EFFECT OF CONTINUOUS SWALLOWING ON RESPIRATION

We examined the effect of continuous swallowing on breathing pattern a nd 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/m in, while the subject breathed through the nose. The number of swallow s increased from a mean of 5.2 (+/- 2.7 SD) swallows/min during the co ntrol period to 9.2 +/- 2.0 to 13.7 +/- 2.9 swallows/min during infusi on of 40 and 100 ml/min, respectively. The duration of interruption of breathing was bolus volume-dependent, increasing from 0.55 +/- 0.09 s ec with a mean bolus volume of 4.6 +/- 1.4 ml to 0.87 +/- 0.23 sec wit h a bolus volume of 8.1 +/- 1.9 ml. The majority of swallows (73 +/- 1 2%) interrupted breathing during inspiration. The mean tidal volume, i nspiratory and expiratory times during swallowing periods were higher than those recorded during the control period, but the mean level of v entilation was not different from control, at all swallowing frequenci es. Repetitive swallowing did not result in a single incidence of aspi ration or coughing. We conclude that mechanisms integrating breathing and swallowing allow repetitive swallowing to occur without compromisi ng ventilation, and that these mechanisms perfectly orchestrate betwee n breathing and deglutition to prevent aspiration.