Coordination between respiration and swallowing: respiratory phase relationships and temporal integration.

The coordination of breathing and swallowing was studied in 13 young healthy adult subjects during the administration of graduated volumes of water (3, 10, and 20 ml). Simultaneous submental electromyography, respiratory plethysmography, and fiber-optic endoscopy revealed a well-timed pattern between physiological respiratory events and related swallowing events. Expiration was the phase of respiration that was most closely associated with deglutition. Respiration was usually maintained at the onset of deglutition and halted before the onset of laryngeal elevation. The apneic interval was approximately 1 s for the 3-, 10-, and 20-ml boluses. A large-volume (100-ml) straw swallow resulted in variable respiration-swallowing patterns and in statistically significant differences (P < 0.01) in the duration of apneic pause and laryngeal excursion. The expiratory phase of respiration resumed nearly 0.50 s before the completion of swallowing. Clinical implications of the findings are addressed and related to aspiration and pulmonary complications in dysphagic patients.