Study abstract
Abstract
This study tested various sources of changes in respiratory
sinus arrhythmia (RSA). Twenty-two healthy participants
participated in three experimental conditions (mental stress,
relaxation, and mild physical exercise) that each consisted
of three breathing parts (normal breathing, breathing compressed
room air, and breathing compressed 5% CO2-enriched
air). Independent contributions to changes in RSA were found
for changes in tonic vagal modulation of heart rate, central
respiratory drive (i.e., PaCO2), respiratory depth,
and respiratory frequency. The relative contributions to changes
in RSA differed for mental stress and physical exercise. It
is concluded that uncorrected RSA will suffice to index
within-subject changes in tonic vagal modulation of heart rate
in most situations. However, if the central respiratory drive
is expected to change, RSA should ideally be corrected for changes
in PaCO2, respiratory depth, and respiratory frequency.