Electroencephalographic and electrocardiographic synchronic activation during sleep apneas detected using coherence wavelet method - Ativação eletroencefalográfica e eletrocardiográfica sincronizada durante apneia do sono detectada por meio do método coherence wavelet

Abstract

Objective: Breath perturbations associated with sleep are accom-panied by cortical micro-awakenings. Seventy per cent of them are visible by direct observation on the polysomnographic study. The re-maining may be evaluated using techniques such as neural networks or by spectral analysis using Fourier’s method. The objective was to establish whether the application of a dynamic mathematical method for polysomnographic tracing enables the identification of an associa-tion frequency of the electroencephalogram and the electrocardiogram as a response to breathing events. Methods:Polysomnographs of 22 patients (14 males and 8 females) with sleep disordered breathing (SDB) and 3 normal subjects (2 males and 1 female). In order to estab-lish the relationship between cortical activation (micro-awakening) and the electrocardiographic (ECG), both signals were analyzed. The mathematical method used consisted of a wavelet band decomposition of the electroencephalographic (EEG) and the ECG signals together with wavelet coherence. Results: The most evident synchronisation pattern occurred between the ECG band corresponding to the high frequencies QRS complex and the EEG alpha band. A correlation was found between the micro-awakening frequency and the frequency of the maximum values of the correlation between the EEG alpha band and the ECG fast band. These frequencies represent synchronization times between 1.5 and 2.8 seconds. Conclusion:Above a cut point of 40 micro-awakenings/hour, the population with a significant myo-cardial activity was grouped showing a significant autonomic activity detectable in the polysomnographic tracing. When sleep fragmenta-tion level is high, a significant myocardial activation appears.