Study objectives: To measure the tracheal diameters (TDs) [transverse (Tr) TD, and anteroposterior (AP) TD] and left main bronchus diameters (LBDs) [Tr and AP] using multiplane CT scan reconstructions with a tridimensional correction of the declination. To evaluate the relationship between clinical variables and CT scan diameters of the tracheobronchial tree. To aid in the selection of a double-lumen tube of appropriate size.
Design: Prospective observational study.
Setting: Private and university hospitals.
Patients: A total of 206 patients (105 women and 101 men) undergoing a CT scan for medical investigations or preoperative evaluation.
Intervention: No intervention.
Measurements and results: TDs and LBDs are greater in men (p < 0.001). The Tr-TD is smaller than AP-TD for men (p < 0.001). The Tr-LBD is greater than AP-LBD in both sexes (p < 0.001). In men, height, Tr-TD, and AP-TD are predictive factors for Tr-LBD, while Tr-TD and AP-TD are the only predictive factors for AP-LBD. In women, Tr-TD and AP-TD are the only predictive factors for Tr-LBD and AP-LBD. The smallest LBD (ie, the lesser of the Tr-LBD or the AP-LBD [called the smallest LBD]) is the Tr-LBD in 25.2% of the cases. The mean (+/- SD) ratio of the smallest LBD/Tr-TD is 0.70 +/- 0.14 for men and 0.65 +/- 0.12 for women. The estimated (Est) LBD is calculated using this ratio. The mean value for Est-LBD minus the smallest LBD is 1.6 +/- 1.3 mm, and this difference is < 1 mm in 40% of male patients and 39% of female patients.
Conclusions: In conclusion, the left main bronchus is most often elliptic, and the smallest LBD cannot be accurately evaluated using patient characteristics or a ratio from TD.