Spectral analysis of heart rate variability using breathing bursts as a time base

Diaphragmatic EMG burst activity is analyzed by means of waveform recognition, yielding a nonlinear time scale where the interval between each EMG burst is taken as one time period. The heart-rate variability data are then suitably interpolated to yield a pseudotime data series with respect to the EMG time base. Spectral analysis of the interpolated EKG rate data reveals a harmonic mode associated with breathing, but with substantially reduced peak width. Using this procedure, the EKG spectrum is averaged over long periods with little peak broadening due to changes in breathing rate