Preoperative airway assessment

A 45-year-old male presents for microlaryngoscopy following the development of a

persistent hoarse voice. He mentions that when he had an appendicectomy age 12, the

anaesthetist told him he had struggled to place his breathing tube. Which one of the

following would MOST PREDICT a potential difficulty with tracheal intubation?

a) Thick beard and moustache

b) Maximal mouth opening of 4 cm

c) Sternomental distance of 12cm

d) Patel’s distance of 6.5 cm

e) Wilson score 1

Answer: c

Explanation

Each of the values is within normal range except the Savva (sternomental) distance,

which below 12.5 cm indicates a potential difficulty with direct laryngoscopy and

intubation. The critical Patel (thyromental) distance is 6 cm, where less than this may

predict a challenging intubation. Delikan’s test grades the extent of neck extension and

of course Mallampati score indicates the extent of intraoral anatomy that can be seen

from inspection through the open mouth. A Wilson score grades five different predictors

of difficult intubation – a score of two or more indicating potential difficulty. A

thick beard may pose a challenge to effective mask ventilation but is not a specific

inhibition to intubation. Beware, however, those patients who have grown a beard to

cosmetically compensate for a relatively small mandible, which might pose a challenge

at laryngoscopy (a mandibular length of <9 cm predicts difficulty). It is important to

distinguish a potentially difficult intubation from a difficult airway or difficult ventilation.

Difficulty with one may be rescued or ameliorated by effectively addressing

the other two. The anaesthetist must be vigilant to detect when two or three may be

concurrently present in order to avert a potentially avoidable disaster.

Reference

Vaughan R. Predicting difficult airways. Contin Educ Anaesth Crit Care Pain 2001; 1(2):

44–7.