Changes of the cardiac baroreflex bandwidth during postural challenges

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation
• Biomedical Engineering

Background:

• Baroreflex sensitivity is commonly assessed using frequency-domain analysis of heart period (HP) and systolic arterial pressure (SAP) variations.
• Quantifying the rapidity of HP response to SAP changes, or baroreflex bandwidth, has remained a challenge.

Purpose of the Study:

• To propose and validate a model-based parametric approach for estimating baroreflex bandwidth from the impulse response function (IRF) of the HP-SAP transfer function (TF).
• To investigate changes in baroreflex bandwidth and associated mechanisms during head-up tilt (HUT) and head-down tilt (HDT).

Main Methods:

• A model-based parametric approach was developed to estimate baroreflex bandwidth using the IRF of the HP-SAP transfer function.
• The method explicitly accounts for mechanisms influencing HP independently of SAP.
• The approach was tested in healthy individuals undergoing graded HUT (15°-75°) and HDT (-25°).

Main Results:

• The monoexponential fitting of the IRF demonstrated the robustness of the method.
• Baroreflex bandwidth significantly decreased during graded HUT, correlating with reduced bandwidth of SAP-independent HP modulation.
• HDT did not affect baroreflex bandwidth, but widened the bandwidth of SAP-independent HP modulation.

Conclusions:

• A novel method for estimating baroreflex bandwidth provides distinct information from baroreflex sensitivity.
• Baroreflex bandwidth dynamics differ between baroreceptor unloading (HUT) and loading (HDT).
• The developed method offers a comprehensive understanding of cardiovascular autonomic control by accounting for SAP-independent influences on heart period.