Variation of respiratory sinus arrhythmia with age

Abstract

Respiratory sinus arrhythmia was measured on 24 male subjects whose agesranged from 21 to 65 yr, using a technique in which respiration was coupledto heart rate, so that there were 6 heartbeats per inspiration and 6 heartbeats per expiration. This voluntary cardiorespiratory coupling reduced the variance of heart rates measured at various points in the respiratory cycle. Fourier analysis was used to obtain the fundamental of heart rate and respiratory volume. A high correlation coefficient (-0.83) was found betweenpercent of variation of heart rate from the average heart rate (PB) and theage of the subject. Linear regression analysis performed on these data produced the equation: PB = 23.2–0.35 (age). Since sinus arrhythmia at thelow respiratory frequencies used probably reflects the viability of the cardiorespiratory control systems, we believe this provides a simple noninvasive method for the study of the overall competence of the system responsiblefor respiratory sinus arrhythmia.