Respiratory variations in pulmonary and systemic blood flow in healthy humans
Article first published online: 18 FEB 2012
© 2012 The Author Acta Physiologica © 2012 Scandinavian Physiological Society
Volume 205, Issue 3, pages 341–348, July 2012
How to Cite
Elstad, M. (2012), Respiratory variations in pulmonary and systemic blood flow in healthy humans. Acta Physiologica, 205: 341–348. doi: 10.1111/j.1748-1716.2012.02419.x
- Issue published online: 18 MAY 2012
- Article first published online: 18 FEB 2012
- Accepted manuscript online: 31 JAN 2012 05:05AM EST
- Manuscript Accepted: 22 JAN 2012
- Manuscript Revised: 3 JAN 2012
- Manuscript Revised: 26 DEC 2011
- Manuscript Received: 5 DEC 2011
- cardiac output;
- spectral analysis
Cardiovascular oscillations are tightly coupled to respiration. Respiratory sinus arrhythmia (RSA) is an important part of heart rate variability with unknown function. Stroke volumes from the right (r-SV) and left (l-SV) side of the heart are assumed to vary differently with respiration, but have not previously been recorded non-invasively and simultaneously in humans. The present study introduces an improved technique for capturing respiratory variations in r-SV.
Six young volunteers were investigated during spontaneous and metronome-paced breathing in the left lateral decubitus position. Heart rate (HR, from ECG), l-SV (from finger blood arterial pressure curve) and r-SV (pulsed ultrasound Doppler) were recorded. Left and right cardiac outputs (l-CO and r-CO) were calculated beat by beat from HR, l-SV and r-SV. Respiratory variations in cardiovascular variables and phase angles were estimated by spectral analysis at respiratory frequency (0.15–0.40 Hz).
The amplitude of respiratory variations in l-CO was 17% of r-CO (94% CI (6%, 35%), P = 0.03). The amplitude of the respiratory variations in l-SV was not different from r-SV (74%, 94% CI (50%, 127%) non-significant). Increases in HR and r-SV were in phase with inspiration, while l-SV decreased during inspiration.
The amplitude of respiratory variations in l-CO is significantly smaller than in r-CO. Respiratory variations in HR and in l-SV are in inverse phase; thus, RSA buffers respiratory variations in l-SV. RSA plays an important role in reducing oscillations in systemic blood flow resulting from respiratory changes in venous return.