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Figure 1: Processes used for sterilizing medical devices.


processes; these are in development, so in the absence of a specific process standard, N ISO  applies. In hospitals, IQ and OQ are normally undertaken by the


There are international standards describing the validation of a number of sterilization processes. These are shown in table 1 along with U.S. national equivalents. It is worth noting that there is no internationally agreed standard for validating VH2


O2


sterilizer manufacturer or supplier and will form part the com- missioning process of new equipment at the site of use. PQ is a site-specific eercise. edical device manufacturers must provide re-processing instructions including the sterilization processes to be used. During PQ, hospitals might rely on these instructions or they may carry out some practical assessment of performance using a variety of monitoring tools. Having validated our process, we must then ensure routine monitoring takes place to make sure the sterilization process remains efficacious, and a number of tools can be used for this purpose.


Routine monitoring of VH2


temperature and time of eposure at a specified concentration of VH2


Any sterilization process will have certain characteristics which contribute to microbial kill. These are called the “process vari- ables.” For VH2


O2 O2 O2 sterilization sterilization, the process variables are the


chamber concentration can also be measured using UV light spectroscopy. PIs only provide information for


O2 O2


. In order to ensure every sterilization process has been effective, the process variables must be routinely monitored, and there are three basic methods for achieving this. Physical Indicators (PIs) employing instruments which measure a process variable. For a VH2 measured. VH2


process, temperature and time are easily


one process variable, so a combination are required to get a full process picture. PIs provide no information about what is hap- pening inside the packs being sterilized. Biological Indicators (BIs)


are a preparation of a living micro-


organism, usually a bacterial spore, which has high resistance to, but is inactivated by, an effective process. BIs react to all of the process variables. Chemical indicators (CIs)


are mitures of chemicals which,


when eposed to specified process variables (called their stated values Ss) will change color. For eample, a CIs Ss may be 2.mg H2


to these conditions the indicator must change color, indicating a pass. The manufacturer must declare the SVs in the instructions or print them on the CI. The international standard N ISO 0-


O2 at 50o specifies the per-


They prove particularly useful for the end user who, as part of their practices, are required to check every pack to ensure eternal and internal indicators have given a correct response.


formance reuirements for si different types of CI. These are shown in table 2 along with their uses. Types ,  and  are for placement inside sterile packs, as required by some guidance documents.5


types  and  H2


N ISO 0- does not provide reuirements for O2


CIs.


sterilization The eposure conditions under which a type  CI should show a pass result (its endpoint) and a fail result are stated in N ISO 0-. For a type  CI, the eposure conditions which give rise to a pass response (Ss) will be specified by the manufacturer ideally having some relationship to the sterilization process being


Chemical indicators for monitoring VH2 O2 Page 48 hpnonline.com • HEALTHCARE PURCHASING NEWS • February 2021 47 C for 0 seconds eposure. hen eposed


Self-Study Test Answers: 1. A, 2. C, 3. A, 4. B, 5. C, 6. B, 7. B, 8. A, 9. B, 10. B


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