COMPARING 2 HEAT AND MOISTURE EXCHANGES WITH ONE VAPORIZING HUMIDIFIER IN PATIENTS WITH MINUTE VENTILATION GREATER-THAN-10 L MIN/

Study objective: To evaluate in patients submitted to minute ventilati on >10 L/min the ability to preserve patients' heat and humidity of tw o heat and moisture exchangers (HMEs) and one vaporizing humidifier (V H). Design: Prospective, randomized, comparative, nonblinded study. Se tting: Intensive care unit of a university hospital. Patients: Nine tr acheally intubated, mechanically ventilated patients, sedated and subm itted to mechanical ventilation with minute ventilation >10 L/min. Int erventions: Using the psychrometric method, relative humidity (RH) and absolute humidity (AH) of inspired gas were obtained as well as tempe rature of inspired gas and tracheal temperatures (maximal and minimal) . Following a randomized order, each patient was ventilated for two 24 -h periods with a vaporizing humidifier (Bennett Cascade 2, Bennett; F rance) and one of two HMEs: Pall Ultipor filter BB50 (Pall Biomedical; France) or DAR Hygroster filter (Peters; France). Both were first tes ted for a 45-min period and then the HME that achieved the best perfor mance in terms of temperature and water preservation was tested for 24 h. Measurements and results: During the 45-min test period, the Pall Ultipor HME achieved a lower performance than the other two systems fo r ally of the studied parameters (p<0.05 to p<0.0001). The DAR Hygrost er HME achieved lower temperature of inspired gas (29.9 vs 32.0 degree s C, p<0.005) and lower absolute humidity (29.3 vs 33.2 mg H2O/L, p<0. 005) than the Bennett Cascade 2. After 24 h of use,lower values of tem perature of inspired gas (28.5 vs 32.0 degrees C, p<0.002) and of AH ( 28.0 vs 33.6 mg H2O/L, p<0.001) were obtained with the DAR Hygroster H ME than with the Bennett Cascade 2. No differences were found between the two systems for the other tested parameters. At that time, no pati ents had RH lower than 97% and absolute humidity lower than 23 mg H2O/ L with the use of the DAR Hygroster HME. Conclusions: In patients with minute ventilation > 10 L/min, the DAR Hygroster HME showed a thermic and humidification capability similar to the reference system, the Be nnett Cascade 2 VH. In these patients, the Pall Ultipor HME had a sign ificantly lower capability.