Description:
Fourteen male subjects were mechanically hyperventilated by intermittent positive pressure breathing. Tidal volume and respiratory frequency were increased approximately three times and one and one-half times control, respectively. Breath-by-breath analyses of CO2 output indicate a loss of approximately 2.5 liters of CO2 from the body stores in 12 min. Only one-third of that volume was restored during the ensuing 12-min recovery period, mostly as a result of hypoventilation rather than apnea. Over the entire recovery period, the volume of CO2 regained by the blood store approximated 75% of the CO2 content lost during hyperventilation. Under the conditions of these experiments, tissues regained less than 20% of the depleted CO2 store. CO2 retention patterns may be more effective than arterial blood or alveolar air analyses in determining a return to a steady state when tissue stores have been considerably reduced. Submitted on August 24, 1961