Postop APAP Fails in High-Risk Sleep Apnea Patients

Laird Harrison

November 03, 2011

November 3, 2011 (Honolulu, Hawaii) — Autotitrating positive airway pressure (APAP) failed to prevent obstructive sleep apnea (OSA) during a study of patients undergoing surgery who were identified as high risk, researchers reported here at CHEST 2011: American College of Chest Physicians Annual Meeting.

"Postoperative APAP did not improve outcomes in patients identified as high risk for OSA," said Susan O'Gorman, MBBCh, a first-year internal medicine resident at the Mayo Clinic in Rochester, Minnesota.

In fact, the devices — a more sophisticated version of the standard continuous positive airway pressure (CPAP) device — actually prolonged the hospital stays of patients with the highest apnea-hypopnea index scores.

The result is disappointing; the team had hoped APAP would help patients who have difficulty sleeping well after surgery.

The prevalence of sleep apnea has been estimated at 22% of adults, and 70% of these cases are undiagnosed, Dr. O'Gorman said. It is a particular problem for patients recovering from surgery, she said.

Current guidelines recommend identifying patients at risk for sleep apnea before surgery, but the benefit of positive airway pressure devices for these patients has not been proven.

To test the efficacy of this approach, Dr. O'Gorman and her colleagues recruited 138 patients 18 to 100 years of age who were scheduled for total hip or knee replacement.

Patients who had a known diagnosis of OSA were excluded from the study, as were those who had received previous CPAP therapy, or who had chronic respiratory insufficiency, claustrophobia, orofacial abnormality, or tracheostomy precluding nasal CPAP.

Before each patient underwent surgery, the researchers used a Flemons questionnaire to estimate the risk for sleep apnea in each patient.

They identified 86 patients at high risk, and randomly divided half of these to receive standard postoperative care and the other half to receive additional APAP. More of the high-risk patients were male, and they had higher mean body mass index scores.

All participants underwent cardiorespiratory sleep studies before being discharged to their homes.

On most measures, patients in the APAP group did not fare any better than those in the standard-care group. Patients with an apnea-hypopnea score of 15 or higher had longer hospital stays (P = .02).

The average hospital stay for patients who used APAP for more than 2 hours per night was 5 days; for those who used it for less than 2 hours per night, it was 4 days — a statistically significant difference (P < .05).

"These were patients who were APAP-naive," said Dr. O'Gorman. "It may not have been the ideal situation to introduce APAP into these patients' care. A log of the patients' [symptoms] showed that they found it uncomfortable, so perhaps that worsened their outcomes."

Session moderator Dennis Auckley, MD, associate professor of medicine at Case Western Reserve University in Cleveland, Ohio, told Medscape Medical News that the results are not definitive.

"It's preliminary work," he said. "It's a well-done study, but it's small. We're still trying to decide how to manage sleep apnea in the postoperative setting. We still don't know exactly how to do that."

Dr. O'Gorman and Dr. Auckley have disclosed no relevant financial relationships. One of her coauthors reports receiving a research grant from ResMed to study therapy of patients with Complex Sleep Apnea Syndrome.

CHEST 2011: American College of Chest Physicians Annual Meeting: Abstract 1071A. Presented October 26, 2011.

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