CPAP for Obstructive Sleep Apnea in the Post-Operative Setting: An Oximetry Evaluation Study

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Objective: To study the prevalence and associations of nocturnal hypoxia following surgery in PAP-treated (CPAP or bilevel pressure support) OSA patients. Patients and Methods: PAP-treated OSA patients presenting for elective surgery (n=38) between August 2007 and October 2008 underwent overnight oximetry monitoring on their prescribed PAP therapy on postoperative night one. The lowest oxygen (O2) saturation (SpO2), time spent with SpO2 <89% and the presence of sleep disordered breathing (saw-tooth oscillations) were determined from the oximetry tracings. Need for supplemental O2, nursing/ respiratory interventions, and complications were recorded. Records were reviewed for the type and duration of surgery and anesthesia, net fluid balance, narcotic / sedative use, demographics and co-morbidities. Results: Seven of 38 subjects (18.4%) spent at least 30 minutes with SpO2 <90% during the night (hypoxic group=HG) on their prescribed PAP therapy. The severity of baseline OSA (total and supine apnea-hypopnea index), pre-CPAP SpO2 (asleep on diagnostic PSG and awake evening after surgery), net fluid balance, and total IV narcotic dose were associated with the HG. Nursing interventions and addition of O2 were more common in the HG, though other adverse events were not. Review of the oximetry tracings suggested 71% of the HG, and 42% of the non-hypoxic group, had findings of uncontrolled sleep apnea. Conclusions: Despite the use of prescribed PAP therapy the night following surgery, some OSA patients become hypoxic. Postoperative oximetry monitoring may be indicated in PAP-treated OSA patients undergoing surgery