Elwyn S. Brown

CARBON DIOXIDE HOMEOSTASIS DURING ANESTHESIA. IV. AN EVALUATION OF THE PARTIAL REBREATHING SYSTEM

SUMMARY Complete removal of carbon dioxide from the bag in the partial rebreathing system is not obtained by inflow rates equal to the patients minute ventilation. Inflow rates comparable to the minute ventilation as measured before rebreathing, resulted in inspired concentrations between 1.2 and 4.2 per cent, averaging 2.0 per cent. The degree of carbon dioxide rebreathing produced by this system was greater with ether anesthesia than with opiate depression. In all patients, use of the method evoked increase in ventilation. Inflow rates of 15 LPM are not sufficient to prevent accumulation of carbon dioxide in all patients, and the commonly used inflow rate of 10 LPM may result in concentrations above 4 per cent of inspired carbon dioxide in spite of excessive hyperventilation.