Electrical modelling of tissue experiments confirms precise locations of resistance and compliance in systemic arterial tree-they are mutually exclusive.

Abstract

This study presents electrical modelling of the arterial system to understand the effect of adrenaline on the aortae and small arteries in terms of their resistance and compliance. There is no categorical documentation in the current literature on the precise locations of arterial resistance (R) and compliance (C) in vasculature. Knowledge of their exact locations in the arterial tree enables re-assessment of the differential action of vasoactive drugs on resistance versus compliance vessels once we resolve beat-to-beat changes in R and C in response to these drugs. Isolated goat aortae and small arteries were perfused with a pulsatile pump and lumen pressures were recorded before and after addition of adrenaline. Equivalent electrical models were simulated, and biological data was compared against the electrical equivalents to derive interpretations. In the aortae, systolic pressure increased, diastolic pressure decreased, pulse pressure increased (P=.018); but the mean pressure remained the same (P=.357). Whereas in small artery, vasoconstriction caused an increase in systolic, diastolic, and mean pressures (P=.028). Simulations allow us to infer that vasoconstriction in the aorta leads to a reduction in compliance, but an increase in resistance if any, is not sufficient to alter the mean aortic pressure. Whereas vasoconstriction in small arteries increases resistance, but a decrease in compliance, if any, does not affect any of the pressure parameters measured. The presented study is first of its kind to give experimental evidence that large arteries and aorta are the only compliance vessels and small arteries are the only resistance vessels.