Effect of carbon dioxide in acute mountain sickness: a rediscovery.

The effect of adding CO2 to inhaled air in six subjects with acute mountain sickness was investigated during a medical expedition to 5400 m.3% CO2 in ambient air increased ventilation and resulted in a rise in PaO2 of between 24% and 40%. There was a 9-28% increase in PaCO2 and a reduction of the respiratory alkalosis normally seen at high altitude. Symptoms of acute mountain sickness were rapidly relieved. In three subjects cerebral blood flow increased by 17-39%, so that oxygen delivery to the brain would have been considerably improved. This study confirms earlier suggestions of the beneficial effect of CO2 inhalation at high altitude.