Detecting cardiorespiratory coordination by respiratory pattern analysis of heart period dynamics - The musical rhythm approach

The purpose of this study was to demonstrate that cardiorespiratory coordination can be unveiled by analyzing solely the heart period data from electrocardiogram (ECG). The analysis was done (1) on the basis of symbolic musical pattern analysis to detect intermittent cardiorespiratory phase coordination and (2) on the quantitative evaluation of respiratory sinus arrhythmia (RSA) to examine long-term frequency coordination between heartbeat and respiration. The methods were applied to 196 ECGs of 98 healthy subjects. The results showed that at night (1) intermittent phase coordination occurred reproducibly in individual subjects, and (2) longterm frequency ratios statistically approached 4:1 over all subjects to within an accuracy of 0.02, although individual values ranged from 2.5-6.0 with a high intraindividual reproducibility (r = 0.94, day A versus day B). Moreover, intermittent phase coordination ratios and long-term frequency ratios corresponded to each other with a remarkably high correlation (r = 0.95). In the light of clinical applications, the coordination analysis presented here has an enormous advantage over those techniques depending on respiratory flow measurements, because the pattern technique requires only ECG recordings, and it is thus applicable over a longer period of time under daily life conditions.