The Principles of Medical Device Decontamination

but regardless of the application, implies that not all microorganisms are destroyed. Disinfection is typically defined as destruction of metabolically active microorganisms and viruses but does not necessarily destroy the more resistant bacterial spores. Where thermal disinfection is not possible, low temperature disinfection can be carried out using a range of biocidal disinfectants. These disinfectants can be formulated using gaseous biocides (e.g. chlorine dioxide or nitrogen dioxide), or liquid biocides. These liquid disinfectants usually consist of an aqueous solution of the active biocidal ingredient formulated with other chemicals to provide a range of other properties, such as corrosion resistance to medical devices, and stability of the formulation. Reusable medical devices that are to be used non-invasively on a patient i.e. in contact with intact skin or mucous membranes, are expected to be first cleaned prior to their subsequent disinfection, before their use (medical devices that are to be used invasively i.e. penetration into tissue, sterile body cavities etc., must be sterilized before being used on a patient). The nature of this processing depends upon the type of medical device and its intended application, and is typically determined according to the Spaulding Classification (as shown in Table 9.1), devised by Dr Earle H. Spaulding. This classification has been used for many decades and has been universally applied to medical devices, where they are categorised as high risk (critical), intermediate risk (semi-critical), and low risk (non-critical) according to the degree of risk for infection involved in use of the medical device. The Centre for Disease Control (CDC) provides a good resource called ‘A Rational Approach to Disinfection and Sterilization’ describing Spauldings classification scheme. 1

Medical Device disinfectants

Chemical disinfectants must be specifically intended for medical device decontamination, and be compatible with the design and materials of the medical device. Common disinfectants include alcohols, chlorine and chlorine compounds, aldehydes such as glutaraldehyde and orthophthalaldehyde, peroxygen compounds such as hydrogen peroxide and peracetic acid, ozone, nitrogen dioxide, phenolics and quaternary ammonium compounds (QAC). These chemicals are typically used alone as the active ingredient, or can be used in combination.

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