Objectives: to determine and compare the microbial retention efficiency of 3 types of heat and moisture exchange (HME) filters.
Design: randomised prospective study.
Setting: Intensive Care Unit at the Middlesex Hospital and the microbiology laboratory of the Department of Academic Microbiology, University College London Medical School.
Measurements and results: An aerosol challenge to each filter using a suspension containing. S. marcescens and the bacteriophage MS2. In total 45 filters of 3 types were tested, 15 previously unused and 30 that had been used in ventilator circuits of 30 patients. The 3 types of filter generally had microbial retention efficiencies of > 99.99% for both S. marcescens and the bacteriophage MS2.
Conclusion: The 3 types of HME filter were effective microbial filters and comparable in their microbial retention.