Chronic Exposure to Low-Dose Carbon Monoxide Alters Hemoglobin Mass and V˙O2max

• Published in: Medicine and science in sports and exercise 2020-09, Vol.52 (9), p.1879-1887
• Main Authors: SCHMIDT, WALTER F. J., HOFFMEISTER, TORBEN, HAUPT, SANDRA, SCHWENKE, DIRK, WACHSMUTH, NADINE B., BYRNES, WILLIAM C.
• Format: Article
• Language: English
• Subjects: Adult; Altitude; Carbon Monoxide - administration & dosage; Erythrocyte Volume - drug effects; Erythropoietin - metabolism; Ferritins - blood; Ferritins - drug effects; Hematocrit; Hemoglobins - drug effects; Hemoglobins - metabolism; Humans; Inhalation Exposure; Male; Oxygen Consumption - drug effects; Physical Conditioning, Human - physiology; Single-Blind Method; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000002330

By blocking the oxygen binding sites on the hemoglobin molecule, chronic low-dose carbon monoxide (CO) administration may produce similar effects to those of exposure to altitude. PURPOSEThis study aimed to determine the effect of chronic low-dose CO application on hemoglobin mass (Hbmass) and V˙O2max. METHODSFor 3 wk, 11 healthy and moderately trained male subjects inhaled a CO bolus five times per day to increase their HbCO concentration by ~5%. Another 11 subjects received a placebo. Hbmass, serum erythropoietin concentration, ferritin, and basic hematological parameters were determined before and weekly during and until 3 wk after the CO inhalation period. V˙O2max tests on a cycle ergometer were performed before and after the CO administration period. RESULTSIn the CO group, Hbmass increased from 919 ± 69 to 962 ± 78 g in week 3 (P < 0.001) and was maintained for the following 3 wk. Reticulocytes (%) and immature reticulocyte fraction significantly increased after 1 wk. Serum erythropoietin concentration tended to increase after 1 wk (P = 0.07) and was suppressed in the postperiod (P < 0.01). Ferritin decreased during the inhalation period (from 106 ± 37 to 72 ± 37 ng·mL, P < 0.001). V˙O2max tended to increase from 4230 ± 280 to 4350 ± 350 mL·min (P < 0.1) immediately after the inhalation period and showed a significant relationship to the change in Hbmass (y = 4.1x − 73.4, r = 0.70, P < 0.001). CONCLUSIONSChronic continuous exposure to low-dose CO enhances erythropoietic processes resulting in a 4.8% increase in Hbmass. The individual changes in Hbmass were correlated to the corresponding changes in V˙O2max. Examination of ethical and safety concerns is warranted before the implementation of low-dose CO inhalation in the clinical/athletic setting as a tool for modifying Hbmass.