Comparability of haemoglobin mass measured with different carbon monoxide-based rebreathing procedures and calculations

Abstract

Background. Measurements of haemoglobin mass (Hb_mass) with the carbon monoxide (CO) rebreathing method provide valuable information in the field of sports medicine, and have markedly increased during the last decade. However, several different approaches (as a combination of the rebreathing procedure and subsequent calculations) for measuring Hb_mass are used, and routine measurements have indicated that the Hb_mass differs substantially among various approaches. Therefore, the aim of this study was to compare the Hb_mass of the seven most commonly used approaches, and then to provide conversion factors for an improved comparability of Hb_mass measured with the different approaches. Methods. Seventeen subjects (healthy, recreationally active, male, age 27.1 ± 1.8 y) completed 3 CO-rebreathing measurements in randomized order. One was based on the 12-min original procedure (CO_original), and two were based on the 2-min optimized procedure (CO_new). From these measurements Hb_mass for seven approaches (CO_originalA-E; CO_newA-B) was calculated. Results. Hb_mass estimations differed among these approaches (p < 0.01). Hb_mass averaged 960 ± 133 g (CO_newB), 981 ± 136 g (CO_newA), 989 ± 130 g (CO_originalE), 993 ± 126 g (CO_originalA,D), 1030 ± 130 g (CO_originalB), and 1053 ± 133 g (CO_originalC). Procedural variations had a minor influence on measured Hb_mass. Conclusions. The relevant discrepancies between the CO-rebreathing approaches originate mainly from different underlying calculations for Hb_mass. Provided Hb_mass enabled the development of conversion factors to compare average Hb_mass values measured with different CO-rebreathing approaches. These factors can be used to develop reasonable Hb_mass reference ranges for both clinical and athletic purposes.

Key Words::

• Carboxyhaemoglobin
• CO-rebreathing
• comparison of methods
• red cell volume
• blood volume

Acknowledgements

We thank Prof. Bernard Marti for important advice and continuous support. Furthermore, the laboratory assistance of Franziska Gyger and Elisabeth Probst, as well as the technical support of Thomas Peter and Michael Weyermann, are gratefully acknowledged. A special thank you goes to Prof. W. Schmidt and his team for the instructions for the optimized CO-rebreathing method. Finally, this study would not have been possible without the great cooperation of our subjects.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.