The Scaling of Blood Pressure and Volume

Round 1

Reviewer 1 Report

The manuscript was revised according to the reviewer's comments. 

This manuscript is ready to publication.

Reviewer 2 Report

I am more satisfied examining the reply of the authors and see no major concerns if the editors see this publication as compatible with the mission of the journal

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript titled "The scaling of blood pressure and volume" describes cardiovascular system scaling.  The authors tried to find a basis for ruling blood pressure and blood volume in the body by deriving scaling rules from the blood flow and entropy production in the circulation. In detail, the problem-solution was tried in two stages, the relationship between blood flow and entropy production and optimization by treating body mass as a parameter through a thermodynamic approach. In methods, the problem-solving approaches were entropy production and elasticity, equations of blood flow to entropy, and elasticity relations were derived. Finally, the authors theoretically proved blood volume scale linearly to body mass and blood pressure be kept constant along mammalian phylogeny. 
This manuscript provides a basis for scaling rules in blood circulation. 
This manuscript is well written and recommended to be published as it is. 

Reviewer 2 Report

Dr. Chaui- Berlinck and Dr. Bicudo present a sophisticated mathematical proof for maintenance of blood pressure despite changes in size of organisms. The authors state that this is of interest in systems where such physiological flows are to be modeled. It is a theoretical paper, and no physiological data is applied. As a paper that outlines a physiological concept, perhaps the format of using methods and results and a discussion are not entirely helpful as the methods section easily seems to blend in with the results section. The case made for their approach relies on some self citation (Citation 28). The rationale and theory for the need for this proof and its significance are hard to follow through the introduction and frequently based on declarative statements that may be read as opinion. There are occasional grammatical errors.

Given that the physical properties of tissue are largely similar in vertebrates, is it unrealistic to presume that their physical response to blood pressure is also largely similar and thus ranges for perfusion pressure are largely conserved among vertebrates? This seems to be somewhat implied in the third paragraph on page 8 but plays a small part in the paper.

Reviewer 3 Report

This is a very interesting and important study.  I am not qualified to assess your mathematics and physics that you have considered, wisely I believe.  I am interested in how your basic information and perhaps your derived formulas could be used to explore how gaining body weight (obesity, e.g.) might lend itself to high blood pressure or even hypertension, a health risk.  I don't require that this be included in any revision of the manuscript, just wanted to let you know that is what question came up for me.    An interesting paper.  Should be published.