Disposable humidifiers in a recovery room--a microbiological evaluation

Humidification, unlike nebulization, does not produce water droplets in the process of producing desiccated gases, and therefore is considered low risk in terms of potential infection sources. However, direct inoculation of bacteria into these units has been shown to produce contaminated effluents. Therefore, the present study was designed to determine if the airborne route of contamination was a potential source of bacterial inoculum for these units and to determine the maximum number of days units remained free of bacterial contamination. Disposable humidifiers were placed in both high and low volume patient areas of the recovery room. Units were used on multiple patients with only the cannula replaced between patients. Our results showed that these units do have the potential for becoming inoculated through the airborne route, but did not produce contaminated effluents greater than background air. Units remained sterile during the entire time in use in both high and low volume areas. In conclusion, our data suggests that each institution should evaluate the usage of disposable humidifiers based on patient parameters and environment rather than manufacturer's guidelines.