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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
Syndrome | Description |
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Down | Large tongue, small mouth make laryngoscopy difficult; small subglottic diameter possible |
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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 |
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
Pathologic State | Difficulty |
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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. |
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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. |
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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 |
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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 |
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Tissue mass makes successful mask ventilation unlikely. |
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
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.)
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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