[Mucus plugs in the ventral bronchi travel less distance than those in the dorsal bronchi: HRCT observation in third-order or smaller bronchi].

Purpose: To examine on HRCT whether there is a difference in the respiratory moving distance of bronchial mucus plugs between ventral and dorsal bronchi.

Materials and methods: We examined 36 ventral and dorsal bronchi of the same order in 18 patients with mucoid impaction depicted on HRCT. CT data were obtained by multidetector-row CT. HRCT images of 0.5 mm thickness and 0.3 mm interval were reconstructed. We selected one slice including a mucus plug take-off from each bronchus. When they were not included in a slice, we reconstructed a 1-3 mm slab-thickness MIP image. In these images we measured the distance between the take-off of each bronchus and the hilar margin of the mucus in same-order ventral and dorsal bronchi. We also measured CT attenuation in the ROI of the subpleural region excluding vessels in the same slice. When the differences in distances (delta D) and CT attenuations (delta C) between inspiration and expiration were obtained, we analyzed the correlation between delta D and delta C in ventral and dorsal bronchi, respectively. We also compared delta D between ventral and dorsal bronchi.

Results: Mean delta C was 36.26 +/- 2.78 HU. Ventral delta D was 6.46 +/- 3.75 mm, and dorsal delta D was 2.57 +/- 1.59 mm. The correlation between delta C and dorsal delta D was significant (r = -0.78, p < 0.005), whereas that between delta C and ventral delta D was not (r = 0.23, p = 0.64). The ventral delta D was significantly smaller than the dorsal (p < 0.05).

Conclusion: Between inspiration and expiration in the supine position, mucus plugs in the ventral bronchi travel less distance than those in the dorsal bronchi.