The Pattern of Sinus Arrhythmia at Different Inspiratory Volumes

Abstract

Sixty healthy adult males were employed in the study of sinus arrhythmia at different inspiratory volumes (VL), to investigate the influence of age and the recovery patterns of the heart rate during the arrhythmia. The pattern of the arrhythmia was examined at six different depths of inspiration in the breath-holding state. The 60 subjects who took part in this study were made up of two age groups: 30 subjects were in the age bracket of 15-25 years, while 30 subjects were above 50 years. The results
show that increase in the depth of inspiration (i.e. increases in pulmonary stretch) modified the arrhythmia by increasing to magnitude. There were no patterns in the arrhythmia to suggest any influences due to age. However, the magnitude of the change in cardiac frequency appeared to be
more pronounced in the younger subjects. In addition the data from this research appears suggestive that heart rate recovers quicker in older people following its phenomenal fluctuations during inspiration. The response of the heart rate examined in expiatory breath-holding showed no discernible effects on the heart rate. While these observations appear to confirm earlier suggestion that the main link between respiration and sinus arrhythmia was probably the inspiratory phase of respiration, the
present data also suggest that the pulmonary stretch receptors mechanism may be greater significance for the site of action in the neural feed-back mechanism that initiates the arrhythmia.