A NOVEL METHOD OF EVALUATION OF 3 HEAT-MOISTURE EXCHANGERS IN 6 DIFFERENT VENTILATOR SETTINGS

Objective: The purpose of this study was to assess and compare the hum idification, heating, and resistance properties of three commercially available heat-moisture exchangers (HMEs). To mimic clinical condition s, a previously validated, new realistic experimental setup and measur ement protocol was used. Design: Prospective, comparative experimental study. Setting: Surgical Intensive Care Unit, University Hospital of Rotterdam. Materials: An experimental set-up consisting of a patient m odel, measurement systems, and ventilator and three different HME type s. Interventions: The air flow, pressure in the ventilation circuit, p ressure difference over the HME, and partial water vapour pressure and temperature at each side of the HMEs were measured. Measurements were repeated every 30 min during the first 2 h and every hour up to 24 h for each HME at six different ventilator settings. The mean inspirator y and maximum expiratory resistance, flow-weighted mean absolute humid ity and temperature outputs, and humidification and heating efficienci es of HMEs were calculated. Measurements and results. The DarHygroster had the highest humidity output, temperature output, humidification e fficiency, and heating efficiency values throughout the study (32.8 +/ - 21. mg/l, 32.2 +/- 0.8 degrees C, 86.3 +/- 2.3 %, and 0.9 +/- 0.01%, respectively) in comparison to the Humid-Vent Filter (25.3 +/- 3.2 mg /l, 31.9 +/- 0.8 degrees C, 72.2 +/- 5.3 % 0.9 +/- 0.02 %, respectivel y) and the Pall Ultipor BB100 breathing circuit filter (23.4 +/- 3 mg/ l, 25.3 +/- 0.7 degrees C, 68.8 +/- 5.9 %, 0.8 +/- 0.02%, respectively ). The inspiratory and expiratory resistance of the HMEs remained belo w clinically acceptable maximum values (2.60 +/- 0.04 and 2.45 +/- 0.0 5 cmH(2)O/l per s, respectively). Conclusion: The Dar Hygroster filter was found to have the highest humidity and temperature output of all three HMEs, the Humid-Vent filter had a satisfactory humidity output o nly at low tidal volume flow rate and minute volume settings, whereas the Pall Ultipore BE 100 never achieved a sufficient humidity and temp erature output.