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In patients with a known infectious disease,
many laboratories prefer to measure ventilatory function
using a pneumotachograph or other electronic sensor, as
these can be more easily cleaned and sterilised than
conventional bellows or water-sealed spirometers.
Although the transmission of respiratory pathogens (e.g.
Mycobacterium avium, M. tuberculosis and
aspergillus species) via spirometers has not been fully
established, the potential risks are difficult to disprove.
During spirometry patients can generate flows up to 14 L/sec
(840 L/min) which can easily mobilise saliva and create
dense macro- and micro-aerosols by entrainment of the fluid
lining the mucous membranes. These can then be deposited in
the equipment. Unless such deposition is prevented or the
equipment is rigorously cleaned and decontaminated, the
chance of cross-infection exists.
Mouthpieces must be disposed of or cleaned and
disinfected between patients because the greatest danger of
cross-infection is via direct contact with bodily fluids.
Since it is usually impractical to effectively decontaminate
the interior surfaces of a spirometer between patients, most
lung function laboratories clean and disinfect their
equipment periodically (weekly or monthly) or use a
disposable, low-resistance micro-aerosol filter inserted
between the subject and spirometer to prevent contamination.
Filters also have the advantage of protecting sensors and
the internal surfaces of the spirometer from damage and
reduce the corroding effects of cleaning agents and
disinfectants. The extent to which the use of filters can
effectively obviate the need for cleaning and disinfection
is unclear. The cost of filters may be offset by reduced
cleaning and disinfection costs. Other laboratories use
disposable mouthpieces containing a one-way valve to prevent
inspiration from equipment, but this is only possible when
performing solely expiratory spirometry. However, their
effectiveness at reducing the risk of cross-infection does
not appear to have been studied.
If disassembling the spirometer for cleaning, it is
essential to:
-
thoroughly dry the components before
reassembling
-
check the spirometer for correct
operation
-
adjust the calibration, if necessary.
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