COMPARING 2 HEAT AND MOISTURE EXCHANGERS, ONE HYDROPHOBIC AND ONE HYGROSCOPIC, ON HUMIDIFYING EFFICACY AND THE RATE OF NOSOCOMIAL PNEUMONIA

Objective: Many heat and moisture exchangers with filter (HMEF) have b een developed. In-house data from companies provide some information a bout their performances; unfortunately, to our knowledge, no comparati ve evaluation in clinical conditions has been undertaken of these newe r products. The aim of this study was to compare the efficiency of two HMEFs, one hydrophobic and one hygroscopic, on humidifying capacity a nd the rate of bronchial colonization and ventilator-associated pneumo nia in ICU patients. Design: Prospective, randomized study. Setting: I CU of a university hospital. Patients: All patients who required mecha nical ventilation for greater than or equal to 24 h during the study p eriod. Interventions: On admission to the ICU, patients were randomly assigned to one of two groups. In one group, the patients were ventila ted with a hygroscopic;device (Humid-Vent Filter Light HMEF; Gibeck; U pplands Vaesby, Sweden). The condensation surface was made of paper (M icrowell) impregnated with CaCl2. The filter membrane was made of poly propylene. In the other group, the patients were ventilated with a hyd rophobic device (Pall BB100 HMEF). The condensation surface was made o f a hydrophobic resin with a hydrophylic layer. The filter membrane wa s made of ceramic fibers. In both groups, HMEFs were changed daily. Me asurements and results: Both groups of patients were similar for the t ested characteristics, including parameters of mechanical ventilation. Sixty-six patients were ventilated for 11.7 +/- 11 days with the Humi d-Vent Filter Light HMEF and 70 patients for 12.2 +/- 12 days with the Pall BE 100. Patients ventilated with the Humid-Vent Filter Light und erwent 6.0 +/- 3.0 tracheal aspirations and 1.7 +/- 2.0 instillations per day, and those with the Pall BE 100, 6.0 +/- 3.0 and 1.6 +/- 2.0 p er day, respectively (not significant [NS]). Abundance of tracheal sec retions, presence of blood, and viscosity, evaluated by semiquantitati ve scales, were similar in both groups. No difference in the rate of a telectasis was observed between the two groups (7.5% and 7.1%, NS). On e episode of tracheal tube occlusion was observed with the Humid-Vent Filter Light HMEF, and one with the other HMEF (NS). One patient in ea ch group (NS) was switched to an active heated humidifier because of v ery tenacious bronchial secretions despite repeated instillations. Tra cheal colonization was observed at a rate of 67% with the Humid-Vent F ilter Light and 58% with the Pall BE 100 (NS). A small, but NS differe nce was observed in the rate of ventilator-associated pneumonia: Humid -Vent Filter Light, 32% (27.1 per 1000 ventilator days); and Pall BE 1 00, 37% (30.4 per 1000 ventilator days). Bacteria responsible for trac heal colonization and pneumonia were similar in both groups. Three pat ients in each group;died from their nosocomial pneumonia. Conclusion: Despite differences in their components, the two HMEFs tested achieved similar performances in terms of humidification and heating of inspir ed gases. Only one episode of endotracheal tube occlusion was detected and very few patients (one in each group) had to be switched to an ac tive heated humidifier. No difference was observed either in the rate of tracheal colonization or of ventilator-associated pneumonia. These data show that the hygroscopic HME (Humid-Vent Filter Light) and the h ydrophobic HME (Pall BE 100) are suited for use in ICU patients.