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Bacterial Colonization in Humidifying Cascade Reservoirs After 24 and 48 Hours of Continuous Mechanical Ventilation

Published online by Cambridge University Press:  02 January 2015

Theresa A. Goularte ,
Marie Manning  and
Donald E. Craven
Theresa A. Goularte
Affiliation:
Department of Medicine, Boston University School of Medicine, Division of Infectious Diseases, Boston City Hospital, Boston, Massachusetts
Marie Manning
Affiliation:
Department of Medicine, Boston University School of Medicine, Division of Infectious Diseases, Boston City Hospital, Boston, Massachusetts
Donald E. Craven*
Affiliation:
Department of Medicine, Boston University School of Medicine, Division of Infectious Diseases, Boston City Hospital, Boston, Massachusetts
*
Hospital Epidemiology Section, Maxwell Finland Laboratory for Infectious Diseases, Boston City Hospital, Boston, MA 02118
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Abstract

We evaluated levels of bacterial colonization in the humidifying cascade reservoirs of 466 mechanical ventilators; 326 reservoirs were cultured after 24 hours and 140 were cultured after 48 hours of continuous mechanical ventilation. Bacterial colonization was absent in 284 (87.1%) of the humidifier reservoirs sampled at 24 hours and 125 (89.3%) of the reservoirs cultured at 48 hours. Levels of bacterial colonization in the remaining humidifiers were low (<100 organisms/mL). The median temperature recorded in the reservoir fluid of 30 different ventilators was 50°C (range 40° to 60°C). In vitro seeding of reservoir fluid at 50°C with 106 organisms/mL of four different species of nosocomial gram-negative bacilli and Staphylococcus aureus demonstrated rapid killing of all five strains over a 6-hour incubation period, and no significant bacterial aerosols were detected. Rates and levels of bacteria in heated humidifier reservoirs are low and nosocomial pathogens survive poorly at the median reservoir temperature of 50°C. We conclude that the heated humidifier reservoir on a mechanical ventilator is an unlikely source of colonization or bacterial aerosols, and therefore it can be changed every 48 hours with the ventilator tubing.

Type
Original Articles
Information
Infection Control & Hospital Epidemiology , Volume 8 , Issue 5 , May 1987 , pp. 200 - 203
Copyright
Copyright © The Society for Healthcare Epidemiology of America 1987

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