A circle system with a rotating wick vaporizer.

The humidity output of a circle system was raised to 28 mg H2O/l by the use of a modified rotating wick vaporizer placed in the center of the soda lime canister and coaxial inspiratory and expiratory limbs. Both the fresh gas inflow and the expired gases passed through the lime and reached a compartment below it. The bag/ventilator connector, bearing a pressure relief valve, opened on the lateral wall of that compartment. Gases returning to the inspiratory valve passed: (1) through a tube in the canister connecting the inferior compartment to the vaporizer above water level, (2) through the upper portion of the vaporizer and around the rotating wick, and (3) through a tube emerging from the top of the vaporizer to reach the inspiratory valve. Thus inspired gases were humidified by the rotating wick constantly replenishing its water content warmed by the reaction of neutralization. The use of coaxial inspiratory and expiratory limbs reduced water condensation outside the canister.