Examination of the airway - Anesthesia Clinical management

Examination of the airway

Direct laryngoscopy (see below) requires neck flexibility, a mouth that can open widely, and no excessive pharyngeal tissue or a large tongue to get in the way. These features cannot be measured directly, but the following steps help us to assess problems that might arise during laryngoscopy:

·           Assess mouth opening: inter-incisor distance should exceed 4 cm in an adult.

·           Determine the mentum–hyoid (>4 cm) or thyromental (>7 cm) distance: shorter distances suggest an anterior or very cephalad larynx, which would be difficult to visualize by laryngoscopy.

·           Investigate the posterior pharynx (modified Mallampati Classification) by hav-ing the sitting patient fully extend his neck, maximally open his mouth, and stick out his tongue with or without phonation. Figure 2.1shows how we classify the visible structures.

·           Determine the ability to move lower in front of the upper incisors, which is a good sign.

·           Evaluate neck mobility: full extension through full flexion should exceed 90°. Patients who require further evaluation include:

o    those with rheumatoid arthritis and/or Down’s syndrome: the transverse ligament that secures the odontoid can become lax, introducing the poten-tial for cervical cord trauma with direct laryngoscopy;

o    trauma patients who may have damaged their cervical spine (Table 2.1).

·           Finally, patients with a history of difficult intubation and any obvious airway pathology (vocal cord tumor, neck radiation scar, congenital malformation, etc.)

·           should be further investigated. Patients with a history of snoring and/or morbid obesity also cause us concern.