Background
Forced-air warming (FAW) is widely used to prevent hypothermia during surgical procedures.
The airflow from these blowers is often vented near the operative site and should
be free of contaminants to minimize the risk of surgical site infection. Popular FAW
blowers contain a 0.2-μm rated intake filter to reduce these risks. However, there
is little evidence that the efficiency of the intake filter is adequate to prevent
airborne contamination emissions or protect the internal air path from microbial contamination
buildup.
Methods
Five new intake filters were obtained directly from the manufacturer (Bair Hugger
505, model 200708D; Arizant Healthcare, Eden Prairie, MN), and 5 model 200708C filters
currently in hospital use were removed from FAW devices. The retention efficiency
of these filters was assessed using a monodisperse sodium chloride aerosol. In the
same hospitals, internal air path surface swabs and hose outlet particle counts were
performed on 52 forced-air warming devices (all with the model 200708C filter) to
assess internal microbial buildup and airborne contamination emissions.
Results
Intake filter retention efficiency at 0.2 μm was 93.8% for the 200708C filter and
61.3% at for the 200708D filter. The 200708D filter obtained directly from the manufacturer
has a thinner filtration media than the 200708C filter in current hospital use, suggesting
that the observed differences in retention efficiency were due to design changes.
Fifty-eight percent of the FAW blowers evaluated were internally generating and emitting
airborne contaminants, with microorganisms detected on the internal air path surfaces
of 92.3% of these blowers. Isolates of Staphylococcus aureus, coagulase-negative Staphylococcus, and methicillin-resistant S aureus were detected in 13.5%, 3.9%, and 1.9% of FAW blowers, respectively.
Conclusion
The design of popular FAW devices using the 200708C filter was found to be inadequate
for preventing the internal buildup and emission of microbial contaminants into the
operating room. Substandard intake filtration allowed airborne contaminants (both
viable and nonviable) to penetrate the intake filter and reversibly attach to the
internal surfaces within the FAW blowers. The reintroduction of these contaminants
into the FAW blower air stream was detected and could contribute to the risk of cross-infection.
Given the deficiencies identified with the 200708C intake filter, the introduction
of a new filter (model 200708D) with substantially lower retention efficiency is of
concern.
Key Words
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Article info
Publication history
Published online: November 22, 2010
Footnotes
Conflict of interest: David Leaper chaired the NICE guideline on SSI prevention and treatment, is a member of the Antimicrobial Resistance and Healthcare Associated Infection advisory committee in the UK, and has served as a consultant/paid lecturer to several healthcare companies in relation to SSI. Mark Albrecht is a researcher funded by Augustine Biomedical + Design. None of the other authors have any conflicts of interest to report.
Identification
Copyright
© 2011 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.
