Background: Respiratory pathogens that pass through the
anesthesia breathing system potentially can infect other patients. This
study was designed to determine if bacteria can pass through
contemporary anesthesia breathing systems and if the environment within
the machine is hostile to these organisms.
Staphylococcus aureus, Pseudomonas aeruginosa, and
Mycobacterium tuberculosis were nebulized into the
expiratory limb of an anesthesia breathing circuit and collected from
the inspiratory and expiratory limbs in an impinger 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
nebulization. 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 following the
nebulization period, large numbers of microorganisms
(1 × 103 to 1 × 105, around 100% of the
nebulized organisms) were collected from the inspiratory gas. Soda lime
itself was not bactericidal for any of the organisms tested, but
solutions of this material with a pH of 12 were bactericidal.
Conclusion: Cross contamination between patients may occur
unless the gas flow through the anesthesia breathing system is
interrupted for > 1 h.
Abbreviations: BHI = brain-heart infusion;
MHA = Mueller-Hinton agar; PBS = phosphate-buffered saline
solution; TB = tuberculosis