An infant circuit with a water vaporizer warmed by carbon dioxide neutralization

A pediatric anesthesia system was constructed by connecting the machine end of a modified Mapleson D system to a soda lime canister containing a water vaporizer heated through the reaction of neutralization of the lime by the CO2 emerging from the breathing tube. The vaporizer was placed in line with the fresh-gas delivery tube of the circuit. The humidity output of the system varied from 15 +/- 1 mg H2O/L with a CO2 output of 15 ml/L to 27 +/- 1.5 mg H2O/L with a CO2 output of 60 ml/min. Rebreathing of CO2 was within acceptable limits as long as fresh-gas inflow remained at 5 L/min. The system compares favorably in respect to its humidity output with all other circuits availabe on the market for pediatric anesthesia.