Submitted on October 12, 2006
Accepted on January 12, 2007
The Impact of Continuous Positive Airway Pressure on the Lower Esophageal Sphincter
Kelly L Shepherd1, Richard Holloway2, David Hillman3, and Peter R Eastwood1*
1 West Australian Sleep Disorders Research Institute, Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia; School of Anatomy and Human Biology, University of Western Australia, Perth, Western Australia, Australia
2 Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, South Australia, Australia
3 West Australian Sleep Disorders Research Institute, Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia
* To whom correspondence should be addressed. E-mail: peter.eastwood{at}health.wa.gov.au.
The lower esophageal sphincter (LES) is the primary barrier to gastroesophageal reflux. Reflux is associated with periods of LES relaxation, as occurs during swallowing. Continuous positive airway pressure (CPAP) has been shown to reduce reflux in individuals with and without sleep apnea, by an unknown mechanism. The aim of this study was to determine the effect of CPAP on swallow-induced LES relaxation. METHODS: Measurements were made in 10 healthy, awake, supine individuals. Esophageal (Pes), LES (PLES), gastric (Pg) and barrier pressure to reflux (Pb=PLES-Pg) were recorded using a sleeve catheter during 5 swallows of 5ml of water. This was repeated at 4 levels of CPAP (0, 5, 10 and 15cmH20). Pressures were measured during quiet breathing and during the LES relaxation associated with a swallow. Duration of LES relaxation was also recorded. RESULTS: During quiet breathing CPAP significantly increased end-expiratory Pes, PLES, Pg and Pb (p<0.05). The increase in Pb was due to a disproportionate increase in PLES compared to Pg (p<0.05). During a swallow, CPAP increased nadir PLES, Pg and Pb and decreased the duration of LES relaxation (4.1s with 0cmH20 CPAP to 1.6s on 15cmH20 CPAP, p<0.001). CONCLUSIONS: Pb increased with CPAP by virtue of a disproportionate increase in PLES compared to Pg. This may be due to either reflex activation of LES smooth muscle, or non-specific transmission of pressure to the LES. The findings suggest CPAP may make the LES less susceptible to reflux by increasing Pb and decreasing the duration of LES relaxation.
