Authors (including presenting author) :
Lee CK(1), Yeung WC(1), Lai KF(1), Tang WK(1), Yip SY(1)
Affiliation :
(1) Central Sterile Supplies Department, New Territories West Cluster
Introduction :
Moist heat sterilization is the most common sterilization modalities in hospital Central Sterile Supplies Department (CSSD). Non condensable gas (NCG) resided in the sterilizer chamber can cause insufficient sterilization to reusable surgical instruments and pose hazard to our patients. It is common for sterilizers to execute a series of sub-atmospheric and super-atmospheric pulses for evacuating NCG to achieve sterilization condition. The daily Bowie Dick (BD) Test is an important test in CSSD to validate the performance of pre-vacuum steam sterilizers for successful sterilization. Commercial BD test Pack complying with ISO 11140-4 are used for the test.
Objectives :
There are various types and designs of BD test packs available in the market nowadays and all with claimed conformance to ISO 11140-4. This situation created substantive difficulty for CSSD manager to choose the most suitable BD test pack for incorporation into daily operation. Our study aims at: 1. Establishing evidence-based method for evaluation of the sensitivity of commercial BD test pack to NCG 2. Evaluating the sensitivity of commercial BD test packs to NCG by conventional steam sterilizers in CSSD under the condition the sterilizers work highly reproducible and using controlled RO water for steam generation.
Methodology :
The following 4 types of BD test samples which all claimed to comply with ISO 11140-4 were sourced for evaluation: 1. Combined Porous Helix type BD test, 2. Electronic type BD test, 3. Traditional type paper BD test pack, 4. Mini BD test pack, 5. Simulated St. Andrew’s cross described by Dr. J.H. Bowie and J. Dick in their paper published in 1963. BD test cycles conforming to EN 285 with identical sterilization conditions but different pre-conditioning settings for sensitivity detection: Method 1 - Adjustment of number of sub-atmospheric pulsing, Method 2 - Installation of Induced Leak Device to induce air leak, Method 3 - Air Detector Function Test (ADFT). All types of BD test packs were given 10 attempts in each BD cycle settings in all the 3 test methods introduced above.
Result & Outcome :
In our study, the Combined Porous Helix type BD test was found to be the most sensitive to NCG while the Electronic type BD had similar sensitivity but the performance repeatability might not be comparable. The Traditional type paper BD and the Mini BD test pack were the least sensitive and the Simulated St. Andrew’s cross was more sensitive to NCG than both of them. All test methods were feasible to be conducted in hospital CSSD and test method 1 was found to be capable of sequencing the sensitivity of BD test packs.
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