Abstract
We have developed a respiratory and heart rate rhythm analysis system to examine circadian changes of autonomic nervous activity. Tweny-four-hour period of electrocardiogram (ECG) and respiratory data were recorded simultaneously by using Holter monitoring system (morpheus, Model- Teijin (Compumedics)). To evaluate the circadian changes of autonomic nervous activity, we have analyzed ECG and respiratory data for every one minute interval by using Least Square Cosine Spectrum Method and extracted five parameters (Period, Mesor, Amplitude, Acrophase, Probability). Of these parameters, we used the Probability as an index to evaluate the regularity of respiratory rhythm. We calculated "Log(1/Probabilty)" and referred to as "RA (Rhythm Adaptability)". The RA of heart rate and respiratory rhythm were higher during sleep and lower during wakefulness, and showed 90-minutes rhythm during sleep. We suspected that the RA might be useful parameter for the evaluation of circadian and ultradian rhythm of autonomic nervous function and sleep state.
