1 Pharyngeal Obstruction

The causes of soft tissue upper airway obstruction at the level of the pharynx include loss of pharyngeal muscle tone resulting from central nervous system dysfunction (e.g., anesthesia, trauma, stroke, coma), anatomic and passive airway abnormalities as seen in obstructive sleep apnea, expanding space-occupying lesions (e.g., tumor, mucosal edema, abscess, hematoma), and foreign substances (e.g., teeth, vomitus, foreign body).

In patients susceptible to obstructive sleep apnea, the geometry of the pharynx can be altered during normal sleep.⁹ Although it is usually oval with the long axis in the transverse plane, the pharynx in patients with obstructive sleep apnea is round or oval with the long axis in the anterior-posterior plane (the lateral walls are thickened).^10,11 This obstruction can often be treated effectively with nasal continuous positive airway pressure and with intraoral devices that advance the mandible as much as the jaw thrust maneuver.^12–14

2 Hypopharyngeal Obstruction

Hypopharyngeal obstruction has been investigated by placing a nasal fiberscope at the level of the soft palate in anesthetized subjects.¹⁵ The epiglottis and the glottic opening can be seen, recorded, and analyzed. The percentage of glottic opening (POGO) seen from this view can be determined. Typically, airflow increases and snoring decreases as POGO increases. However, a POGO of 100% has been documented with airway occlusion, and a POGO of 0% has been documented with no stridor and no obvious impairment to ventilation. Although less than perfect, these evaluations do support the potential for airflow restriction at the hypopharynx and are consistent with the cause being the epiglottis obstructing the airway.

3 Laryngeal Obstruction

Laryngeal obstruction is most often related to increased muscle activity from attempted vocalization or a reaction to foreign substances, such as secretions, vomitus, foreign bodies, and tumors. Obstruction of the laryngeal aperture by a foreign body can directly inhibit airflow. Alternatively, the presence of secretions or blood in the airway can cause laryngospasm. Treatment includes removal of foreign substances and, in the case of laryngospasm, positive-pressure ventilation (PPV) with or without muscle relaxation.

4 Clinical Recognition of Upper Airway Obstruction

Airway obstruction can be partial or complete. Partial upper airway obstruction is recognized by noisy inspiratory or expiratory sounds. The tone of the sounds depends on the magnitude, cause, and location of the obstruction. Snoring is the typical sound of partial airway obstruction in the oropharynx or hypopharynx, and it can be heard during inspiration and expiration. Stridor or crowing suggests glottic (laryngeal) obstruction or partial laryngospasm, and it is heard most often during inspiration. In addition to audible clues, signs and symptoms of hypoxemia or hypercarbia should alert the clinician to the possibility of an airway obstruction.

Complete airway obstruction is a medical emergency that requires immediate attention. Signs of complete obstruction in the spontaneously breathing individual are inaudible breath sounds or the inability to perceive air movement; use of accessory neck muscles; sternal, intercostal, and epigastric retraction with inspiratory effort; absence of chest expansion on inspiration; and agitation.

1 Head Tilt-Chin Lift

The head tilt-chin lift is accomplished by tilting the head back on the atlanto-occipital joint while keeping the mouth closed (teeth approximated) (Fig. 15-4). This technique may be augmented by elevating the occiput 1 to 4 inches above the level of the shoulders (sniffing position) as long as the larynx and posterior pharynx stay in their original position. The head tilt-chin lift is the simplest and first airway maneuver used in resuscitation, but it should be used with extreme caution in patients with suspected neck injuries.

Figure 15-4 A, Lateral xerogram of the head and neck shows the extended position (head tilt) in an awake and supine patient (compare with Fig. 15-3A). The mentum is superior to the hyoid bone, the base of the tongue and the epiglottis are farther from the posterior pharyngeal wall, and the thyroid and cricoid cartilages are at the C4-5 level. The hyoid bone has been raised and elevated from C3-4 to C2-3. B, Diagram of the head tilt-chin lift maneuver.

In some patients, the cervical spine is stiff enough that elevating the head into the sniffing position also elevates the C4-5 laryngeal area, leaving the airway unimproved. In children younger than 5 years, the upper cervical spine is more flexible and can bow upward, forcing the posterior pharyngeal wall upward against the tongue and epiglottis and exacerbating an obstruction. A child’s airway is usually best maintained by leaving the head in a more neutral position than that described for an adult.

2 Jaw Thrust

The jaw thrust maneuver more directly lifts the hyoid bone and tongue away from the posterior pharyngeal wall by subluxating the mandible forward onto the sliding part of the temporomandibular joint (mandibular advancement) (Fig. 15-5). The occluded teeth normally prevent forward movement of the mandible, and the thumbs must depress the mentum while the fingers grip the rami of the mandible and lift it upward. This results in the mandibular teeth protruding in front of the maxillary teeth (after the mouth opens slightly). In practice, the insertion of a small airway sometimes makes this procedure easier because it separates the teeth, allowing the mandible to more easily slide forward. In most people, the mandible is readily drawn back into the temporomandibular joint by the elasticity of the joint capsule and masseter muscles. Consequently, this position can be difficult to maintain with one hand.

Figure 15-5 The triple airway maneuver includes the head tilt-chin lift, jaw thrust, and open mouth. A, Diagrams show three methods of performing the maneuver: (1) the head extended on the atlanto-occipital joint, (2) the mouth opened to take the teeth out of occlusion, and (3) the mandible lifted upward, forcing the mandibular condyles anteriorly at the temporomandibular joint. B, Lateral xerogram of the head and neck show the extended position with jaw protrusion (compare with Figs. 15-3A and 15-4A). Notice that the mandibular incisors protrude beyond the maxillary incisors and that the mandibular condyles are subluxated anteriorly from the temporomandibular joint.

In up to 20% of patients, the nasopharynx is occluded by the soft palate during exhalation when the airway muscles are relaxed. If the mouth and lips are also closed, exhalation is impeded. In these cases, the mouth must be opened slightly to ensure that the lips are parted. When the head tilt-chin lift, jaw thrust, and open mouth maneuvers are done together, it is known as the triple airway maneuver (see Fig. 15-5). The triple airway maneuver is the most reliable manual method to achieve patency of the native upper airway (Box 15-1).

3 Heimlich Maneuver

Airway maneuvers can aid in establishing and maintaining airway patency, but they do not relieve an obstruction due to foreign material lodged in the upper airway. Foreign body obstruction should be suspected after a witnessed aspiration when the patient cannot speak, when spontaneous ventilation is absent, or when PPV remains difficult after routine airway maneuvers have been performed. A Heimlich maneuver (subdiaphragmatic abdominal thrusts) is recommended when coughing or traditional means, such as back blows, are unable to relieve complete airway obstruction due to foreign material (Fig. 15-6 and Box 15-2). The goal is to increase intrathoracic pressure sufficiently to simulate a cough. Alternatively, a forceful chest compression in the manner of a rapidly executed bear hug (for upright patients) or a sternal compression (for supine patients) can also be effective. In emergency situations, the failure of one technique to relieve an obstruction should not preclude additional attempts using the various alternatives.

Figure 15-6 Heimlich maneuver. An airway obstructed by a laryngeal foreign body is opened by compressing the lungs through external pressure on the abdomen, forcing the diaphragm cephalad. An alternative method creates this “external cough” by compressing the thorax directly.

1 Oropharyngeal Airways

An oropharyngeal airway (OPA) is the most commonly used device to provide a patent upper airway. OPAs are manufactured in a wide variety of sizes from neonatal to large adult, and they are typically made of plastic or rubber (Fig. 15-7). They should be wide enough to make contact with two or three teeth on each of the mandible and maxilla, and they should be slightly compressible so that the pressure exerted by a clenched jaw is distributed over all of the teeth while the lumen remains patent. OPAs are frequently designed with a flange at the buccal (proximal) end to prevent swallowing or over insertion. They also feature a distal semicircular section to follow the curvature of the mouth, tongue, and posterior pharynx so that the tongue is displaced anteriorly (concave side against the tongue). An air channel is often provided to facilitate oropharyngeal suctioning.

Figure 15-7 Oropharyngeal airways. A, Guedel Airways in sizes from neonatal to large adult. B, The Ovassapian Airway has a large anterior flange to control the tongue. The airway is open posteriorly (including no posterior flange) so that an endotracheal tube can be inserted with a flexible fiberoptic scope and the assembly later separated.

The most commonly used OPA in adults is the Guedel Airway (see Fig. 15-7). It has a plastic elliptical tube with a central lumen reinforced by a harder inner plastic tube at the level of the teeth and by plastic ridges along the pharyngeal section. Because the airway is completely enclosed (other than the proximal and distal ends), redundant oral and pharyngeal mucosae cannot occlude or narrow the lumen from the side. Its oval cross section allows the four central incisors to make contact with it during masseter spasm.

The Ovassapian Airway has a large anterior flange to control the tongue and a large opening at the level of the teeth (open posteriorly) to allow a flexible fiberoptic bronchoscope and ETT to be passed through it and later disengaged from the airway (see Fig. 15-7). Consequently, it is often employed during fiberoptic intubations to aid in maintaining upper airway patency.

Use of an OPA seems deceptively simple, but the device must be used correctly. The patient’s pharyngeal and laryngeal reflexes should be depressed before insertion to avoid worsening obstruction due to airway reactivity. The mouth is opened, and a tongue blade is placed at the base of the tongue and drawn upward, lifting the tongue off of the posterior pharyngeal wall (Fig. 15-8A). The airway is then placed so that the OPA is just off the posterior wall of the oropharynx, with 1 to 2 cm protruding above the incisors (see Fig. 15-8B). If the flange is at the teeth when the tip is just at the base of the tongue, the airway is too small, and a larger size should be inserted. A jaw thrust is then performed as described previously to lift the tongue off of the pharyngeal wall while the thumbs tap down the airway the last 1 to 2 cm so that the curve of the OPA lies behind the base of the tongue (see Fig. 15-8C). The mandible is then allowed to reduce back into the temporomandibular joint, and the mouth is inspected to ensure that neither the tongue nor the lips are caught between the teeth and the OPA.

Figure 15-8 Techniques for insertion of an oropharyngeal airway: standard technique (A–C) and alternative technique (D) without a tongue blade. A, The tongue blade is placed deep into the mouth and depresses the tongue at its posterior half. The tongue is then pulled forward in an attempt to pull it off the back wall of the pharynx. B, The airway is then inserted with the concave side toward the tongue until the tube is just off the posterior wall of the oropharynx with 1 to 2 cm protruding above the incisors. The tongue blade is then removed. C, A jaw thrust is performed while the thumb taps the airway into place. After the jaw is allowed to relax, the lips are inspected to ensure they are not caught between the teeth and airway. D, In an alternative technique, the airway is placed in a reverse manner (convex side toward tongue) and then spun 180 degrees into place so that the lower section of the airway rotates between the tongue and posterior pharyngeal wall.

An alternative method of placement is to insert the airway backward (convex side toward the tongue) until the tip is close to the pharyngeal wall of the oropharynx. It is then rotated 180 degrees so that the tip rotates and sweeps under the tongue from the side (see Fig. 15-8D). This method is not as reliable as the tongue blade–assisted technique described earlier, and it has the added risk of causing dental trauma in patients with poor dentition.

If the upper airway is not patent after the placement of an OPA, the following situations must be considered. With an OPA that is too small, the pronounced curve may impinge on the base of the tongue, or the tongue may obstruct the native airway distal to the OPA. If a larger OPA still results in obstruction, the curve might have brought the distal end into the vallecula or the OPA might have pushed the epiglottis into the glottic opening or posterior wall of the laryngopharynx. In the lightly anesthetized or awake patient, this stimulation causes coughing or laryngospasm. The best treatment for this problem is to withdraw the OPA 1 to 2 cm. A topical anesthetic spray or a water-soluble local anesthetic lubricant reduces the chance of laryngeal activity, but it should be used judiciously or avoided in patients thought to be at increased risk for aspiration.

Two major complications can occur with the use of OPAs: iatrogenic trauma and airway hyperreactivity. Minor trauma, including pinching of the lips and tongue, is common. Ulceration and necrosis of oropharyngeal structures from pressure and long-term contact (days) have been reported.¹⁶ These problems necessitate intermittent surveillance during extended use. Dental injury can result from twisting of the airway, involuntary clenching of the jaw, or direct axial pressure. Dental damage is most common in patients with periodontal disease, dental caries, pronounced degrees of dental proclination, and isolated teeth.

Airway hyperactivity is a potentially lethal complication of OPA use, because oropharyngeal and laryngeal reflexes can be stimulated by the placement of an artificial airway. Coughing, retching, emesis, laryngospasm, and bronchospasm are common reflex responses. Any OPA that touches the epiglottis or vocal cords can cause these responses, but the problem is more common with larger OPAs. Initial management is to partially withdraw the OPA. If an anesthetic is being administered, deepening the plane of anesthesia (most easily accomplished with an intravenous agent) is often effective in blunting airway hyperreactivity. In cases of laryngospasm, it may be necessary to apply mild positive airway pressure and, in trained hands, to cautiously administer small doses of succinylcholine to achieve resolution.

2 Nasopharyngeal Airways

The nasopharyngeal airway (NPA) is an alternative airway device for treating soft tissue upper airway obstruction. When in place, an NPA is less stimulating than an OPA and therefore better tolerated in the awake, semicomatose, or lightly anesthetized patient. In cases of oropharyngeal trauma, a nasal airway is often preferable to an oral airway. NPAs are pliable, bent cylinders made of soft plastic or rubber in variable lengths and widths (Fig. 15-9). A flange (or moveable disk) prevents the outside end from passing beyond the nares, thereby controlling the depth of insertion. The concavity is meant to follow the superior side of the hard palate and posterior wall of the nasopharynx. The tip of the airway is beveled to aid in following the airway and minimizing mucosal trauma as it is advanced through the nasopharynx. A narrow NPA is often desirable to minimize nasal trauma but may be too short to reach behind the tongue. As an alternative, an ETT of the same diameter may be cut to the appropriate length to provide a longer airway. A 15-mm adapter should be inserted in the cut end of the ETT to prevent migration of the proximal end beyond the naris (see Fig. 15-9).

Figure 15-9 Nasopharyngeal airways. A flange prevents the outside end from passing beyond the nares, controlling the depth of insertion. Alternatively, an endotracheal tube may be cut down to provide a longer airway, with its 15-mm adapter reinserted in the cut end.

Before insertion of an NPA, the nares should be inspected to determine their size and patency and to evaluate for the presence of nasal polyps or marked septal deviation. Vasoconstriction of the mucous membranes can be accomplished with cocaine (which has the added benefit of providing topical anesthesia) or phenylephrine drops or spray. This can also be accomplished by soaking cotton swabs in either of these solutions and then inserting them into the naris (with careful attention to removing the swabs before insertion of the NPA). The NPA is typically lubricated with a water-based lubricant (with or without a water-soluble local anesthetic) and then gently but firmly passed with the concave side parallel to the hard palate through the nasal passage until resistance is felt in the posterior nasopharynx (Fig. 15-10).

Figure 15-10 Insertion of a nasopharyngeal airway. The airway is oriented with its concave side toward the hard palate and inserted straight posteriorly. Gripping the airway near the top allows the tube to bend if there is resistance to passage. If it is gripped too close to the naris, the clinician can generate sufficient force to shear off a turbinate.

When there is resistance to passage, it is sometimes helpful to rotate the NPA 90 degrees counterclockwise, bringing the open part of the bevel against the posterior nasopharyngeal mucosa. As the tube makes the bend (indicated by a relative loss of resistance to advancement), it should be rotated back to its original orientation. If the NPA does not advance with moderate pressure, there are three management options: attempt placement of a narrower tube, redilate the naris, and attempt placement in the other naris. If the tube does not pass into the oropharynx, the clinician may withdraw the tube 2 cm and then pass a suction catheter through the nasal airway as a guide for advancement of the NPA. If the patient coughs or reacts as the NPA is inserted to its full extent, it should be withdrawn 1 to 2 cm to prevent the tip from touching the epiglottis or vocal cords. If the patient’s upper airway is still obstructed after insertion, the NPA should be checked for obstruction or kinking by passing a small suction catheter. If patency of the NPA is confirmed, it is possible that the NPA is too short and the base of the tongue is occluding its tip. In this case, a 6.0 ETT can be cut at 18 cm to provide a longer airway.

Indications for an NPA include relief of upper airway obstruction in awake, semicomatose, or lightly anesthetized patients; in patients who are not adequately treated with OPAs; in patients undergoing dental procedures or with oropharyngeal trauma; and in patients requiring oropharyngeal or laryngopharyngeal suctioning. The contraindications (absolute or relative) include known nasal airway occlusion, nasal fractures, marked septal deviation, coagulopathy (risk of epistaxis), prior transsphenoidal hypophysectomy or Caldwell-Luc procedures, cerebrospinal fluid rhinorrhea, known or suspected basilar skull fractures, and adenoid hypertrophy.

The complications of NPAs consist of failure of successful placement, epistaxis due to mucosal tears or avulsion of the turbinates, submucosal tunneling, and pressure sores. Epistaxis often becomes evident when the NPA is removed, thereby removing the tamponade. It is usually self-limited. Bleeding from the nares usually is attributable to anterior plexus bleeding, and it is treated by applying pressure to the nares. If the posterior plexus is bleeding (with blood pooling into the pharynx), the physician should leave the NPA in place, suction the pharynx, and consider intubating the trachea if the bleeding does not stop promptly. The patient may be positioned on his or her side to minimize the aspiration of blood. An otolaryngology consultation may be necessary to further treat posterior plexus bleeding. The management of submucosal tunneling into the retropharyngeal space is to withdraw the airway and obtain otolaryngology consultation.

1 Anesthesia Circle System

Use of a face mask is a simple and reliable method of airway management for assisted spontaneous ventilation and controlled ventilation of patients during routine anesthesia care. When used as part of an anesthesia circle system, a face mask is used to seal a patient’s airway to allow delivery of a precise composition of respiratory gases and inhaled anesthetics. This includes preoxygenation with spontaneous ventilation, controlled ventilation before endotracheal intubation, rescue ventilation when endotracheal intubation is unsuccessful or not feasible, and spontaneous or controlled ventilation during inhaled general anesthesia by mask alone.

Controlled ventilation by mask is relatively contraindicated in patients at increased risk for aspiration of gastric contents. Problems include the presence of a full stomach, hiatus hernia, esophageal motility disorders, and pharyngeal diverticula. When there is a likelihood of gas insufflating the stomach (e.g., mask ventilation requiring high airway pressures), an adverse patient position (usually any position other than supine), or inability to easily reach the head of the patient, use of a mask for PPV must be done cautiously. Mask ventilation is also relatively contraindicated when there is a need to avoid the head and neck manipulation that may be necessary to maintain the airway. The inability to sustain adequate assisted or spontaneous ventilation is a relative contraindication to further use of a face mask.

Use of a face mask is associated with several potential complications. A poor mask fit or seal can result in gas leaks that prevent the maintenance of positive airway pressure and contaminate the operating room environment with anesthetic gases. Pressure from a malpositioned mask, especially with the use of restraining straps, can potentially cause skin, nerve, and ocular injury. Gastric distention and aspiration constitute the most serious (and potentially lethal) complication of PPV by mask.

2 Resuscitator Bags

The air-mask-bag unit (AMBU) was described in 1955 by Henning Ruben (Fig. 15-14).¹⁷ The AMBU provides an alternative means of controlled ventilation to the standard anesthesia circle system. The bag can be used with a face mask, LMA, or ETT. Its main advantages are that it is self-inflating and readily portable, but it lacks the “feel” (airway compliance and resistance) that the clinician has with a circle system, and it requires a compressed oxygen source to deliver oxygen concentrations above that of room air. Although there are various types of AMBU systems in use, all incorporate one-way valves to allow PPV and to prevent rebreathing. AMBUs are an excellent choice for portable, easy-to-use systems for the delivery of PPV and supplemental oxygen outside of the operating room environment.

Figure 15-14 Adult and pediatric sizes of air-mask-bag unit (AMBU). The AMBU is a portable, self-inflating, easy-to-use system for the delivery of positive-pressure ventilation. It can be used with a face mask, laryngeal mask airway, or endotracheal tube.

1 Intravenous Induction

In the case of general anesthesia by mask airway after intravenous induction, the anesthesia workspace should be prearranged in the standard manner. Equipment for intubation should always be readily available, as should various artificial airway devices, in case difficulty is encountered in mask ventilation of the native airway. All drugs expected to be used should be predrawn into labeled syringes. Premedication with a combination of an anxiolytic (e.g., midazolam), narcotic analgesic (e.g., fentanyl), and antisialogogue (e.g., glycopyrrolate) may be done at the discretion of the anesthesiologist.

Preoxygenation is then performed in the usual fashion, typically followed by an induction dose of intravenous anesthetic (most commonly propofol, but any potent, short-acting sedative or amnestic may be used successfully). This frequently results in apnea (particularly if the patient had been premedicated with a narcotic analgesic), which then mandates that the anesthesiologist manually ventilate the patient. During this period of controlled ventilation by mask, increasing concentrations of inhalation anesthetic are titrated to achieve the desired depth of anesthesia. Ventilation is best controlled until incision, when the increased stimulation is often sufficient to promote spontaneous ventilation. Attempts to achieve spontaneous ventilation before the onset of surgical stimulation usually require a decrease in the depth of anesthesia, and the patient often is too lightly anesthetized when the procedure begins. After the patient resumes spontaneous ventilation, the levels of inhalational anesthetic and narcotic analgesic can be titrated to achieve balanced anesthesia. If upper airway obstruction occurs at any time during this sequence, it should be managed as described in “Nonintubation Approaches to Establish Airway Patency.”

2 Inhalation Induction

Inhalation induction of general anesthesia by mask is most commonly performed in children to avoid the discomfort and difficulty of placing an intravenous catheter in an awake patient. In an adult, inhalation induction is often considered when maintaining spontaneous ventilation is paramount (e.g., airway tumors, anterior mediastinal masses with airway compromise).

The first approach to inhalation induction is to preoxygenate the patient with 100% oxygen and then rapidly increase the inhaled concentration of volatile anesthetic to maximum levels. This is most commonly done with sevoflurane, because it is associated with a minimal degree of airway irritation (compared with desflurane), and its vaporizer can be set to deliver up to 8% inspired concentration (approximately 4 times the minimum alveolar concentration [4 MAC]). This approach frequently works well in young children who are unable to be coached through a slower induction, but it is associated with more bradycardia and coughing.

The second approach, which tends to be effective in older children and adults, involves preoxygenating the patient and then slowly introducing the inhalation agent in an incremental fashion while coaching the patient through the sensations experienced with increasing levels of anesthetic. As the patient nears the second stage of anesthesia (heralded by uneven respirations and agitation), it is common to rapidly increase the concentration of the volatile agent (and introduce up to 70% nitrous oxide) to more quickly achieve a deeper plane of anesthesia. After a sufficient depth of anesthesia is obtained, the concentration of inhalation anesthetic (and intravenous narcotic) can be titrated as described earlier.