Abstract
A Standardization Method for Respiratory Sinus Arrhythmia Using Breathing Frequency (the 2nd report) : Efficiency of Assessing Changes in Cardiac Parasympathetic Activity with Posture : Takayuki KAGEYAMA, et al. Urban Environment and Health Project, National Institute for Environmental Studies-Respiratory sinus arrhythmia (RSA) provides a noninvasive index of cardiac parasympathetic activity, although it appears to be modified by breathing frequency (BF) without any change in the tonic level of vagal activity. In the previous study, we proposed a statistical method for respiratory standardization of RSA amplitude at supine rest. Although RSA amplitude in other postures provide useful information on cardiac autonomic function or activity, they also appear to be modified by BF. We therefore examined RSA amplitude at sitting rest and that at standing rest as functions of BF intentionally maintained constant (0.180.33 Hz) for 1 1 nonsmokers (5 males and 6 females aged 19-28) in order to develop similar respiratory standardization methods in those postures. In those postures, RSA amplitudes linearly decreased with the increase in BF on a log-log scale, regardless of whether it was paced or nonpaced regular breathing. The respiratory modification of RSA amplitude at standing rest was greater than that at sitting rest, and both of them were greater than that at supine rest. This shows that RSA amplitude in the postures during nonpaced regular breathing can be statistically standardized based on the BF according to posture. Applying these methods to the data obtained from another experiment concerned with changes in RSA amplitude with posture, the efficiency of the standardization was confirmed. (J Occup Health 1996: 38: 107-112)
