For the thyromental distance (TMD) (Patil test), ask the patient to extend their head and neck as far as possible. The TMD is the distance from the tip of the thyroid cartilage to the tip of the chin (mentum).

This distance estimates the potential space into which the tongue can be displaced, on laryngoscopy.

This should be greater than 7.0 cm. A distance of less than 6.0 cm is associated with difficult laryngoscopy and predicts 75 % of difficult laryngoscopies.

Combining Patil with Mallampati’s tests (<7.0 cm and Class 3-4) increases specificity to 97 % but reduces sensitivity to 81 %.