O008 Refining the Hypoxic Burden Algorithm by Investigating different Methods for Calculating the SpO2 Baseline

Abstract Introduction Intermittent hypoxia is a key mechanism linking Obstructive Sleep Apnoea (OSA) to cardiovascular disease (CVD). Oximetry analysis could enhance understanding of which OSA phenotypes are associated with CVD risk. The hypoxic burden (HB) is a measure calculated from the oximetry signal that shows promise for predicting CVD mortality, but its calculation is complex. With a view to simplifying its calculation, we investigated three different baseline calculation methods and its impact on predicting CVD mortality for the HB algorithm. Methods Data from Sleep Heart Health Study (SHHS) with CVD mortality outcome and complete covariate information was used. We implemented the HB method of Azarbarzin et al 2018 ERJ. The three baseline methods included an event-based baseline (same as Azarbarzin et al 2018 ERJ), a record-based baseline, and a fixed baseline. The performance of each parameter in predicting CVD mortality was assessed using an adjusted Cox proportional hazard ratio (HR) analysis. Results The best performing method was the record-based baseline method which returned a fully adjusted model hazard ratio of 1.83 (95% CI: 1.03-3.27, p<0.05). The results for the event-based and record-based baseline methods were 1.60 (95% CI: 0.86-3.00, p=0.14) and 1.73 (95% CI: 0.93-3.22, p=0.08) respectively. Discussion HB with the record-based baseline was easier to calculate than the original event-based baseline method by Azarbarzin at al. and resulted in improved CVD mortality prediction performance. We believe that this method provides a step towards providing a novel parameter with easy calculation providing early risk stratification in cardiovascular patients.