Laparotomy disrupts respiratory phase preference for swallow

Abstract

In humans, swallow occurs predominantly in the expiratory phase (E) of breathing. This phase preference for swallow is thought to contribute to airway protection by limiting the passage of material through the pharyngeal airway to periods in which there is little or no inspiratory (I) airflow. This phase preference is currently attributed to central interactions between the swallow and breathing pattern generators. We speculated that peripheral mechanical factors, such as abdominal pressure, would influence respiratory phase preference for swallow. We induced swallowing in anesthetized spontaneously breathing cats by injection of water into the oropharyngeal airway. In animals with intact abdomens, swallow exhibited respiratory phase preference with 83% during E, 7% during I, 7% during E‐I phase transition and 3% during I‐E transition. In animals with open anterior midline laparotomy, only 38% of swallows occurred during E, 33% during I, 17% during the E‐I transition, and 12% during I‐E. Similar percentage occurrences were observed in these animals during 5 or 10% C02. Electromyogram amplitudes of adductor, cricopharyngeus, and thyrohyoid muscles during swallow did not differ between the two groups. The results support an important role for feedback from somatic and/or visceral thoracoabdominal mechanoreceptors in the coordination of swallow and breathing. Supported by NIH HL89104, HL103415, HL109025, HL89071.