Control of ventilation during continuous swallowing.

Abstract

The upper airway performs three distinct functions that must be coordinated to allow maximal operation of each individual system. We tested the ventilatory response to progressive hypercapnia in seven normal adults during continuous swallowing. Swallowing was induced by oral infusion of water while the subject breathed through the nose. Infusion of 40 ml/min resulted in repetitive swallows (rate: 8.1 +/- 4.1 swallows/min, mean +/- SD), but this did not cause a single incidence of coughing or aspiration. Swallows interrupted inspiration and expiration and resulted in compensatory changes in tidal volume and breathing frequency. Continuous drinking did not significantly change the slope of the ventilatory response to hypercapnia. The test was repeated in three subjects swallowing water infused at 60, 80, and 100 ml/min. The slope of the response was also not significantly different from control in these tests. We conclude that continuous swallowing does not override ventilatory control mechanisms in human adults.