IDI - Irish Decontamination Institute...

IDI - Irish Decontamination Institute

/ IDI - Irish Decontamination Institute / Conferences & Congresses / 2008 / V.S.Z Study Day 16 October 2008 - "Does routine testing make sense?" / Report

V.S.Z Study Day 16 October 2008
"Does routine testing make sense?"

16 October 2008
Brouwgebouw Lamot, Van Beethovenstraat 8/10, 2800 Mechelen, Belgium

After a cup of coffee and a visit to the exhibition area, Mr. McDonnel (Steris) gave a brief introduction of the Amsco V-Pro 1 low temperature sterilisation system: a method using vaporized hydrogen peroxide.

Wim Renders (president VSZ, AZ. Sint-Jan Brugge) opened the official part of our study day. In his introduction he stated that CEN ans ISO regulations form the basis of the improvement of the quality our sterilisation departments have undergone. Nevertheless they form the base for practical problems too These regulations are mainly based on and writen by the industrial world, and not always suitable in our working environment. Furthermore participation in the working groups of UNAMEC (Belgian Professional association of manufacturers, importers and distributors of medical devices) is too expensive for V.S.Z.. This prevents the participation of the workingfield. As a result unrealistic norms, for the sterilisation department in the hospital, can see the daylight.

Miel Goovaerts (secretary VSZ, UZA. Edegem) explained the topic of the study day: "Does routine testing make sense?" According to EN 285 7.1.13 the Bowie and Dick test cycle shall have the same air removal stage as the one used in the sterilization cycles for production. And according to the EN ISO 11140-4 annex B4, the Integrated Come-up Exposure (ICE) is not greater than 2312 sK at 134C (or 882sK) at 121C, in the Bowie Dick test cycle. "These limits are intended to ensure that steam admission does not contribute to excessive exposure of the indicator to atypical conditions." Situation in validated steam sterilizers, the indicator had a full colour change at the start of the plateau period of the cycle, as the ICE is twice to six (ore even more?) bigger than accepted. This certainly raises some questions:

  • Can we rely on the alternative Bowie and Dick in cycles with "high ICE"?
  • Are alternatives needed and/or available?
  • Is Bowie and Dick the best daily test with the new types of sterilization cycles and new kind of loads?
  • Does validation confirm compliance to regulations?

Mr. Ras (Tuttnauer, The Netherlands) clarified the main principle of steam sterilisation: dry saturated steam. How to manage and control? An overview of all routine tests, their strengths and waeknesses learned us that the helix test is a complement of the B&D test but not a replacement, it must not be used as charge control as the indicator is assigned to 134C for 3,5 min. Production cycles take longer than 3,5 min, making false positive tests. Electronic tests have the advantage they provide us electronic data, leaving the personal intrepretation of chemical indicators behind.

As Mr. Oort was ill, Mr Suys (Gulllimex, Belgium) burnt the midnight candle, writing us a presentation about whireless control of our cycles, using dataloggers.

After lunch we continued, Mr. Hahnen (3M, Germany)stated another main principle of steam sterilisation: "if you don't get the air out, you can't get the steam in!" Solid, hollow and porous items are and will be part of sterilizer loads, but porous is not hollow and visa versa.This is why tests for air removal and steam penetration must be carried out, using PCD's. (Process Challenge Device, object which simulates the worst case of conditions). The B&D test is a "porous PCD" and the Helix test a "hollow PCD", making the Helix a compliment of the Bowie ad Dick test. Current technologies - incorporating the benefits of both- will become more important. As Brian Kirk has shown that pure physical measurement of pressure and temperature to judge steam quality isn't feasible and practical, a "condensation point"is necessary to accumulate non-condensable gases in a sufficient quantity to make a judgement. Current technologies - incorporating the benefits of both- will become more important , but "What is the critical fail they need to detect?". Physical-electronic test devices have the advantage they deliver non-interpretative results (electonic data) based on the"condensation point", thereby thy can imitate a "hollow load", and replace the alterative B&D test, because they are calibrated against EN towel pack sensitivity.

Mr Kaiser (GKE, Germany) explained us about new methods to monitor steam penetration into complex medical devices (MD) using Medical Device Simulators (MDS) and Batch Monitoring Systems (BMS). First of all: non-condensable gases can be introduced together with steam. Biological and chemical indicators have their limitations, they can only test the kill ability of steam (temperature vs. time). A test of non-condensable gases in the chamber is not possible. In our historical monitoring concept, we check steam penetration with: the 7 kg BD-Test pack (large sterilizers; EN 285) or with the helix test (small sterilizers EN 13060 type B; EN 867-5). Assuming that if the sterilizer works according to the specifications, all goods come out sterile. But this concept is wrong: depending on the penetration requirements of the load the steam penetration may be sufficient, correct or not sufficient. So he suggested the following monitoring concept: define the steam penetration requirements of a load by designing a batch monitoring system (BMS) checking the steam penetration requirements of the load. Depending on the requirements of the load configuration sterilizers with higher penetration characteristics may be required.

Time for a coffee-break. Thereafter Mr. Pattijn (Causa, The Netherlands) clarified the difference between monitoring and validation. Monitoring tells us about the result of that specified process, while validation gives us information about the reproduction and effectiveness of the process. Monitoring is done with chemical and biological indicators. But what about the accuracy of these indicators? Indicators themselve are tested in a BIER or CIER vessel (Biological/Chemical Indicator Evaluator Resistomer); a proces with focus on phase 2 (plateau) of the sterilisation proces. Phase 2 is the only phase that is defined by the norms:, temperature, time and presure (100% saturated steam). This raises the question: "What's the influence of phase 1 (pre-conditioning) and phase 3 (drying) on the indicator. How accurate is the indicator in daily practice? Even Process Challenge Devices are they representative for the instruments we use, the loads we treat? Physical characteristics of the PCD don't correspond to the instruments we treat: density, heat conduction and heat capacity might be different. Therefore physical monitoring and validation are preferable because they provide us information and interaction.

Mr. Bot (Medithema, The Netherlands) closed our study day: time for some humor but nevertheless including the wise words: "In a sterilisator nothing disappears! ", ...always make sure it's clean! As he takes us through the years he worked in our country, we realize we really have achieved something. Due to the courses and conferences, the work of the VSZ: ... bioburden has become a wide spread word, ..., our departments have improved.

Griet Missant

The presentations are available on the V.S.Z website: