Contaminated medication nebulizers in mechanical ventilator circuits. Source of bacterial aerosols

Am J Med. 1984 Nov;77(5):834-8. doi: 10.1016/0002-9343(84)90520-5.


The contamination rates of medication nebulizers inserted into mechanical ventilator circuits were studied. Semiquantitative techniques were used to sample the reservoir fluid from in-line nebulizers during the first 24 hours after a circuit change. In the initial survey, high levels of contamination (organism concentrations above 10(3)/ml) were present in 13 (68 percent) of the 19 nebulizer reservoirs, and bacterial aerosols were produced by 10 (71 percent) of 14 nebulizers. Gram-negative bacilli were the predominant organisms isolated. Nebulizer contamination originated primarily from reflux of contaminated condensate in the ventilator circuit. When nebulizers were cleaned after each treatment, a reduced rate of contamination was found. Small bacterial aerosols (less than 3 microns in size) were produced in vitro after inoculation of nebulizers with gram-negative bacilli in concentrations isolated from in-use nebulizers. Contaminated in-line medication nebulizers generate small-particle bacterial aerosols that may increase the risk of ventilator-associated pneumonia and therefore should be cleaned or disinfected after each treatment rather than every 24 hours.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerosols
  • Bacterial Infections / etiology*
  • Drug Therapy / instrumentation
  • Humans
  • Respiration, Artificial / adverse effects
  • Respiration, Artificial / instrumentation*


  • Aerosols