What is the clinical evidence from this study?

Study design: Other. Intervention: Atropine and propranolol vs. Saline. Primary outcome: R-R interval variability (p=<0.05).

What does this research mean for the field?

Respiratory sinus arrhythmia is modulated by mechanisms other than the baroreflex, and coherent respiratory oscillations in blood pressure can serve as a non-invasive measure of autonomic regulation. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To identify how autonomic blockade alters cardiovascular oscillations, phase coherence, and coupling across varied breathing conditions to clarify mechanisms driving respiratory sinus arrhythmia.

June 6, 2022Frontiers in Network PhysiologyOpen Access

Beyond the Baroreflex: A New Measure of Autonomic Regulation Based on the Time-Frequency Assessment of Variability, Phase Coherence and Couplings

Q: What are the key findings of this study?

Atropine infusion significantly reduced R-R interval variability (p<0.05) and MSNA power during apnea, suggesting respiratory sinus arrhythmia is modulated by mechanisms other than the baroreflex.

Q: What does this research mean for the field?

Respiratory sinus arrhythmia is modulated by mechanisms other than the baroreflex, and coherent respiratory oscillations in blood pressure can serve as a non-invasive measure of autonomic regulation. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To identify how autonomic blockade alters cardiovascular oscillations, phase coherence, and coupling across varied breathing conditions to clarify mechanisms driving respiratory sinus arrhythmia.

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Key result

Atropine reduces R-R interval variability during apnea, suggesting non-baroreflex modulation of respiratory sinus arrhythmia.

P<0.05
n=7

Why the study?

The role of autonomic regulation and the baroreflex in generating respiratory sinus arrhythmia has remained under dispute for decades.

Does autonomic blockade with atropine and propranolol alter cardiovascular oscillations and their interactions compared to saline in human subjects?

Population

7 subjects

Comparison

Saline vs atropine vs propranolol infusion during spontaneous breathing, fixed-frequency breathing, and apnea

Design

Experimental physiological study

Authors

PCPhilip T. ClemsonLancaster University JHJeffrey B. HoagUniversity of Minnesota WCWilliam H. CookeUniversity of Liverpool

Discussion

Member takes

Implication

No immediate practice change in autonomic assessment; leaves open non-baroreflex modulation of respiratory sinus arrhythmia.

Key Points

To identify how autonomic blockade alters cardiovascular oscillations, phase coherence, and coupling across varied breathing conditions to clarify mechanisms driving respiratory sinus arrhythmia.
Assessed 7 subjects receiving intravenous saline, atropine, and propranolol during spontaneous breathing, fixed-frequency breathing, and apnea.
Simultaneously recorded R-R intervals, end-tidal CO2, finger arterial pressure, and muscle sympathetic nerve activity (MSNA).
Calculated power spectra, phase coherence, and directional couplings to quantify cardiovascular variability and system interactions.
Atropine significantly reduced R-R interval variability across all breathing conditions (p < 0.05), decreased MSNA power during apnea, and abolished most significant coherence and coupling interactions.
Atropine suppressed R-R interval power within 0.145–0.6 Hz during apnea and inverted the systolic-to-diastolic pressure phase shift, demonstrating non-baroreflex modulation of respiratory sinus arrhythmia.
Propranolol exerted minimal effects on oscillatory power and maintained baseline cardiovascular coupling interactions.

Structured PICO

Does autonomic blockade with atropine and propranolol alter cardiovascular oscillations and their interactions compared to saline in human subjects?

Population

7 subjects

Intervention

Atropine and propranolol infusion

Comparator

Saline infusion

Outcome

R-R interval variability, muscle sympathetic nerve activity (MSNA) power, phase coherence, and couplings during spontaneous breathing, fixed-frequency breathing, and apneasurrogate

Main Result

p-value: p=<0.05

Atropine-induced reduction in R-R interval power during apnea suggests respiratory sinus arrhythmia is modulated by mechanisms other than the baroreflex, and coherent respiratory oscillations in blood pressure may serve as a non-invasive measure of autonomic regulation.

Cite This Study

Clemson et al. (2022) studied this question. Atropine and propranolol vs. Saline was evaluated on R-R interval variability (p=<0.05). Atropine infusion significantly reduced R-R interval variability (p<0.05) and MSNA power during apnea, suggesting respiratory sinus arrhythmia is modulated by mechanisms other than the baroreflex.

synapsesocial.com/papers/6a1714ea7cba52b0f77beb79 https://doi.org/10.3389/fnetp.2022.891604

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Beyond the Baroreflex: A New Measure of Autonomic Regulation Based on the Time-Frequency Assessment of Variability, Phase Coherence and Couplings

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Cite This Study

Beyond the Baroreflex: A New Measure of Autonomic Regulation Based on the Time-Frequency Assessment of Variability, Phase Coherence and Couplings

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Cite This Study

Also Consider

Also Consider