Tracheal cross-sectional areas from acoustic reflections in dogs.

The cross-sectional area of airways can be estimated from their response to an acoustic pressure pulse introduced at the airway opening. Errors in these area estimates are expected if the airways do not behave rigidly at these frequencies. In eight dogs we tested the accuracy of this technique to estimate tracheal cross-sectional areas by comparing them with area estimates made from radiographic bronchograms. Tracheal areas using this technique were not statistically different from areas determined radiographically. The results indicate that the dog trachea does behave rigidly enough so that this method can be used to measure its cross-sectional area.