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Physical Examination

The patient must be initially subjected to a simple inspection from the front and side to identify obvious problems such as massive obesity, cervical collars, traction devices, external trauma, or any indications of respiratory difficulty such as stridor. The presence of ear and hand anomalies often suggests the presence of a difficult airway. Nostril
TABLE 42-2 -- Selected congenital syndromes associated with difficult endotracheal intubation
Syndrome Description
Down Large tongue, small mouth make laryngoscopy difficult; small subglottic diameter possible

Laryngospasm is common.
Goldenhar (oculoauriculo-vertebral anomalies) Mandibular hypoplasia and cervical spine abnormality make laryngoscopy difficult.
Klippel-Feil Neck rigidity because of cervical vertebral fusion
Pierre Robin Small mouth, large tongue, mandibular anomaly; awake intubation essential in neonate
Treacher Collins (mandibulofacial dysostosis) Laryngoscopy is difficult.
Turner High likelihood of difficult intubation

size and patency are essential to establish before considering nasal intubation. A large beard may make physical examination, mask ventilation, and direct laryngoscopy more difficult. Trimming or removing the beard should be considered when the airway is judged to be difficult or when the surgery (e.g., cervical, intracranial) prevents circumferential securement of the tracheal tube.

Edentulous patients are seldom difficult to intubate unless other associated problems are severe. Protuberant upper incisors can make laryngoscopy difficult and expose the teeth to damage. Isolated loose teeth are particularly prone to damage. These should be noted along with the location of crowns, bridges, braces, and other significant dental work. Bridges and dentures should be removed if possible unless dentures significantly improve mask fit. Very loose teeth are best removed before laryngoscopy to avoid aspiration of a tooth. Patients should be warned of likely damage to teeth in person and in the preoperative note.

Mouth opening, which is largely a function of the temporomandibular joint, is of prime importance to allow the insertion of a laryngoscope blade and subsequent glottic visualization. Adults should be able to open their mouths so that there is a 30- to 40-mm distance (about two large fingerbreadths) between upper and lower incisors.[6] A problem with mouth opening should not be underestimated because it can make visualization of any laryngeal structures impossible. It may be risky to assume that limited mouth opening is caused by a spasm that will reverse after neuromuscular blockade. Conversely, in some patients able to open the mouth widely in the awake state, adequate mouth opening in the anesthetized state was possible only when the mandible was pulled forward.[7] Previous transtemporal neurosurgery may produce severe limitation in mouth opening that was not present during the original anesthesia.

The oral cavity examination is aimed at identifying a long, narrow mouth with a high-arched palate that is associated with difficult intubation. A large tongue in


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TABLE 42-3 -- Selected pathologic states that influence airway management
Pathologic State Difficulty
Infectious epiglottitis Laryngoscopy may worsen obstruction.
Abscess (submandibular, retropharyngeal, Ludwig's angina) Distortion of airway renders mask ventilation or intubation extremely difficult.
Croup, bronchitis, pneumonia (current or recent) Airway irritability with tendency for cough, laryngospasm, bronchospasm
Papillomatosis Airway obstruction
Tetanus Trismus renders oral intubation impossible.
Traumatic foreign body Airway obstruction
Cervical spine injury Neck manipulation may traumatize spinal cord.
Basilar skull fracture Nasal intubation attempts may result in intracranial tube placement.
Maxillary or mandibular injury Airway obstruction, difficult mask ventilation, and intubation; cricothyroidotomy may be necessary with combined injuries
Laryngeal fracture Airway obstruction may worsen during instrumentation.

Endotracheal tube may be misplaced outside larynx and may worsen the injury.
Laryngeal edema (postintubation) Irritable airway, narrowed laryngeal inlet
Soft tissue, neck injury (edema, bleeding, emphysema) Anatomic distortion of airway

Airway obstruction
Neoplastic upper airway tumors (pharynx, larynx) Inspiratory obstruction with spontaneous ventilation
Lower airway tumors (trachea, bronchi, mediastinum) Airway obstruction may not be relieved by tracheal intubation.

Lower airway is distorted.
Radiation therapy Fibrosis may distort airway or make manipulations difficult.
Inflammatory rheumatoid arthritis Mandibular hypoplasia, temporomandibular joint arthritis, immobile cervical spine, laryngeal rotation, and cricoarytenoid arthritis make intubation difficult and hazardous.
Ankylosing spondylitis Fusion of cervical spine may render direct laryngoscopy impossible.
Temporomandibular joint syndrome Severe impairment of mouth opening
  True ankylosis
  False ankylosis (burn, trauma, irradiation, temporal craniotomy)
Scleroderma Tight skin and temporomandibular joint involvement make mouth opening difficult.
Sarcoidosis Airway obstruction (lymphoid tissue)
Angioedema Obstructive swelling renders ventilation and intubation difficult.
Endocrine or metabolic acromegaly Large tongue, bony overgrowths
Diabetes mellitus May have reduced mobility of atlanto-occipital joint
Hypothyroidism Large tongue and abnormal soft tissue (myxedema) make ventilation and intubation difficult.
Thyromegaly Goiter may produce extrinsic airway compression or deviation.
Obesity Upper airway obstruction with loss of consciousness

Tissue mass makes successful mask ventilation unlikely.

relation to oral cavity size may make laryngoscopy more difficult. Mallampati and colleagues[8] emphasized the importance of the base of the tongue in determining the difficulty of laryngoscopy. If the faucial pillars (palatoglossal and palatopharyngeal arches) and uvula cannot be seen in a seated, vocalizing patient with the tongue protruding ( Fig. 42-1 and Fig. 42-2 ), visualization of the glottis is likely to be more difficult than in patients in whom these structures are readily visible. An increase in Mallampati score may occur during pregnancy and correlates with the slightly higher rate of difficult laryngoscopy in this population.[9]

The distance from the inner surface of the mandible to the hyoid bone during neck extension should be at least two large fingerbreadths in adults. If the thyromental space is examined, the comparable distance is 50 mm, which is about three large fingerbreadths. There appears to be no difference in the results of using the hyomental or thyromental distances, except that the thyroid cartilage may be easier to locate. These areas are important because the laryngoscope displaces the tongue into this space, and exposure of the glottis may be inadequate if the space is narrowed or noncompliant. A receding or hypoplastic mandible results in a situation often referred


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Figure 42-1 Illustration of patient in whom faucial pillars, soft palate, and uvula are visible. (From Mallampati SR, Gatt SP, Guigino LD, et al: A clinical sign to predict difficult tracheal intubation: A prospective study. Can Anaesth Soc J 32:429, 1985.)

to as an anterior larynx or high larynx by clinicians. An inability to bring the lower incisors edge to edge with the upper incisors (i.e., impaired mandibular protrusion) is an important warning that laryngoscopy may be difficult.[10] Conversely, if the lower incisors can be brought forward to bite the upper lip beyond the vermilion, mandibular displacement can be expected to aid intubation. The latter case would seem to diminish the impact of the Mallampati score.


Figure 42-2 Illustration of patient in whom none of the three pharyngeal structures is visible. (From Mallampati SR, Gatt SP, Guigino LD, et al: A clinical sign to predict difficult tracheal intubation: A prospective study. Can Anaesth Soc J 32:429, 1985.)

The neck is examined for masses, fixation of the trachea, and mobility, particularly with extension. A patient with a short, thick, muscular neck (e.g., the classic football lineman) with a full set of teeth may pose difficult mask ventilation and very difficult laryngoscopy. Exposure of the larynx requires some degree of flexion (about 35 degrees) in the lower cervical spine and extension (about 80 degrees) in the upper cervical spine, especially at the atlanto-occipital joint ( Fig. 42-3 ). With the curved MacIntosh blade, the maximal cervical motion occurs at the atlanto-occipital and atlantoaxial joints.[11] The patient should be asked to flex and extend the neck maximally, provided


Figure 42-3 Schematic diagram demonstrating the head position for endotracheal intubation. A, Successful direct laryngoscopy for exposure of the glottic opening requires alignment of the oral, pharyngeal, and laryngeal axes. B, Elevation of the head about 10 cm with pads below the occiput and with the shoulders remaining on the table aligns the laryngeal and pharyngeal axes. C, Subsequent head extension at the atlanto-occipital joint creates the shortest distance and most nearly straight line from the incisor teeth to glottic opening.


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there are no contraindications such as suspected or known cervical spine fracture, severe cervical spondylosis with cord or vertebral artery symptoms on motion, or rheumatoid arthritis with atlantoaxial subluxation. Extension of the head can be quantitated by determining the angle of head extension, with the lower neck flexed about 30 to 40 degrees in the sniffing position. Normal extension is 80 degrees, with lesser degrees representing increasing limitation and increased potential for difficult laryngoscopy. A hoarse voice or previous prolonged intubation or tracheostomy should alert the clinician to the possibility of a stenotic airway at some level. The combination of several minor physical anomalies may result in a difficult intubation even when no one single factor is severely abnormal. A number of studies have attempted to combine physical factors to predict difficult intubation with mixed results, but it is not clear that these efforts represent an improvement over the clinical evaluation of a seasoned clinician. Additional problems with preoperative airway assessment tests are that they have only moderate interobserver reliability and depend on the definitions of airway difficulties. Difficult intubations also occur occasionally for reasons that are unexplained, and none of the available indices predicts all difficult intubations. The truly life-threatening problem is the inability to ventilate when intubation is difficult or impossible.

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