The ratio of a patient's height to the thyromental distance is a bedside measure predictive of difficult intubation. This compensates for variation in the thyromental distance related to body size.
Method for measuring the thyromental distance:
(1) full extend the head and close the mouth
(2) measure the distance between the thyroid notch and the lower border of the mental prominence (chin) with a rigid ruler
(3) round the distance to the nearest 0.5 cm
Parameters:
(1) height of the patient in cm
(2) thyromental distance in cm
ratio of height to thyromental distance =
= (height) / (thyromental distance)
Interpretation:
• A ratio >= 25 is associated with difficult laryngoscopy. Other cutoffs (>= 23.5, 29.3) have been reported, which may be related to different ethnic groups.
To read more or access our algorithms and calculators, please log in or register.
