INFECTION PREVENTION & CONTROL
Parametric release and independentmonitoring
Richard Bancroft, BSc (Hons), science and technical director at STERIS Corporation explores alternatives to parametric release when disinfecting or sterilising medical devices.
Reusable medical devices such as surgical instruments are reprocessed in healthcare facilities; this reuse entails washing and disinfecting, inspection, packaging and sterilisation. The process of releasing the load as sterile is of critical importance for patient safety; the load may be released based on the results of physical parameter monitoring of the load and is known as parametric release. In order to improve the safety of medical devices released parametrically, it is preferable that data from the physical parameters that are critical to the success of the process be independent from the process controller data.
Parametric release
The ISO standard, ISO 11139, “Sterilization of health care products - Vocabulary - Terms used in sterilization and related equipment and process standards,” defines parametric release as a declaration that product is sterile, based on records demonstrating that the process parameters were delivered within specified tolerances. The same principles may also be applied to a terminally disinfected product, hence it is a method of assuring disinfection or sterility by monitoring the physical conditions of the applicable process and then release of the load or product based on this data. Parametric release can be used for product release from many sterilisation processes, including steam, ethylene oxide, vaporised hydrogen peroxide, dry heat and ionising radiation, where the sterilisation variables are understood and can be adequately monitored. If the sterilisation variables are not sufficiently understood or cannot be adequately monitored, parametric monitoring is not possible and alternative means of product release are necessary. The same fundamental principles can be applied also to disinfection processes, where the load will be released, of course, as disinfected, rather than sterile. In practice, this requires monitoring and recording that all critical variables were delivered correctly, using direct or indirect measurements. The basic principle behind parametric
release is that sterility (and disinfection) is a probability, determined based on the logarithmic nature of how microorganisms die in a steady state process. A defined microbiological state is hence not easy to assess or measure, and certainly cannot be practically measured on a day to day basis. Parametric release is accepted as the preferential method for the release of disinfected or sterile products. The products or devices to be disinfected or sterilised are exposed, in their final packaging, to predetermined, fully validated disinfection or sterilisation processes using moist heat (either as water or steam), dry heat, or ionising radiation.
Many reusable medical devices are unable to withstand the high temperature steam and dry heat processes, or the material damage that can be caused by ionising radiation, so low temperature disinfection or
38 I
WWW.CLINICALSERVICESJOURNAL.COM
sterilisation is used. These low temperature sterilisation methods typically use chemical disinfectants or sterilants at a temperature that is slightly elevated from room temperature. These low temperature processes use, for example, vaporised hydrogen peroxide or gaseous ethylene oxide. These processes may also be released parametrically, using accumulated process data. Through parametric release, the user can provide assurance that the product or device conforms to specification, eg: disinfected, or sterile. When operating a system of parametric release, it must be understood by all involved that the entire process must be considered, before the load release decision can be made. This requires review and control of the holistic upstream manufacturing and preparation of the load, which, in the case of reusable medical device processing, includes device cleaning, inspection and packaging, as
NOVEMBER 2019
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104
