Ultrasonographic evaluation of tracheal collapse in dogs.

Tracheal ultrasonography was performed to measure the width of the tracheal ring shadow and to assess the clinical relevance of these measurements for identifying tracheal collapse. The first tracheal ring width (FTRW) and thoracic inlet tracheal ring width (TITRW) were measured on both expiration and inspiration. The mean of the FTRW width (129 dogs) was greater in expiration (10.97 plusmn; 1.02 mm, p = 0.001) than that in inspiration (9.86 plusmn; 1.03 mm). For 51 normal dogs, the mean of the TITRW width was greater in expiration (9.05 plusmn; 1.52 mm, p = 0.001) than in inspiration (8.02 plusmn; 1.43 mm). For 78 tracheal collapse dogs, the mean of the TITRW width was greater in expiration (15.89 plusmn; 1.01 mm, p = 0.001) than in inspiration (14.85 plusmn; 1.17 mm). The TITRW/FTRW ratio of the normal dogs was higher (p = 0.001) in expiration (0.81 plusmn; 0.09) than that in inspiration (0.79 plusmn; 0.10). When compared between the normal and tracheal collapse dogs, the TITRW/FTRW ratio was also increased (p = 0.001) both in expiration (1.54 plusmn; 0.09) and inspiration (1.47 plusmn; 0.08), respectively. Based on these results, the cutoff level of the TITRW/FTRW ratio was statistically analyzed according to the receiver operating characteristic curve and it could be set at 1.16 in expiration and at 1.13 in inspiration. We have demonstrated that tracheal ultrasonography is a useful technique for the evaluation of tracheal collapse and it can be a supportive tool together with the radiographic findings for making the correct diagnosis.