Other Predictors of Difficult Intubation

• Obesity – body weight > 110kg

• Mouth opening – inter-incisor distance < 4cm in an adult

• Ability to prognath – a large overbite, or the inability to shift the lower incisors in front of the upper incisors

• Thyromental distance – The distance from the thyroid cartilage to the mentum (tip of the chin) should be > 6.5-7 cm. 

• Mentum-Hyoid distance – Similar to thyromental distance, and should be at least 3‑4 finger-breadths.

Many other factors have been investigated with variable results.