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Bubbling Humidifiers Produce Microaerosols Which Can Carry Bacteria

Published online by Cambridge University Press:  02 January 2015

Frank S. Rhame ,
Andrew Streifel ,
Carter McComb  and
Mike Boyle
Frank S. Rhame*
Affiliation:
Infection Control Program and Cardio-Respiratory Services, University of Minnesota Hospitals and Clinics, the Infectious Diseases Section, Department of Medicine, Department of Laboratory Medicine and Pathology, Epidemiology Division, School of Public Health, and Department of Anesthesiology, University of Minnesota School of Medicine, and the Department of Environmental Health and Safety, University of Minnesota
Andrew Streifel
Affiliation:
Infection Control Program and Cardio-Respiratory Services, University of Minnesota Hospitals and Clinics, the Infectious Diseases Section, Department of Medicine, Department of Laboratory Medicine and Pathology, Epidemiology Division, School of Public Health, and Department of Anesthesiology, University of Minnesota School of Medicine, and the Department of Environmental Health and Safety, University of Minnesota
Carter McComb
Affiliation:
Infection Control Program and Cardio-Respiratory Services, University of Minnesota Hospitals and Clinics, the Infectious Diseases Section, Department of Medicine, Department of Laboratory Medicine and Pathology, Epidemiology Division, School of Public Health, and Department of Anesthesiology, University of Minnesota School of Medicine, and the Department of Environmental Health and Safety, University of Minnesota
Mike Boyle
Affiliation:
Infection Control Program and Cardio-Respiratory Services, University of Minnesota Hospitals and Clinics, the Infectious Diseases Section, Department of Medicine, Department of Laboratory Medicine and Pathology, Epidemiology Division, School of Public Health, and Department of Anesthesiology, University of Minnesota School of Medicine, and the Department of Environmental Health and Safety, University of Minnesota
*
Box 421, Mayo Memorial Building, University of Minnesota Hospitals and Clinics, Minneapolis, MN 55455
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Abstract

It is widely held that bubbling humidifiers do not produce microaerosols, although prior studies have resulted in conflicting evidence. We have studied this phenomenon in a clean room using an airborne particle counter and samplers for airborne bacteria. At gas flow rates between 10 and 80 L/min, a Cascade 1 humidifier produced between 460 and 999 water droplets/L humidified gas. Total water volume aerosolized was approximately 10-8 ml/L humidified gas. Seventy-three percent of the particles had diameters between 1 and 5 microns. With the reservoir containing 6.4 × 106P. aeruginosa/ml, it produced between 2 and 9 P. aeruginosa/Lhumidified gas. Most of the bacteria were in particles of a size likely to be deposited in the lung. This bacterial carryover was between 20 and 150 times the amount predicted by multiplication of the water volume aerosolized times the concentration of bacteria in the humidifier reservoir. An Air Life humidifier produced fewer particles which were also of a size likely to be deposited in the lung and, when the reservoir contained P. aeruginosa, it aerosolized bacteria. Wick-type humidifiers did not produce detectable aerosol or bacterial carry-over. Although the clinical significance of these findings has not been established, they provide a rationale for the CDC recommendations for procedures designed to keep bubbling humidifier reservoir water uncontaminated.

Type
Original Articles
Information
Infection Control & Hospital Epidemiology , Volume 7 , Issue 8 , August 1986 , pp. 403 - 407
Copyright
Copyright © The Society for Healthcare Epidemiology of America 1986

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