Analysis of Heart Rate Variability During Breath-Holding Using Fast and Continuous Calculation of Frequency and Power

Many reports show that the dominant frequency of the high-frequency component (HF: 0.15 to 0.4 Hz) of heart rate time series is synchronized with the respiratory frequency. In this paper, we propose a method for estimating the condition of respiration continuously by using the dominant frequency and power of the HF component (HFP) of the heart rate time series. The dominant frequency and HFP are calculated from the interval between two adjacent extreme points and subtraction of the two neighboring extremals. In the experimental results, high-frequency components did not disappear completely during breath-holding. This result differs from results obtained in previous studies. The subjects were divided into two groups. In one group, the dominant frequency of the HF was significantly increased during breath-holding compared with normal breathing. In the other group, this phenomenon was not observed. On the other hand, the HFP of all subjects decreased significantly during breath-holding compared with normal breathing. The correct rate during breath-holding and the error rate during rest and recovery were calculated using the HFP. In the results, the mean and standard deviation of the correct rate during breath-holding were 65.0 +/- 26.3%. The correct rate for 18 subjects was 80.0 +/- 14.1% and the correct rate for the other 8 subjects was 31.5 +/- 11.9%. Our method is expected to be applicable to the development of respiratory monitors which can measure respiratory conditions continuously in a nonrestrictive manner. (C) 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(6): 24-31, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10324