The optimised CO-rebreathing method: a new tool to determine total haemoglobin mass routinely

Abstract

A routine method to determine total haemoglobin mass (tHb) in clinical practice and sports medicine is non-existent. Radioactive tracers or other dilution procedures like the common CO-rebreathing method (Proc(com)) are impractical, the latter in particular because of the relatively long time of respiration. According to the multicompartment model of Bruce and Bruce (J Appl Physiol 95:1235-1247, 2003) the respiration time can be considerably reduced by inhaling a CO-bolus instead of the commonly used gas mixture. The aim of this study was to evaluate this theoretical concept in practice. The kinetics of the HbCO formation were compared in arterialised blood sampled from an hyperaemic earlobe after inhaling a CO-bolus (Proc(new)) for 2 min and a CO-O(2) mixture (Proc(com)) for approximately 10 min. The reliability of Proc(new) was checked in three consecutive tests, and phlebotomy was used to determine the validity. VO(2max) was determined with and without previous application of Proc(new) and the half-time of HbCO was registered also in arterialised blood after resting quietly and after the VO(2max) test. Proc(new) yielded virtual identical tHb values compared to Proc(com) when HbCO determined 5 min after starting CO-rebreathing was used for calculation. The typical error of Proc(new) was 1.7%, corresponding to a limit of agreement (95%) of 3.3%. The loss of 95 g (19) haemoglobin was detected with an accuracy of 9 g (12). After application of Proc(new) VO(2max) was reduced by 3.0% (3.7) (P=0.022) and half-time was lowered from 132 min (77) to 89 min (23) after the VO(2max) test. Inhaling a CO-bolus markedly simplifies the CO-rebreathing method without reducing validity and reliability and can be used for routine determination of tHb for various indications.

Stability of hemoglobin mass over 100 days in active men

“…This is the first study to investigate Hb mass with serial measurements every few days for several months using a validated technique (3,18) that has the sensitivity to identify minor perturbations of just a few percent. The main finding was little evidence of biological variation, either cyclical or linear, in Hb mass Ͼ2% over 100 days.…”

“…Hb mass for improved oxygen transport is the key variable of interest for an athlete seeking an unfair advantage from transfusion, and it appears that the CO-rebreathing method has sufficient sensitivity to readily detect the removal and reinfusion of 1-2 units of homologous or autologous blood, since this volume would cause changes in Hb mass ϳ5-10% above or below baseline. This magnitude of decrease or increase in Hb mass is Ϫ2 to 5 times more than the measurement error in experienced hands (6,18). Moreover, a measure of Hb mass via CO rebreathing could be readily incorporated into a hematological passport for elite endurance athletes, since it takes only 15 min to complete, uses small samples of blood (ϳ0.6 ml), and is relatively inexpensive.…”

“…Radioactive methods of determining the volume of red blood cells using isotopic tracers such as radioactive chromium ( 51 Cr) are considered the gold standard (12), but they are costly to administer, time consuming, and pose a radiation risk to subjects, particularly if used repeatedly (7). On the other hand, carbon monoxide (CO) rebreathing has been shown to be a valid and reliable method for estimating Hb mass (3,18) and has an error of measurement similar to that of red-cell volume via 51 Cr (7).…”

Ventilatory Chemosensitivity, Cerebral and Muscle Oxygenation, and Total Hemoglobin Mass Before and After a 72-Day Mt. Everest Expedition

“…During a visit to the laboratory either a day before or after the exercise-hypoxia test, total hemoglobin mass was assessed using CO rebreathing (COR) as described in detail by Schmidt and Prommer (2005) and modified by Prommer and Schmidt (2007). In brief, after 15-min resting in a sitting position, the subjects were connected to a specially designed closed spirometric system allowing a CO-bolus application, followed by 2 min rebreathing of approximately 3 L amount of oxygen.…”

The carbon monoxide re-breathing method can underestimate Hbmass due to incomplete blood mixing

“…Since there is no transfer of CO between hemoglobin molecules (Blackmore 1970), only red blood cells passing the pulmonary circulation may be tagged with CO. However, the CO re-breathing procedure is commonly conducted at seated rest (Lundby et al 2007;Morkeberg et al 2011;Prommer et al 2008; Robach et al 2006;Schmidt and Prommer 2005;Steiner and Wehrlin 2011;Ulrich et al 2011) or semi recumbent rest (Garvican et al 2010). In the supine position total blood turnover in large pooling veins may take up to 30 min (Wennesland et al 1962), and likely even longer in the seated position as gravitation promotes blood accumulation in the leg veins.…”