Effects of different respiratory maneuvers on the lower esophageal sphincter in obese patients before and during enesthesia

Obesity increases intra-abdominal pressure and affects lung mechanics. The effects of pressure changes in the airways on esophageal sphincters in obese patients have not been studied before.
The aim of the present study was to evaluate the effects of different respiratory maneuvers on the lower esophageal sphincter (LES) pressure and barrier pressure (BrP) in obese patients before and during anesthesia using High-resolution Solid-State Manometry.

Material and Methods

The study protocol was approved by the Ethics Committee. Eighteen patients with BMI>35kg/m2 undergoing laparoscopic gastric by-pass were studied using a standardized manometric protocol.
The patients underwent ECG, SPO2, blood pressure and BIS monitoring. The manometry catheter was placed transnassally to record pressures from the hypopharynx to the stomach. During baseline measurements the patients were placed in the supine position and LES pressures during expiration were compared to LES pressures during inspiration. Thereafter a Valsalva maneuver and a forced inspiration were performed. Anesthesia was induced with remifentanil and propofol, and rocuronium was used for tracheal intubation. Anesthesia was maintained with sevoflurane and remifentanil. After stabilization of anesthesia, LES pressures were recorded during expiration and inspiration at PEEP 0 and at PEEP 10 cmH2O.

Results 

Before anesthesia the LES pressure was significantly lower during expiration compared to inspiration at normal tidal volumes (p<0.05). LES pressures increased during the Valsalva maneuver (p<0.01) and forced inspiration (p<0.01). 
During anesthesia, LES pressures decreased compared to baseline values before anesthesia (p<0.01). LES pressures were unaffected by increased PEEP.
The barrier pressure was not altered during inspiration compared to expiration before anesthesia. The barrier pressure increased during forced inspiration (p<0.01) but not during Valsalva. During anesthesia, barrier pressures decreased compared to baseline values before anesthesia (p<0.05). Barrier pressures were unaffected by increased PEEP.

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Conclusion

LES pressure was significantly lower during expiration compared to inspiration at normal tidal volumes. LES pressure increased during Valsalva and forced inspiration. Anesthesia induced a decrease in LES and barrier pressures.