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.

(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.)

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

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.

(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.)

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.

(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.)

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.

(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.)

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.

(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.)

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.

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.