Low prognostic value of novel nocturnal oxygen saturation metrics in patients with obstructive sleep apnea and high cardiovascular event risk: post-hoc analyses of the SAVE study.

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Traditional methods for quantifying obstructive sleep apnea (OSA) severity may not encapsulate potential relationships between hypoxaemia in OSA and cardiovascular (CV) risk.Do novel nocturnal oxygen saturation metrics have prognostic value in patients with OSA and high cardiovascular event risk?Post-hoc analyses of the Sleep Apnea CV Endpoints (SAVE) trial.In 2687 individuals, Cox proportional hazards models stratified for treatment allocation were used to determine the associations between clinical characteristics, pulse oximetry-derived metrics designed to quantify sustained and episodic features of hypoxaemia, and CV outcomes. Metrics included: oxygen desaturation index, time <90% oxygen saturation (SpO2), average SpO2 for the entire recording (mean SpO2); average SpO2 during desaturation events (desaturation SpO2); average baseline SpO2 interpolated across episodic desaturation events (baseline SpO2); episodic desaturation event duration and desaturation/resaturation-time ratio; mean and standard deviation of pulse rate.Neither AHI, ODI nor any of the novel SpO2 metrics were associated with the primary SAVE composite CV outcome. Mean and baseline SpO2 were associated with heart failure (hazard ratio [HR] 0.81, 95% confidence interval [CI] 0.69-0.95; P=0.009 and HR 0.78, 95% CI 0.67-0.90; P=0.001, respectively) and myocardial infarction (HR 0.86, 95% CI 0.77-0.95; P=0.003 and HR 0.81, 95% CI 0.73-0.90; P<0.001, respectively). Desaturation duration and desaturation/resaturation-time ratio, with established risk factors, predicted future heart failure (AUC 0.86, 95% CI 0.79-0.93).AHI and ODI were not associated with CV outcomes. In contrast, the pattern of oxygen desaturation was associated with heart failure and myocardial infarction. However, concomitant risk factors remained the predominant determinants for secondary CV events and thus deserve the most intensive management.

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