Table 1.

Components of preoperative physical examination of airway that may indicate difficult intubation^w13

Airway investigation element	Disturbing findings
Length of neck	Short
Thickness of neck	Thick
Range of motion of head and neck	Patient cannot touch tip of chin to chest or cannot extend neck
Visibility of uvula	Not visible when tongue is protruded with patient in sitting position
Shape of palate	Highly arched or very narrow
Thyromental* distance	Less than three ordinary finger breadths
Compliance of mandibular space	Stiff, indurated, occupied by mass, or non-elastic
Length of upper incisors	Relatively long
Normal jaw closure	Prominent “overbite”
Interincisor distances	Less than 3 cm

^*Measured along a straight line from the thyroid notch to the lower border of the mandibular mentum with the head fully extended.