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What are the main considerations in designing a robust steam sterilization process for pouches made with PET/cast PP and medical grade papers?

Last Updated On September 21, 2023

When using steam to sterilize a medical device, there are several factors to consider when designing a robust steam sterilization process.

1. STERILIZATION TEMPERATURE: The peak temperature should be below the melt temperature of all materials in the pouch. In the case of a medical grade paper and PET/cast PP pouch, the polypropylene will have the lowest melt temperature in the pouch. Increasing the difference between the sterilization temperature and PP melt temperature will minimize the risk of seal creep during the sterilization cycle.
2. LOADING THE STERILIZER: Load the sterilizer so the weight of the medical device isn’t exerting force on the pouch seals. Depending on the weight and geometry of the medical device, the pouches may need to be loaded flatly in the sterilizer vs. stacked on their sides. Loading in this manner will minimize forces exerted on the seals during sterilization while the polypropylene is most vulnerable to seal creep.
3. COOL DOWN CYCLE: Ensure the sterilizer has a gradual and adequate cool down period prior to finishing the cycle. The head space in the packages will expand as the surrounding air outside of the packages cool. Although the medical grade paper is porous, the cool down period should be slow enough to allow the pouches to “breathe” to avoid the head space from expanding and creating a positive pressure inside the pouch. In addition, if the pouches aren’t adequately cooled prior to opening the sterilizer door, this sudden temperature change can also create a positive pressure inside the pouch resulting in forces being exerted on the pouch seals while warm. By slowly cooling the sterilization chamber and allowing enough time for the medical device to cool inside the package will minimize stresses exerted on the pouch seals.
4. TESTING: Although seal strength measurements are important to quantify the strength of the seals and ensure they’ll withstand handling, they don’t necessarily verify a sterile barrier was maintained. The entire perimeter of the seal should be inspected to ensure a leaker or channel was not created during the sterilization process.
5. HELPFUL REFERENCES:
   — AAMI TIR 17:2017 Compatibility of Materials Subject to Sterilization
   — ISO 16775:2021 Packaging for terminally sterilized medical devices- Guidance on the application of ISO 11607-1 and ISO 11607-2