The benefit of using a heat and moisture exchanger during short operations in young children

We studied the efficiency of a heat and moisture exchanging filter (HMEF; Pall BB25) as a means of compensating for the heat and moisture loss during anaesthesia in young children using cold and dry gas supplied from open circuits. Forty ASA I children (mean age: 48 months +/- 20; mean weight: 16 +/- 3.5 kg) were randomized into two groups: Group I without HMEF/Group II with HMEF. The two groups did not show any significant differences for morphometric data or ventilation parameters. Relative humidity and temperature measurements in anaesthetic gases were taken using a combined temperature/humidity probe introduced into the circuit. Absolute humidity in the circuit was calculated from these measurements. In Group II, a significant increase (P < 0.001) in absolute humidity was demonstrated (Group I: 12 mg H2O.1(-1) vs Group II: 22 mg H2O.1(-1). This increase appeared immediately after introduction of the HMEF in the circuit and remained constant throughout the duration of the operation. Thus, the use of the device is recommended for young children, even for operations of short duration.