A portable automated assessment tool for sleep apnea using a combined Holter-oximeter.

TL;DR: In this article, the authors presented a system that addresses one component of diagnosing obstructive sleep apnea (OSAS), namely objective measurement of OSA, using ECG and oximetry measurements.

Abstract: OBSTRUCTIVE SLEEP APNEA SYNDROME (OSAS) IS A MAJOR HEALTHCARE PROBLEM AFFECTING AT LEAST 4% OF MEN AND 2% OF WOMEN.1 FIFTEEN million people in the United States alone are believed to have sleep apnea,2 but currently an estimated 80% to 90% of moderate-to-severe OSAS is undiagnosed.3 OSAS is a recognized independent risk factor for the development of cardiovascular diseases.4 Hypertension is found in up to 50% of patients with OSAS, and there is growing evidence supporting an association with ischemic heart disease, stroke, heart failure, atrial fibrillation, and cardiac sudden death.5,6 Long-term observational studies of effectively treated OSAS patients have also shown a significant benefit in reducing cardiovascular mortality and non-fatal cardiovascular events7–9 when compared to untreated patients. Growing recognition of the significance of OSAS has increased pressure on specialist sleep facilities, and in many countries resource constraints have restricted access to in-laboratory polysomnography.10 The diagnosis of OSAS requires the combined assessment of relevant clinical features and the objective demonstration of abnormal breathing during sleep; current evidence indicates that basing the diagnosis on either feature alone is unreliable.11–13 Thus, there is considerable interest in limited diagnostic tools that can be used by sleep physicians as part of an overall strategy to improve access to OSAS diagnosis and treatment.14 In this report we present a system that addresses one component of diagnosing OSAS, namely objective measurement of OSA. We have previously developed a combined single-channel electrocardiogram (ECG) and oximetry analysis system for apnea detection.15 In a retrospective study of 125 patients with suspected sleep apnea, the system achieved a sensitivity and specificity of 96.5% and 95.0%, and positive and negative likelihood ratios of 19.30 and 0.04. The present study prospectively validates the performance of the proposed automated ECG-oximetry system by comparing its performance with simultaneous diagnostic polysomnography in subjects with suspected OSAS. The ability of the system to (a) identify apnea events on an epoch-by-epoch basis and (b) identify or exclude subjects with clinically significant sleep apnea was evaluated. ECG and oximetry measurements were obtained using a portable combined Holter-oximeter to establish the practicality of the recorder and associated software as a portable automated assessment tool. The study was conducted and the results reported with reference to the recommended methodology for study design and measurement of agreement between polysomnography and portable monitors set out in the AASM/ACCP/ATS joint review16 and its companion article.17