What is ethylene oxide?
The French chemist Charles Adolphe Wurtz first produced ethylene oxide (ETO / EO) in 1859. It is a colorless, flammable gas with a strong and highly explosive aroma in the presence of air. Soluble in water and most organic solvents, alcohol, chloroform, ether, among others.
It is active on bacteria, viruses, and fungi acting effectively on spores and vegetative forms.
Currently, for the industrial manufacture of ethylene oxide, ethene and oxygen are used at temperatures between 200 and 300 ° C to produce the gas from the reaction of both components in a silver catalyst.
Characteristics
- Density greater than air
- Colorless
- Strong aroma
- Flammable and highly explosive in the presence of air
- Soluble in water and the largest of organic solvents
- Toxic by inhalation
- Irritating to eyes and respiratory system
Advantages as a sterilizing agent
- Thanks to its excellent propagation and absorption it can cross the folds of the elements easily and reach inaccessible places
- Does not generate adverse reactions in the materials of the components or deformations
- Preserves the integrity of materials with high thermal sensitivity since it is used at low temperatures (between 25 ° C to 60 ° C)
Risks
- It is toxic and carcinogenic by inhalation
- May cause headache, dizziness and nausea/vomiting
- It is irritating to the skin and respiratory system
- May cause skin freeze burns by evaporating very fast under normal pressure and room temperature
Types
At present, ethylene oxide for use in sterilization can be found in two presentations:
- Ethylene oxide (ETO / EO) with carbon dioxide (CO2): both gases have the same molecular weight, which allows them to mix. The higher the proportion of carbon dioxide (CO2), the higher the pressure in the container. This will require reaching a high pressure within the sterilization equipment to preserve the concentration of ethylene oxide internally.
- 100% ethylene oxide (ETO / EO): the entire gas is ethylene oxide. Since carbon dioxide (CO2) is not present in the mixture, sterilization can be performed at lower pressures.
Uses
Most of the ethylene oxide is used as an intermediate in the manufacture of other chemical products such as ethylene glycol used as antifreeze in refrigeration circuits. Besides, it is necessary for the production of polyesters such as polyethylene terephthalate (PET). Only about 2% of world production is used for sterilization.
Ethylene oxide in sterilization
The ethylene oxide gas is sufficient to kill bacteria, mold, and fungi. Currently, it is widely used to sterilize elements that are sensitive to high temperatures.
Among the materials that are most sterilized with ethylene oxide are sanitary materials such as bandages, sutures, syringes, and surgical tools.
What is sterilization with ethylene oxide?
The sterilization of the species with ethylene oxide (ETO / EO) was patented by the American chemist Lloyd Hall in 1938 and is still used today.
The ethylene oxide gas sterilization method is a low-temperature chemical sterilization process ideal for products that have high thermal sensitivity, which means they can not be sterilized with steam or heat methods.
It is used in the sterilization of medical devices and is based on the propagation of ethylene oxide gas (ETO / EO) inside a piece of container equipment where it crosses the various materials that are inside, which allows to reach all corners of the product and eliminate the microorganisms that are there.
Parameters of sterilization with ethylene oxide
- Humidity: the optimum relative humidity (RH) to sterilize with ethylene oxide (ETO / EO) is between 30% and 60%; with higher values of RH the antibacterial activity of this gas decreases because the ETO polymerizes with water and lose its action and with RH under than this value the activity also decreases because there is no proper humidification around the microorganism and it becomes resistant to the penetration of the ETO.
- Exposure time: times vary according to the type of system: diffusion or vacuum; concentration and temperature.
- Temperature: Ethylene oxide is activated at a temperature of 15 ° C; However, it must be taken into account that temperatures above 60 ° C do not increase the efficiency of the method, but instead generate the risk of explosion.
- Concentration: it is activated in levels ranging from 300 mg / L to 600 mg / L, depending on the temperature, humidity, and time of exposure applied.
Sterilization process by ethylene oxide
Sterilization with ethylene oxide is a process of chemical sterilization at a low-temperature ideal for preserving the integrity of products with high thermal sensitivity. It is used mostly in the sterilization of medical materials.
Phases of the process of sterilization with ethylene oxide (ETO)
- Conditioning or preconditioning phaseEthylene oxide will not destroy microorganisms lodged in the dry organic matter, nor will it kill spores that have dried out. Therefore, all objects to be sterilized must be carefully washed to remove any plastic residue or objects from hard surfaces, then they must be prepared by a combined treatment of washing and soaking in water for one hour. Finally, the objects should be dried and placed immediately in the sterilizer.
Objects containing dehydrated spores that cannot be submerged or washed should be stored overnight in a closed chamber, subject to high relative humidity before sterilization. This preparation will provide enough moisture for microorganisms to die with the sterilizing agent.
It is essential that the tubular (a short piece of pipe or tube) do not contain water remaining from the washing process. Remember that, since water acts as a neutralizer of ethylene oxide, some trace of microbial life could be protected by this phenomenon. It will be necessary to disperse with compressed air the elements prone to conserve water before packing them for sterilization.
- Sterilization phaseThe programmed exposure time (12 hours) is expected during which gas will penetrate the container, sterilizing the elements that are inside.
During this phase, it must be checked that the temperature of the equipment does not exceed that allowed to avoid possible accidents, as well as the humidity and adequate pressure to ensure the effectiveness of the process.
Must be maintained the own safety in the sterilized area, corroborate the excellent ventilation of the room, the correct operation of the PPM / LEL gas detectors and the implementation of a scrubber or catalytic system to treat the residues of ethylene oxide.
- Ventilation or aeration phaseAll material sterilized by the ethylene oxide method must be adequately ventilated to eliminate any residual gas. Failure to properly ventilate could leave traces of toxic ethylene compounds that could be hazardous in materials sterilized by this method.
The ventilation time in the Xterie sterilization equipment is 4 hours, with high-velocity internal extraction and dilution through cannulas inside each bag of material.
When removing the load from the equipment, it is necessary to confirm that the elements have been properly sterilized. This is verified through the chemical indicators, corroborating they have veered, and the biological indicators will be grown for later review.
It is necessary to avoid the use of sterilized material immediately upon the removal of the camera. The longer the packs with purified material can be left to vent, the lower the presence of residual gases.
The material can be perfectly sterile and not suitable for use in the operating room because it has not been adequately ventilated.
It is recommended to store materials already removed from the chamber for 24 hours for additional ventilation.
Advantages of sterilization with ethylene oxide
- Ethylene oxide (ETO / EO) allows complete sterilization over the entire surface of the elements due to its high capacity for propagation and penetration.
- Does not generate adverse reactions in the materials of the components or deformations
- It is a highly efficient method of sterilization that guarantees the integrity of equipment or materials that are sensitive to high temperatures
Sterilization equipment by ethylene oxide
When using a toxic and explosive sterilizing agent such as ethylene oxide (ETO / EO), it is highly recommended to use adequate and optimal sterilization equipment that can ensure the integrity of the personnel, as well as the working environment and that are environmentally friendly.
In Xterie we have the best type of equipment for chemical sterilization at low temperature by ethylene oxide
