Removal of bronchial secretions by two-phase gas-liquid transport.

Net outward wave motion of secretions from airways by two-phase gas-liquid transport is favored by higher airflow during expiration than inspiration. This can be accomplished by IRV in which the controlled mode of mechanical ventilation is adjusted such that the inspiratory cycle is prolonged and the expiratory phase is shortened. Studies were done on six anesthetized, nasally intubated sheep. Simulated mucus was instilled into the bronchi at 15-min intervals during I-E ratio of 1:2.7, 1.9:1, and 3:1. The IRV modes of 1.9:1 and 3:1 promoted transport of simulated mucus outward. Neither systemic blood pressure nor cardiac output were altered by IRV. Thus, IRV might be useful in the management of excessive bronchial secretions in mechanically ventilated patients. However, clinical trials of IRV should take into account its potential for producing adverse hemodynamic effects and barotrauma in patients with compromised cardiac function due to auto-PEEP attendant with its usage.