Low-Dose CO₂ Inhalation to Improve Oxygenation and Exercise Capacity at High Altitude: A Double-Blind Pilot Study.

Area of Science:

• Physiology
• Altitude Medicine
• Respiratory Science

Background:

• High altitude exposure causes hypoxia and hypocapnia, impairing exercise performance.
• Carbon dioxide (CO2) inhalation may counteract these effects by increasing respiratory drive.
• A novel device was developed to deliver precise CO2 concentrations with minimal dead space and resistance.

Purpose of the Study:

• To investigate the effects of 2.5% CO2 inhalation on blood gases and exercise performance at high altitude.
• To evaluate a novel CO2 delivery device in a simulated high-altitude environment.

Main Methods:

• Twenty-eight healthy lowlanders were transported to 4505m in Tibet.
• A randomized, double-blind study compared ambient air inhalation with 2.5% CO2 inhalation.
• Arterial blood gases and endurance shuttle walk test (ESWT) were assessed.

Main Results:

• CO2 inhalation significantly increased partial pressure of carbon dioxide (PaCO2) and oxygen (PaO2) compared to ambient air (p < 0.001).
• Heart rate was lower during CO2 inhalation, with no significant changes in pH or respiratory rate.
• ESWT distance was significantly greater with CO2 inhalation (p < 0.001).

Conclusions:

• Inhalation of 2.5% CO2 effectively increases oxygenation (PaO2) at 4505m.
• CO2 inhalation enhances exercise performance at high altitude.
• The novel device successfully delivered CO2 for potential altitude acclimatization benefits.