The Scaling of Blood Pressure and Volume

José Guilherme Chaui-Berlinck,José Eduardo Pereira Wilken Bicudo

doi:10.3390/foundations1010010

José Guilherme Chaui-Berlinck, José Eduardo Pereira Wilken Bicudo

Open Access

https://doi.org/10.3390/foundations1010010

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Journal: Foundations	Publication Date: Sep 20, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: University of Wollongong

Abstract

The cardiovascular system is an apparatus of mass convection, and changes in organismic size impart changes in variables of this system, namely scaling effects. Blood flow depends on pressure and conductance, and the maintenance of flow results in entropy production, that is, loss of available work. In terms of scaling, it is well known that blood pressure is kept constant while blood volume varies linearly with body mass. Yet, such expected rules have never been proven. The present study shows that these scaling rules derive from the simultaneous optimization of blood flow and entropy production in circulation and how these impact the transition from ecto- to endotermy. Thus, for the first time in almost a century of data collection, these observed relationships are explained from a theoretical standpoint. The demonstration presented herein is a building block to form a solid basis for the other scaling rules of the cardiovascular system as well as of other organic systems. The approach is of wide interest in any area where generalized flow is analyzed in terms of system optimization, giving a broad perspective on change in either engineered or naturally evolving systems.

Highlights

Academic Editors: Francisco Castells and Josef JampilekReceived: 20 August 2021Accepted: 6 September 2021Published: 20 September 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Licensee MDPI, Basel, Switzerland.This article is an open access articleFor more than a century, empirical data in mammals has shown that blood pressure does not vary with the mass of the animal
Given that the properties of the blood and vessels are basically the same in a shrew and in a whale (i.e., CG does not change), these results prove that the best solution for optimizing flow and entropy production is to keep blood pressure constant irrespective of the size of the animal
The main goal of the present study was to prove, from a theoretical standpoint, why blood volume should scale linearly with body mass and blood pressure should be kept constant along mammalian phylogeny

Summary

Introduction

For more than a century, empirical data in mammals has shown that blood pressure does not vary with the mass of the animal. For more than a century, empirical data has shown that blood mass (volume) is a somewhat fixed value, around 8% of body mass, irrespective of the size of the animal [1,2,3,4]. Despite the fact that these two variables, namely blood pressure and volume, are central to all other relationships of the cardiovascular system and other organic systems as well, no endeavor has been able to explain the reasons why blood volume scales linearly with body mass while blood pressure remains constant. Relationships between sizes or between a size and a function are of the utmost importance in practically all scientific areas, in Biology and Engineering [5,6,7,8,9]

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