Abstract
What is the central question of this study? Is it necessary to modify the CO-rebreathing method to acquire reliable measurements of haemoglobin mass in patients with chronic mountain sickness? What is the main finding and its importance? The CO-rebreathing method must be modified because of the prolonged CO-mixing time in patients with chronic mountain sickness. After adaptation of the blood sampling method, reliable and valid results were attained. With this modification, it is possible to quantify the extent of polycythaemia and to distinguish between a haemoconcentration and an exclusive enhancement of erythrocyte volume. Patients suffering from chronic mountain sickness (CMS) exhibit extremely high haemoglobin concentrations. Their haemoglobin mass (Hbmass), however, has rarely been investigated. The CO-rebreathing protocol for Hbmass determination in those patients might need to be modified because of restricted peripheral perfusion. The aim of this study was to evaluate the CO uptake and carboxyhaemoglobin-mixing time in the blood of CMS patients and to adapt the CO-rebreathing method for this group. Twenty-five male CMS patients living at elevations between 3600 and 4100m above sea level were compared with ethnically matched healthy control subjects from identical elevations (n=11) and near sea level (n=9) and with a Caucasian group from sea level (n=6). CO rebreathing was performed for 2min, and blood samples were taken for the subsequent 30min. After the method was modified, its reliability was evaluated in test-retest experiments (n=28), and validity was investigated by measuring the Hbmass before and after the phlebotomy of 500ml (n=4). CO uptake was not affected by CMS. The carboxyhaemoglobin mixing was completed after 8min in the Caucasian group but after 14min in the groups living at altitude. When blood was sampled 14-20min after inhalation, the typical error of the method was 1.6% (confidence limits 1.2-2.5%). After phlebotomy, Hbmass decreased from 1779±123 to 1650±129g, and no difference was found between the measured and calculated Hbmass (1666±122g). When the time of blood sampling was adapted to accommodate a prolonged carboxyhaemoglobin-mixing time, the CO-rebreathing method became a reliable and valid tool to determine Hbmass in CMS patients.
Highlights
IntroductionIn clinical practice and in the field of sports medicine, the optimized CO-rebreathing method (oCOR method; Gore et al, 2006; Prommer & Schmidt, 2007; Schmidt & Prommer, 2005) is used to determine the total haemoglobin mass (Hbmass)
In clinical practice and in the field of sports medicine, the optimized CO-rebreathing method is used to determine the total haemoglobin mass (Hbmass)
The calculated Hbmass values in the four groups reached their plateau at different time points after CO rebreathing
Summary
In clinical practice and in the field of sports medicine, the optimized CO-rebreathing method (oCOR method; Gore et al, 2006; Prommer & Schmidt, 2007; Schmidt & Prommer, 2005) is used to determine the total haemoglobin mass (Hbmass). The oCOR method is well tolerated by young trained athletes and by older subjects and patients (Ahlgrim, Schumacher, Wrobel, Waller, & Pottgiesser, 2014; Otto et al, 2017; Wachsmuth et al, 2013). Prerequisites of the method are unrestricted diffusion of CO from the lung to the blood, the complete mixing of CO in the blood, and knowledge of the volumes of CO that have diffused out of the blood. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society
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