Do the components of heat and moisture exchanger filters affect their humidifying efficacy and the incidence of nosocomial pneumonia?

Objectives: To compare the efficiency of two heat and moisture exchange fil ters (HMEFs) of different compositions of the humidifying capacity and the rate of bronchial colonization and ventilator-associated pneumonia in patie nts in the intensive care unit (ICU). Design: Prospective, randomized study. Setting: ICU of a university hospital. Patients: All patients who required mechanical ventilation for 24 hrs or mo re during the study period. Interventions: At admission to the ICU, patients were randomly assigned to one of two groups. In one group, the patients were ventilated with Humid Ve nt Filter Light HMEF. The condensation surface was made of paper impregnate d with CaCl2. The filter membrane was made of polypropylene. In the other g roup, the patients were Ventilated with the Clear ThermAl HMEF (Intersurgic al, France). The condensation surface was made of plastic foam impregnated with AlCl2. The filter membrane was made of two poly mer fibers (modacrylic and polypropylene). In both groups, HMEFs were changed daily. Measurements and Main Results: Seventy seven patients were ventilated for 1 9 +/- 7 days with the Humid-Vent Filter Light HMEF and 63 patients for 17 /- 6 days with the Clear ThermAl HMEF. Patients ventilated with the Humid-V ent Filter Light underwent 8.7 +/- 3.7 tracheal aspirations and 1.2 +/- 2.0 instillations per day and those with the Clear ThermAl, 8.2 +/- 3.9 and 1. 5 +/- 2.4 per day, respectively (NS). The abundance of tracheal secretions and the presence of blood and viscosity, as evaluated by semiquantitative s cales, were similar in both groups. One episode of tracheal tube occlusion was observed with the Humid-Vent Filter Light HMEF and none with the other HMEF (NS). Tracheal colonization was observed at a rate of 91% with the Hum id-Vent Filter Light and 97% with the Clear ThermAl (NS). The rate of venti lator-associated pneumonia was similar in both groups (35%). Bacteria respo nsible for tracheal colonization and pneumonia were similar in both groups. Conclusions: Despite differences in their components, the two HMEFs that we re tested achieved similar performances in terms of humidification and heat ing of inspired gases. Only one episode of endotracheal tube occlusion was detected, and very few patients (three in each group) had to be switched to an active heated humidifier. No difference was observed either in the rate of tracheal colonization or of ventilator-associated pneumonia. These data show that the Humid-Vent Filter Light and the Clear ThermAl HMEFs are suit ed for use with ICU patients.