Respiratory sinus arrhythmia stabilizes mean arterial blood pressure at high-frequency interval in healthy humans
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Arterial blood pressure variations are an independent risk factor for end organ failure. Respiratory sinus arrhythmia (RSA) is a sign of a healthy cardiovascular system. However, whether RSA counteracts arterial blood pressure variations during the respiratory cycle remains controversial. We restricted normal RSA with non-invasive intermittent positive pressure ventilation (IPPV) to test the hypothesis that RSA normally functions to stabilize mean arterial blood pressure.
Ten young volunteers were investigated during metronome-paced breathing and IPPV. Heart rate (ECG), mean arterial blood pressure and left stroke volume (finger arterial pressure curve) and right stroke volume (pulsed ultrasound Doppler) were recorded, while systemic and pulmonary blood flow were calculated beat-by-beat. Respiratory variations (high-frequency power, 0.15–0.40 Hz) in cardiovascular variables were estimated by spectral analysis. Phase angles and correlation were calculated by cross-spectral analysis.
The magnitude of RSA was reduced from 4.9 bpm2 (95 % CI 3.0, 6.2) during metronome breathing to 2.8 bpm2 (95 % CI 1.1, 5.0) during IPPV (p = 0.03). Variations in mean arterial blood pressure were greater (2.3 mmHg2 (95 % CI 1.4, 3.9) during IPPV than during metronome breathing (1.0 mmHg2 [95 % CI 0.7, 1.3]) (p = 0.014). Respiratory variations in right and left stroke volumes were inversely related in the respiratory cycle during both metronome breathing and IPPV.
RSA magnitude is lower and mean arterial blood pressure variability is greater during IPPV than during metronome breathing. We conclude that in healthy humans, RSA stabilizes mean arterial blood pressure at respiratory frequency.
KeywordsHeart rate variability Cardiac stroke volume Spectral analysis Blood pressure variability Intermittent positive pressure ventilation
Heart rate measured from ECG
Intermittent positive pressure ventilation
Cardiac output from the left cardiac ventricle
Stroke volume from the left cardiac ventricle, estimated from blood pressure wave
Mean arterial blood pressure
Cardiac output from the right cardiac ventricle
- RE, RESP
Respiratory sinus arrhythmia
Stroke length from the pulmonary artery
Stroke volume from the right cardiac ventricle, estimated from ultrasound Doppler
We are grateful for the technical assistance from Torun Flatebø and Thomas R. Wood. Maja Elstad is financed by the Norwegian Research Council. The present study also received funding from S. G. Sønneland Foundation, Oslo.
Conflict of interest
The authors declare that they have no conflict of interest.
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