Hypoxic Burden Calculation in Patients with Obstructive Sleep Apnea Diagnosed by Peripheral Arterial Tonometry: Diagnostic Accuracy and Clinical Implications

Background: The apnea–hypopnea index (AHI3%) is the conventional metric for grading obstructive sleep apnea (OSA) severity but does not capture the cumulative depth and duration of oxygen desaturation. Hypoxic burden (HB), which integrates desaturation area per hour, may better reflect physiologic load. The diagnostic performance and clinical utility of HB derived from peripheral arterial tonometry home sleep apnea testing (PAT-HSAT) remain uncertain. Methods: We performed a single-center retrospective diagnostic study of consecutive adults undergoing PAT-HSAT (WatchPAT®) between 2016 and 2025. After prespecified exclusions, 1,171 patients with pAHI3% ≥5 events/h were analyzed. HB (%·min/h) was computed from ODI4%-defined, event-linked desaturations and normalized by total sleep time. Diagnostic accuracy was evaluated for moderate-to-severe (pAHI3% ≥15) and severe OSA (pAHI3% ≥30) using ROC curves, Youden-derived thresholds, and standard performance metrics. HB distributions were cross-tabulated against AASM severity categories to assess physiologic heterogeneity. Results: HB demonstrated good discrimination for pAHI3% ≥15 (AUC 0.867, 95% CI 0.846–0.888) and strong discrimination for pAHI3% ≥30 (AUC 0.897, 95% CI 0.879–0.916). A threshold of ≥16.6 %·min/h identified moderate-to-severe OSA with 90.1% sensitivity and 58.7% specificity. Substantial heterogeneity was observed within pAHI3% strata: 30% of mild, 49.2% of moderate, and 26.6% of severe OSA patients had HB values discordant with their AASM category. Overall, 35.4% of the cohort were physiologically “reclassified” by HB. Conclusion: HB derived from PAT-HSAT provides good-to-excellent diagnostic discrimination, supports rule-out for moderate-to-severe OSA and rule-in for severe OSA, and identifies clinically relevant heterogeneity within AASM categories. Incorporating HB into routine PAT-HSAT reporting may refine risk stratification and guide personalized management. External validation with PSG and clinical outcomes is warranted. Clinical Trial Registration: Not applicable.