Determination of airway humidification in high-frequency oscillatory ventilation using an artificial neonatal lung model - Comparison of a heated humidifier and a heat and moisture exchanger

Objective:Thus far only few data are available on airway humidification dur ing high-frequency oscillatory ventilation (HFOV). Therefore, we studied th e performance and efficiency of a heated humidifier (HH) and a heat and moi sture exchanger (HME) in HFOV using an artificial lung model. Methods: Experiments were performed with a pediatric high-frequency oscilla tory ventilator. The artificial lung contained a sponge saturated with wate r to simulate evaporation and was placed in an incubator heated to 37 degre es C to prevent condensation. The airway humidity was measured using a capa citive humidity sensor. The water loss of the lung model was determined gra vimetrically. Results: The water loss of the lung model varied between 2.14 and 3.1 g/h d uring active humidification; it was 2.85 g/h with passive humidification an d 7.56 g/h without humidification. The humidity at the tube connector varie d between 34.2 and 42.5 mg/l, depending on the temperature of the HH and th e ventilator setting during active humidification, and between 37 and 39.9 mg/l with passive humidification. Conclusion: In general, HH and HME are suitable devices for airway humidifi cation in HFOV. The performance of the ventilator was not significantly inf luenced by the mode of humidification. However, the adequacy of humidificat ion and safety of the HME remains to be demonstrated in clinical practice.