Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>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.</jats:p>
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<jats:title>Purpose</jats:title>
<jats:p>This study aimed to determine the effect of chronic low-dose CO application on hemoglobin mass (Hbmass) and V˙O<jats:sub>2max</jats:sub>.</jats:p>
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<jats:title>Methods</jats:title>
<jats:p>For 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˙O<jats:sub>2max</jats:sub> tests on a cycle ergometer were performed before and after the CO administration period.</jats:p>
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<jats:title>Results</jats:title>
<jats:p>In the CO group, Hbmass increased from 919 ± 69 to 962 ± 78 g in week 3 (<jats:italic toggle="yes">P</jats:italic> < 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 (<jats:italic toggle="yes">P</jats:italic> = 0.07) and was suppressed in the postperiod (<jats:italic toggle="yes">P</jats:italic> < 0.01). Ferritin decreased during the inhalation period (from 106 ± 37 to 72 ± 37 ng·mL<jats:sup>−1</jats:sup>, <jats:italic toggle="yes">P</jats:italic> < 0.001). V˙O<jats:sub>2max</jats:sub> tended to increase from 4230 ± 280 to 4350 ± 350 mL·min<jats:sup>−1</jats:sup> (<jats:italic toggle="yes">P</jats:italic> < 0.1) immediately after the inhalation period and showed a significant relationship to the change in Hbmass (<jats:italic toggle="yes">y</jats:italic> = 4.1<jats:italic toggle="yes">x</jats:italic> − 73.4, <jats:italic toggle="yes">r</jats:italic> = 0.70, <jats:italic toggle="yes">P</jats:italic> < 0.001).</jats:p>
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<jats:title>Conclusions</jats:title>
<jats:p>Chronic 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˙O<jats:sub>2max</jats:sub>. 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.</jats:p>
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