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Overview Of ETO Sterilization For Medical Devices

Introduction

Sterilization is a critical process for ensuring the safety and efficacy of medical devices. Among the various sterilization methods, Ethylene Oxide (ETO) has emerged as a sterilization method of choice because of its advantages compared with other methods. Due to its potent virucidal, sporicidal, and bactericidal properties, EO is a superb sterilizing agent. In this blog, we will discuss ETO sterilization role, process, regulatory standards and maintaining the integrity of medical equipment.

Understanding ETO Sterilization

Ethylene Oxide is a colourless & flammable gas that effectively eliminates microorganisms on medical devices. Its ability to penetrate packaging materials and reach every nook and cranny of complex and heat-sensitive devices. This makes ETO an ideal choice for sterilizing items.

ETO Sterilization Process

The ETO sterilization process involves exposing medical devices to a carefully controlled environment containing the gas. This controlled environment ensures the eradication of bacteria, viruses, and other microorganisms without compromising the integrity of the devices. The process typically includes preconditioning, gas exposure, and aeration phases, all meticulously managed to meet regulatory standards.

ETO Sterilization Cycle

There are three main stages in a typical EtO sterilization cycle:

Cycle time is usually more than 14 hours.

  • Preconditioning: To maintain the optimal levels of humidity, pressure, and temperature in this stage chamber environment. To make room for gas to enter, the chamber’s air is first eliminated. To make sure the environment and personnel are safe, a leakage test is carried out. Since EtO works best in a humid atmosphere, some steam is then introduced into the chamber to humidify the load. Steam from the jacket or hot water from the heater heats the chamber. To reduce temperature swings, the jacket is often kept at the same temperature around the clock.
  • Sterilization: The real sterilisation procedure takes place in the second step. To ensure that the EtO is reaching every area of the load and to maintain a high humidity level, a particular amount of steam is added when the EtO enters the chamber through evaporation. The real sterilisation stage begins once the load and chamber have reached the necessary concentration. Since many different types of plastic materials absorb EtO, it’s critical to maintain the proper concentration. EtO is occasionally introduced to the chamber after a period in order to accomplish this. To accomplish safe and effective sterilisation, it is crucial to make sure that the chamber has the right concentration of ETO.
  • Aeration (Degassing):

    The longest and most crucial stage of the ETO sterilisation cycle is aeration. As previously discussed, substances like rubber and plastics may collect gas, and if this gas is applied to patients, it may cause harmful tissue damage! To eliminate any leftover ETO gas and enable absorbed gas to re-evaporate from the sterilised goods, it is crucial to have an excessive aeration step. At a temperature between 30°C and 50°C, HEPA-filtered air is circulated over the load to achieve this. This aeration treatment is often performed for 48 hours, which causes an extremely delayed instrument turnaround. It is necessary to have a certain infrastructure, including gas-tight ventilation pipes that lead to a catalyst or the roof.

    But there are a few benefits. The chamber of an ETO steriliser can be exceptionally large—up to 7 m³. They are frequently used to sterilise large batches of goods that steam sterilisation is unable to achieve. Prior to entering the hospital, gauze and non-woven materials such as disposable gowns must be sterilised. Since steam will deteriorate or distort these materials, ETO is frequently used to sterilise them.

    In conclusion, ETO sterilisation needs to be reserved for situations in which no other approach is suitable.

ETO-Sterilization-Cycle

Benefits of ETO Sterilization

  • Compatibility with a Wide Range of Materials: ETO is compatible with various materials, including plastics, metals, and electronic components.
  • Sterility Assurance and Treatment Efficacy

Advantages of ETO

  • Low temperature
  • High efficiency – destroys microorganisms including resistant spores
  • Large sterilizing volume/ chamber capacity
  • Non corrosive to plastic, metal and rubber materials

Disadvantages of ETO

  • Excessively Long cycle
  • Safety concerns – carcinogenic to humans
  • Hazardous residues on surgical tools and tubing: toxicity concerns
  • Not recommended for flexible scope
  • ETO is flammable
  • Needs a separate ventilation system, safety equipment, and specific room conditions.
  • comparatively high yearly expenses for consumables, maintenance, and repairs

Penetration of Packaging

Unlike some other sterilization methods, ETO can penetrate packaging materials. This is particularly advantageous for ensuring the sterility of devices even after they have been sealed in their final packaging.

Low Temperature

ETO operates at relatively low temperatures compared to steam sterilization. This makes it suitable for devices sensitive to heat, preventing potential damage during the sterilization process.

Challenges and Safety Considerations

While ETO sterilization is highly effective, it comes with certain challenges. The gas is potentially hazardous to human health, requiring stringent safety measures. Residual ETO must be carefully monitored and controlled to ensure it falls within acceptable limits, avoiding any harm to end-users.

Regulatory Compliance

Given the potential risks associated with ETO, regulatory bodies have established strict guidelines for its use. Manufacturers must adhere to these regulations to guarantee the safety and efficacy of sterilized medical devices.

Standards for Sterilization

ISO 11135: 2014

This standard specifies requirements for the development, validation and routine control of ethylene oxide sterilization process for medical devices in both the industrial and healthcare settings and it acknowledges the similarities and differences between the two applications.

ISO 10993-7: 2008

This standard specifies allowable limits for residual ethylene oxide and ethylene chlorohydrin in individual EO- sterilized medical devices, procedures for the measurement of Ethylene oxide and ethylene chlorohydrin and methods for determining compliance so that the device may be released.

ISO 11737-1: 2008

This standard specifies requirements and provides guidance on the enumeration and microbial characterization of the population of viable microorganisms on or in a healthcare product, component, raw material or package.

ISO 11737-2:2009

This specifies the criteria for the test of sterility on medical devices that have been exposed to a treatment with sterilizing agents reduced relative to that anticipated to be used in routine sterilization processing. These tests are intended to be performed when defining, validating or maintaining a sterilization process.

Conclusion

Ethylene Oxide sterilization plays a pivotal role in ensuring that a wide range of medical devices meet the highest standards of safety and efficacy. Despite its challenges, when managed with precision and in compliance with regulations, ETO sterilization stands as a reliable and indispensable method in the arsenal of techniques safeguarding the health and well-being of patients worldwide.

References

1. Ethylene oxide sterilization of medical devices; A review

2. ISO 10993-7:2008

3. ISO 1135:2014

4. ISO 11737-1:2018

5. ISO 11737-2:2009

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