Time and frequency domain methods for heart rate variability analysis: a methodological comparison

The notion that vagal control of the heart closely parallels a variety of psychophysiological phenomena has become widely accepted; however, until relatively recently there has been no simple or noninvasive method of quantifying it. This study quantitatively evaluates and compares two of the most common methods for measuring respiratory-related heart rate fluctuations: Spectral analysis and the Forges technique of detrended, filtered variance. Low-frequency power was removed from instantaneous, 4 Hz RR interval signals using either a first-order linear (Spectral) or third-order parabolic (Porges) polynomial. The Forges technique resulted in signal amplification at a few specific frequencies. The frequency range and effect of amplification were functions of the sampling frequency and the frequency content of the signal