In a series of approximately 300 patients intubated in the ED, operators were unable to complete a Mallampati assessment in three quarters of them, citing lack of patient cooperation and critical illness as the main reasons. This is in keeping with work by Richard Levitan, lending further support to the lack of applicability of routine pre-operative airway assessment methods in critical care.

Feasibility of the preoperative Mallampati airway assessment in emergency department patients
J Emerg Med. 2010 Jun;38(5):677-8