Reproducibility of the CO rebreathing technique with a lower CO dose and a shorter rebreathing duration at sea level and at 2320 m of altitude

Abstract

Total hemoglobin mass (Hb_mass) is routinely assessed in studies by the carbon monoxide (CO) rebreathing. Its clinical application is often hindered due to the consequent rise in carboxyhemoglobin (%HbCO) and the concern of CO toxicity. We tested the reproducibility of the CO rebreathing with a CO dose of 0.5 mL/kg body mass (CO_0.5) compared to 1.5 mL/kg (CO_1.5) and when shortening the CO rebreathing protocol. Therefore, CO rebreathing was performed 1×/day in eight healthy individuals on four consecutive days. On each day, either CO_0.5 (CO_0.5-1 and CO_0.5-2) or CO_1.5 (CO_1.5-1 and CO_1.5-2) was administered. Venous blood samples to determine %HbCO and quantify Hb_mass were obtained prior to, and at 6 (T₆), 8 (T₈) and 10 min (T₁₀) of CO rebreathing. This protocol was tested at sea level and at 2320 m to investigate the altitude-related measurement error. At sea level, the mean difference (95% limits of agreement) in Hb_mass between CO_0.5-1 and CO_0.5-2 was 26 g (–26; 79 g) and between CO_1.5-1 and CO_1.5-2, it was 17 g (–18; 52 g)_. The respective typical error (TE) corresponded to 2.4% (CO_0.5) and 1.5% (CO_1.5), while it was 6.5% and 3.0% at 2320 m. With CO_0.5, shortening the CO rebreathing resulted in a TE for Hb_mass of 4.4% (T₈ vs. T₁₀) and 14.1% (T₆ vs T₁₀) and with CO_1.5, TE was 1.6% and 5.8%. In conclusion, the CO dose and rebreathing time for the CO rebreathing procedure can be decreased at the cost of a measurement error ranging from 1.5-14.1%.

Keywords:

• Anemias
• hematology
• method selection and validation
• blood and cardiovascular physiology
• blood gases

Acknowledgements

The authors would like to thank all participants for their commitment and time investment in this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was funded by the Partnership for Clean Competition PCC [grant ID 100100 R318] and partly funded by the World Anti-Doping Agency (WADA). The Centre for Physical Activity Research (CFAS) is supported by TrygFonden [grants ID 101390 and ID 20045].