Ten Days of Intermittent, Low-dose Carbon Monoxide Inhalation does not Significantly Alter Hemoglobin Mass, Aerobic...

Area of Science:

• Exercise Physiology
• Human Physiology
• Biomedical Science

Background:

• Carbon monoxide (CO) rebreathing is a standard method for assessing hemoglobin mass (Hbmass).
• Emerging research indicates CO may function as a physiological signaling molecule.
• Potential signaling roles of CO raise questions about its use in repeated Hbmass measurements.

Purpose of the Study:

• To investigate the physiological effects of intermittent, low-dose CO inhalation over 10 days.
• To determine if CO exposure alters hemoglobin mass (Hbmass).
• To assess changes in aerobic performance predictors and exercise tolerance following CO exposure.

Main Methods:

• A randomized, single-blind, placebo-controlled trial involving 18 recreationally active men.
• Participants inhaled either a low-dose CO bolus (1.2 ml kg(-1) for 30s) or placebo (room air) daily for 10 days.
• Hemoglobin mass, aerobic capacity, and exercise tolerance were measured before and after the intervention, with testing >16 hours post-exposure to avoid acute effects.

Main Results:

• CO inhalation successfully elevated carboxyhemoglobin levels by approximately 4.4% after each exposure.
• No significant differences were observed between the CO and placebo groups in Hbmass (p=0.99).
• Key performance indicators including peak oxygen uptake (p=0.59), peak power output (p=0.10), and exercise tolerance (p=0.60) remained unchanged.

Conclusions:

• Chronic, low-dose CO inhalation does not appear to significantly alter Hbmass or key physiological markers of aerobic performance.
• These findings support the validity of using CO rebreathing for serial Hbmass measurements within a 12-day timeframe.
• The study suggests that the potential signaling effects of CO do not interfere with Hbmass assessment or exercise capacity in this context.