Beyond a Single Hypoxic Burden Value: Hypoxic Burden Ratio Assessed by Peripheral Arterial Tonometry in Obstructive...

Hypoxic burden (HB) integrates the depth and duration of nocturnal oxygen desaturation in obstructive sleep apnea (OSA), but a single HB value may conceal distinct hypoxemic profiles. We explored the relationship between two automated HB measures derived from peripheral arterial tonometry-based home sleep apnea testing (PAT-HSAT) data: desaturation area under the SpO₂ baseline (HB_baseline) and area under 90% SpO₂ (HB_<90%).

We performed a retrospective cross-sectional study of 2136 adults with OSA, diagnosed by a peripheral arterial tonometry-derived apnea-hypopnea index based on 3% desaturation criteria (pAHI3%) ≥5 events/h. Three operational HB groups were designated according to the relationship between HB_baseline and HB_<90%. Type 1 was characterized by measurable HB_baseline (>0%·min/h) and HB_<90% = 0%·min/h; the HB_baseline/HB_<90% ratio was not calculable because the denominator was zero. Among patients with measurable HB_<90%, Type 2 was defined by an HB ratio ≥1 and Type 3 by an HB ratio <1. These three groups were prespecified as exploratory operational categories.

Type 1, Type 2, and Type 3 comprised 506 (23.7%), 1108 (51.9%), and 522 (24.4%) patients, respectively. The percentage of total sleep time (TST) with SpO₂ below 90% (T90) had median values of 0.1%, 5.4%, and 63.6% in Types 1, 2, and 3, respectively. Types 2 and 3 had similar median pAHI3% (26.3 and 28.8 events/h) but markedly different median HB_<90% (6.0 and 86.5%·min/h). HB_baseline correlated strongly with pAHI3% across all groups (Spearman ρ, 0.9295-0.9378), whereas HB_<90% correlated moderately with pAHI3% in Types 2 and 3 (ρ=0.6292 and 0.6209; all P<0.001).

The relative magnitude of HB_baseline and HB_<90% provides an exploratory operational framework for describing distinct hypoxemic profiles in OSA beyond a single HB value. The framework is descriptive and hypothesis-generating; its clinical, prognostic, mechanistic, and therapeutic utility has not been established and requires external and longitudinal validation.