Voluntary control of breathing does not alter vagal modulation of
heart rate.
Patwardhan, Abhijit R., Joyce M. Evans, Eugene N. Bruce, Dwain L.
Eckberg, and Charles F. Knapp.
Center for Biomedical Engineering, University of Kentucky,
Lexington, Kentucky 40506, Departments of Medicine and Physiology,
Medical College of Virginia and Hunter Holmes McGuire Department of
Veterans Affairs Medical Center, Richmond, Virginia 23249
APStracts 2:0096A, 1995.
Variations in respiratory pattern influence the heart rate spectrum.
It has been suggested, hence, that metronomic respiration should be
used to correctly assess vagal modulation of heart rate using
spectral analysis. On the other hand, breathing to a metronome has
been reported to increase heart rate spectral power in the high or
respiratory frequency region; this finding has led to the suggestion
that metronomic respiration enhances vagal tone or alters vagal
modulation of heart rate. To investigate whether metronomic breathing
complicates the interpretation of heart rate spectra by altering
vagal modulation, we recorded the electrocardiogram and respiration
from 8 volunteers during three breathing trials of 10 minutes each:
1) spontaneous breathing (mean rate of 14.4 breaths/min), 2)
breathing to a metronome at the rate of 15, 18 and 21 breaths/min for
2, 6 and 2 minutes, and 3) breathing to a metronome at the rate of 18
breaths/min for 10 minutes. Data were also collected from 8
volunteers who breathed spontaneously for 20 minutes and breathed
metronomically at each subject's mean spontaneous breathing frequency
for 20 minutes. Results from the three, 10 minute breathing trials
showed that heart rate power in the respiratory frequency region was
smaller during metronomic breathing than during spontaneous
breathing. This decrease could be explained fully by the higher
breathing frequencies used during metronomic breathing trials 2 and
3. When the subjects breathed metronomically at each subjects mean
breathing frequency, the heart rate powers during metronomic
breathing were similar to those during spontaneous breathing. Our
results suggest that vagal modulation of heart rate is not altered
and vagal tone is not enhanced during metronomic breathing.
Received 10 January 1994; accepted in final form 27 January 1995.
APS Manuscript Number A35-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.