Acute exposure to carbon monoxide inhalation and/or hot water immersion transiently increases erythropoietin in females but not in males

The use of acute carbon monoxide inhalation (COi) and hot water immersion (HWI) are of growing interest as interventions to stimulate erythropoietin (EPO) production. However, whether EPO production is further augmented when combining these stressors and whether there are sex differences in this response are poorly understood. Therefore, we measured circulating EPO concentration in response to acute COi and HWI independently and in combination and determined whether the responses were altered by sex. Participants completed three study visits—COi, HWI, and combined COi and HWI—separated by 1 week in a randomized, balanced, crossover design. Renal blood velocity was measured during all interventions, and carboxyhaemoglobin was measured during and after COi. Serum samples were analysed every hour for 6 h post‐intervention for EPO concentration. HWI decreased renal blood velocity (46.2 cm/s to 36.2 cm/s) (P