The Principles of Medical Device Decontamination

Leak testing of endoscopes This is in effect a subcategory of failure to clean; holes in an endoscope allow patient body fluid to enter internal spaces where they evade removal by cleaning and contact with disinfectant. Failure to carry out an adequate leak test (i.e. to the manufacturer’s specifications) prior to each reprocessing is a major decontamination failure. Such a failure is uncommon with lumened endoscopes but less so with nasendoscopes (non-lumened endoscopes usually used outside the endoscopy department).

Inadequate chemical disinfection

Chemical disinfection is prone to fallibility and can be compromised by many factors. The more controlled the process the less fallible it is likely to be. The most important factors are: using a disinfectant with the right micro-biocidal range, good pre- cleaning and adequate exposure time of all surfaces requiring disinfection. Effective exposure to non-gaseous disinfectants can only occur whilst that disinfectant is wet. The disinfectant molecules need to migrate into their target via a liquid bridge; once the disinfectant dries, this can no longer happen. So, if, for example, the disinfectant from a wipe dries after 30 seconds but the item is then left for an additional 4 minutes and 30 seconds before reuse, the effective disinfection time is 30 seconds, not 5 minutes. Inadequate chemical disinfection can range from minor, e.g. a disinfectant used a few days after its use by date, to major, e.g. failure of a disinfectant to make any contact with an area of a reprocessed device. Inadequate steam sterilisation Steam sterilisation involves a vast overkill. To be accepted as sterilisation, a process needs to achieve at least a 1 in a million chance of a processed item being non- sterile. The steam sterilisation parameters normally used are robust rather than scientifically derived and probably achieve a substantially higher probability than this. Minor inadequacies of sterilisation parameters will not result in any real chance of sterilisation failure. This should not occur and items that have been through such failed sterilisation cycles should not knowingly be used, but these are not major decontamination failures.

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