Ethylene oxide (EO) remains a mainstay sterilization method for many medical devices. With its use, however, come some disadvantages, including the issue of residuals—and how to minimize them.

Residuals are the trace amounts of EO gas and its byproducts that can remain on devices sterilized with EO. They pose potential health risks—including carcinogenic effects—to both healthcare providers and patients, especially those subject to exposure over long periods of time.

The good news is developers can take steps to reduce exposure to EO and lower residual risk. The trick is to understand that EO residuals are not just a sterilization concern. They are a design issue—and opportunity. Developers who factor residuals into the design of their products are more likely to move swiftly through the sterilization process, launch safely, and stay on time and on budget.

Incorporate EO Residual Planning in the Design Phase

1. Evaluate how your device materials respond to EO sterilization.

Be aware that some adhesives and delicate electronic components may degrade during the EO process or retain harmful EO residuals. Some, such as cellulose, cotton, and certain polymers, plastics, and foams, absorb and hold onto EO longer. To ensure you choose the best materials for your project, use a non-production (engineering) run to test material compatibility. It can be wise to consult with an EO sterilization provider for expert guidance early on in the development process.

2. Consider device shape.

Tight spaces and complex layers can trap EO and slow down off-gassing. To address this, design with simpler shapes and smoother surfaces to reduce areas where EO can get trapped. Think about airflow in the design, particularly if the device has cavities, and avoid dead ends inside the device whenever possible.

3. Incorporate package design into sterilization.

Packaging design significantly impacts EO absorption and off-gassing rates. For example, you’ll want to avoid limited or obstructed breathable surfaces (such as large adhesive labels), as they can prevent EO from venting properly. All packaging must be EO-permeable (e.g., paper, plastic, Tyvek peel pouches). Avoid aluminum foil or nylon as EO cannot penetrate these materials.

Paper-based materials like cardboard absorb EO. The more absorbent the materials, the more EO is required. To reduce the amount of EO required with paper-based materials—which will minimize residuals as well as overall sterilization cost—manufacturers can take these steps:

• Limit the amount of paper included in the packaging.
• Use thinner, single-page IFU.
• Replace printed IFUs with electronic versions when regulatory guidelines allow.
• Change the shipping box to corrugated plastic or another material.
• Remove the product from the corrugated boxes and sterilize it in shelf boxes.

4. Get specific in technical files.

Ensure the device’s technical file clearly connects residual data to how the device will be used, including details on the related risks of that use. Explain exposure limits, worst-case scenarios, and any changes to standard methods. If the company has plans to sell the device internationally, build in a safety margin to meet the toughest requirements, keeping in mind that some markets—especially in the European Union—typically require more detailed justification based on device and patient type.

5. Consider an alternative.

While EO sterilization is effective and appropriate for many medical devices, good alternatives exist. Many manufacturers are now moving to chlorine dioxide sterilization, which is non-carcinogenic, effective, and efficient. While CD still leaves behind some residuals (like chloride, chlorite, and chlorate), they are much less harmful than EO’s byproducts. CD sterilization is also a good alternative if the materials to be sterilized are sensitive to heat, since it sterilizes at a lower temperature than EO.

Conclusion

Issues with EO residuals are not confined to the sterilization process. They begin with design and material choices. If you wait until it’s time to sterilize to consider EO residuals, you could face costly product changes and delays in getting to market. From testing material compatibility early in the development process to evaluating alternative sterilization methods, developers can go a long way in reducing EO residuals.

Jim Kasic is the founder and chairman of Boulder iQ. With more than 30 years of experience in the Class I, II, and III medical device industry, he holds more than 40 U.S. and international patents. His career includes experience with companies ranging from large multinational corporations to startups with a national and international scope. Kasic has served as president and CEO of Sophono, Inc., a multinational manufacturer and distributor of implantable hearing devices, which was acquired by Medtronic. He also was the president of OrthoWin, acquired by Zimmer-BioMed. He received a B.S. in physics and an M.S. in chemical/biological engineering from the University of Colorado, and an MBA from the University of Phoenix. He can be reached at jim.kasic@boulderiq.com or on LinkedIn.