Advantages of a new humidification technique

Recently, an active HME (AHME) (Humid-Heat, Gibeck) has been developed. The AHME combines a HME with a unit which adds humidity and heat to the patient-side of the HME. The supply of humidity and heat is automatically regulated, in order to achieve 100% humidity of inspired gases at 37°C. The operation of AHME requires only the user-set input of the patient minute ventilation. We evaluated the potential advantages of the AHME over a conventional active humidifier.

Methods

The study included seven mechanically ventilated patients. In each patient, the AHME was used for 24 h and then substituted with a conventional active humidifier (F&P) (MR730, Fisher & Paykel) with a heated wire in the inspiratory limb, for the next 24 h. AHME was preset to keep the temperature of inspired gases at 37°C. The F&P was set to 37°C in the humidifier-chamber, and to 37°C at the Y piece. The AHME and the F&P were compared in terms of: humidity and temperature output, water consumption and condensate in the water traps. The humidity output was evaluated on the basis of the condensate in the flex tube, which was scored from 0 (absent) to 3 (excessive).

Results

Minute ventilation did not differ during application of AHME and of F&P. Both devices kept the set temperatures, and provided adequate humidification, as assessed by the condensate in the flex tube. However, when the F&P was used, there was formation of condensate in the ventilator tubings, and the water traps needed to be emptied on average eight times (range: 6–9) per day. No condensation of water was found in the ventilator tubings with AHME. Compared with F&P, the AHME remarkably reduced the water usage.

Conclusion

Compared to a conventional active humidifier, the AHME provides equivalent humidification, with the advantages of both reducing the time-expenditure for handling, and of eliminating the risk caused by water condensation in the ventilator tubings.

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