Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults.

Respiration and swallowing were recorded simultaneously by inductance plethysmography, submental electromyography, and a throat microphone in 10 normal subjects during eating and drinking tasks that included single boluses of varying volume (5-20 ml) and consistency presented with a syringe and cup, a 200-ml drink taken with and without the use of a straw, and a sandwich meal. Swallows were associated with a brief swallow apnea (SA) lasting approximately 1 s. Swallow effects on the duration or tidal volume of the preswallow, postswallow and swallow-associated breathing cycles varied depending on bolus characteristics and presentation. Expiration before and after the SA was the preferred pattern with all drinking and eating tasks. Inspiration followed SA in < 5% of single-bolus swallows, but this pattern increased significantly with a 200-ml drink administered by cup or by straw and during a sandwich meal (23.8 +/- 5.2, 27.0 +/- 2.6, and 16.3 +/- 2.7%, respectively. Hence, the swallow-associated breathing pattern seen with single-bolus swallows may not reflect that associated with regular eating and drinking behavior. This finding implies that the risk of aspiration may be reduced by teaching patients prone to aspiration to simplify the complex behavior of eating and drinking to a series of single-bolus swallows.