Central Service - Issue 3/2001
J.A.A.M. van Asten: Sterilisation is IT!
- What's New in Standardisation: LTSF Sterilizers - Requirements and Testing
- Reinhard Kurth President of the RKI
- An Internal Matter: Central Service on CD-ROM
- Formaldehyde (LTSF) Sterilisation: International Conference in Hamburg, May 17 - 18, 2001
- Hospital Hygiene Congress Foundation: Prize Award 2000 and Call for Papers for 2001
- Study Visit of the Belgian V.S.Z. to an Instrument Manufacturer
C. Justi, V. Amato, K. Antloga, S. Harrington, G. McDonnell:
Demonstration of a Sterility Assurance Level for a Liquid Chemical Sterilisation Process
(Zentr Steril 2001; 9 (2): 163-176)
Sterilisation, as a terminal process, is preferred for all reusable medical devices, but many heat-sensitive or lumened devices cannot be practically or adequately sterilised by traditional methods. Many new and developing technologies, including liquid chemical products and processes have been introduced for reprocessing these devices but may not provide the same level of sterility assurance. The methodology described in this report is proposed to determine and validate the minimum conditions for individual liquid chemical sterilisation processes. The process studied demonstrated log-linear kinetics at minimum process conditions defined, allowing for the extrapolation of a minimum sterility assurance level of 10-6 for the process. The control of process variables and an understanding of process limitations was shown to be critical and should be investigated, consistent with other technologies. Further, the activity of the process may vary depending on the device construction materials and should be used to confirm the process efficacy.
J. Gömann, U. Kaiser, R. Menzel:
Air Removal from Porous and Hollow Goods using Different Steam Sterilisation Processes
(Zentr Steril 2001; 9 (3): 177-186)
The difference between the air-removal characteristics from a porous and a hollow device was investigated in steam sterilisation processes using vacuum and trans-atmospheric air-removal procedures. The standard Bowie-Dick test pack based on European Standard EN 285 was selected as a reference porous load and a process challenge device as described in EN 867-5 was selected as a hollow device. Air-removal measurements were carried out according to the requirements of European standard EN 867-4. To demonstrate correct air removal and hence successful steam penetration, thermoelectrical measurements as well as chemical and biological indicators were used.
Both the porous and the hollow device demonstrated successful air removal in the standard vacuum air-removal procedure (see figure 1).
Tests conducted under otherwise similar conditions in two trans-atmospheric air-removal cycles (figure 2 and 3) showed adequate steam penetration of the porous laundry pack, but air was not successfully removed from the two hollow devices (process challenge devices - PCDs) under these conditions, and growth of biological indicators was seen after sterilisation in all hollow PCDs.
In standard EN 285 the porous test pack is currently the only mandatory test to evaluate the sterilisation process in respect of the quality of air removal. However, the experiments carried out clearly demonstrate that sterilisation processes that successfully remove air from porous loads show quite different air-removal characteristics from hollow devices. Because hollow devices of the most diverse designs meanwhile account for an important portion of the sterile goods used in the healthcare service and a steriliser must, pursuant to EN 285, furnish proof that it meets minimal performance requirements in order to qualify for use in the healthcare sector, its performance capabilities must be defined also in respect of hollow instruments.
To assure successful sterilisation also of these hollow devices and instruments such as tubes and minimally invasive surgical (MIS) instruments etc. in sterilisers as per EN 285, suitable reference test systems for hollow devices must be used for type testing, validation and routine monitoring of steam sterilisation processes.
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