Coupling analysis in sleep medicine by means of symbolic coupling traces

Abstract

Directional coupling analysis of bivariate time series is an important subject of current research. A new method based on symbolic dynamics for the detection of time-delayed coupling will be presented. It is called ‘symbolic coupling traces’ and is defined as the symmetric and diametric traces of the bivariate word distribution. This approach allows the quantification of delayed couplings. The ‘symbolic coupling traces’ method is applied to signals of heart rate and systolic blood pressure in patients suffering from obstructive sleep apnea (OSA) in order to display the change of the cardiovascular regulation by means of continuous positive airway pressure (CPAP) therapy. OSA is a sleep disorder with a high prevalence that causes pathological changes in cardiovascular regulation during the night and also during daytime. We investigated whether the treatment of OSA at night by means of continuous positive airway pressure (CPAP) improves the day time consequences. Twenty-eight patients with OSA, 18 with arterial hypertension, 10 with normal blood pressure, were investigated at baseline and with three months of CPAP treatment. Ten age and sex matched healthy control subjects were investigated for comparisons. We recorded a resting period with 20 min quiet breathing. The coupling analysis of the resting periods by means of symbolic coupling traces approach indicated an effect of the CPAP therapy on the baroreflex reaction in hypertensive patients where influences of the systolic blood pressure on the heart rate changed from pathological patterns to adaptive mechanisms of the normotensive patients (p<0.05). © 2012, by Walter de Gruyter Berlin Boston. All rights reserved.