Perform intubation while maintaining manual in-line cervical immobilization without applying traction. Rapid sequence induction intubation should be strongly considered for all patients. Once sedatives and paralytics have taken effect, remove the cervical collar and maintain manual stabilization. After intubation, secure the endotracheal tube and replace the cervical collar.

The narrowest portion of the adult airway is the rima glottidis, the area between the vocal cords.

In an awake patient, with the head in the neutral position (i.e., neither flexed nor extended), air moves freely through both the oropharynx and nasopharynx. In most normal subjects, the same is true during sleep. Abnormalities of any of the component parts of the upper airway can impede airflow during respiration while awake; alternatively, impeded airflow may only become evident during sleep (e.g., as snoring or obstructive apnea). Consequently, a directed history and physical examination should be performed prior to any procedure on the airway.

A history of nasal polyps or nasal septal deviation mandates caution prior to nasotracheal intubation, transnasal passage of a fiberoptic scope, or insertion of a nasal airway. The patient's sleeping partner is often the best source of information about snoring and apnea, manifestations that may result from a variety of upper airway abnormalities, including soft-tissue redundancy, masses, polyps, stenosis, or lymphoid hypertrophy from the nose to the hypopharynx and larynx. Vocal changes or abnormalities may suggest abnormalities of the vocal cords and warrant preintubation evaluation.

Orotracheal intubation is preferred because of the technical difficulty of nasotracheal intubation as well as the complications of bleeding, elevated intracranial pressure, and possible passage of the endotracheal tube through a fractured cribiform plate into the cranium.

The physical examination of the airway is preceded by a conversation with the patient. Hoarseness, stridor, tachypnea, and coughing suggest potential upper airway problems. The examination then can be pursued systematically beginning with the nasopharynx. The patient's ability to breathe through a single nostril (when the mouth is closed and the other nostril occluded) indicates that the passage is relatively patent. Asymmetry often exists between the two sides and, whenever possible, instrumentation should be performed on the more patent side. The ability to open the mouth is limited in patients with temporomandibular joint disease. The temporalis muscle may be scarred or fibrotic (e.g., secondary to prior radiation) resulting in restricted mandibular mobility. Fractures to the mandible produce limited ability to open the mouth that, when the limitation is caused by muscle spasm, disappears with anesthesia. Some fractures functionally affect the mobility of the jaw, irrespective of anesthetic state. Inability to open the mouth more than 40 mm is considered to be clinically significant. The patient's dentition should also be assessed prior to elective management of the airway. Protruding maxillary incisors (“buck teeth”) interfere with direct laryngoscopy by restricting the extent to which the laryngoscope blade can be aligned with the trachea. Dental caps and other prostheses are fragile and easily damaged during laryngoscopy. The laryngoscope may become lodged in gaps between the maxillary teeth during instrumentation and interfere with intubation. Severe dental caries or periodontal diseases make it easier to dislodge teeth during airway instrumentation. The edentulous patient often has an atrophic mandible and large tongue and may be difficult to ventilate by mask because of poor fit of the mask. Intubation of the trachea in such a patient becomes difficult because the tongue, no longer constrained by the teeth, interferes with visualization of the larynx. Abnormalities of the tongue, hard palate, tonsillar pillars, and hypopharyngeal structures can impede or prevent intubation. Normally the tongue is small and sufficiently flexible to be displaced by a laryngoscope blade during visualization of the vocal cords. However, the tongue is enlarged in obese patients, those with angioedema or impaired lymphatic drainage (e.g., after cervical surgical procedures or trauma), or in the setting of certain neoplasms. Burns, scars, or radiation of the submandibular soft tissue prevent lateral displacement of the tongue into the oropharynx during laryngoscopy. Similarly, in patients with small jaws (“receding chins”), displacement or flattening of the tongue during laryngoscopy is difficult, making intubation a challenge. A hyomental distance (the distance from the hyoid bone to tip of the mandible) of less than 6 cm should raise awareness of potential difficulty with intubation. A cleft or high, arched palate is seen in a variety of congenital abnormalities of the facial bones, including the Treacher Collins, Pierre Robin, Klippel–Feil, Goldenhar, Beckwith–Wiedemann, and Crouzon syndromes, as well as the mucopolysaccharidosis. Affected patients are difficult or impossible to intubate using standard approaches.3 Intraoral, oropharyngeal, hypopharyngeal, and laryngeal lesions, as well as tonsillar hypertrophy, can interfere with both laryngoscopy and ventilation by mask. The epiglottis can be infiltrated, inflamed, floppy, or enlarged by fat. The retropharyngeal and lateral pharyngeal spaces are continuous and therefore subject to expansion by processes that involve the mediastinum (e.g., the presence of edema, blood, pus, or soft-tissue emphysema). Patients with epiglottitis and parapharyngeal swelling often exhibit a characteristic posture, sitting upright in the sniffing position and drooling. The preferred position for visualization of the vocal cords is the sniffing position (Fig. 146-2). However, this position may be unsuitable in some patients or impossible to achieve in others.

The sniffing position with the oral, pharyngeal, and tracheal axes.

If orotracheal intubation is not successful, intubate the patient using a retrograde Seldinger technique, fiberoptic-guided intubation, or cricothyroidotomy depending on the equipment available immediately, the clinical status of the patient and the procedures with which the physician is most skilled.

The normal range for flexion and extension of the neck ranges from 90 to 165 degrees. A variety of disorders limit this range. Patients with cervical osteophytes or ankylosing spondylitis, who are often fixed in an anteroflexed head position, may be difficult to intubate. Halo fixation imposes similar constraints. Rheumatoid arthritis, which may affect the cervical spine even in asymptomatic patients, may be problematic. By the age of 75 years, the normal aging process results in as much as a 20% reduction in cervical spine mobility. Injury to the cervical spine or the presence of a cervical collar also impairs the ability of the laryngoscopist to position the head. Finally, patients with short, muscular necks have limited neck mobility and redundant soft tissue in the mouth and submandibular space, making airway visualization a challenge. A variety of other anatomic features, including large breasts or a barrel chest, can complicate airway management by interfering with the excursion of the butt of the laryngoscope blade. During pregnancy, the oral and pharyngeal mucosae are swollen and bleed easily. When associated with a diminished functional residual capacity and increased volume of acidic gastric contents, intubation becomes quite hazardous. The epidemic of obesity in Western societies has created a new population of patients with airway “abnormalities.” Patients with a body mass index greater than 30 may be at increased risk for obstructive sleep apnea and gastroesophageal reflux. On physical examination, these patients often have some combination of macroglossia, a narrower, bulkier oropharynx, decreased neck mobility—all of which can complicate airway management. Some patients have a cervical fat pad, which may prevent optimal head positioning during intubation.4 Based upon anatomical considerations, clinicians commonly employ the Mallampati scale (Table 146-1)5 to evaluate objectively the airway's suitability for placement of the endotracheal tube. The ability to visualize the soft palate, fauces, tonsillar pillars, and uvula is used to predict the degree of difficulty in exposing the larynx. A careful examination of the airway, coupled with attention to difficulties during prior procedures and the physical features described above, permit adequate preparation for instrumentation of the difficult airway.

In addition, consider a temporizing device, such as a laryngeal mask airway, in the patient who is difficult to intubate. After intubation, confirm endotracheal tube position by auscultation over the lung fields and epigastrium. Additional devices, such as color capnometers and aspiration devices may be used to confirm tube placement. Data show that any single test of endotracheal tube position is substantially less accurate than using two tests of position. Immediate portable chest X-ray must also be used to visualize endotracheal tube position. After successful intubation, place an orogastric tube. Avoid nasogastric tubes in patients with head trauma for the same reasons that nasotracheal intubation is to be avoided.

Any change in the patient's condition or oxygen saturation and any substantial movement of the patient, such as to or from a computed tomography (CT) gantry, necessitates revaluation of the endotracheal tube position by auscultation.

The emergency physician must be familiar with advanced airway techniques to be able to perform rapid sequence induction intubation and guarantee definitive airway access in any patient especially those with head injuries.