Pulse Oximetry Markers for Cardiovascular Disease in Sleep Apnea

Patients suffering from sleep apnea have an increased risk to develop cardiovascular diseases. Evidence suggests that the apnea hypopnea index (AHI) does not correlate well with this risk, therefore, there is a clinical need to define markers beyond the AHI to phenotype sleep apnea. This study investigates the use of pulse oximeter parameters to determine the cardiovascular status of sleep apnea patients. Oxygen saturation (SpO2) and pulse photoplethysmography (PPG) features were extracted around SpO2 drops and averaged per patient. A random forest backwards wrapper was used to extract the feature set which could differentiate best between cardiovascular controls and patients who suffered from a cardiovascular event. A dataset of 975 patients was used for this study, 90 of them were used for training.The results show that sleep apnea patients with a cardiovascular comorbidity tend to have more severe oxygen desaturations, and often do not have a complete resaturation to their baseline SpO2. A decreased variability in the PPG pulse upslope, could point to less arousals in these patients. The classifier based on the SpO2 features combined with age obtained the best performance with an averaged test AUC of 77.7 %.