The (Q) over dot - (V) over dotO2 diagram: An analytical interpretation of oxygen transport in arterial blood during exercise in humans

Anew analysis of the relationship between cardiac output ((Q) over dot) and oxygen consumption ((V) over dot(O2)) is presented ((Q) over dot - (V) over dot(O2) diagram). Data from different sources in the literature have been used for validation in three conditions: exercise and rest in normoxia, and exercise in hypoxia. The effects of changes in arterial oxygen concentration (Ca-O2) on (Q) over dot are discussed, as well as the effects of predominant sympathetic or vagal stimulation. Differences appear depending on whether Ca-O2 is varied by means of changes in blood haemoglobin concentration or changes in arterial oxygen saturation. The present (Q) over dot - (V) over dot(O2) diagram allows comprehensive description of oxygen transport in exercising humans; it expands applicability of the historical (Q) over dot - (V) over dot(O2) relationship to include Ca-O2 variations; it opens. new pathways for understanding underlying mechanisms; it allows computation of (Q) over dot from Ca-O2 and (V) over dot(O2) measurements, when (Q) over dot cannot be measured. (C) 2014 Elsevier B.V. All rights reserved.