Emergency Airway Management

Published on 24/06/2015 by admin

Filed under Emergency Medicine

Last modified 22/04/2025

Print this page

This article have been viewed 14746 times

Chapter 20 Emergency Airway Management

Swaminatha V. Mahadevan

For online-only figures, please go to www.expertconsult.com

Emergency airway management encompasses assessment, establishment, and protection of the airway in combination with effective oxygenation and ventilation. Timely and effective airway management can literally mean the difference between life and death, and it takes precedence over all other clinical considerations.

Airway management in the wilderness must often be provided in austere or unusual environments under less-than-ideal circumstances. Many of the resources that are readily accessible in a hospital or emergency department setting are not available in the wilderness, so improvisation may prove invaluable.

Airway Anatomy

Internally, the airway is composed of many structures and well-defined spaces. It originates in the nasal and oral cavities (Figure 20-1). The nasal cavity extends from the nostrils to the posterior nares or choanae. Because resistance to airflow through the nose is almost twice that of the mouth, patients who require high flow rates (e.g., during exercise) often breathe through their mouths. The nasopharynx extends from the end of the nasal cavity to the level of the soft palate. Tonsillar lymphoid structures are the primary impediments to airflow through the nasopharynx. The oral cavity is bounded by the teeth anteriorly, hard and soft palates above, and the tongue below. The oropharynx, which communicates with the oral cavity and the nasopharynx, extends from the soft palate to the tip of the epiglottis. The tongue is the principal source of obstruction in the oropharynx.

FIGURE 20-1 Lateral airway anatomy.

(Redrawn from Mahadevan SV, Garmel GM, editors: An introduction to clinical emergency medicine: Guide for practitioners in the emergency department, Cambridge, UK, 2005, Cambridge University Press. Courtesy Chris Gralapp. http://www.biolumina.com.)

The oropharynx continues as the laryngopharynx (hypopharynx), which extends from the epiglottis to the upper border of the cricoid cartilage at the level of the C6 vertebral body. The larynx, which lies between the laryngopharynx and trachea, serves as an organ of phonation and a valve to protect the lower airway from aspiration. The larynx is made up of muscles, ligaments, and cartilages, including the thyroid, cricoid, arytenoids, corniculates, and epiglottis.

The flexible epiglottis, which originates from the hyoid bone and base of the tongue, covers the glottis during swallowing and provides protection from aspiration. During laryngoscopy, the epiglottis is an important landmark for airway identification and laryngoscopic positioning. The vallecula is the space at the base of the tongue that is formed posteriorly by the epiglottis and anteriorly by the anterior pharyngeal wall. The laryngeal inlet is the opening to the larynx that is bounded by the epiglottis, aryepiglottic folds, and arytenoid cartilages. The glottis is the vocal apparatus, which is made up of the true and false vocal cords and the glottic opening, which is a triangular fissure between the vocal cords and the narrowest segment of the adult larynx.

Externally identifiable landmarks are also important to airway assessment and management (Figure 20-2). The mentum is the anterior aspect of the mandible that forms the tip of the chin. The hyoid bone forms the base of the floor of the mouth. The thyroid cartilage forms the laryngeal prominence (i.e., the “Adam’s apple”) and the thyroid notch. The cricoid cartilage, which lies inferior to the thyroid cartilage, forms a complete ring that provides structural support to the lower airway. The cricothyroid membrane lies between the thyroid and cricoid cartilages and serves as an important site for surgical airway management.

FIGURE 20-2 External airway anatomy.

Knowledge of the anatomic differences between adults and infants is integral to effective pediatric airway management. These important differences are summarized in Table 20-1 and Figure 20-3.

TABLE 20-1 Anatomic Airway Differences Between Children and Adults

Anatomy	Clinical Significance
Large intraoral tongue that occupies a relatively large portion of the oral cavity	High anterior airway position of the glottic opening as compared with that of an adult
High tracheal opening: C1 in infancy as compared with C3 or C4 at the age of 7 years and C4 or C5 in adulthood	Straight blade preferred over curved blade to push distensible anatomy out of the way to visualize the larynx
Large occiput that may cause flexion of the airway; large tongue that easily collapses against the posterior pharynx	Sniffing position is preferred; the large occiput actually elevates the head into the sniffing position in most infants and children; a towel may be required under the shoulders to elevate the torso relative to the head in small infants
Cricoid ring is the narrowest portion of the trachea as compared with the vocal cords in adults	Uncuffed tubes provide an adequate seal, because they fit snugly at the level of the cricoid ring; correct tube size is essential, because variable expansion cuffed tubes are not used
Consistent anatomic variations with age, with fewer abnormal variations related to body habitus, arthritis, or chronic disease	<2 yr old, high anterior
	2-8 yr old, transition
	>8 yr old, small adult
Large tonsils and adenoids may bleed; more acute angle between the epiglottis and the laryngeal opening results in nasotracheal intubation attempt failures	Blind nasotracheal intubation not indicated for children; nasotracheal intubation failure
Small cricothyroid membrane	Needle cricothyroidotomy difficult and surgical cricothyroidotomy impossible in infants and small children

Modified from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.

FIGURE 20-3 Anatomic airway differences between infants and adults. The anatomic differences particular to infants include the following: (1) a higher and more anterior position for the glottic opening (note the relationship of the vocal cords to the chin–neck junction); (2) a relatively larger tongue in the infant that lies between the mouth and the glottic opening; (3) a relatively larger and more floppy epiglottis in the infant; (4) the cricoid ring is the narrowest portion of the pediatric airway; in adults, the narrowest portion is the vocal cords; (5) the position and size of the cricothyroid membrane in the infant; (6) the sharper and more difficult angle for blind nasotracheal intubation; and (7) the larger relative size of the occiput in the infant.

(Redrawn from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

Assessment of the Airway and Recognition of Airway Compromise

Assessment of the airway begins with an evaluation of airway patency and respiratory function. The goal is to determine whether the airway is patent and protected and whether breathing is present and adequate. This is accomplished by inspection, auscultation, and palpation, which is commonly known as the “look, listen, and feel” approach.

Visual signs of airway compromise include agitation, obtundation, and cyanosis. Blue, gray, or ashen skin—especially around the eyes, lips, and nail beds—is a worrisome finding. Significant airway compromise may manifest without cyanosis; examples include an allergic reaction with upper airway edema and vasodilation (causing flushed red skin) and unconsciousness as a result of carbon monoxide poisoning.

Bradypnea, tachypnea, and irregular respirations may be signs of impending respiratory compromise. Breathing that is shallow, deep, or labored may indicate respiratory insufficiency. Respiratory muscle fatigue may result in recruitment of the accessory muscles of respiration; this is clinically manifested as suprasternal, supraclavicular, or intercostal retractions. Traumatic injury to the chest (e.g., flail chest) or an aspirated foreign body may result in paradoxic or discordant chest wall movement.

In children, visual signs of airway compromise and respiratory distress include tachypnea, cyanosis, drooling, nasal flaring, and intercostal retractions. A child with severe upper airway obstruction may sit upright with the head tilted back (i.e., “sniffing” position) to straighten the airway and reduce occlusion. A child with severe lower airway obstruction may sit up and lean forward on outstretched arms (i.e., “tripod” position) to augment accessory muscle function.

Under most circumstances, hearing the victim speak with a normal voice suggests that the airway is adequate at that moment. Unusual sounds or noisy respirations may be present with partial airway obstruction. Snoring indicates partial airway obstruction at the pharyngeal level; gurgling may be heard with blood or secretions in the airway; stridor may be associated with partial airway obstruction at the level of the larynx (inspiratory stridor) or at the level of the trachea (expiratory stridor); hoarseness suggests a laryngeal process.

The central face and mandible should be assessed for structural integrity, because injuries to these structures may lead to airway distortion and compromise. The anterior neck should be carefully inspected for penetrating wounds, asymmetry, or swelling that may herald impending airway compromise. The palpation of subcutaneous air suggests direct airway injury.

In the unconscious victim, feel for air movement at the mouth and nose. Open the mouth to inspect the upper airway, taking care not to extend or rotate the neck. Identify and remove any vomitus, blood, or other foreign bodies. Look for swelling, bleeding, or other abnormalities of the oropharynx. The gentle use of a tongue blade may facilitate this task. The victim’s ability to spontaneously swallow and handle secretions is an important indicator of intact airway protective mechanisms. In the unconscious victim, absence of a gag reflex has traditionally been linked with loss of protective airway reflexes.

Auscultation of the lung fields should demonstrate clear and equal breath sounds. Diminished breath sounds may result from a pneumothorax, hemothorax, or pleural effusion. Wheezing and dyspnea are often associated with lower airway obstruction.

Opening the Airway

Opening the airway and ensuring airway patency are essential for adequate oxygenation and ventilation; these are the first priorities of airway management. The conscious victim uses protective reflexes and the musculature of the upper airway to maintain a patent airway and to protect against aspiration of foreign substances, gastric contents, or secretions. In the severely ill, compromised, or unconscious victim, these protective airway mechanisms may be impaired or absent. Upper airway obstruction in the unconscious victim most commonly results from posterior displacement of the tongue and the epiglottis at the level of the pharynx and the larynx. Head positioning, manual airway techniques, and mechanical airway adjuncts may be employed to alleviate upper airway obstruction.

Head Positioning

If the mechanism of injury or physical examination raises concern for cervical spine injury, the head and neck should be stabilized in the neutral position. Care should be taken to not flex, extend, or rotate the victim’s head. After cervical spine immobilization, the airway should be reevaluated for obstruction.

The optimal head position for airway alignment and patency varies with age. A supine infant’s large occiput contributes to flexion of the head and neck and resultant airway obstruction; this may be alleviated by elevating the shoulders with a small towel (Figure 20-4). In children, slightly extending the head into the sniffing position helps to relieve airway obstruction. In adults, placing a folded towel or article of clothing under the occiput, which flexes the neck at the torso, followed by gentle hyperextension of the head at the atlanto-occipital joint, provides for the optimal alignment of the airway axes.

FIGURE 20-4 A, The clinical determination of optimal airway alignment with the use of a line passing through the external auditory canal and anterior to the shoulder. B, The application of the line to determine the optimal position. In this small child, the occiput obviates the need for head support, yet the occiput is not so large as to require support of the shoulders. Note that the line traversing the external auditory canal passes anterior to the shoulders. With only slight extension of the head on the atlanto-occipital joint, the sniffing position is achieved.

(Redrawn from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

Manual Airway Techniques

Manual airway techniques are effective but often require continuous involvement of a single provider to maintain airway patency.

Head Tilt With Chin Lift

The head tilt with chin lift (Figure 20-5) is a simple and effective technique for opening the airway. The palm of one hand is placed on the victim’s forehead and applies firm backward pressure to tilt the head back. Simultaneously, the fingers of the other hand are placed under the bony part of the chin and lifted to bring the chin forward. These fingers support the jaw and maintain the head-tilt position. This maneuver extends the neck and should not be used if cervical spine injury is a concern.

FIGURE 20-5 Head tilt with chin lift.

Jaw Thrust With Head Tilt

If a cervical spine injury is not suspected, the jaw thrust with head tilt maneuver may be used to gain additional forward displacement of the mandible. Position yourself at the top of the victim’s head, and then grasp the angles of the mandible with both hands and lift to displace the jaw forward while tilting the head back.

Jaw Thrust Without Head Tilt

If a cervical spine injury is suspected or cannot be excluded, the jaw thrust without head tilt (Figure 20-6) can be performed while maintaining neutral cervical spine alignment. With this maneuver, the jaw thrust is performed without extending or rotating the neck.

FIGURE 20-6 Jaw thrust without head tilt.

Tongue Traction

If the patient is unconscious or in extremis, the airway may be opened temporarily by attaching the anterior aspect of the victim’s tongue to the lower lip with two safety pins (Figure 20-7). An alternative to piercing the patient’s lower lip is to pass a string through the safety pins and then secure the end of the string to the victim’s shirt button or jacket zipper (Figure 20-8), thereby exerting traction on the tongue.

FIGURE 20-7 Tongue traction. The airway may be opened temporarily by attaching the anterior aspect of the victim’s tongue to the lower lip with two safety pins.

FIGURE 20-8 Tongue traction. An alternative to piercing the lower lip is to pass a string through the safety pins and then exert traction on the tongue by securing the end of the string to the victim’s shirt button or jacket zipper.

Mechanical Airway Adjuncts

Several airway adjuncts are available to maintain airway patency while freeing up the health care provider to perform other duties.

Oropharyngeal Airway

The oropharyngeal airway (OPA) is an S-shaped device that is designed to hold the tongue away from the posterior pharyngeal wall (Figure 20-9). When the OPA is properly placed, it prevents the tongue from obstructing the glottis, and also provides an air channel and suction conduit through the mouth. These devices are most effective for unconscious and semiconscious victims who lack a gag reflex or cough. Use of an OPA in a victim with a gag reflex or cough is contraindicated, because the OPA may stimulate retching, vomiting, or laryngospasm.

FIGURE 20-9 Oropharyngeal airway.

OPAs are made of disposable plastic, and come in varying sizes to accommodate children and adults. The size is based on the distance in millimeters from the flange to the distal tip. The proper OPA size is estimated by placing the OPA’s flange at the corner of the mouth so that the bite-block segment is parallel with the victim’s hard palate; the distal tip of the airway should reach the angle of the jaw.

Two types of OPAs are commonly employed. The Guedel makes use of a tubular design, whereas the Berman is distinguished by having airway channels on each side.

Technique for insertion

1 Open the mouth and clear the pharynx of any secretions, blood, or vomitus. Remove dentures or partial dental plates, if present.

2 In an adult or older child, insert the OPA upside down or at a 90-degree angle to avoid pushing the tongue posteriorly during insertion. Slide it gently along the roof of the mouth. As the OPA is inserted past the uvula or the crest of the tongue, rotate it so that the tip points down the victim’s throat.

3 In a child, grasp the tongue and gently pull it forward or use a tongue blade to displace it inferiorly and anteriorly. Insert the OPA with the tip pointing toward the tongue and throat (i.e., the intended position after placement).

4 The OPA flange should rest against the victim’s lips, and the distal portion should rest on the posterior pharyngeal wall. If the OPA is too short, it may displace the tongue into the hypopharynx and occlude the airway. If the OPA is too long, it may displace the epiglottis and thereby cause an airway obstruction.

Nasopharyngeal Airway

The nasopharyngeal airway (NPA) is an uncuffed trumpet-like tube that provides a conduit for airflow between the nares and the pharynx (Figure 20-10). The NPA is inserted through the nose rather than the mouth, and it has a flange at the outer end to prevent displacement or slippage beyond the nostril. These devices are better tolerated than are OPAs, and they are commonly used with intoxicated or semiconscious victims. They are also effective when trauma, trismus (i.e., clenched teeth), or other obstacles (e.g., wiring of the teeth) preclude OPA placement. NPAs are contraindicated in victims with basilar skull or facial fractures, because inadvertent intracranial placement may occur.

FIGURE 20-10 Nasopharyngeal airway.

NPAs made of soft and pliable rubber or plastic come in varying sizes to accommodate children and adults. Sizes (as indicated by internal diameter) range from 12 to 36 Fr. Proper NPA length is determined by measuring the distance from the tip of the patient’s nose to the tragus of the patient’s ear.

Technique for insertion

1 Lubricate the nasopharyngeal airway with a water-soluble lubricant to minimize resistance in the nasal cavity. Do not use petroleum jelly or a non–water-based lubricant.

2 If the NPA has a beveled (angled) edge, place the airway in the nostril with the bevel directed toward the nasal septum.

3 Gently insert the NPA straight back along the floor of the nasal passage (i.e., perpendicular to the coronal plane of the face).

4 If resistance is met, rotate the tube slightly, reattempt insertion through the other nostril, or try a smaller-diameter tube. Do not force insertion of the tube, because injury to the nasal mucosa can result in bleeding.

5 After insertion, the NPA flange should rest on the victim’s nostril, and the distal portion of the airway should rest in the posterior pharynx, behind the tongue.

Any flexible tube of appropriate diameter and length can be used as an improvisational substitute for the NPA. Examples include a Foley catheter, radiator hose, solar shower hose, siphon tubing, or an inflation hose from a kayak flotation bag or sport pouch. An endotracheal tube (ETT) can be shortened and then softened in warm water to substitute for a commercial nasal trumpet. The flange can be improvised with the use of a safety pin through the nostril end of the tube (Figure 20-11).

FIGURE 20-11 Improvised nasal trumpet.

Although OPAs and NPAs help to establish artificial airways, they do not provide definitive airway protection from aspiration.

Recovery Position

In the spontaneously breathing unconscious victim who is not at risk for cervical spine injury, the recovery position (Figure 20-12) allows for airway patency while reducing the risk of aspiration. In the recovery position, the tongue is less likely to fall back and occlude the airway, and vomitus is more likely to be expelled than inhaled. Even a diminutive rescuer can place a large person in the recovery position if the proper technique is employed.

FIGURE 20-12 Recovery position.

Foreign-Body Airway Obstruction

Foreign bodies—most commonly a piece of meat—may cause partial or complete airway obstruction. A victim with partial airway obstruction can usually phonate or produce a forceful cough in an attempt to expel the foreign body. When encountering a victim with a partially obstructed airway, if air exchange is adequate, do not interfere with the person’s attempts to clear the airway. Encourage forceful coughing, and closely monitor the victim’s condition. If the obstruction persists or if air exchange worsens or becomes inadequate, the victim should be managed as if a complete airway obstruction exists. Worrisome findings that should prompt immediate aggressive airway management include a weak or ineffective cough, increased respiratory difficulty, decreased air movement, and cyanosis.

A person with a complete airway obstruction cannot speak (aphonia), exchange air, or cough. The person will often grasp the neck (i.e., the universal distress signal for choking) and open the mouth widely. The unconscious victim with complete airway obstruction will not demonstrate any typical chest movements or other signs of adequate air exchange. Individuals with complete airway obstruction from a foreign body require immediate medical attention. Failure to rapidly relieve the obstruction can lead to cardiac arrest.

A complete summary of the treatment for complete airway obstruction caused by foreign bodies in adults and children is provided in Table 20-2.

TABLE 20-2 Relief of Choking

Suction

All sick or injured victims are at risk for airway obstruction and pulmonary aspiration, typically of gastric contents or blood. Life-saving interventions, such as bag-mask ventilation (BMV), may increase this risk. Suction is essential for removal of vomitus, secretions, blood, and foreign bodies that may occlude the airway or increase the risk for pulmonary aspiration.

Portable suction devices, which are available from a number of manufacturers, are ideal for the wilderness setting. These portable units should provide enough vacuum flow for adequate pharyngeal suction. Portable devices may be powered by oxygen, air, or electricity, or they may be manually powered (Figure 20-13, online). Hand-operated units are popular because they are lightweight, compact, reliable, and inexpensive. All units should have large-bore, nonkinking suction tubing, an unbreakable collection container, and a sterile disposable suction catheter.

FIGURE 20-13 A, RES-Q-VAC suction device. B, S-SCORT Jr Quickdraw battery-powered handheld device.

(A from Repro-Med Systems, Inc. product information; B redrawn from SSCOR, Inc. product information.)

Flexible (i.e., “French”) suction catheters are used to suction the nose, mouth, and oropharynx, whereas rigid suction catheters are used to suction the mouth and the oropharynx. These suction catheters should not be inserted beyond the base of the tongue. Adults should not be suctioned for more than 10 to 15 sec to prevent oxygen deprivation; children should be suctioned for less time. Care should be taken when using rigid suction catheters in children, because stimulation of the oropharynx may cause bradycardia. A bulb syringe may be used to suction the nose and mouth of infants up to 4 months old because they are obligate nose breathers.

If time permits and supplies are available, a “mucus trap” suction device can be improvised from a jar with two holes poked in its lid and two tubes or straws duct taped into the holes (Figure 20-14). One straw goes to the rescuer, who provides suction, and the other is directed toward whatever has accumulated in the airway. The jar serves to trap the removed secretions, thereby preventing the rescuer from suctioning bodily fluids or foreign substances (e.g., mud) directly into his or her mouth.

FIGURE 20-14 Improvised mucus trap suction device.

In the absence of suction or in the presence of large pieces of foreign material, visible debris can be swept from the mouth of an unconscious victim with the use of a finger that is gloved or wrapped in cloth. When using this “finger-sweep” technique with infants and children, be sure to use your little finger. Never attempt to blindly sweep the mouth if you do not see debris. In addition, do not probe the mouth of a conscious victim, because this may precipitate gagging, vomiting, and aspiration. Victims without risk for cervical spine injury may be placed in the recovery position (i.e., with the head turned to the side) to facilitate clearing the mouth.

Supplemental Oxygen

Supplemental oxygen therapy should be provided to all sick or injured people with cardiac disease, respiratory distress, shock, or trauma, even if their measured arterial oxygen tension is normal. Start with a high oxygen concentration and then titrate downward to maintain adequate oxygenation. Although oxygen should never be withheld from a hypoxic patient with respiratory distress, care should be exercised when administering oxygen to patients with chronic hypercarbia (e.g., patients with chronic obstructive pulmonary disease). Unmonitored treatment of such patients with high oxygen concentrations can result in respiratory depression from diminished hypoxic ventilatory drive.

A variety of oxygen delivery techniques may be employed, depending on the desired oxygen concentration and clinical circumstances (see Chapter 76).

Ventilation

Even with an open airway and supplemental oxygen, a person who is not adequately ventilating cannot conduct sufficient gas exchange. Adequate ventilation implies the inhalation of enough air to deliver oxygen to the alveoli and exhalation of enough air to facilitate the removal of carbon dioxide. The sequence of interventions for the inadequately ventilating victim is opening the airway and then providing positive-pressure ventilation (i.e., via mouth-to-mouth, mouth-to-nose, mouth-to-mask, or BMV).

It is advisable to use barrier protection (e.g., a face shield) when performing mouth-to-mouth or mouth-to-nose ventilation. Face shields are clear plastic or silicone sheets that feature a centrally located one-way valve. They are placed over a victim’s face to allow rescue breathing while preventing direct contact with the victim. Face shields are compact, flexible, portable, and manufactured by a number of companies.

Rescue Breathing

Rescue breathing techniques that make use of exhaled air from the rescuer will deliver approximately 16% to 17% inspired oxygen concentration to the victim, ideally producing an alveolar oxygen tension of 80 mm Hg.

Mouth-to-Mouth Ventilation

Mouth-to-mouth ventilation is an efficient approach to assisting ventilation. Failure to use a barrier device during mouth-to-mouth ventilation places the rescuer at risk for exposure to infectious bodily fluids.

Mouth-to-Nose Ventilation

Some people have conditions (e.g., injuries to the mouth or mandible, missing teeth or dentures) that make mouth-to-mouth ventilation ineffective. Under such circumstances, mouth-to-nose ventilation should be considered. The mouth-to-nose technique is similar to mouth-to-mouth ventilation, with a few specific differences.

Mouth-to-Mask Ventilation

Mouth-to-mask ventilation is the safest and most effective technique for rescue breathing (Figure 20-15). The pocket face mask or a similar barrier device allows the rescuer to provide ventilation without making direct contact with the victim’s mouth and nose. The mask has a one-way valve in the stem to prevent exhaled gases and bodily fluids from reaching the health care provider. In addition, a disposable high-efficiency particulate air filter may be inserted into the pocket mask to trap infectious air droplets and secretions.

FIGURE 20-15 Rescuer using mouth-to-mask ventilation. The rescuer is providing rescue breathing with a face mask and supplemental oxygen during cardiopulmonary resuscitation. The rescuer is using the cephalic technique (i.e., the rescuer is positioned at the top of the victim’s head). Both of the rescuer’s hands are used to hold the mask securely in position while keeping the victim’s airway open. The rescuer’s thumbs and forefingers hold the mask in place while the third, fourth, and fifth fingers of each hand lift the jaw (i.e., jaw thrust) and maintain an open airway with the head tilted. Alternatively, the thumbs and a portion of the rescuer’s palms can anchor the mask, and the index and remaining fingers can lift the jaw and hold it against the mask.

(Redrawn from American Heart Association, International Liaison Committee on Resuscitation: Guidelines 2000 for cardiopulmonary resuscitation and emergency cardiovascular care. Part 6: Advanced cardiovascular life support. Section 3: Adjuncts for oxygenation, ventilation and airway control, Circulation 102:I95, 2000.)

The pocket face mask is made of a soft plastic material and can be folded and carried in a pocket. Some masks are available with an oxygen inlet to allow for supplemental oxygen administration. These devices are available in a number of sizes.

Technique

1 Open the airway using the head tilt with chin lift approach if cervical spine trauma is not suspected.

2 Connect the one-way valve to the mask.

3 If available, connect oxygen tubing to the inlet port, and set the flow rate at 15 L/min.

4 Position yourself at the head of the victim.

5 Clear the victim’s airway of vomitus, secretions, and foreign bodies, if necessary.

6 Insert an oral or nasopharyngeal airway.

7 Place the mask on the victim’s face.

8 Apply pressure to both sides of the mask with the thumb side of the palms to create an airtight seal. Apply upward pressure to the mandible (i.e., jaw thrust) using the index, middle, and ring fingers of both hands while maintaining a head tilt.

9 Take a deep breath and exhale into the port of the one-way valve, and observe for chest rise.

10 Allow the victim to passively exhale between breaths.

Bag-Mask Ventilation

The self-inflating ventilation bag with face mask (i.e., the BMV device) provides a means for emergency ventilation with high concentrations of oxygen. The device is equipped with several valves that allow coordinated airflow into and out of the victim. This includes a one-way valve that prevents exhaled air from reentering the victim’s lungs (Figure 20-16). When it is attached to a high-flow oxygen source (15 L/min), the BMV device can supply an oxygen concentration of nearly 100%. The adapter of the face mask is interchangeable with an ETT, so the same bag can be used after intubation.

FIGURE 20-16 Detailed view of a bag-mask ventilation device. A, The rescuer provides ventilation with a bag and mask attached to an oxygen supply. The rescuer is using the E-C technique to hold the mask to the face by creating a “C” with the thumb and forefinger while lifting the jaw along the bony portion of the mandible with the last three fingers of the same hand; these fingers make the “E.” The second hand squeezes the bag while the rescuer watches the victim’s chest to ensure that the chest rises with each ventilation. The rescuer is keeping the victim’s airway open with both a head tilt and a jaw thrust. B, Details of a bag-mask ventilation system with supplemental oxygen. The system consists of a self-refilling bag with an oxygen inlet; either a no pop-off valve or a pop-off valve (as shown) that can be disabled during resuscitation to ensure the delivery of adequate tidal volumes despite high pressures; and standard fittings (in this case, the bag is joined with a standard fitting to a mask). This system is capable of delivering high concentrations of oxygen, because it contains an oxygen reservoir. If additional gas is required during ventilation, it is drawn from the oxygen reservoir rather than from room air so that a high concentration of oxygen can be delivered during ventilation.

Competence with a BMV device is a vital emergency skill and prerequisite to the use of paralytic agents for endotracheal intubation. When using the single-hand mask hold technique, substantial proficiency is required to use only one hand to maintain an adequate mask seal, to position the victim’s head, and to ensure airway patency while using the other hand to ventilate with the proper tidal volume, neither underventilating or hyperventilating the patient. Although the mastery of solo BMV technique is imperative, recruitment of another individual allows one person to perform a jaw thrust and to ensure a good mask seal with both hands while the second individual squeezes the bag.

Successful BMV depends on an adequate mask seal and a patent airway. Placement of an oral airway should always be considered before BMV. Slow and gentle ventilation minimizes the risk for gastric inflation and subsequent regurgitation. The efficacy of BMV can be determined by watching the chest rise and fall, feeling resistance in the bag, and monitoring the victim’s oxygen saturation. Smaller BMV devices are employed for infants and children to prevent overinflation and subsequent barotrauma. In the absence of a BMV device that precisely regulates the volume of air transferred by the device, the amount of air transferred by BMV is a clinical estimate that is based on patient weight.

Definitive Airway Management

The presence of a definitive airway implies patency and protection. Provision of a definitive airway requires a tube in the trachea with the cuff inflated, secured in place, and attached to an oxygen-rich ventilation device. Whether in the wilderness or at the hospital, inability or failure to secure a timely and definitive airway can lead to disastrous or fatal consequences for the victim. Approaches to definitive airway management include immediate oral endotracheal intubation, awake oral intubation, rapid sequence oral intubation, nasotracheal intubation, and surgical airways (e.g., cricothyrotomy).

Although the ultimate decision to endotracheally intubate a patient can be complicated and may depend on a variety of clinical factors, several clinical situations mandate definitive airway management: (1) failure of ventilation or oxygenation; (2) the patient’s inability to maintain or protect the airway; (3) the potential for deterioration on the basis of the patient’s clinical presentation; and (4) patient safety and protection.

Immediate Oral Intubation (Crash Intubation)

Individuals who present with respiratory arrest, agonal respirations, or deep unresponsiveness require immediate oral intubation without the use of paralytic or sedative medications. Advantages of crash intubation are technical ease and rapidity. Disadvantages include the potential for increasing intracranial pressure from the stress of intubation and inducing vomiting and subsequent aspiration.

Awake Oral Intubation

Awake oral intubation is an approach that makes use of titrated intravenous sedation and liberal topical airway anesthesia before inspection of or intubation of an awake victim’s airway. This approach conveniently allows for preservation of the victim’s protective airway reflexes and spontaneous respirations while the laryngoscopist takes a gentle “awake” look at the glottis, vocal cords, and internal airway anatomy. The decision to intubate the victim immediately or to perform a controlled rapid sequence oral intubation depends on the potential for progression of airway difficulty or compromise. During the “awake” look, the clinician might elect to intubate a victim with an airway burn or anaphylaxis with progressive airway swelling, because that moment may be the most opportune time for airway management.

Rapid Sequence Oral Intubation

Rapid sequence intubation (RSI) is a coordinated series of procedures that allows for the rapid intubation of a victim without interposed BMV. Because victims who require emergent intubation may not have fasted, BMV can inadvertently lead to gastric distention, regurgitation, and aspiration.

To perform RSI, the victim is first preoxygenated to allow for a period of apnea without interposed assisted ventilation. Sequential administration of an induction agent and a rapidly acting neuromuscular blocking agent induces a state of unconsciousness and paralysis, respectively. This allows the victim to be intubated without the need for BMV. The steps that make up RSI can be thought of as “the eight P’s” (Table 20-3).

TABLE 20-3 The Eight P’s of Rapid Sequence Intubation

Time	Action
Zero minus 10 min	Preparation
Zero minus 5 min	Preoxygenation
Zero minus 3 min	Pretreatment
—Time zero—	Paralysis with induction
Zero plus 20-30 sec	Protection and positioning
Zero plus 45 sec	Placement
Zero plus 45 sec	Proof
Zero plus 1 min	Postintubation management

Preparation

Before RSI, careful preparation is essential to achieve success. The mnemonic SOAP ME summarizes the necessary preparatory steps and essential equipment (Table 20-4).

TABLE 20-4 SOAP ME Mnemonic

Suction	Suction should be tested and readily available at the bedside.
Oxygen	A high-flow oxygen mask and a bag-valve ventilation device should be ready for use.
Airway equipment	At least two functioning laryngoscope handles and the appropriately sized and shaped laryngoscope blades should be obtained. The anticipated blade of choice should be clicked into position to ensure that the light functions properly. An endotracheal tube (ETT) should be chosen on the basis of the patient’s anatomy, and one of a smaller size should be prepared as well. The average adult male will require a 7.5- or 8.0-mm ETT, and the average adult female will need a size 7.0 or 7.5 mm. In children, the ETT size in mm may be estimated by the formula 4 + (age in years/4). The ETT cuff should be inflated to test for an air leak. A stylet should be inserted within the ETT to shape it into a configuration that will facilitate insertion into the airway. Care must be taken to ensure that the tip of the stylet does not protrude from the end of the ETT or through the small distal side port (i.e., Murphy’s eye).
Pharmacy	The patient should have at least one intravenous line placed, and patency of the line should be verified. The specific rapid sequence intubation medications, proper dosing, and sequence of administration should be determined, and the agents should be drawn up and labeled.
Monitoring Equipment	Cardiac monitoring, blood pressure monitoring, and pulse oximetry are mandatory for all patients. If available, an end-tidal carbon dioxide monitor should be readied as well. In a wilderness setting, many of these hospital-based amenities may not be available.

(Redrawn from Mahadevan SV, Garmel GM, editors: An introduction to clinical emergency medicine: Guide for practitioners in the emergency department. Cambridge, UK, 2005, Cambridge University Press. Courtesy Chris Gralapp. http://www.biolumina.com.)

Cricoid pressure should also be applied when the victim requires positive-pressure ventilation before, during, or after intubation attempts. Positive-pressure ventilation, whether from rescue breathing or a BMV device, may lead to gastric distention, compromised diaphragmatic excursion, and an increased risk for emesis or gastric rupture. By employing Sellick’s maneuver during positive-pressure ventilation, air will be directed to the lungs rather than the stomach, thus avoiding these complications.

Positioning

The airway may be thought of as having three separate axes: oral, pharyngeal, and laryngeal. Proper positioning of the head before laryngoscopy can help to align these three axes, thereby improving visualization of the glottis and greatly increasing the likelihood of a successful intubation. In the neutral position, these axes are misaligned (Figure 20-18).

FIGURE 20-18 Head on a bed, neutral position. LA, Laryngeal axis; OA, oral axis; PA, pharyngeal axis.

(Redrawn from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

Placing a small pillow or a similar-sized object under an adult’s occiput flexes the lower cervical spine relative to the torso and aligns the pharyngeal and laryngeal axes (Figure 20-19). Positioning the patient in the sniffing position with the extension of the head on the neck aligns all three axes (Figure 20-20).

FIGURE 20-19 Head elevated on pad, neutral position. LA, Laryngeal axis; OA, oral axis; PA, pharyngeal axis.

(Redrawn from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

FIGURE 20-20 Head elevated on a pad, head extended on neck. LA, Laryngeal axis; OA, oral axis; PA, pharyngeal axis.

(Redrawn from Walls RM, Murphy MF, Luten RC, et al, editors: Manual of emergency airway management, ed 2, Philadelphia, 2004, Lippincott Williams & Wilkins.)

Patients with potential cervical spine injury should be maintained in the neutral position.

Placement

During RSI, administration of a paralytic agent will predictably lead to paralysis and apnea. With adequate preoxygenation, arterial oxygen saturations remain normal despite this apnea. Complete muscular paralysis can be confirmed by gently grasping the patient’s jaw and checking for flaccidity. Wait until the patient is completely relaxed before proceeding with intubation.

With the laryngoscope in the left hand, gently open the mouth with the right hand. Insert the laryngoscope into the right side of the patient’s mouth, and then sweep the tongue to the left. The curved (Macintosh) blade is slid into the vallecula; the straight (Miller) blade is positioned below the epiglottis. The handle is pushed along the axis of the handle at a 45-degree angle to the patient’s body. Care should be taken not to “crowbar” with the laryngoscope, because this may injure the patient’s teeth.

If the glottic aperture is not readily visible, the intubator or an assistant may elect to perform the BURP maneuver: this involves placement of the right hand on the thyroid cartilage and is followed by application of backward, upward, rightward pressure to help to bring the glottis into view (Figure 20-21). The resulting displacement of the thyroid cartilage backward against the cervical vertebrae, upward or as superiorly as possible and laterally to the right, has been found to significantly improve the view of the glottis during laryngoscopy.

FIGURE 20-21 The BURP maneuver (backward, upward, rightward pressure).

When the glottis is clearly visible, use the right hand to gently insert the ETT until the cuff is about 2 to 3 cm past the vocal cords. For adult males, the 23-cm marker of the ETT should be located at the corner of the mouth; this should be 21 cm for adult women. When the ETT is in place, remove the stylet and inflate the cuff. An air leak should not be audible with a BMV.

If the patient is adequately preoxygenated, the laryngoscopist may make multiple attempts at intubation before arterial oxygen desaturation occurs. If available, a dedicated team member should focus on the patient’s cardiac rhythm, blood pressure, and oxygen saturation, and he or she should alert the intubator to any abnormalities. After any unsuccessful intubation attempt, recheck the patient’s position, and make any necessary adjustments. It is important to “change something” (e.g., the size or type of laryngoscope blade) before taking a second look to ensure that the same mistake or problem is not encountered again.

Proof (Confirmation of Endotracheal Tube Placement)

Proper ETT positioning within the trachea needs to be confirmed after every intubation. Failure to recognize an inadvertent esophageal intubation can be disastrous for both the patient and physician. Sellick’s maneuver should not be released until after confirmation of correct ETT placement.

Methods that are used to detect ETT placement include clinical assessment, pulse oximetry, end-tidal carbon dioxide (ETCO₂) detection, and aspiration techniques. Chest radiography assesses ETT position but does not confirm ETT placement within the trachea.

Clinical Assessment

Classic clinical observations that are used to confirm correct ETT placement include the following: (1) seeing the ETT passing through the vocal cords during intubation; (2) auscultation of clear and equal breath sounds over both lung fields; (3) absence of breath sounds when auscultating over the stomach; (4) observation of symmetric chest rise during ventilation; and (5) observation of “fogging” of the ETT during ventilation. All of these clinical findings are subject to failure and should not serve as the sole means for confirming ETT placement.

Pulse Oximetry

A drop in oxygen saturation after intubation should raise concern for an esophageal intubation; however, this drop may be delayed for several minutes if the patient was adequately preoxygenated. For certain patients (e.g., those with hypotension), oxygen saturation measurement may be unreliable or difficult to detect. Although pulse oximetry is important to assess after endotracheal intubation, it should not be the primary indicator of successful ETT placement.

End-Tidal Carbon Dioxide Detection

Detection of exhaled carbon dioxide is a highly reliable method for identifying proper placement of the ETT within the trachea. A colorimetric ETCO₂ detector is a small disposable device that connects between the bag and the ETT. When this device detects ETCO₂, its colorimetric indicator changes from purple to yellow; absence of this color change for six manual ventilations indicates that the tube is incorrectly placed in the esophagus. A false-positive color change may occur if the tube is placed just above the glottis. A false-negative color change may occur (even with correct ETT placement) in some cases of cardiac arrest and profound circulatory collapse as carbon dioxide production and delivery to the lungs abruptly decline.

Aspiration Devices

Aspiration appliances (e.g., bulb and syringe aspiration devices) may also be used for confirmation of ETT placement. The bulb aspiration device is a round and compressible plastic globe (i.e., “turkey baster”) that is first compressed and deflated and then placed within the ETT and released. If the bulb reexpands rapidly, the ETT is likely in the trachea, whereas failure to reexpand or delayed reexpansion suggests that the ETT is in the esophagus. Syringe aspiration devices are large syringes (usually 30 mL [1 oz]) that are inserted into the ETT. The syringe plunger is then drawn back rapidly to allow for brisk aspiration of a large amount of air. The rapid and easy flow of air suggests tracheal intubation, whereas resistance suggests esophageal intubation.

Postintubation Management

After verification of correct ETT placement within the trachea, the tube should be secured (i.e., taped or tied) to prevent movement or migration. The patient’s blood pressure and other vital signs should be repeated. Bradycardia after intubation is worrisome for hypoxia and should prompt exclusion of an esophageal intubation. Hypertension after intubation suggests inadequate sedation. Hypotension after intubation may result from a tension pneumothorax, decreased venous return, the induction agent, or a cardiac cause.

After intubation, consideration should be given to long-term sedation, analgesia, and paralysis. A benzodiazepine such as midazolam (0.1 to 0.2 mg/kg), diazepam (0.2 mg/kg), or lorazepam (0.05 to 0.1 mg/kg) may be given initially for sedation and repeated for any signs of awareness. An opioid agent such as fentanyl (3 to 5 mcg/kg) or morphine sulfate (0.1 mg/kg) may also be administered for additional patient comfort. Nondepolarizing NMBAs such as pancuronium (0.1 mg/kg) or vecuronium (0.1 mg/kg) may be used for long-term paralysis; a repeat dose that is one-third of the initial dose may be given after 45 to 60 minutes if any motor activity is detected.

Nasotracheal Intubation

There are certain clinical circumstances, such as the spontaneously breathing patient who presents with a difficult airway, in which RSI may not be advisable. In the patient with anatomic features that may pose a challenge to RSI and BMV, awake nasotracheal intubation (NTI) may provide a better alternative, because it can be performed while preserving the patient’s spontaneous respirations.

Technique

1 Prepare the mucosa to facilitate tube passage and to minimize the risk for epistaxis. Instill 2 to 3 drops of a topical vasoconstrictor agent such as phenylephrine hydrochloride (0.25%) or oxymetazoline (0.05%) in each naris. Anesthetize the nasal mucosa using a 4% cocaine pack or 2% lidocaine jelly.

2 Select a cuffed ETT that is sized 0.5 to 1.0 mm smaller than would be used for orotracheal intubation. The tube should be lubricated with a water-soluble lubricant to facilitate passage.

3 The patient may be seated or reclined while the clinician stands to the side of the patient.

4 The tube is inserted into the more patent of the two nares. The right side is preferable because the tube bevel will face the septum, thus avoiding Kiesselbach’s plexus. If going through the left nares, consider inserting the tube “upside down” and then rotating it so that the curve follows the posterior nasopharynx when the turbinates are passed.

5 Direct the tube straight back along the nasal floor toward the occiput, and rotate it 15 to 30 degrees with advancement. When the tube nears the glottis, listen for airflow within the tube with each breath.

6 When maximal airflow is heard, quickly and gently advance the tube. A cough will likely be heard with passage of the tube into the trachea. The tube should be advanced to 32 cm at the nares in the adult male and to 27 to 28 cm in the adult female.

7 Confirm the tube’s position with an ETCO₂ detection device. Because the tube is placed blindly, it may also be misdirected into the esophagus, the piriform sinus, or the vallecula, although this is rare. When this occurs, withdraw the tube slightly, redirect it, and retry the procedure. If the tube becomes caught on the vocal cords, rotate the tube slightly to realign the bevel with the cords. Occasionally, externally manipulating the larynx posteriorly or laterally with one’s nondominant hand will facilitate successful passage.

NTI is absolutely contraindicated in the apneic patient, because air movement is essential to placement of the ETT. NTI is also contraindicated in patients with the possibility of cribriform plate injury, basilar skull fracture, or midface fracture out of concern that the tube may enter the cranial vault. Patients with bleeding disorders or coagulopathy may develop massive epistaxis from NTI. Other contraindications include combativeness; increased intracranial pressure; neck hematoma; upper airway obstruction or anatomic alteration from trauma, edema, or infection; and the need for immediate airway management. Blind nasotracheal intubation is not generally recommended for patients with neck trauma; it can be especially dangerous when there is a possibility of dislodging a clot. In addition, the distorted anatomy leads to a higher failure rate for blind nasotracheal intubation.

Epistaxis and nasal turbinate injury from blind NTI can be greatly reduced by pretreatment with vasoconstrictor agents and proper technique. Long-term complications (e.g., sinusitis, turbinate destruction) are uncommon and result from multiple intubation attempts or prolonged intubation.

Alternative Airway Adjuncts and Techniques

In certain wilderness conditions and settings, tracheal intubation may be difficult or impossible. Under such circumstances, alternative airway adjuncts or techniques may be employed to provide an airway. Alternative airways that require blind passage of the device into the airway may be simpler to master than passing an ETT under direct vision. To achieve good outcomes with these devices and techniques, health care providers must maintain a high level of knowledge and skills through frequent practice and field use.

Laryngeal Mask Airway

The laryngeal mask airway (LMA) is a modified ETT with an inflatable oval cuff (i.e., the laryngeal mask) at its base (Figure 20-22). The LMA is blindly inserted into the pharynx and advanced until resistance is felt as the distal portion of the tube locates in the laryngopharynx. Inflation of the collar provides a seal around the laryngeal inlet to facilitate tracheal ventilation.

FIGURE 20-22 Laryngeal mask airway (LMA). A, The LMA is an adjunctive airway that consists of a tube with a cuffed mask-like projection at the distal end. B, The LMA is introduced through the mouth into pharynx. C, When the LMA is in position, a clear and secure airway is present. D, During insertion, the LMA is advanced until resistance is felt as the distal portion of tube locates in the hypopharynx. The cuff is then inflated. This seals the larynx and leaves the distal opening of the tube just above the glottis to provide a clear and secure airway (dotted line).

Although the LMA does not provide a definitive airway or ensure absolute protection against aspiration, studies have shown that aspiration is uncommon and that regurgitation is less likely with an LMA as compared with a BMV device. The LMA provides ventilation equivalent to that with the tracheal tube. The LMA may have advantages over traditional endotracheal intubation when access to the victim is limited, when the possibility of unstable neck injury exists, or when appropriate victim positioning for tracheal intubation is impossible. However, studies have shown that a small proportion of patients cannot be ventilated, even when the LMA is successfully inserted.

An updated version of the original LMA called the intubating ILMA facilitates blind endotracheal intubation by allowing for the passage of an ETT through the device and into the trachea with a high degree of success.

Combitube

The Combitube is a double-lumen, dual-cuffed airway; one lumen functions as an esophageal airway, whereas the other performs as a tracheal airway (Figure 20-23). The Combitube is typically blindly inserted and advanced until the victim’s teeth lie between two guide marks that are printed on the tube. The distal end of the tube most commonly finds its way into the esophagus. The pharyngeal and distal balloons are then inflated, thus isolating the oropharynx above the upper balloon and the esophagus or trachea below the lower balloon. The location (i.e., esophagus or trachea) of the distal orifice is then ascertained, and the victim is ventilated through the appropriate opening. One lumen contains ventilating side holes at the hypopharyngeal level and is closed at the distal end; the other lumen has a distal open end with a cuff that is similar to that of a tracheal tube.

FIGURE 20-23 Esophageal–tracheal Combitube.

(Redrawn from Skinner D, Swain A, Peyton R, et al, editors: Cambridge textbook of accident and emergency medicine, Cambridge, UK, 1997, Cambridge University Press.)

Advantages of the Combitube over BMV include isolation of the airway, reduced aspiration risk, and more reliable ventilation. Because laryngoscopy and visualization of the vocal cords are not necessary for insertion, use of the Combitube is easier to teach, learn, and practice compared with tracheal tube placement. In addition, ventilation and oxygenation with the Combitube compare favorably with those achieved with the use of a tracheal tube.

Fatal complications with the Combitube may result from incorrect identification of the position (trachea or esophagus) of the distal lumen. For this reason, an ETCO₂ or esophageal detector device should be used in conjunction with the Combitube. Another possible complication is esophageal trauma.

King LT

The King LT airway is a single-lumen, dual-cuffed airway with ventilation outlets between the pharyngeal and esophageal cuffs. The King LT is inserted blindly, and a single pilot balloon inflates both cuffs simultaneously. Although it is similar to the Combitube, the King LT is shorter, easier to insert, and easier to inflate. Ventilation capability seems to be similar to that of the Combitube and the LMA. The device’s airway seal may be lost after insertion and require deflation of the balloons and repositioning. The King LT airway is available in newborn through adult sizes.

Video Laryngoscopy

Video laryngoscopes, which consist of a micro video camera and a modified laryngoscope, transmit images of the glottis to an external monitor to allow for intubation while looking at the video screen. As compared with traditional laryngoscopy, video laryngoscopes such as the GlideScope provide superior glottic views and greater airway anatomic detail without requiring alignment of the airway axes. As a result, the GlideScope is associated with high intubation success rates and less cervical spine movement. Although rigorous trials to assess performance are limited, clinical experience (including that of the author) indicates that these devices are highly effective. The GlideScope Ranger is a rugged, portable, battery-operated unit that is designed for field use.

Fiber-optic Intubation

Fiber-optic techniques for endotracheal intubation have emerged as invaluable tools for difficult airway management and include fiber-optic intubating bronchoscopes and rigid fiber-optic laryngoscopes. These devices may allow for awake intubation in select victims for whom RSI or insertion of a laryngoscope blade may be disadvantageous. Use of fiber-optic devices may be difficult in the setting of uncontrolled secretions or active bleeding, because visualization is impaired.

Lighted-Stylet Intubation

By transilluminating the soft tissues of the neck, a lighted-stylet apparatus can be used to facilitate blind ETT placement within the trachea. Devices such as the Rusch Trachlight take advantage of the anterior location of the trachea relative to the esophagus. When the ETT and the lighted stylet correctly enter the glottic opening, a well-defined and circumscribed glow can readily be seen in the anterior neck. If the tip of the tube is correctly placed in the esophagus, the light glow is diffuse and not readily seen. Lighted stylets may have a role in management of difficult airways as a result of anatomic difficulties (e.g., restricted mouth opening), severe facial trauma, and victims with limited neck mobility. Despite the absence of absolute contraindications to using the lighted stylet, this device should probably be avoided in any victim with an unknown cause of upper airway obstruction.

Retrograde Intubation

Retrograde intubation is an invasive technique that involves needle puncture of the cricothyroid membrane followed by threading a guidewire retrograde through the vocal cords and into the mouth or nose. The wire is then used to guide the ETT through the glottis. Kits are commercially available. Retrograde intubation may play a role in difficult airways as a result of anatomic abnormalities, upper airway trauma, and victims with limited neck mobility caused by cervical spine immobilization.

Digital Intubation

Digital or tactile intubation is a technique in which the index and long fingers of the nondominant hand are used to identify the epiglottis and then manually direct an ETT into the larynx. It may be useful when poor lighting, poor positioning, copious airway secretions, or equipment failure make laryngoscopy difficult or impossible. Digital intubation requires a profoundly unresponsive victim and is relatively contraindicated in the semiconscious victim with intact oropharyngeal reflexes. Other relative contraindications include caustic ingestions, thermal burns, and upper airway foreign bodies.

Surgical Airway Management

Surgical airway management involves creation of an opening directly into the trachea by surgical means and includes both cricothyrotomy and needle cricothyrotomy with percutaneous transtracheal ventilation.

Cricothyrotomy

Cricothyrotomy is the creation of a surgical opening through the cricothyroid membrane to allow placement of an ETT or cuffed tracheostomy tube. The proximal ends of these tubes can be connected to a BMV device for oxygenation and ventilation. The primary indication for cricothyrotomy is need for a definitive airway in the victim in whom orotracheal or blind NTI has failed, is contraindicated, or is extremely difficult. Clinical scenarios include the victim with severe facial trauma for whom conventional airway management is extremely complicated or unfeasible, the victim with severe laryngeal edema, or the victim with upper-airway foreign-body obstruction that cannot be alleviated with the Heimlich maneuver or direct laryngoscopy.

The primary contraindication to cricothyrotomy is young age. As a result of anatomic considerations, the procedure is extremely difficult for children who are less than 10 to 12 years old, and is generally avoided in this population. Other contraindications to cricothyrotomy include preexisting tracheal or laryngeal pathology, anatomic obliteration of the landmarks (e.g., hematoma), coagulopathy, and operator inexperience with the procedure. Complications of cricothyrotomy include incorrect airway placement, hemorrhage, tracheal or laryngeal injury, infection, pneumomediastinum, subglottic stenosis, and voice change.

Standard Surgical Cricothyrotomy

Technique (Figure 20-24)

1 Identify the thyroid cartilage; this is the only V-shaped structure encountered when palpating the anterior neck. The cricothyroid space is the gap immediately caudad to the thyroid cartilage.

2 Prepare the neck in sterile fashion. With the nondominant hand holding the thyroid cartilage, make a vertical midline incision with a No. 11 scalpel from the thyroid cartilage caudad about 3 to 4 cm (1.18 to 1.57 inches) (A).

3 Place a tracheal hook through the cricothyroid space, and hold cephalad traction with the nondominant hand (B, C, and D).

4 Make a transverse incision across the exposed cricothyroid membrane (E and F). If time permits, insert silk stay sutures in the trachea (G and H). Dilate the space using the Trousseau dilator while maintaining traction with the hook (I, J, and K).

5 Place a Shiley cuffed tracheostomy tube through the cricothyroid membrane, initially aiming posteriorly then redirecting caudad once through the membrane (L). The tracheal hook may be removed before insertion of the tube to avoid damaging the tube.

FIGURE 20-24 Standard surgical cricothyrotomy.

(Redrawn from Walls RM: Cricothyrotomy. In Rosen P, Chan TC, Vilke GM, et al, editors: Atlas of emergency procedures, St Louis, 2001, Mosby.)

Rapid Four-Step Cricothyrotomy

Technique

1 From a position at the head of the victim, palpate and identify the landmarks, especially the cricoid and thyroid cartilages and the cricothyroid membrane (Figure 20-25).

2 Incise the cricothyroid membrane and the overlying skin simultaneously with a single horizontal 1.5-cm (0.6-inch) incision using a No. 20 scalpel. While maintaining the blade within the airway, slide a tracheal hook along the caudal side of the blade into the wound.

3 Orient the hook caudally, and place gentle traction on the cricoid ring; this typically widens the incision. Then remove the blade from the airway.

4 The ETT is then placed through the incision into the airway and secured.

FIGURE 20-25 Rapid four-step cricothyrotomy. A, Step 1: Palpation (location of the cricoid membrane externally). B, Step 2: Incision (horizontal incision of the skin and soft tissues through the cricoid membrane). C, Step 3: Traction (application of caudal traction to the cricoid ring). D, Step 4: Intubation (passage of the tracheal tube).

(Redrawn from Brofeldt BT, Panacek EA, Richards JR: An easy cricothyrotomy approach: The rapid four-step technique, Acad Emerg Med 3:1060, 1996.)

Improvised Cricothyrotomy

For circumstances in which formal cricothyrotomy equipment is not available, a knife and a hollow device (as a substitute for the tracheostomy tube) may be used. An improvised cricothyrotomy could be performed using a modified intravenous macro drip chamber or the cut barrel of 1- or 3-mL syringe (see Chapter 23). Any small hollow object (e.g., a ballpoint pen casing, a sports-bottle straw) may be employed as the cricothyrotomy tube; however, devices with an internal diameter of at least 3 mm (0.12 inch) provide the best gas exchange.

Needle Cricothyrotomy with Percutaneous Transtracheal (Translaryngeal) Jet Ventilation

An alternative surgical airway procedure is needle cricothyrotomy with percutaneous transtracheal jet ventilation (TTJV). With this technique, a transtracheal catheter is inserted through the cricothyroid membrane into the trachea and connected to a jet ventilation system that includes high-pressure tubing, an oxygen source at 50 psi, and an in-line one-way valve for intermittent administration of oxygen. One hundred percent oxygen is then delivered at 12 to 20 bursts/min. The inspiratory phase should last 1 second, and the expiratory phase should last 2 to 4 seconds. Advantages of this technique include simplicity, safety, and speed. There is typically less bleeding as compared with cricothyrotomy, and age is not a contraindication, thereby making this the preferred surgical airway technique for children who are less than 12 years old. During TTJV, the upper airway must be free of obstruction to allow for complete exhalation; otherwise, the victim is at risk for barotrauma from air “stacking.” All victims who are receiving TTJV should have an oral and nasal airway placed. Unlike cricothyrotomy, TTJV does not provide complete airway protection; therefore it should be considered a temporizing measure until a definitive airway can be established.

Technique

1 Stand to one side of the victim at the level of the neck. Expose the neck, and identify the landmarks, especially the cricoid and thyroid cartilages and the cricothyroid membrane.

2 Prepare the neck with an antiseptic solution, and provide local anesthesia if time permits.

3 Immobilize the larynx between your thumb and middle finger while your index finger identifies the cricothyroid membrane.

4 Attach a large-bore (12- to 16-gauge) over-the-needle catheter to a 20-mL syringe. Hold the needle and syringe in the dominant hand. Direct the needle caudally through the cricothyroid membrane at a 30-degree angle to the skin while maintaining negative pressure on the syringe. As soon as the needle enters the trachea, the syringe should fill easily with air.

5 Advance the catheter to the hub while simultaneously removing the needle. Reconfirm catheter position within the trachea.

6 Connect the catheter to the jet ventilation system.

Commercial kits with cannulas that have been designed for cricothyrotomy or percutaneous translaryngeal ventilation are available. Several of these employ the Seldinger technique for catheter placement, whereas others rely on direct percutaneous placement of the airway device. These kits include Nu-Trake, PCK-Portex, Pertrach, QuickTrach, and the Melker emergency cricothyrotomy catheter.

In terms of expedition kit portability, three transtracheal puncture emergency airway devices deserve special mention. LifeStat manufactures a keychain emergency airway set that consists of a sharp-pointed metal trocar introducer that fits through a straight metal cannula that screws into a metal extension with a universal 15-mm (0.6 inch) male adaptor. Lightweight and less than 7.6 cm (3 inches) long, the three-component apparatus is attached to a separate and detachable keychain (Figure 20-26). Cook Critical Care offers a 6-Fr reinforced-catheter emergency transtracheal airway catheter (order number C-DTJV-6.0-7.5-BTT) with a molded Luer-Lok connection for jet ventilation or the added assembly of a 15-mm (0.6 inch) adaptor for standard modes of positive-pressure ventilation. Cook Critical Care also offers the Wadhwa Emergency Airway Device (order number C-WEAD-100). This lightweight and impact-resistant assembly disassembles to yield a 12-Fr Teflon-coated cricothyrotomy catheter with a removable metal stylet, a molded plastic Luer-Lok connection for oxygen or jet ventilation, and a flexible nasopharyngeal airway adhered to a molded plastic flange (Figure 20-27). Both the cricothyrotomy catheter and the NPA screw into the Wadhwa case to provide a low-resistance extension and a 15-mm (0.6 inch) male connection for standard positive-pressure ventilation equipment.