Data have shown that sleep apnea-specific intermittent hypoxemia, defined via hypoxic burden (HB), was able to predict cardiovascular disease (CVD)-related mortality. However, according to researchers led by Neda Esmaeili, HB is calculated based on manual scoring of hypopneas and apneas, an approach that is slow and inconsistent. They developed a novel oximetry-based method to quantify HB using automatically identified blood oxygen desaturation signals.
The original calculation for HB was based on an ensemble average of SpO2 signals during patient-specific search windows, which were time-fitted to the end of scored respiratory events.
Comparatively, the novel method was based on average SpO2 signals during patient-specific search windows that were time-fitted to an interval surrounding the minimum of all identified desaturations, with a threshold of ≥2% (3% and 4% in sensitivity analysis). A patients’ oximetry-derived hypoxic burden (HBOxi) was then characterized as the total area under all desaturation curves within the search window divided by the total sleep time.
Streamlining Qualification of Hypoxic Burden From Hypoxemia
Esmaeili and colleagues applied their novel method to the original HB cohort of 5655 patients (52.8% female; mean age, 63.2 ± 11.3 years) from the Sleep Heart Health Study. According to their report, the Spearman’s rank correlation between the original median HB of 34.4% min/h (interquartile range [IQR], 18.4-59.8) and the median HBOxi of 34.5% min/h (IQR, 21.6-53.8) was 0.81 (P<.001).
The authors then used logistic and Cox regression models to estimate risk for excessive daytime sleepiness (EDS), hypertension, and CVD-related mortality per each 1 standard deviation increase in HBOxi.
Notably, HBOxi demonstrated significant associations similar to HB with EDS (adjusted odds ratio [aOR], 1.17; 95% CI, 1.09-1.26), hypertension (aOR, 1.13; 95% CI, 1.05-1.21), and CVD-related mortality (adjusted hazard ratio, 1.15; 95% CI, 1.01-1.30) after adjusted analysis.
Overall, the study authors concluded HBOxi “was highly correlated with the hypoxic burden based on manually scored apneas and hypopneas and was associated with EDS, [hypertension], and CVD mortality,” and they suggested this methodology could be implemented in wearable technologies that measure oxygen saturation.