Changes in tracheal cross-sectional area during Mueller and Valsalva maneuvers in humans.

Pressure-area behavior of the excised trachea is well documented, but little is known of tracheal compliance in vivo. Extratracheal tissue pressures are not directly measurable, but transmural pressure for the intrathoracic trachea is inferred from intra-airway and pleural pressure differences. Extramural pressure of the cervical trachea is assumed to be atmospheric. The difference in transmural pressure between the intra- and extrathoracic tracheal segments should be exaggerated during Mueller and Valsalva maneuvers. We used the acoustic reflection technique to measure tracheal areas above and below the thoracic inlet during these isovolume-pressure maneuvers. We found that 10 cmH2O positive pressure increased tracheal area in the extrathoracic segment by 34 +/- 16% (mean +/- SD) and in the intrathoracic segment by 35 +/- 15%. There was a reduction in area of 27 +/- 16 and 24 +/- 14%, respectively, for the extra- and intrathoracic segments with 10 cmH2O negative pressure. We conclude that the effective transmural pressure gradients do not vary significantly between intra- and extrathoracic tracheal segments.