient in the supine position with the head at the level of the lower part of the intubator’s sternum (Fig. 4-9, step 2). To maintain the best mechanical advantage, keep your back straight and do not hunch over the patient; bend only at the knees (Fig. 4-10). Keep the left elbow relatively close to the body and flex it slightly to provide better support. In a severely dyspneic patient who cannot tolerate lying down, perform direct laryngoscopy with the patient seated semi-erect and the clinician on a step stool behind the patient.⁵⁶

Figure 4-9 Direct laryngoscopy.

Figure 4-10 Proper positioning of the clinician, patient, and assistant for tracheal intubation. The following points are demonstrated: the difficult airway cart is adjacent to the patient, the suction device is at the head of the bed, the patient is in the “sniffing position” with the occiput elevated and the clinician’s right hand ready for additional adjustment if necessary, the bed is elevated and the clinician is at the appropriate distance from the patient, and the laryngoscope handle is angled at 45 degrees.

Grasp the laryngoscope in the left hand with the back end of the blade pressed into the hypothenar aspect of your hand. Draw the patient’s lower lip down with your right thumb, and introduce the tip of the laryngoscope into the right side of the patient’s mouth (Fig 4-9, step 3). Slide the blade along the right side of the tongue while gradually displacing the tongue toward the left as you move the blade to the center of the mouth (Fig. 4-9, step 4). If you initially place the blade in the middle of the tongue, it will fold over the lateral edge of the blade and obscure visualization of the airway. Placing the blade in the middle of the tongue and failing to move the tongue to the left are two common errors that prevent visualization of the vocal cords (Fig. 4-11).

Figure 4-11 Common problems encountered when using a laryngoscope. A, The laryngoscope blade is under the middle of the tongue, with the sides of the tongue hanging down and obscuring the glottis. B, The tongue is not pushed far enough to the left and is obscuring the glottis. C, Correct blade position with the tongue elevated and to the left. D, Use of the curved (Macintosh) laryngoscope blade. E, Use of the straight (Miller) blade.

As you move the tip of the blade toward the base of the tongue, exert force along the axis of the laryngoscope handle by lifting upward and forward at a 45-degree angle (Fig. 4-9, step 6). The direction of this force is critical because if the force is too horizontal or too vertical, poor visualization will result. The epiglottis should come into view with this maneuver. It may help to have an assistant retract the cheek laterally to further expose the laryngeal structures. Avoid bending the wrist because it can result in dental injury if the teeth are used as a fulcrum for the blade.

The step after visualization of the epiglottis depends on which laryngoscope blade is being used. With the curved blade, place the tip into the vallecula, the space between the base of the tongue and the epiglottis (Fig. 4-11D). Continued anterior elevation of the base of the tongue and the epiglottis will expose the vocal cords. If the tip of the blade is inserted too deeply into the vallecula, the epiglottis may be pushed down and obscure the glottis.²² When using the straight blade, insert the tip under and slightly beyond the epiglottis and directly lift it up (Fig. 4-11E). If the straight blade is placed too deeply, the entire larynx may be elevated anteriorly and out of the field of vision. Gradually withdraw the blade to allow the laryngeal inlet to drop down into view. If the blade is deep and posterior, the lack of recognizable structures indicates esophageal passage; gradually withdraw the blade to permit the laryngeal inlet to come into view.

Infants and Children

It is helpful to appreciate the anatomic differences between children and adults when intubating pediatric patients (Fig. 4-12 and Table 4-2). Children’s proportionately larger heads naturally place them in the sniffing position, so a towel under the occiput is rarely necessary (Fig. 4-13). The large head of newborns can result in a posterior positioning of the larynx that prevents visualization of the vocal cords. A small towel under the infant’s shoulders should correct this problem. The head may also be floppy and may benefit from stabilization by an assistant. The child’s increased tongue-to-oropharynx ratio and shorter neck hinder forward displacement of the tongue and, coupled with a U-shaped epiglottis, can make visualization of the glottis difficult. Consequently, direct laryngoscopy in infants and young children is generally best performed with a straight blade: Miller size 0 for premature infants, size 1 for normal-sized infants, and size 2 for older children. The infant’s larynx lies higher and relatively more anterior. If no laryngeal structures are visible after laryngeal pressure, gradually withdraw the blade. Inadvertent advancement of the blade into the esophagus is a common error.

TABLE 4-2

Comparison of the Airway in Adults and Children

Figure 4-12 Sagittal section of the neck of an infant. Note that in small children, the neck is shorter and the larynx is located more cephalad. (From Snell RS, Smith MS, eds. Clinical Anatomy for Emergency Medicine. St Louis: Mosby–Year Book; 1993:16.)

Figure 4-13 Oral intubation in a child with a straight blade. The proportionately large floppy head of a child may present some difficulty, and an assistant may be required to hold the child’s head straight.

Sellick’s Maneuver, External Laryngeal Manipulation, Bimanual Laryngoscopy, and BURP

The differences between Sellick’s maneuver, external laryngeal manipulation (ELM), and backward, upward, rightward pressure (BURP) are often misunderstood. Sellick’s maneuver is the application of cricoid pressure with the intent of preventing regurgitation and aspiration, not to improve visualization during laryngoscopy. ELM is the application of pressure on the thyroid cartilage during laryngoscopy to help optimize visualization of the glottis. BURP is often the best combination of forces that need to be applied to the thyroid cartilage during ELM. Bimanual laryngoscopy refers to use of the right hand to perform ELM.

Sellick’s Maneuver: There is some good evidence that Sellick’s maneuver (cricoid pressure) helps prevent gastric inflation during bag-mask ventilation.57–62 The only evidence suggesting that cricoid pressure prevents regurgitation consists of five cadaver studies,^62–66 one small human study,⁶⁷ and some case reports⁶⁸—poor evidence by today’s standards of evidence-based medical practice.^57,69 Furthermore, there are many reports of significant regurgitation and aspiration regardless of the application of Sellick’s maneuver.^70–73 Despite the lack of evidence, many experts believe that Sellick’s maneuver is critical during RSI.^74–77

Because aspiration has dire consequences and Sellick’s maneuver has traditionally been considered integral to patient safety during emergency airway management,⁶⁹ it is reasonable to apply cricoid pressure as long as it does not interfere with ventilation and intubation. Unfortunately, there is significant evidence that it can interfere with ventilation and intubation, so it is best to apply Sellick’s maneuver on a case-by-case basis with full understanding of the benefits and drawbacks of cricoid pressure.⁶⁹

When applied during bag-mask ventilation, Sellick’s maneuver reduces tidal volume, increases peak inspiratory pressure, and prevents good air exchange.58,60,61,78–85 There are mixed data about the effects of cricoid pressure during larynoscopy,⁸⁶ but several studies have shown that it worsens visualization of the larynx.^87–89 Cricoid pressure also decreases successful insertion of and intubation through LMAs.^90–97

Because of lack of evidence of the utility of Sellick’s maneuver and evidence of adverse effects, routine use of cricoid pressure during bag-mask ventilation of patients in cardiac arrest is not recommended in the 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.⁹⁸ Also, it is recommended that cricoid pressure be released immediately if there is any difficulty either intubating or ventilating a patient in an emergency setting.^{69,73,81,99,100} In addition, it is reasonable to release or relax cricoid pressure during insertion of an LMA, during intubation with an intubating LMA (ILMA), or if ventilation with the LMA is difficult.^57,69,96

Some authors believe that improper technique is to blame for the many reported failures of Sellick’s maneuver.⁵⁷ The proper technique for applying Sellick’s maneuver is to place the thumb and middle finger on either side of the cricoid cartilage and the index finger in the center anteriorly.⁶² Apply 30 N (6.7 lb) of force to the cricoid cartilage in the posterior direction.^57,77 As a reference, about 40 N of digital force on the bridge of the nose will usually cause pain.⁵⁷

External Laryngeal Manipulation, Bimanual Laryngoscopy, and BURP: ELM is the application of pressure on the thyroid cartilage in an attempt to improve the view of the larynx during laryngoscopy. Multiple studies have shown that ELM performed by the laryngoscopist (bimanual laryngoscopy) is superior to having an assistant apply anterior neck pressure.88,101 Bimanual laryngoscopy is best because the direction and amount of force that will optimize laryngeal exposure is variable. BURP is sometimes optimal, but it often worsens the laryngoscopic view,⁸⁸ so it is best to move the larynx in a variety of directions to determine the optimal ELM. The best way to quickly apply a variety of different forces to the larynx to determine the optimal ELM is by manipulation of the larynx with the laryngoscopist’s right hand (Fig. 4-14).¹⁰¹

Figure 4-14 External laryngeal manipulation (ELM) (or bimanual laryngoscopy). A, ELM step 1. The laryngoscopist optimizes view of the larynx by reaching around to the patient’s neck with the right hand and manipulating the thyroid cartilage while performing laryngoscopy. B, ELM step 2. The assistant’s hand replaces the laryngoscopist’s hand on the anterior aspect of the neck and maintains the position of the larynx while the laryngoscopist places the tracheal tube.

Operator-directed posterior displacement of the larynx during laryngoscopy was described by Brunnings in 1912.¹⁰² After Sellick described the use of cricoid pressure to avoid regurgitation in 1961, it became common to have an assistant apply anterior neck pressure during laryngoscopy.⁶² In 1993 Knill reported that having an assistant apply BURP to the cricoid or thyroid cartilage improved visualization of the glottis during two cases of difficult laryngoscopy.¹⁰³ In 1993 Takahata and coworkers performed a prospective study of 630 intubations and found that BURP produced better laryngeal exposure than just backward pressure did in patients with difficult laryngoscopy.¹⁰⁴ However, a 2005 prospective crossover trial by Snider and colleagues found no benefit with routine application of the BURP maneuver.¹⁰⁵

Studies by Benumof, Levitan, and colleagues have demonstrated that it is best to apply pressure on the thyroid cartilage (not the cricoid cartilage) and suggested that ELM should be applied by the laryngoscopist’s right hand, not by an assistant.88,101,106 They also found that the direction of force required for optimal ELM was not always upward and rightward and that the amount of backward pressure was variable.⁸⁸ In a 1996 study of 181 patients, Benumof and Cooper found that external manipulation was optimal when applied to the thyroid cartilage in 88% of patients and to the cricoid cartilage in only 11% of patients.¹⁰¹ In a 2006 cadaveric study of 1530 laryngoscopies by 104 laryngoscopists, Levitan and associates found that bimanual laryngoscopy was more effective than both BURP and cricoid pressure for optimizing laryngeal exposure (Figs. 4-15 and 4-16; see also Fig. 4-14).⁸⁸ In addition, they found that cricoid pressure worsened the view of the larynx in 29% of cases and BURP worsened it in 35%.⁸⁸ Finally, in a 2002 study of eight first-year emergency medicine residents performing 271 intubations in an operating room setting, Levitan and colleagues found that bimanual laryngoscopy (ELM performed by the laryngoscopist) consistently improved laryngeal exposure by novice intubators (see Fig. 4-12).¹⁰⁶

Figure 4-15 The epiglottis is elevated and visualization of the vocal cords is improved by applying pressure on the hypoepiglottic ligament and external laryngeal manipulation. (Courtesy of Richard M. Levitan, MD, Airway Cam Technologies, Inc., Wayne, PA. Used with permission.)

Figure 4-16 Note the assistant manipulating the anterior part of the neck and retracting the cheek for better visualization.

Passing the Tube

Once the vocal cords have been visualized, the final step is to pass the tube under direct vision through the vocal cords and into the trachea. It is best to use a malleable stylet for all emergency intubations. The best stylet shape is straight with a 35-degree hockey-stick bend at the proximal cuff (“straight-to-cuff”). In a 2006 study, Levitan and colleagues showed that stylet bend angles greater than 35 degrees made ET tube passage more difficult.¹⁰⁷

Hold the tube in your right hand and introduce it from the right side of the patient’s mouth. Distraction of the cheek may greatly aid overall visualization. Advance the tube toward the patient’s larynx below the line of sight with the bend facing upward. When advanced in this manner the tube does not obstruct the view of the larynx until the last possible moment before the tube enters the larynx. If the patient is not chemically paralyzed, pass the tube during inspiration, when the vocal cords are maximally open. It enters the trachea when the cuff disappears through the vocal cords. Advance the tube 3 to 4 cm beyond this point. It is not enough to see the tube and the cords; watch the tube pass through the vocal cords to ensure tracheal placement. Directly observing the tube pass through the cords is the best way to immediately confirm correct placement. If part of the glottis is visualized but it is difficult to pass the tube, consider using a bougie (tracheal tube introducer).

Tracheal Tube Introducer (Bougie)

If direct laryngoscopy does not bring the vocal cords fully into view, a tracheal tube introducer may be used to facilitate intubation. This adjunct is a long, thin, semirigid introducer that, with the aid of a laryngoscope, is passed through the laryngeal inlet and over which an ET tube is advanced through the cords and into the trachea. The technique, originally described more than 60 years ago by Macintosh,¹⁰⁸ was recommended for patients in whom visualizing the vocal cords was difficult. It has also been shown to be effective when the laryngeal inlet cannot be visualized at all.¹⁰⁹ It is the most common airway adjunct used in British EDs for complicated intubations.¹¹⁰ Its efficacy has been demonstrated prospectively during difficult intubations in the operating room, as a pivotal component of a difficult airway algorithm in the operating room, and when compared with conventional laryngoscopy in the ED.^33,111,112

A variety of tracheal tube introducers are available today (Fig. 4-17). The original adjunct was called the gum elastic bougie, or simply “the bougie,” and is currently available in a reusable form for both adult and pediatric patients (Eschmann Tracheal Tube Introducer, Portex Sims, Kent, UK). The adult size comes in two forms, a 60-cm (15-Fr) version with a short, 40-degree hockey-stick curve at the end and a straight one that is 70 cm. The adult version can accommodate a 5.5-mm ET tube. The pediatric version is 70 cm (10 Fr) and straight and can accommodate a 4.0-mm tube. A polyethylene introducer designed for single use is also available and comes only in the 60-cm version (Flextrach ETTube Guide, Greenfield Medical Sourcing, Austin, TX). A variation of this concept is the FROVA Introducer (Cook Critical Care, Bloomington, IN), a plastic introducer with a similar profile to the others except that it has a hollow lumen through which the patient can be ventilated when an accompanying adapter is attached.

Figure 4-17 Several types of tracheal tube introducers. The classic introducer, the gum elastic bougie (A), is reusable and comes in curved- and straight-tipped adult forms and a straight pediatric form. The straight bougies (B) are 70 cm long and the curved-tipped bougies are 60 cm long. The blue introducer (C, Flextrach ETTube Guide) is polyethylene and designed for single use and comes only in a curved-tipped adult form (60 cm). D, Create a 60-degree bend in the distal portion of the introducer if the laryngeal inlet cannot be seen on laryngoscopy.

Consider using a tracheal tube introducer when a difficult airway is anticipated; it can also be helpful in all intubations when visualization of the laryngeal inlet is limited. A trauma patient with cervical spine precautions is a typical example. The presence of blood and vomitus is rarely a significant complicating factor. Its safety record is impressive despite decades of use, and only two complications have been reported, perforation of the pharyngeal wall after recent head and neck surgery ¹¹³ and atelectasis from blood clots after mild bronchial trauma.¹¹⁴

Shaping the introducer may not be necessary in many cases, but with difficult laryngeal views, create a 60-degree bend in the distal introducer (see Fig. 4-17D).¹¹⁵ Ideally, tracheal tube introducer-assisted intubation is a two-person procedure (Fig. 4-18). Use the laryngoscope in the normal fashion to obtain the best possible view of the larynx. If the cords are in full view, proceed with intubation with a styletted ET tube. If the view is suboptimal, an assistant can pass the tracheal tube introducer to the operator for placement anterior to the arytenoids and into the larynx. If only the epiglottis is visible, place the introducer, with a 60-degree distal bend, just under the epiglottis and direct it anteriorly. With the laryngoscope still in place and the introducer stabilized by the operator, the assistant slides the ET tube over the introducer. Pass the tube through the larynx. Just before entering the larynx, rotate the tube 90 degrees counterclockwise to avoid having the tip of the ET tube get caught on the laryngeal structures (Fig. 4-19).⁴³ Withdraw the laryngoscope and confirm proper tube placement. While securing the ET tube, ask the assistant to remove the introducer.

Figure 4-18 Two-person tracheal tube introducer technique. The introducer is handed to the clinician after the best glottic view has been obtained. A, The clinician places the introducer (the black line positioned at the teeth indicates the proper introducer depth to ensure stable positioning within the trachea while providing enough length to grasp the end of the introducer before passing the tube). B, An assistant passes the tracheal tube over the introducer as the clinician holds the introducer steady. C, The clinician passes the tracheal tube with a 90-degree counterclockwise rotation as the tube approaches the glottis, and the assistant withdraws the introducer.

Figure 4-19 A common cause of difficulty when railroading an endotracheal (ET) tube over a tracheal tube introducer. A, The tip of the ET tube is caught on the right arytenoid as it is being railroaded over the introducer. B, Corrective maneuvers: (1) withdrawal of the ET tube 2 cm to disengage the arytenoids and (2) counterclockwise 90-degree rotation of the ET tube to orient the bevel posteriorly. C, The bevel of the ET tube is facing posteriorly and allows smooth passage through the glottis. (A-C, Courtesy of Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis.)

There are a number of confirmatory findings after successful introducer placement. If any portion of the arytenoids is visible and the introducer was seen to pass anterior to them without resistance, the introducer is in the airway. Unlike seeing an ET tube “go through the cords” when in fact the laryngeal inlet may have been momentarily obscured by the tube or balloon, the smaller-caliber introducer does not obscure the view of the glottis and thus avoids this potential pitfall. In addition to better visual confirmation, successful passage is indicated, up to 90% of the time, by feeling clicks produced by the angled tip of the introducer as it strikes against the tracheal rings.¹¹⁶ An assistant will also usually feel confirmatory movement in the airway if the anterior aspect of the neck is palpated. If there is still any question whether the introducer is in the airway, advance it at least 40 cm, at which point resistance should be felt as the introducer passes the carina and into a main bronchus. If this is not felt, the introducer is most likely in the esophagus. Withdraw it and reattempt placement.

Several technical points should be emphasized. The first is that it is important to create a curve in the distal portion of the introducer when the laryngeal inlet is not visible. This is not uniformly appreciated, even in England where the bougie is used commonly.¹¹¹ It is a mistake to think that the factory-formed curve at the tip will be sufficient to access the glottis in these situations. Although there may be some benefit to lubricating the distal end of the introducer, in emergency intubations, lubricating the full length of the introducer makes it slippery and hard to handle without conferring any obvious advantage. Lubricating the ET tube, conversely, remains critical for smooth passage through the vocal cords. A common error when first using the tracheal tube introducer is to remove the laryngoscope before passing the ET tube over the introducer. This often results in difficulty placing the tube because it is displaced posteriorly by the weight of the pharyngeal soft tissues and gets hung up on the laryngeal structures. Reinsert the laryngoscope. Pull the tube back 2 cm to disengage the soft tissue. Rotate the tube 90 degrees counterclockwise and then readvance it. In instances in which it is difficult to get the introducer sufficiently anterior to access the laryngeal inlet, make sure that the introducer lines up with the operator’s line of vision. If the introducer enters the mouth at a significant angle above this line, most often when the clinician is too close to the patient, it may be deflected posteriorly by the lip or intraoral structures and escape the attention of the operator. This creates the impression that the introducer is “too floppy.”

In the prehospital setting, where assistance might not be available, the laryngoscope should be removed to mount the ET tube onto the introducer. Once the tube is on the introducer, reinsert the laryngoscope and advance the introducer through the glottic opening. Advance the ET tube while rotating it 90 degrees counterclockwise to ensure successful passage into the trachea. Mounting the tube onto the introducer to insert them as a unit is not advised because it is often difficult to direct the introducer into the laryngeal inlet as it moves within the ET tube.

Laryngospasm

If the patient is not paralyzed, laryngospasm, or persistent contraction of the adductor muscles of the vocal cords, may prevent passage of the tube. Inadequate anesthesia is often the cause. Pretreat with topical lidocaine to decrease the likelihood of laryngospasm occurring. Lidocaine, 2% or 4%, can be sprayed directly onto the vocal cords. An infrequent but effective means of achieving tracheal anesthesia is transtracheal puncture and injection of a bolus of 3 to 4 mL of lidocaine through the cricothyroid membrane. Laryngospasm is usually brief and often followed by a gasp. Be ready to pass the tube at this moment. Occasionally, the spasm is prolonged and needs to be disrupted with sustained anterior traction applied at the angles of the mandible, the jaw-lift maneuver. Do not force the tube at any time because it could cause permanent damage to the vocal cords. Consider using a smaller tube. Prolonged, intense spasm may ultimately require muscle relaxation with a paralyzing drug (see Chapter 5). Pediatric patients are far more prone to laryngospasm than adults are.¹¹⁷ In a child, if vocal cord spasm prevents passage of the tube, a chest-thrust maneuver may momentarily open the passage and permit intubation.¹¹⁸

Positioning and Securing the Tube

Secure the ET tube in a position that minimizes both the chance of inadvertent, main stem endobronchial intubation and the risk for extubation. The tip should lie in the midtrachea with room to accommodate neck movement. Because tube movement with both neck flexion and extension averages 2 cm, the desired range of tip location is between 3 and 7 cm above the carina.¹¹⁹

The average tracheal length is between 10 and 13 cm. On a radiograph, the tip of the tube should ideally be 5 ± 2 cm above the carina when the head and neck are in a neutral position. On a portable radiograph, the adult carina overlies the fifth, sixth, or seventh thoracic vertebral body. If the carina is not visible, it can be assumed that the tip of the tube is properly positioned if it is aligned with the third or fourth thoracic vertebra. In children, the carina is more cephalad than in adults, but it is consistently situated between T3 and T5. In children, T1 is the reference point for the tip of the ET tube.¹²⁰

Estimate the proper depth of tube placement before radiographic confirmation by using the following formulas, in which length represents the distance from the tip of the tube to the upper incisors in children 121,122 and from the upper incisors¹²³ or the corner of the mouth¹²⁴ in adults:

Children:	Tracheal tube depth (cm) = [age (yr)/2] + 12
Adults:	Tracheal tube depth (cm) = 21 cm (women)
	Tracheal tube depth (cm) = 23 cm (men)

In adults, this method has been shown to be more reliable than auscultation in determining the correct depth of placement.¹²³ One can anticipate that tall male patients will often require deeper placement, to 24 or 25 cm, and that short women will often require a shallower placement of 19 or 20 cm.

Inflate the cuff to the point of minimal air leak with positive pressure ventilation. In an emergency intubation, inflate with 10 mL of air and adjust the inflation volume after the patient is stabilized.

After placement of the tracheal tube, auscultate both lungs under positive pressure ventilation. Take care to auscultate posterolaterally because auscultation anteriorly can reveal sounds that mimic breath sounds but arise from the stomach. With the tube in position and the cuff inflated, secure the tube in place. Attach commercial ET tube holders, adhesive tape, or umbilical (nonadhesive cloth) tape securely to the tube and around the patient’s head (Figs. 4-20 and 4-21). Position the tube at the corner of the mouth, where the tongue is less likely to expel it. This position is also more comfortable for the patient and allows suctioning. A bite block or oral airway to prevent crimping of the ET tube or damage from biting is commonly incorporated into the system used to secure the tube.

Figure 4-20 Technique for taping an endotracheal tube. The method illustrated can be replaced by using a commercial holder or tracheostomy cloth tie. Avoid taping the lips.

Figure 4-21 A, A commercial disposable tube holder is ideal and preferred to secure an endotracheal (ET) tube without the use of messy tape. B, A plastic disposable ET holder firmly secures the ET tube with a small clamp. C, When positioning a patient for transfer to another bed or for a chest radiograph, ensure the integrity of the ET tube by placing the right hand firmly against the right side of the face while holding the tube securely with the same hand. The other hand immobilizes the neck. (B, Courtesy of Laerdal Medical, Wappingers Falls, NY.)

Unintentional extubation can have disastrous consequences, particularly if the patient was difficult to intubate initially. Secure the ET tube immediately after correct placement has been confirmed. Orotracheal intubation is associated with a higher rate of unplanned extubation than NT intubation is.¹²⁵ During transport, moving the intubated patient, or taking radiographs, designate one person to tend to the ET tube to avoid unplanned extubation. Inadequate sedation is another risk factor for unplanned extubation.¹²⁵ If long-acting paralytics have not been administered, consider sedation or physical restraints to prevent self-extubation by an agitated or confused patient.

Confirmation of Tracheal Tube Placement

Clinical Assessment: Confirm tracheal placement clinically by seeing the tube pass through the vocal cords (Table 4-3). If any question remains, apply posterior pressure on the ET tube while the laryngoscope is still in place and expose the tube by altering the angle as it passes between the cords.¹²⁶ Absent or diminished breath sounds, any sound or vocalization, increased abdominal size, and gurgling sounds during ventilation are clinical signs of esophageal placement. If the patient can moan or groan, the tube is not in the trachea! Critically, esophageal placement is not always obvious. One may hear “normal” breath sounds if only the midline of the thorax is auscultated. The presence of condensation of the ET tube as a means of confirming tracheal placement may also be misleading. Blinded observers noted condensation of the ET tube during ventilation in 23 of 27 esophageal intubations in an animal model.¹²⁷ One way to clinically assess tracheal placement after several ventilations or during spontaneous respiration is to note whether air is felt or heard to exit through the tube after cuff inflation. If tidal volume is adequate, the exit of air should be obvious. It is important to note that when an appropriately sized tube is placed in the trachea, the patient cannot groan, moan, or speak. Vocalization strongly suggests esophageal placement.

TABLE 4-3

Assessing Proper Tube Placement

TEST	INTERPRETATION
Observe the tube pass through the vocal cords	Accurate way to ensure placement; if in doubt, look again after intubation
Auscultation of breath sounds over the chest	May be misleading, especially if only the midline is examined; listen in both axillae
Auscultation over the stomach	Gurgling indicates esophageal placement
Condensation (fog) forms inside the tube with each breath	Quite reliable
Observe the chest rise with positive pressure and fall with release	Generally reliable if good chest rise is present; may be absent in patients with a small tidal volume or severe bronchospasm
Feel air exiting from the end of the tube after inflation	Reliable
Air remains in the lung after the end of the tube is occluded and exits when the occlusion is removed	Reliable, but one may “ventilate” a closed area of the esophagus
Ask the patient to speak; listen for moaning or other sounds	If the tube is in proper place, no sound is possible
Chest radiograph	Generally reliable but can be misleading
End-tidal CO₂ measurements	Reliable if a good persistent waveform is present; can be misleading with nasotracheal intubation if the tip is curled supraglottically: it will give a positive CO₂ reading
Aspiration technique	Tracheal location with a patent tube if 30-40 mL of air is aspirated without resistance; probable esophageal location if unable to aspirate the syringe easily or delayed bulb refill occurs; can be misleading with nasotracheal intubation if the tube has curled supraglottically
Fiberoptic bronchoscope	Reliable if tracheal rings are seen down the endotracheal tube
Lighted stylet down the endotracheal tube	Reliable if transillumination seen in the low midline portion of the neck
Ultrasound detection of tracheal tube location	Appears to be reliable but not well studied

Asymmetric breath sounds indicate probable main stem bronchus intubation. Because of the angles of takeoff of the main bronchi and the fact that the carina lies to the left of midline in adults, right main stem intubation is most common and is indicated by decreased breath sounds on the left side. When asymmetric sounds are heard, deflate the cuff and withdraw the tube until equal breath sounds are present. Bloch and coworkers ¹²⁸ reported accurate pediatric tracheal positioning if after noting asymmetric breath sounds the tube is withdrawn a defined distance beyond the point at which equal breath sounds are first heard: 2 cm in children younger than 5 years and 3 cm in older children.

Esophageal Detector Device: An aspiration technique used to determine ET tube location was first described by Wee in 1988.¹²⁹ The technique takes advantage of the difference in tracheal and esophageal resistance to collapse during aspiration to locate the tip of the tracheal tube. After intubation, attach a large syringe to the end of the ET tube and withdraw the plunger of the syringe. If the tube is placed in the trachea correctly, the plunger will pull back without resistance as air is aspirated from the lungs. If the tracheal tube is in the esophagus, resistance is felt when the plunger is withdrawn because the pliable walls of the esophagus collapse under the negative pressure and occlude the end of the tube. Another device that uses the same principle as syringe aspiration is the self-inflating bulb (e.g., Ellick device).

In the initial study conducted in an operating room, tube placement was identified correctly in 99 of 100 cases (51 esophageal, 48 tracheal).¹²⁹ The result was considered equivocal in the remaining case. That tube was removed and found to be nearly totally occluded with purulent secretions. Slight resistance was noted in one patient with right main stem intubation; the resistance decreased when the tube was pulled back. Before use, always check the esophageal detector device for air leaks. If any connections are loose, the leak may allow the syringe to easily be withdrawn, thereby mimicking tracheal location of the tube.

When using the aspiration technique, apply constant, slow aspiration to avoid occlusion of the tube from tracheal mucosa drawn up under the high negative pressure. If the tracheal tube is placed correctly, 30 to 40 mL of air can be aspirated without resistance. If air was initially aspirated and some resistance is then encountered, the tracheal tube should be pulled back between 0.5 and 1.0 cm and rotated 45 degrees. This takes the tube out of the bronchus if it has been placed too deeply and changes the orientation of the bevel if the tube has been temporarily occluded with tracheal mucosa. Air is easily aspirated if the tube was in the trachea, but repositioning it will make no difference if the tube was in the esophagus. The syringe aspiration technique can be used before or after ventilation of the patient. Apply continuous cricoid pressure pending confirmation of proper tube placement. Inflation of the tube cuff has no effect on the reliability of the test.¹³⁰ This device is reliable, rapid, inexpensive, and easy to use.¹³⁰

A squeeze-bulb aspirator is an alternative to the syringe technique. Attach the bulb to the ET tube and squeeze; if the tube is in the esophagus, it is accompanied by a flatus-like sound followed by absent or markedly delayed refilling. Insufflation of a tube in the trachea is silent with instantaneous refill. An early study with the Ellick evacuator bulb device reported that 82% of esophageal intubations were identified.¹³¹ A later study using a slightly different bulb device (Respironics, Murrysville, PA) found that all 45 esophageal intubations were detected.¹³² The device is cheap, easy to use, and operated single-handedly in less than 5 seconds.¹³¹ The bulb should not be used in freezing temperatures because of loss of elasticity. Confusion may occur if the esophageal tube is tested more than once because subsequent inflations may be silent. With repeated assessments, false-positive refilling of the bulb may occur as a result of instillation of air during the first attempt. This observation has led to a recommendation that the bulb be compressed before it is attached to the ET tube. Delayed, though complete refilling of the bulb may occur with bronchial tube placement or placement in the more pliable pediatric airway. The bulb suction modification of the aspiration technique has not been studied as thoroughly as the syringe technique.

A significant number of false positives occur with esophageal detection devices (the tube is correctly placed in the trachea, but the device suggests that it is in the esophagus). These patients are almost uniformly obese. Fiberoptic evaluation found that the tracheal wall was invaginated into the ET tube because of the negative pressure.¹³³ In such circumstances, if the intubation was felt to be successful, visually confirm that the ET tube went through the cords. Alternatively, if the patient has a perfusing rhythm and an expired CO₂ device is available, it should be used. To date, there has been one reported case of unrecognized esophageal intubation undetected by the syringe aspiration technique.¹³⁴ In this case there was marked gastric distention from forceful bag-mask ventilation. The esophageal detection device is not reliable in confirming tracheal tube depth and position after intubation because easy aspiration of air will occur if the tip of the tube is located supraglottically (expired CO₂ will also be misleading).

End-Tidal CO₂ Detector Devices: A high level of CO₂ in exhaled air is the physiologic basis for capnography and the principle on which end-tidal CO₂ pressure (Petco₂) detectors were developed (see Chapter 2). Continuous waveform capnography is recommended by the American Heart Association guidelines as the most reliable method of confirming and monitoring correct placement of an ET tube (class I, level of evidence [LOE]). This recommendation is based on multiple studies showing 100% accuracy of waveform capnography for detecting correct ET tube placement.⁹⁸ Continuous waveform capnography is accurate even in cardiac arrest. Patients with prolonged cardiac arrest will still have a typical square waveform but a low Petco₂ value.

When waveform capnography is not available, emergency providers may have to rely on colorimetric CO₂ indicators, which correspond to CO₂ levels flowing through the device when placed on the tracheal tube adapter (Fig. 4-9, step 10). The typical device displays opposite colors (e.g., yellow and purple) to indicate low levels of CO₂ in esophageal gas versus the high levels of CO₂ exhaled from the respiratory tree. Handheld quantitative or semiquantitative electronic CO₂ monitors are also available. Eventually, all prehospital defibrillators will have advanced monitoring capability that includes capnography.

A multicenter study of a colorimetric device demonstrated an overall sensitivity of 80% and a specificity of 96%.¹³⁵ In patients with spontaneous circulation and an inflated tracheal tube cuff, the sensitivity and specificity were 100%. The poor sensitivity (69%) noted in patients in cardiac arrest was due to the fact that low exhaled CO₂ levels were seen with both very-low-flow states and esophageal intubation. The device must be used with caution in cardiac arrest victims. CO₂ levels return to normal after return of spontaneous circulation. Furthermore, colorimetric changes may be difficult to discern in situations with reduced lighting, and secretions can interfere with the change in color. Regardless of the monitoring device, patients should be ventilated for a minimum of six breaths before taking a reading. Otherwise, recent ingestion of carbonated beverages can result in spuriously high CO₂ levels with esophageal intubation.¹³⁶ Colorimetric changes do not rule out glottic positioning of the tip of the ET tube. Adequate ventilation and oxygenation may be achieved in the glottic position, but there is still a risk for aspiration in the absence of a protected airway and the potential for further tube dislodgment. Glottic positioning may be difficult to detect clinically. The only signs may be persistent cuff leak or diminished chest rise with ventilation. Radiographic evidence or direct visualization confirms the diagnosis.¹³⁷

Ultrasound Detection of Tracheal Tube Location: Some early data suggested that ultrasound may play a future role in identifying tube location after intubation. There are two reports and both are small. The first study, performed with cadavers, had a sensitivity of 100% and a specificity of 97%.¹³⁸ The second study, which was conducted in the operating room, had both a sensitivity and specificity of 100%.¹³⁹

Comparison of Detector Devices: In the setting of spontaneous circulation, both syringe aspiration and Petco₂ detection are highly reliable means of excluding esophageal intubation. An animal study comparing these techniques with clinical assessment and measuring the speed and accuracy of determining tube placement demonstrated that both the syringe esophageal detector device and Petco₂ detection were highly accurate, approaching 100%.¹⁴⁰ The esophageal detector device was more rapid, with determination in 13.8 seconds versus 31.5 seconds for Petco₂ detection. The detector device remained accurate when air was insufflated into the esophagus for 1 minute, thus simulating unrecognized esophageal placement. Clinical assessment alone yielded an alarming 30% rate of failure to identify esophageal intubation. In the setting of cardiac arrest, the aspiration method is more reliable than CO₂ detection because its accuracy is not dependent on the presence of blood flow.

An unequivocal method for determining tracheal tube location uses the fiberoptic scope. Passage of the scope through the tube with visualization of the tracheal rings confirms ET placement and position within the trachea. Placement of a lighted stylet down the tracheal tube and successful transtracheal illumination can also be used to determine correct ET placement.¹⁴¹

At present, there is no perfect device for confirmation of ET tube placement in all situations. Be aware of the limitations of each device and ideally rely on input from multiple means of confirmation to ensure tracheal placement of the ET tube.

Complications of Intubation

Failure to achieve adequate ventilation and oxygenation is the most serious complication of tracheal intubation. The potential for hypoxia exists just before intubation as more conservative oxygenation methods are attempted and then fail, during difficult intubation when ventilation is halted for an attempt at intubation, and after intubation when esophageal intubation goes undetected. Because irreversible cerebral anoxia occurs within minutes, conservative airway management maneuvers should be limited to 2 to 3 minutes; failure to achieve adequate oxygenation should lead to a quick decision to intubate.

As a guide, limit intubation attempts to the amount of time that a single deep breath can be held. This is especially important in a child because the functional residual capacity of a child’s lungs is less than that of an adult. Historically, the maximum recommended duration of an intubation attempt in an apneic patient has been 30 seconds, followed by a period of bag-mask ventilation before intubation is attempted again. However, longer attempts at intubation are permissible when guided by accurate data from an oxygen saturation monitor because oxygen saturation may remain in the normal range for much longer in patients who have been preoxygenated. As a general rule, intubation attempts may continue if oxygen saturation is above 90% and should be interrupted for bag-mask ventilation when oxygen saturation drops below 90%.

Assessment of tube location is the top priority immediately after placement. The best assurance of tracheal placement is to see the tube pass through the vocal cords. Techniques to assess tube placement were discussed earlier. If esophageal intubation is discovered, removal of the tube may be followed by emesis. Apply cricoid pressure during tube removal and maintain it until the intubation is successful. Keep a large-bore suction tip readily available should vomiting occur. Alternatively, leave the first tube in the esophagus to serve as a temporary gastric-venting device and as a guide to intubation until tracheal intubation is achieved.

Though seldom associated with serious complications, unrecognized placement of the tip of the ET tube in the right main stem bronchus may cause hypoxia, atelectasis, pneumothorax, and unilateral pulmonary edema.¹⁴² Obtain a chest radiograph soon after intubation to confirm tube positioning. Endobronchial intubation was clinically unrecognized without a chest film in 7% of prehospital intubations in one study.¹⁴³ Persistent asymmetric breath sounds after correct tube positioning suggests unilateral pulmonary pathology (e.g., main stem bronchus obstruction, pneumothorax, hemothorax).

Prolonged efforts to intubate can also cause cardiac decompensation. Pharyngeal stimulation can produce profound bradycardia or asystole, thereby confirming the need for an assistant to monitor cardiac rhythm throughout the intubation. Keep atropine available to reverse the vagal-induced bradycardia that may occur secondary to suctioning or laryngoscopy. Prolonged pharyngeal stimulation may also result in laryngospasm, bronchospasm, and apnea.

Generally, dentures are removed for intubation but kept in place for bag-mask ventilation. Check for loose or missing teeth before and after orotracheal intubation. Look for any avulsed teeth not found in the oral cavity on the postintubation chest film. Broken teeth are the most common complication of laryngoscopy.¹⁴⁴ Laceration of the mucosa of the lips, especially the lower lip, may occur. Tracheal or bronchial injuries are rare but serious and usually occur in infants and the elderly as a result of their decreased tissue elasticity.¹⁴⁵

Vomiting with aspiration of gastric contents is another serious complication that can occur during intubation. Case reports of both adult respiratory distress syndrome and chronic lung disease are thought to be due to aspiration of activated charcoal.145,146 In patients who are obtunded or who are at high risk for seizures or vomiting, consider tracheal intubation before the administration of activated charcoal.

There are ongoing concerns that direct laryngoscopy may cause or worsen spinal cord injury in a patient with an unstable cervical spine injury. These concerns are essentially theoretical, with no credible data to prove or disprove a true effect. Many anesthesiologists prefer awake fiberoptic intubation in this setting, but no data support one approach over another. A cadaveric study of intubation during fluoroscopy showed that direct laryngoscopy with in-line immobilization in the setting of complete C4-5 ligamentous instability did not result in clinically significant movement.¹⁴⁷ The greatest degree of motion occurs at the atlanto-occipital junction and decreases with each sequential interspace, and studies of cervical spine instability at these higher levels have not been performed.¹⁴⁸ It can also be argued that cadaveric studies do not accurately depict the trauma setting, and yet this model is probably going to remain the best one available. Unless new information emerges regarding the risks of orotracheal intubation with direct laryngoscopy, it appears to be a safe approach when performed in conjunction with in-line immobilization.

Intubation can be complicated by a persistent air leak. This is generally caused by failure of either the cuff or the pilot balloon or by positioning the cuff balloon between the vocal cords. If the cuff balloon is leaking, replace the tracheal tube (see “Changing Tracheal Tubes” later in this chapter). If the pilot balloon is determined to be leaking, this can usually be remedied without changing the tube.¹⁴⁹ An incompetent one-way balloon valve can be fixed by placing a stopcock in the inflating valve. Reinflate the cuff and shut off the stopcock to solve the problem. If the leak involves the pilot balloon or if the distal inflation tube has been inadvertently severed, cut off the defective part and slide a 20-gauge catheter into the inflation tube. Then connect the stopcock to the catheter, inflate the cuff, and close the stopcock.

Tracheal stricture used to be a significant late complication of long-term intubation with low-volume, high-pressure cuffs. The use of high-volume, low-pressure cuffs has markedly decreased the incidence of this complication.¹⁵⁰ Tubes with high-pressure cuffs are obsolete and should be avoided.

Conclusion

Direct laryngoscopy is the most common means of securing a definitive airway. With adequate preparation and emphasis on preoxygenation and positioning, it is usually successful. RSI has rendered patients much more amenable to direct laryngoscopy for emergency airway management (see Chapter 5). Once the patient is paralyzed, it becomes the clinician’s supreme responsibility to ventilate, oxygenate, and protect the patient’s airway. Mastery of direct laryngoscopy fulfills part of this obligation. Being prepared for failure and having a successful backup plan fulfills this responsibility. The remainder of this chapter is devoted to adjuncts and alternatives to direct laryngoscopy.

Video and Optical Laryngoscopes

Review Box 4-2 Video laryngoscopy: indications, contraindications, complications, and equipment.

Several video and optical laryngoscopes are transforming airway management. These devices are all somewhat similar in that they use video, fiberoptics, or mirrors to visualize the larynx. They provide a better view of the glottis with less effort and have a shorter learning curve than direct laryngoscopy does. Only the Macintosh shaped video laryngoscopes are designed to sweep the tongue aside and allow either a direct or video view of the larynx. The other devices are made to look around the curve of the tongue rather than lifting it or pushing it aside, so they are more angulated. The drawback of more angulated devices is that getting an excellent view of the vocal cords does not always correlate with easy intubation 151,152 because it can be difficult to manipulate the ET tube around the sharp curve of the blade. Adding a tube channel to the blade obviates the need to manipulate the ET tube around the sharp curve but may add other complexities.¹⁵¹ Because expense is a major impediment to the widespread use of video laryngoscopy, the relatively inexpensive Airtraq device (see category 3 below) may be a good choice in settings in which difficult intubation is rare and funding is limited.⁴

Video and optical laryngoscopes can be divided into three broad catagories ¹⁵²:

1. Video laryngoscopes with standard Macintosh blades (Storz C-MAC, GlideScope Direct Intubation Trainer, McGrath MAC, Venner A.P. Advance Mac Blade)

2. Video laryngoscopes with angulated blades (GlideScope, McGrath Series 5, Storz D-Blade)

3. Video or optical laryngoscopes with a tube channel (Airtraq, Pentax AWS, KingVISION)

See the following sections for pictures and manufacturers of each device.

Video Laryngoscopes with Standard Macintosh Blades

These devices have blades that are exactly the same or very similar to a standard English or German Macintosh direct laryngoscope. They all have a digital camera adjacent to the light source a few centimeters proximal to the tip. Each of these devices can be used for either conventional direct laryngoscopy or video laryngoscopy. The Storz C-MAC is the only device in this group that has been sufficiently tested (Fig. 4-22).^153–161 The laryngeal view obtained on the video monitor is better than the direct view in most patients.^154,156 The improved laryngeal view provided by the camera is especially helpful in morbidly obese patients and in trauma patients who require cervical spine immobilization.^153,160

Figure 4-22 The Storz C-MAC video laryngoscope.

Background

The Storz Video Macintosh Laryngoscope was introduced into clinical practice by Kaplan, Berci, and colleagues in 2002.¹⁵⁹ The latest version of this device, the Storz C-MAC, is smaller, more portable, and cheaper.¹⁵² It also has a wider field of view because the camera is on the blade instead of in the handle.¹⁶² The C-MAC consists of a one-piece blade, a cable, and a monitor. It can record digital video or still images onto a Secure Digital memory card. Older versions of this device were referred to as the Storz Video Macintosh Laryngoscope, Storz BERCI DCI Video Laryngoscope, Storz V-MAC BERCI DCI, and Storz Berci-Kaplan Videolaryngoscope.^{154,156,161,163} The GlideScope Direct Intubation Trainer, McGrath MAC, and Venner A.P. Advance Mac Blade appear similar in design, but they are all very new and untested.

Anatomy and Physiology

When the tip of the Storz C-MAC is advanced into the vallecula, it gives an 80-degree-wide field of view and offers a panoramic view of the glottis. Moving slowly and using a progressive visualization technique to find the tongue, epiglottis, posterior cartilages, and vocal cords (as with direct laryngoscopy) is the best approach to performing laryngoscopy with the C-MAC.

Pathophysiology

There is limited research but some data that the Storz C-MAC provides better glottic visualization and decreases the number of intubation attempts in patients with cervical spine immobility and morbid obesity.153,160

Indications

The Storz C-MAC may be a good option for routine intubations at academic institutions that are teaching novice intubators. In 2008, Howard-Quijano and coauthors published a prospective, randomized, crossover study of 37 novice intubators (medical students and residents) who performed 222 intubations with the Storz Video Macintosh system.¹⁵⁵ The novice intubators performed only direct laryngoscopy and were not allowed to see the video monitor in any case. Intubations were randomized so that either the instructors could see the video monitor or it was covered by a drape. Novice intubators were given 2 minutes to intubate before the instructor took over. When instructors were allowed to see the video monitor, the novice intubators had a 69% success rate and a 3% rate of esophageal intubation. When instructors were blinded to the video monitor, the novice intubators had a 55% success rate and a 17% rate of esophageal intubation. Also, a 2008 manikin study by Low and associates showed that novices who learned direct laryngoscopy skills via the Storz Video Macintosh system found it easier to intubate, had more confidence, and exhibited improved knowledge of airway anatomy.¹⁶³

Use of the C-MAC may also be indicated when direct laryngoscopy is difficult. In 2006, Kaplan and coauthors published a prospective multicenter trial in which the direct laryngoscopy view was compared with the video view during 865 intubations with the Storz Video Macintosh system.¹⁵⁷ They reported 7 cases in which the direct view of the larynx was easy and the video view was difficult and 100 cases in which the direct view was difficult and the video view was easy. In 2009, Jungbauer and colleagues studied 200 patients with Mallampati class III or IV anatomy.¹⁵⁶ They randomized patients to intubation with direct laryngoscopy or with the Storz Video Macintosh system. The success rate with direct laryngoscopy was 92% and the success rate with the Storz Video Macintosh system was 99%. Finally, in 2010 Cavus and coworkers published a report of three patients in whom there was unexpected difficulty with direct laryngoscopy but good glottic visualization and successful intubation on the first attempt with the Storz C-MAC.¹⁶²

Two studies compared the Storz C-MAC with the GlideScope and McGrath systems. A 2009 study of 450 patients with normal airways by van Zundert and colleagues showed that those intubated with the Storz C-MAC were intubated more quickly and had a higher first-pass success rate than did those intubated with the GlideScope or McGrath MAC.¹⁶¹ Another study compared the C-MAC with the GlideScope and McGrath in 150 morbidly obese patients and found that those intubated with the C-MAC had significantly fewer intubation attempts and a shorter intubation time.¹⁶⁰

In addition, the C-MAC may be useful in trauma patients with cervical spine immobilization. Two studies suggest that the C-MAC provides better visualization of the glottis and decreases the number of intubation attempts in manikins with a stiff cervical spine.¹⁶³

Video Laryngoscopes with Angulated Blades

The GlideScope (Verathon, Bothell, WA), McGrath Series 5 (Aircraft Medical Ltd., Edinburgh, United Kingdom), and Storz D-Blade (Karl Storz, Tuttlingen, Germany) video laryngoscopes are similarly shaped devices that have sharply angulated, nonchanneled, and narrow-flanged blades.151,152,164,165 All of these devices have a distal angulation of about 60 degrees and a digital camera a few centimeters proximal to the tip. These blades do not allow laryngoscopy by direct visualization. They are designed to follow the natural curvature of the upper airway and look around the tongue rather than displace it. Excellent visualization of the glottis is nearly always achieved when the distal tip of the blade is in or near the vallecula. Because the point of reference is from the location of the camera near the distal tip of these devices, they reliably provide a panoramic view of the larynx that cannot be achieved with direct laryngoscopy. Both the GlideScope and the McGrath allow easy visualization of the larynx, even with inexperienced providers or difficult airway anatomy.^{160,161,164,166–171} However, maneuvering the ET tube around the severe angle of the blade and into the trachea is more difficult, and this is where problems can occur.¹⁵¹ In one large trial involving inexperienced GlideScope operators, the device was abandoned in 3.7% of intubations despite the fact that an excellent view of the glottis was achieved in most of these cases.¹⁶⁴

Background

In 2001 the original GlideScope video laryngoscope became the first commercially available video laryngoscope. The first report of its use was a case report of management of a difficult airway.¹⁷² Three GlideScope models are now available: the GVL, which has a reusable plastic handle and a mountable monitor; the Cobalt AVL, which uses disposable plastic blades to cover a reusable video baton with a mountable monitor; and the Ranger, which has a small portable monitor and the choice of a reusable blade or a video baton with disposable blades (Ranger Single Use). All GlideScope models have a lens antifog mechanism and digital recording capability.

The McGrath portable video laryngoscope is another device with similar characteristics but is more compact. It became available in 2005, and the current model is called the McGrath Series 5 (Fig. 4-23). The shape of the blade is very similar to that of the GlideScope, but it has a small video monitor (1.7 inches diagonally) on the end of the handle. It also has an adjustable-length, detachable metal blade (camera stick) that is covered by a disposable plastic blade during use, so no part of the handle or metal blade makes contact with the patient. It has no recording capability.

Figure 4-23 The McGrath Series 5 video laryngoscope.

The Storz D-Blade became available in 2010 and also has a blade shape similar to that of the GlideScope. It is an optional blade for use with the Storz C-MAC system and has the same functionality as the other C-MAC blades but does not allow the option of direct visualization of the larynx. It was designed specifically for difficult intubations.

The GlideScope and its use are discussed as representative of this class of indirect video-assisted laryngoscopes with thin, sharply angulated and unchanneled blades.

Indications

The GlideScope, McGrath Series 5, and Storz D-Blade may be especially useful when direct laryngoscopy is difficult or fails. In 2010, Noppens and coauthors reported a series of 61 patients with failed direct laryngoscopy, all with Cormack-Lehane grade III and IV views, who subsequently had good laryngoscopic views and 95% were successfully intubated with a McGrath video laryngoscope.¹⁷³ In 2011, Cavus and colleagues published a very similar series of 20 patients with grade III and IV views who had failed direct laryngoscopy but subsequently had good laryngoscopic views and were all successfully intubated with the Storz D-Blade.¹⁷⁴ There are many case reports of easy intubations with the GlideScope and McGrath video laryngoscopes after failed direct laryngoscopy.^172,175 In addition, several case reports show that the GlideScope and McGrath can facilitate successful awake intubation in patients with known or suspected difficult airways.^176–178

A significant advantage of the more angulated video laryngoscopes is that they can provide a good view of the larynx when the neck is in the neutral position. Not surprisingly, there are several small studies and case reports demonstrating that the GlideScope and McGrath provide good laryngoscopic views and a high rate of successful intubation in patients with cervical spine immobilization.179–181 In 2006, Lai and associates published a series of 12 patients with ankylosing spondylitis and difficult direct laryngoscopy. Eight of these patients were able to be intubated nasotracheally with the GlideScope.¹⁸² There is also a case report of a patient with severe ankylosing spondylitis who was easily intubated on the first attempt with the McGrath.¹⁸³

Finally, the GlideScope is useful for routine intubations by inexperienced or novice intubators. In a 2009 study by Nouruzi-Sedeh and coworkers, 20 novices each intubated five patients with direct laryngoscopy and five patients with the GlideScope. They had a 51% success rate with direct laryngoscopy and a 93% success rate with the GlideScope.¹⁶⁹

Contraindications

Contraindications to using angulated video laryngoscopes are not well described in the literature. As with any video or optical device, blood or secretions on the lens may decrease visualization of the larynx. Fogging was a problem with older fiberoptic devices, but this problem is rare with the newer video devices. Limited mouth opening (<2 cm) can make insertion of these devices more challenging. The biggest contraindication is probably lack of experience or absence of a rigid stylet to allow the operator to maneuver the ET tube around the sharp angle of the blade.¹⁵¹

Procedure and Technique

Grasp the video laryngoscope in the left hand and place it in the patient’s mouth with the scissor technique. Under direct vision, advance it through the oropharynx along the midline of the tongue (Fig. 4-24, step 4). Then look up at the monitor while continuing to advance the blade down the midline of the tongue, progressively identifying the base of the tongue and the epiglottis. With a gentle lifting motion, place the tip of the blade in the vallecula. Elevate the epiglottis and expose the laryngeal inlet (Fig. 4-24, step 5). If the glottis is not well visualized, tilt the handle back slightly to enhance exposure. Manipulate the neck externally to enhance visualization. If more exposure is required, place the tip of the blade under the epiglottis and gently lift and tilt back. While attempting to optimize the laryngeal view, be careful to not place the blade too close to the laryngeal inlet because it may tip the larynx anteriorly and inferiorly and thus make it more difficult to access the laryngeal inlet and pass the tube through it.

Figure 4-24 Video laryngoscopy (GlideScope). Note that there are times when the operator does not look at the screen but rather uses direct vision (steps 4 and 6).

Use a rigid steel GlideRite stylet, which has the same 60-degree curve as the blade of the GlideScope, McGrath, and D-Blade. Alternatively, a malleable stylet with a 60-degree distal bend or a bougie may be acceptable, but these devices may fail if tube passage is challenging. Pass the ET tube through the oropharynx under direct vision until it passes under the curve of the blade, and then look for it on the monitor (Fig. 4-24, step 6). Decrease the chance of soft tissue injury by carefully passing the ET tube along the side of the GlideScope.¹⁸⁴ When the tip of the ET tube comes into view, direct it into the glottis and advance it to the appropriate depth (Fig. 4-24, step 8). If a malleable stylet or bougie is used, it may be difficult to get the tube to go anterior enough. If a malleable stylet must be used, try introducing the tube from the right side of the patient and rotating it 90 degrees and vertically into a midline position behind the tongue. This will help the tip of the stylet maintain its shape as it passes through the oropharynx. Another option is to use a Parker Flex-It intubation stylet to direct the tip of the ET tube anteriorly.¹⁶⁴ It is important to realize that the fixed steel (GlideRite) stylet needs to be withdrawn as the ET tube is passed through the vocal cords because the tip of the stylet will be essentially pointing toward the ceiling as it approaches the laryngeal inlet (Fig. 4-24, step 9). The large knob on the proximal end of the GlideRite stylet is designed to be pushed up by the tip of the intubator’s thumb, thus making ET tube advancement and stylet withdrawal a one-handed procedure.

Complications

Several relatively minor complications have been reported with use of the GlideScope. There are case reports of injury to the soft palate and tonsillar pillars, as well as two cases of puncture of the right palatopharyngeal arch, one requiring surgical repair.184–186

Summary

Video-assisted laryngoscopy is a major advancement in visualization of the laryngeal inlet. These devices are very promising because they provide an improved laryngeal view and have a shorter learning curve than direct laryngoscopy does. The majority of intubation failures are due to an inability to pass the tube through the larynx despite excellent glottic views.¹⁶⁴ Using a fixed steel stylet (GlideRite stylet) helps, but does not eliminate this problem.¹⁵¹ Advancements need to be made in achieving tracheal intubation once the glottis is seen. The addition of a tube channel obviates the need to maneuver the ET tube around the sharp angle of the blade, and channeled devices are described in the next section.

Video and Optical Laryngoscopes with a Tube Channel

Four devices allow indirect video or optical visualization of the larynx and also provide a channeled blade to guide the ET tube through the vocal cords. The Airtraq (Prodol Meditec S.A., Vizcaya, Spain) and Pentax AirWay Scope (AWS) (Pentax, Tokyo) are the only devices in this group that have been sufficiently tested (Figs. 4-25 and 4-26). The KingVISION (King Systems, Noblesville, IN) and Venner A.P. Advance Difficult Airway Blade (DAB) (Venner Medical, Singapore) are very new and essentially untested. The ET tube is inserted into the channel before the device is placed in the airway, and the channel guides the ET tube into the trachea once the glottis is visualized. This design helps alleviate the most common problem associated with video and optical laryngoscopy, difficulty placing the ET tube despite an excellent view of the glottis. Several small studies have demonstrated the utility of the Airtraq and Pentax AWS, but the KingVISION is very new and untested.

Figure 4-25 The Airtraq intubation device. The device pictured uses prisms and mirrors so that the larynx can be visualized via the eyepiece. There is also an optional video system available (not pictured) that can project the image to a wireless display recorder.

Figure 4-26 The Pentax AWS (Air Way Scope).

Background

The concept of a laryngoscope shaped like the natural curvature of the upper airway and containing a channel to guide the ET tube is not new, but the addition of optics and video just recently made this concept a reality.187–190 The advantage of these devices is that they provide an excellent view of the glottis with little need for maneuvering and they eliminate the requirement for the hand-eye coordination needed to pass the ET tube around an acute curve.^191–193

Anatomy and Physiology

All three of the channel-guided devices have the same curvature as the normal upper airway. They allow visualization of the glottis by looking around the tongue instead of trying to straighten the airway and push the tongue out of the way. They consistently provide a better view of the glottis and may lead to less airway trauma and hemodynamic stimulation than occurs with direct laryngoscopy.188,194,195

Indications

Difficult intubation with direct laryngoscopy is an indication for using a channel-guided optical or video device. The Airtraq and Pentax AWS have a high rate of success in patients with known or predicted difficult airways.168, 188,194 In 2009, a study by Asai and colleagues reported 270 patients with difficult airways by direct laryngoscopy (grade III and IV views) and found that 268 of these patients (99.3%) had good glottic visualization and were easily intubated with the Pentax AWS.¹⁹⁴ In a 2009 trial of patients with expected difficult airways, Malik and coworkers randomized 75 patients to direct laryngoscopy, the Pentax AWS, or the GlideScope.¹⁶⁸ The rate of successful intubation was 84% with direct laryngoscopy, 96% with the GlideScope, and 100% with the Pentax AWS.

The Airtraq and Pentax AWS are particularly useful for difficult airways because of cervical spine immobilization and morbid obesity.196–199 In 2007, Ndolo and coauthors published a study of 106 morbidly obese patients who were randomized to intubation with direct laryngoscopy or the Airtraq.²⁰⁰ All patients randomized to the Airtraq were successfully intubated, but six patients in the direct laryngoscopy group required rescue intubation with the Airtraq. In 2007, Maharaj published a study of 40 patients with cervical spine immobilization who were randomized to direct laryngoscopy or the Airtraq.¹⁹⁸ All patients randomized to the Airtraq group were intubated on the first attempt and were intubated faster and with less difficulty than the direct laryngoscopy group. Dhonneur, Ndoko, and their colleagues described alternative techniques for insertion of the Airtraq into the mouths of morbidly obese patients.^199,200 They rotated the device 90 to 180 degrees for initial insertion of the distal tip into the patient’s mouth and then rotated it into the normal orientation before advancing it into the hypopharynx.

In 2008, Enomoto and associates studied 203 patients with manual in-line neck stabilization who required intubation.¹⁹⁷ They randomized these patients to intubation with direct laryngoscopy or the Pentax AWS. The intubation success rate with direct laryngoscopy was 89% versus 100% with the Pentax AWS. A similar study by Liu and coworkers in 2009 included 70 patients with manual in-line stabilization of the cervical spine and randomized them to intubation with the Pentax AWS or the GlideScope.¹⁶⁶ They reported a 100% rate of successful intubation with the Pentax AWS and 89% with the GlideScope. In addition, two studies used fluoroscopy to compare cervical spine motion during intubation with direct laryngoscopy versus intubation with the Pentax AWS.^201,202 Both studies found that intubation with the Pentax AWS caused less movement of the upper cervical spine than direct laryngoscopy did.

The Airtraq is generally used during RSI but may also be used for awake intubation of patients with difficult airways.203,204 When compared with direct laryngoscopy, both the Airtrach and Pentax AWS consistently provide better visualization of the glottis and have a higher rate of successful intubation.^{168,188,189,194,197} Most impressively, two small studies and one large trial have shown that the Airtraq has a very high rate of success after failed direct laryngoscopy.^4,188,189 In 2011, Amathieu and coauthors reported the results of a large prospective trial in which they used an algorithm that specified use of the Airtraq as a backup for all cases of failed RSI with direct laryngoscopy.⁴ They had 28 patients who could not be intubated with direct laryngoscopy after multiple attempts, including the use of a bougie. Intubation with the Airtrach was successful in 27 of 28 of these patients (97%), and the other patient was intubated with an ILMA.⁴

Contraindications

The greatest drawback of channeled video and optical devices is that copious amounts of blood or secretions can obscure the view. Because they do not allow a direct line of sight to the larynx, visualization and intubation are dependent on the video or optical image. If blood or fluid covers the tip of the lens, the image is obscured. This problem can be minimized by aggressively suctioning the hypopharynx before placing the device in the mouth.

Inability to open the mouth or severely limited mouth opening is a contraindication to using the channel-guided devices just described. However, if the patient’s mouth opening is more than about 2 cm, these devices can succeed in cases in which direct laryngoscopy would be impossible. The normal adult-size Airtraq requires 18 mm of mouth opening, and the pediatric and infant sizes require 12.5 mm. The Pentax AWS requires about 20 mm of mouth opening.

Procedure

Before beginning the procedure check that you are using the correct size device, make sure that it is functioning properly, and choose the correct size ET tube for the device and the patient. Insert the ET tube into the channel of the device and position it in the channel so that it is not covering the video or optical lens. Insert the tip of the blade into the mouth vertically so that the handle of the device is pointed toward the patient’s feet. Rotate it into the pharynx and hypopharynx along the midline of the tongue until the tip is in the vallecula. If the glottis is not visualized immediately, try backing the blade out 1 to 2 cm and lift the device gently in the direction of the handle (toward the ceiling). A common mistake is to insert the blade too deep initially, which offers a narrower view of the glottis and may make intubation difficult. When the vocal cords are well visualized in the center of the video or optical image, advance the ET tube through the cords by sliding it forward within the channel. If the ET tube does not go through the cords, pull it back and realize that you need to adjust the position of the entire device to change the trajectory of the tube. If the tube tends to go posterior to the vocal cords, lift the device toward the ceiling and tip the handle back slightly (while avoiding contact with the upper teeth), and then advance the tube again. Alternatively, pass a bougie through the ET tube and direct the curved tip up and through the vocal cords.

When using the Pentax AWS, it is important to know that the ET tube leaves the channel in line with the tip of the blade (more anterior than the Airtraq). Therefore, when the tip of the AWS blade is in the vallecula, the tube often strikes the epiglottis when it is advanced. To avoid this problem, advance the tip of the AWS blade posterior to the epiglottis (as with straight-blade laryngoscopy), and lift the epiglottis out of the way before advancing the ET tube.

Dhonneur, Ndoko, and colleagues described alternative techniques for insertion of the Airtraq in morbidly obese patients.199,200 They rotate the device 90 to 180 degrees for initial insertion of the distal tip into the patient’s mouth and then rotate it into the normal orientation (handle toward the patient’s feet) before advancing it into the hypopharynx. This helps alleviate problems with the handle of the device striking the patient’s chest during insertion.

Aftercare

A common mistake when using laryngoscopes with a tube channel is to quickly remove the laryngoscope after the ET tube is advanced into the trachea. Because the ET tube is already inside the trachea, it is best to attach a resuscitation bag and start ventilating the patient. After giving several breaths, stabilizing oxygenation, and confirming tracheal placement with capnography, slowly and carefully remove the device while providing ongoing ventilation. It is appropriate to leave the laryngoscope in place for a few minutes after intubation to allow visual reconfirmation of proper tracheal placement, particularly if there is a problem with ventilation or oxygenation immediately following intubation. When removing the tube from the channel of these devices, hold the end of the ET tube firmly in the right hand and carefully wiggle the laryngoscope to the left. When the tube slides out of the channel, slowly rotate the laryngoscope out of the patient’s mouth. Reconfirm tracheal placement with capnography and adjust the depth of the ET tube as needed.

Complications

No significant complications have been reported with the tube channel video and optical devices. Because the blades of these devices are rigid and cannot be directly visualized after entering the mouth, they have potential for soft tissue damage. Complications of other video laryngoscopes are primarily a result of blind ET tube placement through the mouth and pharynx, and the tube channel devices eliminate this problem.

Intubating Laryngeal Mask Airways

Review Box 4-3 Intubating laryngeal mask airway: indications, contraindications, complications, and equipment.

ILMAs are unique devices because they are easy to insert, provide excellent ventilation and oxygenation (better than bag-mask ventilation), and also provide a reliable means of tracheal intubation.35,205–208 Many clinicians who have used the Fastrach ILMA in an emergency setting insist on having this device in their difficult airway tool kit.* It is impossible to overstate the value of this device for failed emergency RSI, and unlike other rescue devices, a large volume of data support its use in general and in the setting of failed RSI.^† Subsequently, it has become the primary rescue device for failed RSI in many emergency departments.

There are many different LMAs and other extraglottic devices on the market, and this can cause confusion. Although several extraglottic devices (see Chapter 3) can be used for rescue ventilation or oxygenation, only the devices discussed here can also provide a reliable means of tracheal intubation. The Fastrach is the only device in this group that has been extensively tested and the only ILMA that can reliably facilitate blind intubation (without fiberoptic guidance).^‡

Indications

The LMA Fastrach is indicated as an alternative to bag-mask ventilation or as a conduit for intubation of difficult airways.²¹² In the cannot-intubate/cannot-ventilate scenario it is a reliable rescue device. In this situation, adequate ventilation with the ILMA is possible in nearly all cases.^2,4,96 The ILMA is more successful for ventilation and intubation of difficult airways than the LMA Classic.⁹⁶ For inexperienced providers, ventilation with the ILMA is usually superior to face mask ventilation.²¹⁹

The ILMA can also be used as a primary ventilation and intubation device in patients with difficult airways.²¹² Studies of difficult airway management with the ILMA show that almost all patients can be adequately ventilated with the ILMA and 94% to 99% can be intubated through the device.^§ Patients who are difficult to intubate by direct laryngoscopy are often easy to intubate with the ILMA because many anatomic factors that cause difficult direct laryngoscopy do not affect placement or function of the LMA Fastrach.^35,36

The LMA Fastrach is especially useful in patients with difficult face mask ventilation because of a beard, severe facial trauma or obesity, since none of these factors inhibit Fastrach placement. When brisk bleeding above the glottis makes ventilation and intubation difficult, the Fastrach can prevent aspiration of blood and facilitate blind or fiberoptic intubation. In patients requiring urgent cricothyrotomy or percutaneous needle insertion into the trachea, the ILMA can be used to counteract anterior neck pressure. In this capacity, the Fastrach provides temporary ventilation and aids in stabilization of the cervical spine during the surgical airway procedure.

Contraindications

One limitation of the ILMA is that it cannot be used in infants and small children because the smallest size, a No. 3, is not suitable for patients smaller than 30 kg. The LMA is the preferred rescue device for these patients.

LMAs are contraindicated in patients with less than 2 cm of mouth opening. They are unlikely to be successful in patients with grossly distorted supraglottic anatomy from disease processes or postradiation scarring. They are also relatively contraindicated in awake patients because of the high risk for emesis when the gag and airway reflexes are intact.

Intubation through the LMA Fastrach

The majority of intubations through the ILMA are performed blindly by using either the designated LMA ET tube or a standard ET tube. Regardless of the tube used, it is critical that the ILMA be optimally adjusted before attempting blind intubation through the device.

The LMA ET tube, also known as the LMA Fastrach, is designed specifically for the ILMA. There are two versions of the LMA ET tube: a reusable and a single-use disposable. The reusable version is made of silicone and the single-use version is made of polyvinyl chloride (PVC). The specialized LMA ET tubes are soft and straight and have a midline-beveled tip. These features are designed to allow the LMA ET tubes to emerge from the ILMA mask at an acute angle and to minimize potential injury to the vocal cords and esophagus. The drawback of the specialized Fastrach ET tubes is that they have low-volume high-pressure cuffs, which could potentially cause ischemic damage to the trachea, and there are no clinical data on how long these tubes can remain in place.²²² Use of a standard ET tube for intubation through the LMA Fastrach has been well studied and is the current practice in many EDs.^223–225 Another option is to use a Parker Flex-Tip ET tube (see Fig. 4-7).²²⁶

Procedure and Technique

Before intubation through the ILMA, make sure that the patient is ventilating optimally through the device. Determine this by manually ventilating the patient while holding the ILMA handle with a “frying-pan” grip. If any resistance is felt, adjust the handle by slight rotation in the sagittal plane and then lift the entire device toward the ceiling (see the “Chandy maneuver,” Fig. 4-27, step 3).

Figure 4-27 Endotracheal (ET) intubation with the intubating laryngeal mask airway (ILMA) (Fastrach).

Before inserting the ET tube, lubricate it generously. Advance the ET tube with the curve opposite that of the LMA Fastrach curve (Fig. 4-27, step 5). When the tube has advanced to 15 cm, the tip will start to emerge from the LMA Fastrach mask. Just before advancing the tube, use the frying-pan grip and apply a slight anterior lift (not a tilt) to further align the aperture of the ILMA with the glottis (second part of the “Chandy maneuver,” Fig. 4-27, step 6). Do not use a levering action. While holding the handle in this position, gently pass the tracheal tube to about 16.5 cm. In this position the ET tube will push the epiglottic elevating bar up and may now come in contact with the larynx or esophagus. If cricoid pressure is being applied, decrease it because it may interfere with passage of the ET tube through the glottis. If no resistance is encountered, advance the tube into the trachea until the tracheal tube adapter comes in contact with the proximal end of the ILMA tube (Fig. 4-27, step 7). Do not use force when advancing the tube.

If the ET tube does not pass into the trachea easily, withdraw the ET tube to the 15-cm mark and readjust the position of the LMA Fastrach. If the tube meets resistance at about 17 cm, this may indicate a fully down-folded epiglottis or impaction of the tip of the tube against the anterior laryngeal wall. Rotating the tube may overcome impaction of the tip. To correct a down-folded epiglottis, remove the ET tube and perform the “up-down maneuver” by rotating the ILMA outward 5 to 6 cm without deflating the mask and then sliding it back into the hypopharynx (see Chapter 3, Fig. 3-9, steps 9 and 10). If these maneuvers are unsuccessful, it is likely that the wrong size LMA Fastrach is being used. Consider using a fiberoptic scope to guide intubation (also see the “Insertion Technique and Maneuvers Guide,” on the company website: www.lmana.com).

Once the LMA ET tube has passed into the trachea, inflate the tube cuff and attempt to ventilate the patient. Check for proper tube placement with a Petco₂ detector. If the tube is in the trachea, deflate the cuff of the ILMA. There is no rush to remove the ILMA; it can remain in place for an hour or longer if more pressing patient care issues need to be addressed first.

Using a Standard ET Tube

Use of a standard ET tube is not recommended by the manufacturer, but it is a well-studied and common practice.224,227–229 The manufacturer warns that using a standard ET tube may be associated with a greater likelihood of laryngeal trauma, but there are no reports of such trauma in the literature. The only report of significant trauma with blind intubation through the LMA Fastrach is a case report of esophageal perforation and subsequent death caused by use of the specialized LMA ET tube.²³⁰ A laboratory study showed that a standard PVC ET tube exerts 7 to 10 times more pressure on distal structures than the silicone LMA ET tube does, but the clinical relevance of this finding is unknown.^223,231 Some experts suggest warming the tip of a standard PVC ET tube (to soften it) before insertion through the LMA Fastrach.^224,227,229

Because of the potential for injury with blind intubation through the ILMA, use fiberoptic guidance if there is any difficulty. If using a standard ET tube, insert the ET tube with its curvature opposite the curvature of the LMA Fastrach tube (Fig. 4-27, step 5). This allows the ET tube to exit the Fastrach at a less acute angle and then to advance into the trachea more easily.^213,229

If intubation through the LMA Fastrach fails, the device can still be used to provide ventilation and oxygenation during more invasive airway procedures, such as retrograde intubation or cricothryotomy.²³²

Fiberoptic Intubation through the LMA Fastrach

A fiberoptic bronchoscope (FOB) can be used to verify the position of the larynx either before or during intubation. When intubating through the ILMA over an FOB, a standard ET tube is sufficient and there is no reason to use the specialized LMA ET tube. Before passing the FOB through the ILMA, advance the ET tube through the ILMA to 15 cm. At a 15-cm depth the view through the FOB should show the glottis beyond the epiglottic elevating bar. Advance the ET tube 1.5 cm before advancing the FOB. This protects the fiberoptic elements from being damaged by the epiglottic elevating bar. The view at 16.5 cm should show the vocal cords and trachea. Advance the FOB into the trachea and then pass the ET tube over the FOB. If the vocal cords are not visualized immediately, see the LMA Fastrach “Insertion Technique and Maneuvers Guide,” described previously.

LMA Fastrach Removal

To remove the ILMA, deflate the cuff (Fig. 4-27, step 8), but be careful to not deflate the ET tube cuff. Start by removing the ET tube adapter. Then hold the proximal end of the ET tube in place while rotating the ILMA out of the hypopharynx. As the ILMA passes over the ET tube and out of the mouth, hold the ET tube in place with the stabilizer rod provided with the ILMA (see Fig. 4-27, step 9). When the ET tube pilot balloon comes in contact with the stabilizer rod, remove the stabilizer rod to allow the pilot balloon to travel through the ILMA tube. Then reattach the ET adapter and resume ventilation. Adjust the depth of the ET tube as needed.

Intubation through the LMA Classic

The recommended technique for tracheal intubation through the LMA Classic uses an FOB and has a high success rate but requires a smaller ET tube and some adjustment maneuvers.233,234 Blind intubation through a nonintubating LMA (LMA Classic or LMA Unique) has a poor success rate and is not recommended.^235–237 Using a tracheal tube introducer as a guide through the LMA is also unlikely to be successful and is not recommended.^238,239

Fiberoptic Intubation through the LMA Classic: After ensuring that the LMA is ventilating properly, place a well-lubricated ET tube into the LMA tube and advance it to a depth of 24 cm (No. 5 LMA), so that the tip of the ET tube has just passed the fenestrations. Pass a lubricated FOB through the ET tube and advance it through the vocal cords. If the epiglottis is deflected downward, manipulate the tip of the FOB under the epiglottis until the vocal cords come into view. Pass the ET tube over the FOB and into the trachea, and then inflate the ET tube cuff and ventilate the patient. Check for correct ET tube placement with a Petco₂ detector.

Alternatively, place a hollow introducer, such as an Aintree Intubation Catheter (Cook Critical Care, Bloomington, IN; www.cookmedical.com), in conjunction with an FOB, through the LMA and into the trachea (Fig. 4-28). Remove the LMA while leaving the exchange catheter as an introducer for the ET tube, much like a conventional tracheal tube introducer.

Figure 4-28 Laryngeal mask airway (LMA) as a conduit for intubation. A hollow introducer (Aintree Intubation Catheter, 60 cm) is placed though an LMA and into the trachea with the help of a fiberoptic scope. The LMA is then withdrawn while leaving the introducer in place. The tracheal tube is then railroaded over the introducer into the trachea.

Cricoid pressure may impede placement and intubation through the LMA.93,94 Release cricoid pressure, if necessary, to accomplish these procedures.

Complications When Intubating through LMAs

Although most patients can be safely intubated blindly through the ILMA, there is a small chance of injury to the larynx or esophagus, especially with multiple blind attempts. There is one case report of a death caused by esophageal perforation during blind intubation through the ILMA. Consider using fiberoptic guidance if blind intubation is difficult or if the clinician is inexperienced. Intubation through a nonintubating LMA is not recommended unless facilitated by an FOB.

Summary

LMAs provide an excellent means of oxygenation and ventilation when face mask ventilation is difficult or impossible. In addition, the LMA Fastrach is particularly useful when managing patients who are difficult to intubate with direct laryngoscopy. By facilitating the management of difficult or failed ventilation and difficult or failed intubation, the LMA Fastrach is an indispensable component of the difficult airway algorithm.

Flexible Fiberoptic Intubation

Review Box 4-4 Flexible fiberoptic intubation: indications, contraindications, complications, and equipment.

Flexible fiberoptic intubation with an FOB is the most common technique used by anesthesiologists for known difficult airways. Physicians who perform fiberoptic intubations daily have a success rate of nearly 100% when using this technique for difficult intubations.²⁴⁰ In the ED, with more difficult intubating conditions and less experienced fiberoscopists, the success rate is 50% to 90%.^241–244 The most common reason cited for failure of flexible fiberoptic intubation in the operating room is clinician inexperience.²⁴⁵ In the ED, failure is most often attributed to poor visibility from blood, vomitus, and other secretions.^241–243 Mlinik and colleagues²⁴³ found that successful ED fiberoptic intubations averaged 2 minutes whereas failures averaged 8 minutes. They recommended consideration of alternative approaches if intubation attempts take more than 3 minutes. ED clinicians have the opportunity to develop fiberoptic laryngoscopy skills when performing diagnostic nasopharyngoscopy on ambulatory patients.

Flexible fiberoptic intubation is often the best method for intubating awake patients with a known difficult airway. It can be accomplished via the nasal or oral route and is better tolerated than direct laryngoscopy. It usually provides excellent visualization of the airway and permits evaluation of the airway before placement of the tube. The expense of the equipment, its fragility, and the length of time required to both achieve and maintain technical proficiency are drawbacks.

FOBs are graded according to their external diameter (in millimeters). FOBs specifically designed for ET intubations are available from several companies (Pentax, Olympus, Machida, Storz, and Fujinon). A practical size for an intubating scope is about 4 mm. Although it is physically possible to pass a 4.5-mm (0.5 mm larger) tracheal tube over the scope, the fit is tight. As a rule, the tracheal tube should be about 1 mm larger than the intubating scope. The size of the working channel, the port that allows suction, administration of oxygen, and passage of fluid or catheters, is another important dimension when evaluating FOBs. A working channel of about 2 mm is desirable to allow adequate suction of secretions. Very thin nasopharyngoscopes, with diameters of 3.0 to 3.5 mm, have no working channel but can be used for pediatric tracheal intubation.

Indications and Contraindications

Patients with known or suspected difficult airways are good candidates for awake or semi-awake fiberoptic intubation. Patients with distorted airway anatomy, including swelling of the mouth or tongue, upper airway abscess or infection, morbid obesity, cervical spine injury, trismus, and penetrating and blunt neck trauma, are all good candidates for awake fiberoptic intubation. Patients with laryngeal tumors, especially those with a history of radiation therapy encompassing the cervical region, may be impossible to intubate by any other nonsurgical method. An FOB can also be helpful when assessing and intubating patients with airway obstruction from presumed foreign body aspiration. Flexible fiberoptic intubation is best used as the initial approach to tracheal intubation, but it may be used as a rescue device when other methods fail.²⁴⁶ Flexible fiberoptic intubation can also be performed through an ILMA or LMA after difficult ventilation or failed intubation.

Contraindications to the nasal approach are severe midface trauma and coagulopathy. Patients who are likely to receive thrombolytics should also be excluded. Although there are no clear contraindications to fiberoptic orotracheal intubation, active airway bleeding and vomiting are relative contraindications because successful fiberoptic intubation is rarely achieved in these settings. If the clinician is inexperienced in fiberoptic intubation, significant hypoxia is another relative contraindication.

Procedure and Technique

Preparation of the upper airway is important for successful awake or semi-awake fiberoptic intubation. Deliver local anesthetic to the upper airway by one of several methods. Nebulized lidocaine (4 to 6 mL of a 4% solution) can be used to anesthetize the entire upper airway if time permits. Lidocaine (3 mL of a 4% solution) can also be injected percutaneously through the cricothyroid membrane via a 20-gauge needle, thereby providing anesthesia to the larynx and trachea. Some laryngeal and tracheal anesthesia can also be achieved by transoral spray with a laryngeal tracheal anesthetic set. Finally, lidocaine (4%) can be sprayed through the working channel of the fiberoptic scope during the procedure via the “spray as you go” technique. The maximum dose of lidocaine for airway anesthesia is 3 to 4 mg/kg (about 200 mg in an adult). Sedation for fiberoptic intubation can be accomplished with ketamine, etomidate, propofol, fentanyl, alfentanil, or midazolam (see Chapter 5). The goal of sedation is to preserve spontaneous respiration but limit patient movement and reaction to the procedure. A combination of good topical anesthesia and mild sedation allows the best chance for successful intubation.

The optimal position of the neck is extension, as opposed to the slight cervical flexion desired when using direct laryngoscopy. Extension allows better visualization of the glottis by elevating the epiglottis off the posterior pharyngeal wall. This is especially pertinent in a comatose patient who lacks the muscle tone necessary to maintain an open airway. If problems arise with the tongue and soft tissues falling back and obscuring the view of the FOB, apply a jaw-lift maneuver or grasp the tongue and pull it forward and away from the soft palate and posterior pharyngeal wall. This also moves the epiglottis away from the posterior pharyngeal wall and facilitates exposure of the cords. Extend the head to accomplish the same objective.

Fiberoptic intubation may be performed with the patient in the upright, semi-upright, or supine position. Stand facing the patient or at the patient’s head, depending on personal preference. The upright and semi-upright positions help keep pharyngeal soft tissue from obstructing the airway. The upright position may be more familiar to emergency clinicians who are skilled at diagnostic nasopharyngoscopy.

The greatest impediment to successful fiberoptic intubation is an inability to visualize the larynx because blood or secretions have covered the optical element and cannot be removed. Suction actively just before introduction of the FOB. Once the scope is in place, suction minor secretions through the fiberoptic suction port. Significant blood and secretions are best removed by high-flow oxygen through the suction port, which serves simultaneously to remove blood and secretions, defog the tip, and increase the inspired O₂ content. The setup required for oxygen insufflation should be available immediately, if not already attached to the suction port before the scope is inserted. Once the scope has entered the trachea, difficulty advancing the ET tube may be encountered. The tip of the tube most commonly catches on the right arytenoid cartilage or vocal cord. To fix this, withdraw the tube 2 cm, rotate it counterclockwise 90 degrees, and readvance the tube to remedy the problem (see Fig. 4-19).

Nasal Approach

The nasal approach is technically easier than the oral approach because the angle of insertion allows better visualization of the larynx with minimal manipulation of the FOB. Patient cooperation is also less critical with this approach. In an unconscious patient, the tip of the scope is also less likely to impinge on the base of the tongue with a nasal approach.

If conditions permit, choose the most patent nostril. In a cooperative patient, determine this by simply occluding each nostril and asking the patient to identify the nostril that is easiest to breathe through. Identify the most patent nostril by direct vision or by gently inserting a gloved finger that is lubricated with viscous lidocaine into the nostrils. If time is not an issue, an effective method to dilate the nasal cavity and administer an anesthetic is to pass a lidocaine gel–lubricated nasopharyngeal airway (nasal trumpet) into the selected nostril. Leave this airway in place for several minutes, and introduce progressively larger trumpets.

To prepare the nose and upper airway, administer vasoconstrictors, topical anesthetics, and lubricants. Vasoconstrictors such as 0.25% or 1.0% phenylephrine drops, oxymetazoline (Afrin) spray, or 4% cocaine spray can limit epistaxis. Ample 2% lidocaine gel in the nasal cavity helps the tube negotiate the nasopharynx without complication. Hypopharyngeal anesthesia, as described previously, minimizes gagging and laryngospasm. Place the well-lubricated ET tube in the nostril first to a depth of about 10 cm and then pass the scope through it. Alternatively, mount the ET tube over the scope and first pass the scope through the nostril (Fig. 4-29). Either sequence is acceptable. The advantage of first passing the tracheal tube through the nose is that it avoids the possibility of secretions covering the scope and positions the scope just above the laryngeal inlet. Its disadvantages are that NT placement may cause bleeding and, in some patients, the tube may not pass easily into the nasopharynx. In some patients the mouth is not accessible at all because of trismus, swelling, or trauma (e.g., angioedema caused by an angiotensin-converting enzyme [ACE] inhibitor), so the nasal route is the only option for fiberoptic intubation (Fig. 4-30).

Figure 4-29 Fiberoptic intubation. Note that the tracheal tube is first premounted on the scope. The fiberoptic scope enters the trachea and then serves as a guide over which the tracheal tube is passed. Larger image, The nasal approach. Inset, Use of an oral intubating airway via the oral approach. (Courtesy of Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis.)

Figure 4-30 A, This patient with life-threatening angiotensin-converting enzyme inhibitor-induced angioedema is in severe distress, and oral intubation is impossible. B, Fiberoptic nasotracheal intubation is a good choice, but it is very difficult, if not impossible, in a struggling patient. Ketamine anesthesia allowed patient cooperation and administration of supplemental oxygen. A less ideal option is blind nasotracheal intubation. Tracheostomy may be required. Note: In this case the tracheal tube was premounted on the scope before the scope was passed into the patient’s nose. Alternatively, the tube may be first passed about 10 cm through the nose, and then the scope passed through the tube and into the trachea.

Prepare the most patent nostril and advance the ET tube until it makes the bend into the nasopharynx. If negotiating this bend is difficult, place a well-lubricated FOB through the tube and into the oropharynx to serve as a guide for the ET tube. Once the tracheal tube is in the oropharynx, perform thorough oropharyngeal suctioning before introducing the scope into the ET tube. Advance the FOB toward the larynx. The epiglottis and vocal cords are seen with little or no manipulation of the tip of the FOB in 90% of patients.²³⁶ Advance the scope and keep the cords in view by making frequent minor adjustments of the tip of the scope.

In a comatose or obtunded patient, the tongue and other soft tissues may obscure the view of the larynx. This can be alleviated by asking an assistant to pull the tongue forward or apply a chin- or jaw-lift maneuver. Advance the scope through the larynx to the carina and pass the ET tube over the firmly held FOB into the trachea. Remember that in adults, the average distance from the naris to the epiglottis is 16 to 17 cm. If the scope has been advanced much beyond this distance and the glottis is still not seen, the scope is probably in the esophagus.²⁴⁷ If the scope meets resistance at about this same level and only a pink blur is visible, the tip of the scope is probably in a piriform sinus. Transillumination of the soft tissues may confirm this and indicate the necessary corrective maneuvers.

Oral Approach

Oral fiberoptic intubation is indicated when nasal intubation is contraindicated, most commonly because of severe midface trauma or clinician inexperience. Skilled fiberoscopists often find the oral approach just as easy as the nasal approach. For the less experienced, though, the oral approach may be more difficult because the path of the scope is less defined by the surrounding soft tissue and the tip of the scope is more likely to impinge on the base of the tongue or vallecula. Keeping the scope in the midline and elevating the soft tissue by pulling the tongue forward or applying the jaw-lift maneuver will minimize this difficulty. Because the oropharyngeal axis is not as well aligned with the larynx as the nasopharyngeal axis is, more scope manipulation is required when using the oral approach.

Difficulty with the oral approach can be minimized by using an oral intubating airway (Fig. 4-31). This adjunct resembles an oropharyngeal airway but is longer and has a cylindrical passage through which the FOB and tracheal tube are passed. The tip of this airway lies just cephalad to the epiglottis and ensures midline positioning. Make sure that the patient is either adequately anesthetized or obtunded before the oral airway is placed to minimize gagging or vomiting. Place a well-lubricated FOB, premounted with an ET tube, through the oral intubating airway and fiberoptically intubate the trachea (Fig. 4-29, upper right inset). Advance the ET tube over the scope and into the trachea. This may require the same counterclockwise maneuver as described with the nasal approach. After successful intubation, the oral airway can be left in place as a bite block or may be removed over the ET tube after removal of the tube adapter. Some oral intubating airways can be removed from the mouth without disconnecting the ET tube adapter.

Figure 4-31 Examples of oral intubating airways. The Williams Airway Intubator (left) cradles the endotracheal (ET) tube in an open, curved guide, whereas the Ovassapian Fiberoptic Intubating Airway (right) positions the ET tube on the posterior surface of the intubation airway.

An alternative approach to the traditional oral fiberoptic intubation for an anticipated difficult airway requires two clinicians. One performs direct laryngoscopy, places the tip of the fiberoptic scope under the epiglottis, and blindly advances it while the second clinician, holding the body of the scope, directs the tip fiberoptically through the cords (Fig. 4-32).

Figure 4-32 Two-person fiberoptic intubation for difficult intubation. The laryngoscopist obtains the best hypopharyngeal exposure and directs the fiberoptic tip in the direction of the glottis. The second clinician, who manipulates the tip of the fiberoptic scope, directs the laryngoscopist to slowly advance the tip until it has successfully passed through the cords.

Complications

Complications of fiberoptic orotracheal intubation include hypoxia from prolonged intubation attempts, emesis, and laryngospasm. Oxygen saturation monitoring should alert the clinician to hypoxia. Most complications seen with fiberoptically guided NT intubation are associated with passing the ET tube through the nasopharynx. Epistaxis is the most common, followed by other nasopharyngeal injuries. A rare but potentially significant complication may result if on blind advancement of the fiberoptic scope through the ET tube the tip of the scope exits through Murphy’s eye (distal side port of the ET tube).²⁴⁸ Attempts at passing the ET tube through the larynx will fail because the tip of the tube, now extending off the midline, will catch on the laryngeal structures. To avoid this complication, introduce the scope before placing the ET tube.

Summary

The primary advantages of fiberoptic intubation are the ability to visualize upper airway abnormalities, to negotiate difficult airway anatomy, and to carefully perform tracheal intubation under visual guidance. Fiberoptic intubation is noninvasive and well tolerated. Its major limitation as an emergency airway is poor visibility because of blood and secretions; in this setting it is best to avoid the FOB. Procedural time can be another limitation. Fiberoptic intubation requires more practice than many other methods of airway management, and considerable experience should be obtained before using the FOB in an airway emergency. Fiberoptic intubation is more likely to be successful if used early in the management of a difficult airway rather than as a last resort after repeated failure with direct laryngoscopy.

Optical Stylets

A class of devices that incorporates fiberoptics into a semirigid metal or metal-reinforced stylet was introduced in the late 1990s. These devices can be used in conjunction with direct laryngoscopy or as stand-alone intubating devices. They have been shown to require direct laryngoscopic assistance in 8% to 20% of cases and in general are more successful when used in this way.249,250 Pass the tip of the fiberoptic stylet, with its overlying ET tube, under the epiglottis and direct it through the glottis and into the trachea. Visibility can be hampered by blood and secretions, but less so than with flexible fiberoscopy.²⁵¹ These devices are far more intuitive and require less practice than an FOB does. The Shikani Optical Stylet and Levitan FPS Scope (Clarus Medical, Minneapolis) are examples of these malleable optical stylets (Fig. 4-33). The Shikani Optical Stylet is most often used similarly to the Trachlight, with the added feature of fiberoptic visualization of anatomic structures lying just beyond the tip of the tube. The Levitan FPS Scope is designed to be used with a laryngoscope and serves as a stylet for the tracheal tube while providing fiberoptic visualization if required. The Bonfils Retromolar Intubation Fiberscope (Storz Endoscopy, Culver City, CA) is rigid but otherwise structurally and functionally similar to the Shikani. The distal end of the Bonfils has a fixed curve of 40 degrees, whereas the other scopes are malleable up to 120 degrees. Power for the Shikani and Bonfils stylets may be supplied by either an external source or batteries. Video cameras can be attached to the eyepiece of all of these devices but have the drawback of making them less maneuverable. The Bonfils is available with an integrated video module. The Levitan stylet is shorter than the other devices, and although it conforms more to the normal length of a stylet, it currently requires that the tube be cut at 27.5 to 28 cm before mounting it on the stylet. It can accommodate down to a 5.5-mm-ID tube. The Shikani stylet comes in two sizes, the adult, which accommodates a 5.5-mm-ID tube, and a pediatric version, which goes down to a 3.5-mm-ID tube. An adjustable plastic ET tube stop is located proximally on the stylet, secures the tube at the desired length, and provides a means for oxygen supplementation during the procedure.