A Standardization Method for Respiratory Sinus Arrhythmia at Supine Rest as an Index of Cardiac Parasympathetic Activity Using Breathing Frequency

A Standardization Method for Respiratory Sinus Arrhythmia at Supine Rest as an Index of Cardiac Parasympathetic Activity Using Breathing Frequency: Takayuki K ageyama , et al. Urban Environment and Health Project, National Institute for Environmental Studies —Two spectral components of heart rate variability, respiratory sinus arrhythmia (RSA) and Mayer wave‐related sinus arrhythmia (MWSA) provide noninvasive indices of cardiac vagal activity and systemic sympathetic activity with vagal modulation, respectively. But the basic problem that breathing frequency (BF) appears to modify RSA without any change in the tonic level of vagal activity remains, indicating the need for respiratory standardization. In the present study, RSA amplitude at supine rest was examined as a function of BF intentionally maintained constant (0.18‐0.33 Hz) for 11 nonsmokers (5 males and 6 females aged 19‐28) with consideration of time after meals, which may affect RSA. The amplitude calculated by autoregressive spectral analysis linearly decreased with the increase in BF on a log‐log scale. This held in the case of RSA for nonpaced regular breathing with the mean BF corresponding to the center frequency of RSA. The amplitude during nonpaced regular breathing could therefore be statistically standardized to that at BF of, e.g., 0.25 Hz, which agreed well with that at the paced BF of 0.25 Hz (r = 0.958). This suggests a simple, efficient method for the reliable assessment of vagal activity based on RSA amplitude and of sympathetic activity indicated by the ratio of MWSA amplitude to RSA amplitude.