A cadaver study to measure the adult glottis and subglottis: defining a problem associated with the use of double-lumen tubes

Abstract

Objective: To test the hypothesis that the adult cricoid diameter is the same or less than that of the glottis.

Design: Prospective.

Setting: A city mortuary.

Participants: Adult cadavers undergoing autopsy.

Interventions: After removal of the organs, the trachea was opened above the first ring to allow access to the cricoid from below, and the cricothyroid membrane was cut so that passage of measuring sounds through the vocal cords from above could be confirmed.

Measurements and main results: In 79 male and 55 female cadavers, the largest of a graduated series of cylindrical sounds that the cricoid ring would accommodate was noted. Then the biggest size possible that could pass through the glottis was measured. Height and weight were recorded. In 68% of males and 76% of females, glottic diameter was greater than subglottic; in all other cases, it was the same. In none was it smaller. Correlation between height and cricoid diameter was 0.24 for male cadavers and 0.21 for female cadavers. Regression analysis showed females to average a cricoid diameter 3.5 mm less than males of the same height.

Conclusions: The ruling diameter of the adult larynx is not the glottis but the cricoid ring. Its correlation with height is extremely poor, and it averages 3.5 mm less in females than males of the same height. These findings are important for thoracic anesthesiologists.