Evaluating the clinical value of the hypoxia burden index in patients with obstructive sleep apnea

We aimed to develop a novel index, the hypoxia burden index (HBI), that reflects the degree and duration of oxygen desaturation, and to determine whether this index is better than the apnea hypopnea-index (AHI) for evaluating obstructive sleep apnea (OSA) and cardiovascular diseases morbidities.

We retrospectively analyzed 459 adult subjects who underwent overnight polysomnography (PSG) in this study. The HBI was calculated by dividing the total desaturation area of SpO₂ below 90% by the TST measured in seconds. Correlations between the HBI and PSG parameters and the cardiovascular diseases (CVDs) of inpatients were explored.

For the 459 participants, the HBI was highly correlated with the AHI (r = 0.690), lowest oxygen saturation (SpO₂min) (r = -0.733), and proportion of cumulative sleep time with SpO₂ below 90% in total sleep time (TST) (CT90%) (r = 0.801). The HBI was mildly correlated with Epworth sleepiness scale score, morning systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Among the significantly different parameters in the CVD and non-CVD groups in 202 inpatients (age, sex, the longest time of apnea, AHI, and HBI), only age, sex, and HBI [OR 1.006 (1.001-1.011), p = 0.021] were independently correlated with CVDs.

The HBI considers both hypoxia duration and severity during sleep. It may have potential value in predicting the clinical outcomes of OSA based on its correlation with ESS scores and morning blood pressure as well as its independent association with the prevalence of CVDs, whereas the AHI is not significantly associated with CVD prevalence.