Patients with obstructive sleep apnea (OSA) who are administered oxygen therapy postoperatively may develop elevated levels of carbon dioxide (CO2), according to researchers, reports Anesthesiology News.

The study, which used transcutaneous CO2 to measure CO2, found that 11.3% of study patients (14/123) had elevated CO2 in their blood, exceeding 55 mm Hg, “indicating a degree of respiratory depression in postoperative nights, mostly in the first post-op night,” said senior author Frances Chung, MBBS, FRCPC, professor of anesthesiology at University Health Network, University of Toronto.

“When the health care team gives oxygen supplementation to patients in wards after discharge from the PACU, we may not think about CO2 levels,” Dr. Chung said. “Most of us monitor oxygen saturation by oximetry and do not monitor respiratory rate and CO2 on a regular basis.”