The sterilization process must consistently deliver all critical process parameters to each and every component contained within the load, to a degree that will ensure a 10 -6 sterility assurance level (SAL) without causing any deleterious effect to the product or its sterile barrier packaging. However, the process engineer must also identify and evaluate relationships that may exist between any given process parameter(s), the product being sterilized, and the equipment used. The critical parameters of an EtO sterilization cycle are typically given as temperature, pressure, humidity, EtO concentration, and gas dwell time. However, by following a structured method that systematically examines and considers each of these variables, the process engineer can design, validate, and routinely sterilize with a safe and efficacious process.
It is here, in fact, that one notices how EtO processes possess a greater number of variables in comparison with other sterilization technologies. Atmospheric and barometric pressure are constant, with atmospheric pressure at 14.7 psia.Īn effective EtO process can be properly designed for almost every type of medical device and permeable packaging configuration, provided that all variables are assessed through thorough process design and development.
Preconditioning and aeration are performed externally to the sterilizer.All process gases are presumed to behave as ideal gases.There is no stratification of process gases.Water vapor and process nitrogen are the only inert gases considered in the flammability calculations performed during the air-elimination and gas-purge phases.The following assumptions were made for the purpose of explaining the rationale behind the design of the cycles and the options available: This article is intended to guide the reader through the components of each phase of two hypothetical 100% EtO with nitrogen processes. Photo courtesy Spectros Instruments, Inc. Mid-infrared gas spectrometer measures EtO and water vapor during sterilization. The four phases are: (1) air removal, (2) steam injection and conditioning dwell, (3) EtO injection and gas dwell, and (4) gas purge and air inbleed.
Typically, the EtO process can be broken down into four basic phases, each of which needs careful planning to ensure a safe and efficacious process. Validated EtO processes can be run in sterilizers ranging from BIER vessels of a few cubic feet to industrial-sized vessels exceeding 4500 cu ft. An MD&DI December 1998 Column ETO STERILIZATIONīy following a structured method, process engineers can design and validate safe and efficacious EtO steilization cycles.Īmong the sterilization technologies currently available to the medical device industry, 100% ethylene oxide (EtO) gas remains one of the most popular.