3 Key Factors That Influence EO Residual Levels
Material Composition
Two similar devices made of different materials are likely to have two distinct ethylene oxide (EO) residue profiles. This is because materials vary in their ability to absorb, retain and release EO. Materials also vary in their ability to produce ethylene chlorohydrin (ECH) residual following EO sterilization. In particular, materials that contain a source of free chloride ions exhibit the greatest risk and wide differences in the concentration of ECH formed following EO sterilization. Materials such as PVA, PLA, and PGLA should also be avoided, as degradation can occur due to the moisture involved in EO sterilization.
Consider using materials low in EO absorption and retention when selecting EO as a final sterilization method.
Device Packaging
Packaging materials effect penetration and dissipation of EO gas during sterilization. Thus, packaging materials also effect the penetration and dissipation of EO and ECH residual levels.
Other than the packing material itself, packaging density (the fraction of the space filled by the items being sterilized compared to the total packing space available) effects EO and ECH residual levels. Packing density of the shipping container itself (how densely the shipping container is packed with sterilized packages) effects EO and ECH residual concentrations, as well.
Packing material, packing density, and shipping container packing density should all be evaluated when deciding the optimal plan for EO sterilization of your device.
EO Sterilization Cycle Parameter
EO sterilization cycle parameters to consider include:
- EO gas concentration
- EO gas exposure time
- EO gas exposure temperature
- Type of EO cycle (pure EO or EO mixture)
- Amount of humidity
- Gas re-evacuations
- Air washes
- Product loading density (configuration of the product load in the sterilizer)
In particular, humidity, temperature, and air flow influence ECH formation in the product after removal from the sterilizer. At a minimum, consider the humidity, temperature, and air flow present following removal of EO sterilized medical devices from the sterilizer. Humidity, temperature, and air flow influence both EO off-gassing during the aeration phase and ECH formation.
Ethide Labs is a contract testing organization that specializes in Sterilization Validations and EO Residual Testing. Ethide Labs provides in-vitro cytotoxicity tests in-house and outsources in-vivo cytotoxicity work for toxicity testing of medical devices, products, and drugs. Ethide Labs also offers Microbiology Testing, Bioburden Testing, Environmental Monitoring, Bacterial Endotoxin Testing, Package Integrity Testing & Cytotoxicity Testing services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility.
References
International Organization for Standardization. Biological evaluation of medical devices — Part 7: Ethylene oxide sterilization residuals. Geneva (Switzerland): ISO; 2008. (ISO 10993-7:2008).
