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Transfer function analysis of the circulation: unique insights into cardiovascular regulation
J P Saul1, R D Berger, P Albrecht
1Harvard-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Cambridge 02139.
The American Journal of Physiology
|October 1, 1991
Summary
This study reveals how the autonomic nervous system influences heart rate and arterial pressure during breathing. Vagal activity significantly impacts respiratory sinus arrhythmia (RSA) and arterial pressure, while sympathetic effects are less pronounced.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
- Respiratory Mechanics
Background:
- Transfer function analysis precisely characterizes respiratory sinus arrhythmia (RSA) in humans.
- Understanding the autonomic nervous system's role in RSA and its link to arterial pressure is crucial.
Purpose of the Study:
- To determine transfer functions between respiration, heart rate (HR), and arterial pressures.
- To characterize sympathetic and vagal contributions to these relationships.
- To dissect mechanical links between respiration and arterial pressure from RSA effects.
Main Methods:
- 14 healthy subjects underwent controlled, erratic respiratory rate changes.
- Pharmacological autonomic blockade (atropine, propranolol) and posture changes were employed.
- Transfer functions analyzed relationships between respiration, HR, and arterial pressures.
Main Results:
- Pure vagal HR modulation showed higher magnitude and no phase delay compared to sympathetic.
- Both mechanical respiratory effects and RSA significantly influenced arterial pressure.
- RSA's contribution to arterial pressure was significant for vagal, not sympathetic, HR modulation.
- Mechanical effects linked to lung volume changes, greater in systole and standing position.
Conclusions:
- Vagal activity plays a key role in RSA's impact on arterial pressure.
- Mechanical forces of respiration directly affect arterial pressure, particularly during systole and upright posture.
- Findings support a circulatory control model based on experimental transfer functions.