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Cardiocirculatory coupling during sinusoidal baroreceptor stimulation and fixed-frequency breathing.
C Keyl1, M Dambacher, A Schneider
1Department of Anesthesiology, University Medical Center Regensburg, University of Regensburg, 93042 Regensburg, Germany. Keyl@rkanaw1.ngate.uni-regensburg.de
Clinical Science (London, England : 1979)
|August 5, 2000
Summary
Respiratory sinus arrhythmia (RSA) is debated to originate centrally or via baroreflexes. This study suggests baroreflex mechanisms contribute to RSA, challenging purely central origins, particularly during fixed-frequency breathing.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
Background:
- The origin of respiratory sinus arrhythmia (RSA), the fluctuation in heart rate synchronized with breathing, is debated.
- It remains unclear whether RSA arises primarily from central neural coupling or from baroreflex feedback mechanisms.
Purpose of the Study:
- To investigate the contribution of baroreflex mechanisms to RSA.
- To compare cardiocirculatory coupling during breathing with coupling during artificial baroreflex stimulation.
Main Methods:
- 17 healthy subjects underwent sinusoidal stimulation of carotid baroreceptors using neck suction at frequencies of 0.2 Hz and 0.1 Hz.
- Heart rate and blood pressure fluctuations were analyzed using discrete Fourier-transform and transfer function analysis.
- Comparison was made between spontaneous respiratory fluctuations and baroreflex-induced oscillations.
Main Results:
- Baroreceptor stimulation induced heart rate fluctuations comparable in magnitude to RSA.
- Systolic blood pressure fluctuations from neck suction were smaller than respiratory blood pressure fluctuations.
- While 0.1 Hz neck suction increased blood pressure and RR interval variability, the phase relationship remained unchanged.
Conclusions:
- The findings do not support RSA originating predominantly as a central phenomenon.
- Baroreflex mechanisms appear to contribute to respiratory fluctuations in heart rate, especially under fixed-frequency breathing conditions.