Modeling the effect of alterations in hemoglobin concentration on VO2max

Studies investigating the effects of experimental alterations in hemoglobin concentration on VO2max have been equivocal. The objectives of this study were: 1) to develop a comprehensive model of the oxygen transport system based on a lumped parameter model of the cardiovascular system and 2) to test the new model's ability to predict VO2max changes observed in studies that have manipulated [Hb]. The resulting model demonstrates that blood volume changes that accompany venesection or blood doping may account for the apparent lack of a consistent [Hb]:VO2max relationship. A 1 l drop in blood volume is predicted to reduce VO2max by approximately 20%. A decrease in hemoglobin concentration of 2.6 g.dl-1 is needed to achieve a similar decrement. The accuracy of the model in predicting VO2max changes was tested by comparing the variance of the differences between predicted and observed changes in 19 studies with the total within-subject variance for VO2max measurement. This analysis indicates that there was no significant difference between the changes in VO2max observed and those predicted if a measurement error of 6.3% or greater was assumed. Analysis of data in the literature using our modified lumped parameter model reinforces those studies that have found VO2max changes to parallel changes in total body hemoglobin. The model developed is potentially useful for more accurately predicting changes in VO2max from alterations in hemoglobin concentration and/or blood volume.