Coordination of eating, drinking and breathing in adults.

The coordination of breathing and swallowing was studied in seven normal males at rest, as well as during eating and drinking. Ventilation was monitored using respiratory inductive plethysmography and swallowing was recorded by submental electromyogram. Swallowing occurred almost exclusively in expiration. Two hundred and seventy-one swallows were seen and only two occurred in inspiration. The mean expiratory duration (Te) of breaths containing a swallow was significantly greater than the mean Te of all breaths during the same period. There was no change in mean tidal volume (VT), inspiratory duration (Ti), expiratory duration (Te), mean inspiratory flow (VT/Ti) or minute ventilation (VE) between the periods of normal breathing, eating and drinking. However, breathing became more irregular during eating and drinking. The mean coefficient of variation of VT, Te, and VT/Ti was significantly greater during eating and drinking than at rest. The coefficient of variation for VT was 22 + 3 percent, 36 +/- 5 percent, and 41 +/- 5 percent during the initial period of resting breathing, eating and drinking. For VT/Ti it was 24 +/- 6 percent, 43 +/- 14 percent and 44 +/- 8 percent during resting breathing, eating and drinking. We conclude that swallowing is almost exclusively an expiratory activity. This may play a protective role in preventing aspiration. Although the level of ventilation is maintained constant during eating and drinking, the pattern of breathing becomes increasingly irregular. This may contribute to dyspnea during meals in some patients with lung disease.