Airway protective mechanisms, reciprocal physiology of the deglutitive axis

Abstract

In the setting of shared embryonic origin and anatomical continuity, the upper airway, aerodigestive tract and the esophagus participate in an elaborate stimulatory mechanism that in response to either mechanical or acid stimulation enhances the barriers against entry of gastric content into the pharynx and trachea, clear the pharyngeal content and closes the glottis, and increases the tracheal mucus secretion whereby enhancing the airway protection. Parallel to this stimulatory mechanism there exist a number of inhibitory reflexes. This results in relaxation of the lower esophageal sphincter and inhibition of primary and secondary esophageal peristalsis potentially weakening the airway protection against aspiration of gastric contents. Overall balance of these mechanisms and conditions associated with the recruitment of involved reflexes comprise the reciprocal physiology of the upper airway and upper GI tract which are the topic of ongoing investigations. This chapter provides a concise description of these mechanisms which are involved in protection of the airway against aspiration during transit of material through deglutitive axis.