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R-R variability detects increases in vagal modulation with phenylephrine infusion
D M Bloomfield1, S Zweibel, J T Bigger
1Department of Medicine, Columbia University, New York, New York 10032, USA.
The American Journal of Physiology
|June 5, 1998
Summary
High-frequency power accurately reflects vagal modulation, increasing with phenylephrine infusion. This study confirms its utility in detecting increased vagal activity during baroreceptor activation.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
- Heart Rate Variability Analysis
Background:
- High-frequency power (HF) from R-R interval variability analysis quantifies vagal modulation.
- Previous findings suggested HF power might decrease with phenylephrine, contradicting increased vagal activity indicated by prolonged R-R intervals.
Purpose of the Study:
- To investigate the relationship between phenylephrine infusion and HF power.
- To clarify the limitations and utility of HF power in assessing vagal modulation during baroreceptor activation.
Main Methods:
- Phenylephrine was infused at escalating doses (0.4, 0.8, 1.2 µg/kg/min) in 10 healthy subjects.
- Power spectral analysis of R-R variability was performed.
- Systolic blood pressure, R-R intervals, and HF power were measured.
Main Results:
- Phenylephrine caused dose-dependent increases in systolic blood pressure (118 to 129 mmHg) and R-R intervals (881 to 1274 ms).
- Logarithm of HF power significantly increased with rising phenylephrine doses (5.83 to 7.73 ln(ms²)).
Conclusions:
- HF power increases progressively with phenylephrine infusion.
- These findings support HF power's capability to detect enhanced vagal modulation during baroreceptor activation induced by phenylephrine.