Adjustment of stores of carbon dioxide during voluntary hyperventilation.

Carbon dioxide is stored in the body in various forms, including carbonic acid, bicarbonate and carbamino compounds. The various stores of CO2 can be considered to be in the lung, blood, soft tissues and bone. In an adult human, these stores are thought to be in the order of 120 liters of CO2.’ It is common knowledge that hyperventilation will reduce the level of CO2 in the blood; however, only a small fraction of the total CO2 of the body is in the blood. Questions arise, then, as to how much CO can be eliminated by hyperventilation, from where does it come and in what manner does elimination proceed. Several studies have been made of exchanges of CO2 in animals and in man. In 1916, Liljestrand’ found within the first hour of hyperventilation by men that 0.8 to 1.0 liter of stored CO2 was eliminated for each 1 per cent decrease in alveolar concentration of CO2. Brocklehurst and Henderson,’ and Adolph and associates’ subsequently derived widely varying values for the CO2 capacity of the body. Several investigators have studied the CO2 stores of animals.’3’ From hyperventilation experiments on anesthetized dogs, Farhi and Rahn’ found that alveolar CO2 tension declined in an exponential manner and calculated that one half of the readily available stores of CO2 was eliminated in 4 minutes. The present study was undertaken to obtain additional information on the rate of elimination of CO2 during hyperventilation in man, which might contribute to an eventual better understanding of clinical conditions such as CO2 retention and narcosis.