The potential for dissemination of Mycobacterium tuberculosis through the anesthesia breathing circuit

Background: Respiratory pathogens that pass through the anesthesia breathin g system potentially can infect other patients. This study was designed to determine if bacteria can pass through contemporary anesthesia breathing sy stems and if the environment within the machine is hostile to these organis ms. Methods: Staphylococcus aureus, Pseudomonas aeruginosa, and Mycobacterium t uberculosis were nebulized into the expiratory limb of an anesthesia breath ing circuit and collected from the inspiratory and expiratory limbs in an i mpinger system that provided a quantitative determination of the number of organisms entering the circuit and the number that would reach the patient in the inspiratory gas. Bacteria were collected before, during, and after n ebulization, A second experiment determined if a saturated solution of soda lime was bactericidal. Results: When the gas flow through the circuit was interrupted for <1 h fol lowing the nebulization period, large numbers of microorganisms (1 x 10(3) to 1 x 10(5), around 100% of the nebulized organisms) were collected from t he inspiratory gas. Soda lime itself was not bactericidal for any of the or ganisms tested, but solutions of this material with a pH of 12 were bacteri cidal. Conclusion: Cross contamination between patients may occur unless the gas f low through the anesthesia breathing system is interrupted for > 1 h.