Carbon monoxide inhalation to increase haemoglobin mass: a canary in a coal mine for sport?

Abstract

The desire to enhance athletic performance drives research into potential ergogenic aids. Carbon monoxide (CO) is a colourless, odourless and poisonous gas that is difficult to detect, making it known as the ‘silent killer’.1 Despite its toxicity, CO has found varied applications in medicine and sport.2–9 Although CO can serve as a tool for monitoring performance gains through the measurement of haemoglobin mass (Hbmass),8 9 research surrounding its potential use as an ergogenic aid has raised ethical concerns.1 This editorial describes the legitimate applications of CO in sports and ways it may be exploited as an ergogenic aid to enhance athletic performance. At the turn of the 20th century, pioneering research by John Haldane revealed that CO binds to haemoglobin with greater affinity than oxygen, forming carboxyhaemoglobin (COHb), limiting the oxygen-carrying capacity of the blood and leading to anaemic hypoxia.2 This finding stemmed from Haldane’s earlier research on miners that led to his idea of using canaries in coal mines. These birds, more sensitive to CO, were used as early warning signs to detect toxic gas levels, alerting miners to evacuate before CO concentrations became lethal. The toxic effects of CO are proportional to COHb concentrations, with moderate adverse effects (eg, fatigue, headache, nausea) typically presenting with COHb >10–20% and progressing in severity to heart failure, coma and death as COHb concentrations increase.2 These fundamental discoveries, coupled with advances in respiratory physiology and gas analysis techniques, laid the foundation for the applications discussed herein. One of the most significant advancements was the development of the CO rebreathing …