Although heart rate is under the influence of several different nerves, the vagus is partly responsible for the variability in heart rate associated with respiration. This respiratory sinus arrhythmia (RSA) is characterized by a slowing of the heart rate during exhalation and an increase in heart rate during inhalation. Vagal influence on heart rate variability has been quantified in a multitude of ways. One of these methods, spectral analysis, utilizes a Fourier-transform equation to decompose the heart period waveform into power bands that correspond to frequencies. Specifically, the “high-frequency power band” (HF-HRV) corresponds to the frequency range of .15 to to .40 Hz, and is thought to reflect variability in heart rate due to respiration, as well as the influence of the vagus nerve (Berntson et al., 1997). Another common technique to obtain vagally-influenced heart rate variability is a peak-to-valley procedure, which uses both heart rate and respiratory data to derive a measure of RSA (Grossman, 1983). While it is not currently feasible to quantify global parasympathetic activity, RSA is a relatively easy, non-invasive measure of parasympathetic control of the
Although heart rate is under the influence of several different nerves, the vagus is partly responsible for the variability in heart rate associated with respiration. This respiratory sinus arrhythmia (RSA) is characterized by a slowing of the heart rate during exhalation and an increase in heart rate during inhalation. Vagal influence on heart rate variability has been quantified in a multitude of ways. One of these methods, spectral analysis, utilizes a Fourier-transform equation to decompose the heart period waveform into power bands that correspond to frequencies. Specifically, the “high-frequency power band” (HF-HRV) corresponds to the frequency range of .15 to to .40 Hz, and is thought to reflect variability in heart rate due to respiration, as well as the influence of the vagus nerve (Berntson et al., 1997). Another common technique to obtain vagally-influenced heart rate variability is a peak-to-valley procedure, which uses both heart rate and respiratory data to derive a measure of RSA (Grossman, 1983). While it is not currently feasible to quantify global parasympathetic activity, RSA is a relatively easy, non-invasive measure of parasympathetic control of the