Consequences of Obstructive Sleep Apnea on Respiratory Function Following Weight-loss Surgery

The investigators propose to compare two different treatments, continuous positive airway pressure (CPAP) versus breathing of atmospheric pressure, in subjects with obstructive sleep apnea (OSA)recovering from weight loss surgery in the post anesthesia care unit (PACU). WE hypothesize that subjects with OSA will have a higher Apnea-Hypopnea Index (AHI) with desaturation and the investigators expect that post-operative CPAP treatment in the PACU will significantly improve the AHI and therefore improve patient safety in the PACU. The investigators also hypothesize that subjects with OSA have a greater decrease in oxygen saturation in response to opioid administration by patient-controlled opioid analgesia (PCA).