Corrected formula for estimating peripheral blood flow by impedance plethysmography

Area of Science:

• Biomedical Engineering
• Physiology
• Medical Instrumentation

Background:

• Conventional formulas for peripheral blood flow calculation using impedance plethysmography have limitations.
• The accuracy of the blood flow index (BFI) derived from these formulas can be affected by variations in blood resistivity.
• Observed anomalies in systolic wave amplitudes in impedance plethysmograms of patients with edema require explanation.

Purpose of the Study:

• To highlight the limitations of the conventional formula for computing peripheral blood flow from impedance plethysmograms.
• To propose and validate a corrected formula for a more accurate blood flow index (BFI).
• To explain anomalies in impedance plethysmography waveforms observed in edematous patients.

Main Methods:

• A conductivity cell experiment was designed to assess the dependence of BFI on mean resistivity.
• The conventional formula for BFI computation was analyzed.
• A corrected formula for BFI was developed and tested against experimental data.

Main Results:

• The conventional BFI was found to be dependent on the mean resistivity of the conductivity cell.
• The corrected BFI demonstrated independence from the mean resistivity, indicating improved robustness.
• The study provides an explanation for anomalies in systolic wave amplitudes in impedance plethysmograms of patients with edema.

Conclusions:

• The conventional formula for calculating peripheral blood flow from impedance plethysmography is limited by blood resistivity.
• A corrected formula offers a more reliable blood flow index (BFI) that is independent of resistivity.
• The findings contribute to a better understanding and interpretation of impedance plethysmography data, particularly in edematous conditions.