Dampfdurchdringung in dünnwandigen Kanälen und helixförmigen Prüfkörpern

Introduction: Medical instruments with narrow channels are often sterilized in steam sterilization processes. Helix shaped Process Challenge Devices (PCDs) are used to mimic steam penetration in such medical devices. Little to no literature has been found indicating to which extent these devices correctly predict the steam penetration in medical instruments. The aim of the present study is to improve the understanding of steam penetration in narrow channels and helix shaped PCDs. Materials and Methods: Using a local steam density measurement technique based on infra-red absorption, the steam penetration during a steam sterilization process has been measured in various dead-end channels and channels with an additional volume connected to the closed end. Results: The steam fraction at the end of the tube at the start of the sterilization phase was found to be independent on the channel diameter in the region of 0.7 to 5 mm. Such diameters are representative for most channels in medical devices used for minimally invasive surgery. An added volume at the channel end changed the steam penetration drastically. Conclusion: The results explain the observed, sometimes counter intuitive, behaviour of the steam penetration in hollow channels reported in the literature. Moreover they indicate that the behaviour of the so-called hollow A PCD is not yet sufficiently understood to use such a device as a steam penetration test.