The effect of esophageal acid volume on arousals from sleep and acid clearance.

To assess the effect of different volumes of acid infused into the esophagus, seven normal volunteers were studied in the waking and sleep state. All subjects were studied for three nights in the sleep laboratory, which included complete polysomnographic monitoring and esophageal pH recording. Multiple infusions of either 5, 15, or 25 ml of 0.1 N HCL were administered each night. Similar infusions were also accomplished in the waking state. The results showed a significant (p less than 0.05) decrease in the arousal from sleep with 25-ml vs 5-ml infusions. During sleep, the latency to the first swallow was significantly (p less than .05) shorter with the 25-ml infusion when compared with that of the 5-ml infusion. While awake, the infusion volume did not affect the latency to the first swallow. The acid clearance times were not significantly altered by the different volumes infused. It is concluded that the larger volumes of acid in the esophagus create an afferent "warning" signal to the central nervous system to produce a rapid arousal from sleep along with a shortened interval to the first swallow. These responses rapidly empty the larger acid volumes from the esophagus.