A method for determining segmental resistances in the microcirculation from pressure-flow measurements

Area of Science:

• Physiology
• Biophysics
• Vascular Biology

Background:

• Microcirculation analysis traditionally requires specific structural assumptions.
• Understanding the functional characteristics of microvessels is crucial for diagnosing vascular diseases.

Purpose of the Study:

• To develop and validate a novel method for analyzing microcirculation using an electrical analog.
• To characterize the functional properties of microvessels, including pressures and resistances, without assuming specific structures.

Main Methods:

• Utilized an electrical analog model and open circuit impedance functions to analyze microcirculation.
• Employed gradual occlusion of microvessels in rabbit omentum to measure pressure and flow.
• Calculated Thévenin's equivalent resistance by plotting flow against pressure during occlusion.

Main Results:

• Demonstrated a linear relationship between pressure and flow changes during microvessel occlusion.
• Identified maximum Thévenin's equivalent resistance downstream to occluded arteries and upstream to occluded veins.
• Observed distinct responses to topical versus intravenous norepinephrine, affecting resistance and pressure differently.

Conclusions:

• The developed method effectively defines microcirculatory functional characteristics using two pressures and two equivalent resistances.
• This technique provides a versatile tool for assessing vascular components and their responses to various stimuli.
• The findings highlight the differential impact of vasoactive agents on microcirculatory resistance and pressure.