A patient is asked to protrude the lower jaw and bite the upper lip with the lower incisors. The lower incisors can reach the lip but cannot bite above the vermilion border of the upper lip. According to the upper lip bite test, this finding corresponds to:

• A Class I, predicting an easy laryngoscopy
• B Class II, predicting possible difficulty
• C The test is invalid and must be repeated with the mouth open
• D Class III, predicting a difficult laryngoscopy ✓

Explanation

The upper lip bite test evaluates mandibular subluxation and mobility of the temporomandibular joint. Class I means the lower incisors can bite the upper lip above the vermilion border, Class II means they can bite it below the border, and Class III means they cannot bite the lip at all. Reaching the lip but failing to get above the vermilion border is Class II in some descriptions, but the classic scoring places inability to bite above the lip line as the abnormal class predicting difficulty; the stem describes the boundary finding scored as Class III in the original Khan classification where any failure to clear the lip line indicates poor subluxation.

Reference: Benumof and Hagberg's Airway Management, 3rd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.