Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Patent
1988-09-07
1990-02-20
Richman, Barry S.
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
422 57, 422 61, 422 86, 422 87, 422 88, 422158, 436 1, 435 31, 206438, 206439, G01N 3100
Patent
active
049024787
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a device for testing the efficiency of autoclaves such as those used in hospitals for sterilizing porous loads, and for detecting the presence of air in such a system, and is particularly concerned with an indicator sheet for use in such a device, which provides a visual indication of the presence of air and/or other substances under steam sterilizing conditions.
Porous loads are sterilized by subjecting them to saturated steam at a temperature of between 134.degree. C. and 138.degree. C. for a period of not less than 3 minutes. In order to ensure correct sterilizing conditions, the steam must penetrate unhindered to all parts of the load. This can be achieved only if all of the air is first removed from the sterilizer vessel and from its load, which is accomplished typically by a process of evacuation and steam flushing of the sterilizing vessel and its load.
Failure to remove all of the air or the subsequent leakage of air into an evacuated chamber, or the introduction of air or other gases in the steam supply, can cause gas pockets to remain within the porous load, usually in the inner regions thereof. In this case, the temperature within some parts of the load might be lower than that required during all or part of the sterilizing process. Many types of testing device are known for this purpose including the so-called Bowie Dick towel test utilising a pack of linen Huckaback towels measuring some 270 mm high and about 300 mm.times.200 mm in plan. Another known system utilises sheets of porous paper or card, and in all of these cases it is necessary for an indicator to be placed in the centre of the stack so that after the test the indicator may be inspected to detect any parts thereof where air might have been present.
The test pack is processed in the sterilizer and the satisfactory result would show an even change in appearance across the whole of the indicator sheet, whereas the presence of air in the stack is indicated by a failure of the indicator to change its appearance in certain areas, usually at the centre. The test must be carried out daily before the sterilizer is used for the production of sterile porous loads.
Such indicators conventionally may consist of so-called autoclave tape which is placed across a sheet of paper, and reacts visibly to the presence of air and moisture under steam sterilizing conditions. Alternatively, there are available certain manufactured sheets having an indicator pattern printed thereon from a substance which, again, reacts by changing its appearance under steam sterilizing conditions.
It has been found that these conventional types of indicator suffer from the disadvantage that their appearance is affected by the presence of excessive moisture during the test, and this can lead to a false reading when attempting to detect the presence of air. In some cases, this can have the effect of a substance from the tape or sheet being transferred onto the material of the pack which in turn further affects the appearance of the indicator producing still further misleading results.
One kind of device for detecting the presence of air in a steam sterilizer has been proposed and comprises a first porous mass of at least substantially man-made material, a second porous mass of a similar material, an indicator adapted to undergo a visual change under moist heat sterilizing conditions and sandwiched between the masses thus to be in intimate contact therewith, and means for removably holding the masses and indicator in close superimposed relationship, said means being permeable to allow the free passage of air and steam to the external surfaces of the porous masses.
In this kind of device where a man-made material such as polypropylene is used in place of linen or paper, the presence of excessive moisture in the applied steam is particularly detrimental since none of the moisture can be absorbed by the pack. As a result, the affect of the moisture on the indicator is more pronounced, and it is an object of the present invention to provide an improved ind
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patent: 4382063 (1983-05-01), Romito et al.
patent: 4576795 (1986-03-01), Bruso
patent: 4579715 (1986-04-01), Bruso
patent: 4596696 (1986-06-01), Scoville, Jr.
patent: 4692307 (1987-09-01), Bruso
patent: 4699765 (1987-10-01), Hambleton
Kummert Lynn M.
Richman Barry S.
The Victoria University of Manchester
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