Following an outbreak of hepatitis C in surgical patients in Australia
, it has been suggested that transmission can take place as a result o
f contaminated anaesthetic circuits. It has therefore been recommended
that filters should be placed between patients and breathing systems
with a new filter being used for each patient. Although nosocomial pne
umonia is a major manifestation of hospital-acquired infection, it is
unclear whether contamination of ventilator circuits is implicated in
the aetiology of this condition. Some data suggest that bacteria canno
t survive well in anaesthetic circuits and several studies have failed
to demonstrate significant contamination of circuits in clinical situ
ation. Several outbreaks of pneumonia related to contaminated anaesthe
tic equipment have been described, but many of these were controlled b
y appropriate decontamination of the respiratory equipment. Although v
entilator filters are used by the majority of intensive care units and
filters do have the ability to filter bacteria and viruses, there are
few data suggesting that the use of filters reduce the rate of pulmon
ary infections in long-term ventilated patients. Furthermore, to chang
e filters between operations would have significant financial implicat
ions, and there is no conclusive evidence that they would reduce cross
infection. Until more data are available on the role of filters in bo
th long-term ventilated patients and operations, standard hygienic mea
sures such as appropriate disinfection protocols are still the most ef
fective way of reducing ventilator-associated infections.