P. Grossman et M. Kollai, RESPIRATORY SINUS ARRHYTHMIA, CARDIAC VAGAL TONE, AND RESPIRATION - WITHIN-INDIVIDUAL AND BETWEEN-INDIVIDUAL RELATIONS, Psychophysiology, 30(5), 1993, pp. 486-495
Respiratory sinus arrhythmia (RSA) is frequently employed as an intra-
and interindividual index of cardiac parasympathetic tone, although t
he relationship of RSA to interindividual differences in cardiac vagal
tone remains questionable. Our study examined between- and within-sub
ject relations among RSA, cardiac vagal tone, and respiratory paramete
rs. Twenty-nine young adults performed two sessions of tasks under no
medication and single and double autonomic blockade (intravenously adm
inistered propranolol and atropine). Parasympathetic tone was determin
ed from heart period responses to complete vagal blockade. Results ind
icated the following. Resting RSA does not accurately predict individu
al differences in cardiac vagal tone. However, RSA and heart period to
gether do predict such individual differences reasonably well. The rel
ationship between individual variations in RSA and vagal tone is not i
mproved by controlling respiratory parameters. Substantial cardiac vag
al activity occurs during inspiration, and intraindividual variations
in respiratory measures confound the association between RSA and cardi
ac vagal tone.