Night-to-night repeatability of supine-related obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) experience respiratory events with greater frequency and severity while in the supine sleeping position. Postural modification devices (PMDs) prevent supine sleep, although there is a paucity of guidance to help clinicians decide when to use PMDs for their patients. In order for PMDs to treat OSA effectively, patients must experience respiratory events in the supine sleeping position consistently from night to night and must have a low nonsupine apnea and hypopnea index (AHINS). OBJECTIVES: To document the repeatability of traditionally defined supine predominant OSA on consecutive polysomnography, to determine whether the consistency of the supine-predominant phenotype can be improved by altering the definition of it, and to determine whether a low AHINS is repeatable from night to night. METHODS: We recruited 75 patients for polysomnography on two separate nights. Patients were classified as having supine OSA on each night on the basis of traditional and novel definitions, and the classification systems used were compared on the basis of agreement from night to night. MEASUREMENTS AND MAIN RESULTS: The definition of supine OSA with the highest level of agreement from night to night incorporates a supine AHI (AHIS) to AHINS ratio >/=4:1. In addition, agreement exists for males, but there is poor agreement for female patients, regardless of the definition applied. An AHINS /=4:1 and an AHINS