Humidifiers for oxygen therapy: what risk for reusable and disposable devices?


INTRODUCTION. Nosocomial pneumonia accounts for the vast majority of hospital-acquired infections. Although numerous medical devices have been discussed to be potential vehicles of microorganisms, very little is known about the role played by oxygen humidifiers as potential sources of nosocomial pathogens. The purpose of this research was to analyze the rate of microbial contamination of reusable and disposable oxygen humidifiers used during therapy, and, thus, to speculate their potential role in the transmission of respiratory pathogens.

METHODS. Water samples from reusable and disposable oxygen humidifiers were gathered from different wards where nosocomial pneumonia has a higher incidence rate due to “critical” clinical conditions of inpatients. The samples were collected always after a period of 5 days from initial use for both the types of humidifiers. Samples were processed using standard bacteriological techniques and microbial colonies were identified using manual and automated methods.

RESULTS. High rates of microbial contamination were observed in samples from reusable oxygen humidifier employed in medical (83%), surgical (77%) and emergency (50%) areas. The most relevant pathogens were Pseudomonas aeruginosa, amongst Gram-negative bacteria, and Staphylococcus aureus, amongst Gram-positive bacteria. Other pathogens were detected in lower percentage. Disposable oxygen humidifier samples showed no contamination.

CONCLUSIONS. This research presents evidence of the high rate and type of microbial contamination of reusable humidifiers employed for oxygen therapy. These devices might thus be involved in the transmission of potential pathogens. For the purpose of preventing nosocomial pneumonia, it is advisable to substitute reusable oxygen humidifiers with safer disposable ones.


Isa Picerno

Margherita Ferrante