ToS, or Terminology of Service, explains the limitations of a sterilization process. Specifically, Clause D.8.6 of 11135 requires BIs to have a D-value equal to or greater than the bioburden they represent. In order to measure BI resistance to EO Testing, the D-value is typically determined in an experimental design that involves a homogenous population of microorganisms and an equivalent level of lethality. Consequently, current experimental design can only provide data after one sublethal EO cycle.
Depending on the product, EO-sterilized materials can be classified according to their ability to absorb, retain, or release ethylene oxide. In addition, EO-sterilization standards require periodic analysis and sampling of products to establish a decay curve. EO analysis at multiple time points can be used to determine quarantine times prior to product release. Generally, the process involves analyses of products at three to five time points.
The EO cycle requires breathable materials such as Tyvek. This material is proven effective by the Tyvek Transition Project. Medical papers may also be suitable for EO. In addition to breathable materials, SBS-coated SBS must undergo proper testing to ensure the integrity of the EO process. Gurley Porosity and Air Resistance Testing, or GPRAT, are two examples of testing protocols that need to be completed for SBS materials.
ISO 11135:2014 requires a product test of sterility (ToS) for ethylene oxide-sterilization. The ToS is typically conducted to demonstrate compliance. In this case, it is performed on BIs generated from a process challenge device (BI).
EO sterilization involves a low-level exposure to heat, moisture, or radiation. It can be used for a wide range of materials, including polymeric components commonly used in medical devices. AAMI TIR 17 details material compatibility. This process can also be used in final packaging, as the EO penetrates sealed containers. ISO 11135 outlines validation requirements for EO sterilization.
EtO is the most common way of sterilizing medical devices. This method is extremely effective because it is a low-temperature gaseous process that penetrates many types of materials. EtO is an alkylating agent that disrupts the reproductive and cellular processes of microorganisms. It also penetrates packaging and makes contact with all accessible surfaces. In addition, it provides sterility assurance without using toxic chemicals.