Prediction of cardiovascular risk from peripheral pulse wave

Abstract

Various studies have shown an association of high prevalence of hypertension, coronary artery disease, stroke and atherosclerosis concerning people who suffer from sleep disordered breathing [1]. Apnea and hypopnea cause temporary elevations of blood pressure in association with blood oxygen desaturation, arousal and sympathetic activation. This has been linked to chronically elevated blood pressure during daytime and, ultimately, sustained hypertension. But there are also several other reasons which lead to the fact that almost 50% of deaths in Germany can be traced back to diseases of the cardiovascular system [2].In this study a novel algorithm is presented, which extracts parameters from arterial oxygen saturation (SpO2) and photoplethysmographic pulse wave - which both can be measured by a common pulse oxymeter - in order to detect signs of an increased cardiovascular risk (CV-risk). In addition, a subset of the extracted parameters were used for screening of an existing sleep apnea disease.A cohort of 61 sleep lab patients underwent sleep polygraphy (SOMNOcheck2, WEINMANN, Germany) during which SpO2 and photoplethysmographic pulse wave were recorded. The relation between the computed parameters and individual cardiovascular risk score, derived by an established risk matrix [5], was analysed. In a second step the accuracy of automatically calculated respiratory disturbance index (RDI) and manually scored Apnea-Hypopnea-Index (AHI) was determined.Four of five considered pulse wave parameters showed highly significant correlations to the individual risk score.Besides, the correlation coefficient of r = 0.967 between manual scored AHI and automatically calculated RDI suggests an excellent ability of the algorithm to recognise sleep disordered breathing. Bland-Altmann analysis showed a mean difference of -0.6 between the two parameters.The results show, that it is possible to calculate a reasonable CV-risk from signals, which already today are measured in routine during sleep diagnostic procedures. Synchronously, a sleep apnea screening of high accuracy is performed.