EFFECT OF CONTINUOUS SWALLOWING ON RESPIRATION

We examined the effect of continuous swallowing on breathing pattern and ventilation in 7 adult subjects. Repetitive swallowing was induced by oral infusion of water at a variable rate of 40, 60, 80 or 100 ml/min, while the subject breathed through the nose. The number of swallows increased from a mean of 5.2 (+/- 2.7 SD) swallows/min during the control period to 9.2 +/- 2.0 to 13.7 +/- 2.9 swallows/min during infusion of 40 and 100 ml/min, respectively. The duration of interruption of breathing was bolus volume-dependent, increasing from 0.55 +/- 0.09 sec with a mean bolus volume of 4.6 +/- 1.4 ml to 0.87 +/- 0.23 sec with a bolus volume of 8.1 +/- 1.9 ml. The majority of swallows (73 +/- 12%) interrupted breathing during inspiration. The mean tidal volume, inspiratory and expiratory times during swallowing periods were higher than those recorded during the control period, but the mean level of ventilation was not different from control, at all swallowing frequencies. Repetitive swallowing did not result in a single incidence of aspiration or coughing. We conclude that mechanisms integrating breathing and swallowing allow repetitive swallowing to occur without compromising ventilation, and that these mechanisms perfectly orchestrate between breathing and deglutition to prevent aspiration.