Should we reevaluate the variables for predicting the difficult airway in anesthesiology?

Anesthesiologists have often been confronted with the difficult question of determining which patient will present an increased difficulty for endotracheal intubation. The limits of the previously reported morphometric airway measurements for predicting difficult intubation have inadequately addressed the normal patient population variables. We designed this prospective study to investigate the age and sex-related changes in the morphometric measurements of the airway in a large group of patients without anatomic abnormality and a group of cadavers. Hyomental, thyromental, sternomental distances, neck extension, and Mallampati scores were evaluated in 12 cadavers and in 334 patients. Patients were allocated to three groups based on age: Group 1 (20-30 yr), Group 2 (31-49 yr), and Group 3 (50-70 yr). Male and female sex differences were also evaluated. Hyomental distance was the only variable not affected by age. In addition, the mean population values were less than the threshold values suggested as criteria for difficult endotracheal intubation. All the other criteria were age-dependent and inversely affected by the increase in age. Male sex was also a distinction for increased measurements of all the morphometric distances. The mean degree of neck extension was similar in both sex groups. This study provides a more comprehensible approach to the morphometric measurements of the human airway. Adequate data of normal values may help the clinician to identify patients that are outside the range and therefore may be challenging.

This study was performed to establish data on the average values of airway morphology in the adult population of different age groups and sex. Hyomental, thyromental, sternomental distances and neck extension values were measured on 12 cadavers and 334 patients.