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

Study Objectives: Resource limitations have raised interest in portable monitoring systems that can be used by specialist sleep physicians as part of an overall strategy to improve access to the diagnosis of sleep apnea. This study validates a combined electrocardiogram and oximetry recorder (Holter-oximeter) against simultaneous polysomnography for detection of sleep apnea. Design: Prospective study. Setting: A dedicated sleep disorders unit. Participants: 59 adults presenting for evaluation of suspected sleep apnea. Interventions: NA. Measurements and Results: An automated algorithm previously developed for sleep apnea detection was applied to the electrocardiogram and oximetry measurements. The algorithm provides (a) epoch-by-epoch estimates of apnea occurrence and (b) estimates of overall per-subject AHI. Using separate thresholds of AHI ≥15 and AHI 20 and 0.04 respectively, with 16.7% of subjects having intermediate test results (AHI 5-14/h). Regardless of AHI, 85.3% of respiratory events were correctly annotated on an epoch-by-epoch basis. AHI underestimation bias was 0.9/h, and the antilogs of log-transformed limits of agreement were 0.3 and 2.7. Correlation between estimated and reference AHI was 0.95 (P < 0.001). Conclusion: Combined Holter-oximeter monitoring compares well with polysomnography for identifying sleep apnea in an attended setting and is potentially suitable for home-based automated assessment of sleep apnea in a population suspected of having sleep apnea