Use of Ambulatory Overnight Oximetry to Investigate Sleep Apnea in a General Internal Medicine Practice

Abstract

To examine how clinical factors and results from ambulatory overnight oximetry related to recommendations for further sleep evaluation in patients with clinically suspected obstructive sleep apnea syndrome. We reviewed 100 medical records selected randomly from 375 consecutive patients for whom ambulatory overnight oximetry had been ordered by internists and completed between September 1, 2001, and May 1, 2002. We analyzed relationships among clinical Information, oximetry results, resultant recommendations, and patient follow-up data. Only 21 of 100 patients had normal results from ambulatory overnight oximetry; 5 were referred for further sleep consultation. Abnormal results from ambulatory overnight oximetry were seen in 79 patients, but only 51 were referred for further sleep evaluation. Abnormal results from ambulatory overnight oximetry were associated with only a small increased likelihood of referral (likelihood ratio, 2.7; confidence interval, 1.2-6.0). Those with an oxygen desaturation index (number of desaturation events per hour of recording time) of greater than 15 received sleep consultation at a median of 8 days after completion of oximetry, whereas those with an oxygen desaturation index of 6 to 10 were evaluated in a median of 42 days (P=.60). All 17 patients who had minimum oxygen saturation of less than 80% were referred for further evaluation. Abnormal results from ambulatory overnight oximetry per se may not substantially influence internist referral of patients with clinically suspected sleep apnea for further sleep evaluation. Rather, severity of oximetry abnormalities is used along with other patient-related factors and sleep study accessibility to prioritize the need and urgency of further evaluation.