The Effect of Intermittent Exposure to 3% C02 on Respiration

An investigation was conducted to determine whether intermittent exposure to 3% CO2 results in a saturation of the body with carbon dioxide and whether a compensation of the respiratory acidosis is induced by carbon dioxide inhalation. One healthy male subject was exposed for six days, 15 hours daily, to a CO2 concentration rising from 0 3% at normal oxygen concentrations of 20 21% O2. Average data of physiological measurements made (A) prior to and (B) at the end of the 15-hour exposure to CO2 concentration, rising linearly from 0 3% CO2 were PAC0 (A); 40.7 mm Hg; ' ATM (> 42 mm &An () mm Hg? An <> ' C02 ^2 2 mm Hg; V£(A): 6.28 L/m; VE (B). 12e09 L/m> Pi^ determined at the end of the nine-hour air breathing rose from the third day on to reach, at the fifth day, a peak higher than the corresponding value following 15 hours of CO2 inhalation. During the sixth day of intermittent exposure to CO2, Ar<o on air returned to control values. This finding indicates that after three days the nine-hour period of air breathing was insufficient to eliminate the CO2 accumulated during the 15-hour period of CO2 breathing. Ventilatory response to 5% CO2 was increased during intermittent exposure to CO2 and the slope of the CO2 tolerance curve was also increased.