The relationship between the diameters of the adult cricoid ring and main tracheobronchial tree: a cadaver study to investigate the basis for double-lumen tube selection.

OBJECTIVE: Previous investigation of the adult cadaver larynx has shown that the cricoid diameter never exceeds that of the glottis. This further analysis looks at the anatomic relationships between the diameter of the cricoid ring and those of the main tracheobronchial tree to discover how they relate to double-lumen tube selection.

DESIGN: Prospective.

SETTING: A city mortuary.

PARTICIPANTS: Adult cadavers undergoing autopsy.

INTERVENTIONS: The trachea was partially transected above the first ring to expose the cricoid cartilage from below and was then further opened with a progressive longitudinal incision to allow access to the tracheobronchial tree.

MEASUREMENTS AND MAIN RESULTS: In 59 male and 49 female white cadavers, the largest of a graduated series of cylindrical sounds that the cricoid ring would accommodate was noted. They were then used to measure the maximum diameters of the main tracheobronchial tree. In both sexes, the mean diameter of the cricoid was shown to be the same as that of the left main bronchus, the left main bronchus to cricoid ratio almost invariably exceeded 83% (against the maximum double-lumen tube tip-to-body ratio of 80%), and the coefficient of correlation (r) between the cricoid and left main bronchial diameters was 0.6. For the trachea and left main bronchus, r was 0.5 in male cadavers and 0.45 in female cadavers.

CONCLUSIONS: The dimensions of the cricoid ring best define those of the main bronchi. Knowing its diameter should assist anesthesiologists with double-lumen tube selection.