Active medical device: which sterilization method to use?
There are several sterilization methods with differing pros and cons. Based on the anticipated production volume, two are suitable for this active medical device: Ethylene Oxide (EtO) and gamma ray.
EtO is a preferred sterilization method for equipment with integrated-electronics; the catch is the integrated battery needed to power up the medical device. To be eligible for EtO sterilization, the medical device should be designed so that the battery compartment is completely sealed off. In this case it is impermeable for gases which makes ignition of the highly flammable EtO impossible. The design requirement that the battery compartment must be sealed and impermeable should be known and implemented at the beginning of the design process. It is costly in both time and money to modify the device design at later stages. Another aspect to keep in mind is that sealing off the battery compartment would result in compliance issues with the WEEE Directive. This directive requires batteries to be removed from any separately collected WEEE.
An alternative to EtO sterilization is using gamma radiation. However, beside being very effective in destroying living organisms, the gamma rays emitted equally affect polymers and semiconductors. The extent of the effect would strongly depend on the dose used for sterilization. Similarly to sealing the battery compartment for EtO sterilization, there are design requirements that should be considered when gamma radiation sterilization is used. Specifications for electrical components like LEDs should be taken into account at early stages of device development. Poor choice of electronic components might lead to their destruction during the sterilization process.
Finally, it is the sterilization party that, after studying the medical device design and materials used, will give a verdict if the device is compatible with the sterilization method preselected by a manufacturer.
Unless the preselected electronic components would be found suitable for gamma radiation by the sterilization party, redesign of a device is the only option remaining. LEDs unsuitable for gamma radiation would compromise the device’s safety or render it unoperational. Also, without the device being changed, the EtO sterilization facilities would not accept it for processing due to the explosion risk.
The impact of the sterilization process requirements on the design and materials is often underestimated when designing a medical device. “To cross that bridge when we come to it” is the wrong approach in terms of medical device development. As shown in this case, it might result in needing to change the design of your device to make it suitable for sterilization.