Laryngeal closure is accomplished by the intrinsic or extrinsic muscles of the larynx. Tight closure, as seen in laryngospasm, results from contraction of the external laryngeal muscles, which force the mucosal folds of the quadrangular membrane into apposition (Fig. 15-2). Muscle groups also extend from the thyroid cartilage to the hyoid and cricoid cartilages. When they contract, the interior mucosa and soft tissue (ventricular and vocal folds) are forced into the center of the airway, and the thyroid shield is deformed (compressed inward), providing a spring to reopen the airway rapidly after these muscles relax.⁸ The larynx closes at the level of the true cords by action of the intrinsic muscles of the larynx during phonation, but this closure is not as tight as the laryngospasm described earlier.

Figure 15-2 Laryngeal closure. Schematic frontal views (A) of the airway at the larynx show a patent airway (left) with a centrally located air column and the hyoid bone superior to the thyroid shield. Obliteration of the air column (right) is caused by apposition of the ventricular and vocal folds, and approximation of the hyoid bone to the thyroid cartilage is caused by contraction of the thyrohyoid muscle. Lateral (B) and frontal (C) xerograms were obtained during Valsalva-induced laryngeal closure. In the lateral view, notice the thyrohyoid approximation. An abrupt airway cutoff (with lack of an air column within the thyroid shield) can be seen at the C4-5 level in the frontal view.

Opening of the pharynx and larynx is achieved by elongating and unfolding the airway from the hyoid to the cricoid cartilage.⁸ Several muscle groups tether the various airway structures to one another to form a functional airway apparatus. When the head is tilted, the chin and mandible are displaced forward on the temporomandibular joint. This produces maximum stretch at the hyoid-thyroid-cricoid area. The hyoid bone is pulled in an anterior direction along with the epiglottis and base of the tongue, which opens the oropharynx. The ventricular and vocal folds flatten against the sides of the thyroid cartilage, opening the laryngeal airway.⁸

The inferior and middle constrictors close the superior part of the esophagus (cervical sphincter) to prevent regurgitation. Muscle relaxants open the airway by relaxing the intrinsic and extrinsic laryngeal muscles that close the airway, but they also relax the pharyngeal constrictors, potentially permitting regurgitation and aspiration of gastric contents. Balancing airway patency and airway protection represents the major dilemma of airway management without, and while placing, an endotracheal tube (ETT).

B Upper Airway Obstruction

Upper airway obstruction is a common airway emergency necessitating nonintubation airway manipulation and airway devices. Soft tissue obstructions may occur at the level of the pharynx, hypopharynx, or larynx. Recognition of upper airway obstruction is an essential clinical skill that depends on observation, suspicion, and clinical data.

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.

II Nonintubation Approaches to Establish Airway Patency

Prevention and relief of airway obstruction are the focus of this chapter. The preceding information on airway anatomy and airway obstruction constitutes essential background for understanding airway maneuvers. When possible, rapid, simple maneuvers should take precedence in the management of this problem.

When the muscles of the floor of the mouth and tongue relax, the tongue may cause soft tissue obstruction by falling back onto the posterior wall of the oropharynx. It is also possible for the epiglottis to overlie and obstruct the glottic opening or to seal against the posterior laryngopharynx. This effect can be exaggerated by flexing the head and neck or opening the mouth, or both (Fig. 15-3), because the distance between the chin and the thyroid notch is relatively short in the flexed position. Any intervention that increases this distance straightens the mentum-geniohyoid-hyoid-thyroid line and therefore elevates the hyoid bone further from the pharynx. The elevated hyoid then secondarily elevates the epiglottis through the hyoepiglottic ligament, potentially alleviating the obstruction.

Figure 15-3 A, Lateral xerogram of the head and neck in the neutral position in an awake and supine patient shows the mentum is directly anterior to the hyoid bone, the base of the tongue and the epiglottis are close to the posterior pharyngeal wall, and the thyroid and cricoid cartilages are at the C5-6 level. Notice that an oropharyngeal airway could easily touch the tip of the epiglottis, pushing it downward. B, Frontal view of the same patient shows the air column within the thyroid shield with its narrowest site at the level of the vocal cords (C5-6). C, Diagram of a patient with a flexed neck shows the tongue in apposition to the posterior pharyngeal wall.

A Simple Maneuvers for the Native Airway

Two well-described, simple maneuvers can lengthen the anterior neck distance from the chin to the thyroid notch: head tilt-chin lift and jaw thrust.

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.