The respiratory sinus arrhythmia as a function of breathing frequency revisited

The respiratory sinus arrhythmia (RSA) depends on the tidal volume and respiratory rate. The amount of RSA decreases in a non-linear way as a function of respiratory rate. We investigated 12 healthy volunteers at 3 different respiratory rates 8/min (0.13 Hz), 12/min (0.2 Hz) and 18/min (0.3 Hz). R-R interval tachogram were interpolated using a step-like heart rate variability (HRV) algorithm. This HRV-algorithm shows a frequency characteristic which depends on respiratory rate and mean heart rate. This affects the absolute value of the RSA, which has been corrected for this frequency dependence. In the power spectrum, the area of the RSA as a function of breathing frequency was measured. A non-linear behavior is found which is considerably different to uncorrected spectra. >