An introduction about EO Sterilization

1. EO Sterilization
An overview
Prepared by:
Md. Jabed Khan
Executive (Microbiology)
JMI Syringes and Medical Devices Ltd.

2. Basic Concepts
• What is Sterilization?
• What is EO gas?
• Uses of EO gas
• Effect of EO gas

3. Sterilization
• Any process that eliminates, removes, kills, or deactivates all
forms of life (such as Bacterria, Virus, Fungi etc.) and
other biological agents (such as spores, prions
and unicellular eukaryotic organisms)
• Sterilization can be achieved through various means,
including:
Heat (Dry heat, Autoclave), Chemicals (Formaldehyde,
Gluteralsehyde, NO, EO), Irradiation (Ionizing, Non-
Ionizing), High pressure, and Filtration.

4. Ethylene Oxide (EO) Gas
• Ethylene oxide is a colorless and flammable gas with a faintly sweet
odor.
• It is a highly toxic gas and acts by damaging DNA and as a alkylating
agent
• It is a flammable, carcinogenic, mutagenic, irritating,
and anaesthetic gas.
• Ethylene oxide (EO) gas treatment is one of the common methods used
to sterilize, pasteurize, or disinfect items because of its wide range of
material compatibility.

5. Uses of EO Gas
• It is used to process items that are sensitive to processing with other
methods, such as radiation (gamma, electron beam, X-ray), heat (moist
or dry), or other chemicals.
• Ethylene oxide treatment is the most common sterilization method,
used for approximately 70% of total sterilizations, and for over 50% of
all disposable medical devices.
• Ethylene oxide is highly effective, as it penetrates all porous materials,
and it can penetrate through some plastic materials and films.
• Ethylene oxide kills all identified microorganisms such as bacteria
(including spores), viruses, and fungi (including yeasts and moulds),
and is compatible with almost all materials even when repeatedly
applied.

6. Effect of EO Gas
• Exposure to EO can cause difficult breathing and blurred vision in
addition to eye pain and sore throat
• Exposure can also cause dizziness, nausea, headache, convulsions,
blisters and can result in vomiting and coughing
• Both human and animal studies show that EO is a carcinogen that may
cause leukemia and other cancers
• Residual levels of ethylene oxide and ethylene chlorohydrin (ECH) may
be present after EO sterilization and must be evaluated by the device
manufacturer to assure they meet predefined maximum limits.
• In EO sterilization there are more process variables to control than
with steam or radiation.

7. Sterilization Process
1. Preconditioning
2. Conditioning
3. Gas Injections and
Exposure
4. Aeration/Air
Flushing

8. 1. Preconditioning
What is Preconditioning?
• Preconditioning is to provide
the bacteria with an ideal
growing environment so that
endospores will become
exposed to the Ethylene Oxide.
The endospore consists of the
bacteriums DNA.
Why Preconditioning?
• Attainment of minimum
temperature and moisture content
required prior to sterilization
• This will assure that the
sterilization process is
reproducible regardless of external
influences such as varying climatic
conditions.

9. 2. Conditioning
What is Conditioning?
• To safely deliver the EO at least
97% of the air must be removed
from the chamber, which is called
initial vacuum or initial evacuation.
• To facilitate a static environment
steam is injected and maintained at
a predefined pressure, this is called
Humidification.
Why Conditioning?
• Allows the process to be performed
below the flammability limits of EO.
• During initial evacuation the
product can lose a significant
amount of moisture. This moisture
must be replaced prior to
introducing the ethylene oxide. This
is accomplished by humidification.

10. 3. Gas Exposure
What is Gas Exposure?
• Introduces the validated sterility
assurance level of EO to the
sterilization load.
• Sterilantis (EO) injected into the
sterilization chamber to a pre-
determined pressure.
• The sterilization load dwells
(exposure to the sterilant) for a
specified amount of time.
Why Gas Exposure?
• To ensure the product is properly
sterilized
• To confirm that the gas penetrate or
soak into all areas of the product
• To ensure the product is exposed to
heat, relative humidity and gas for a
predetermined time

11. 4. Aeration
What is Aeration?
• Performing a series of post-
exposure vacuums to remove EO
gas and their residues is called
Aeration
• A maximum working pressure and
heat must be selected for each air
flush
Why Aeration?
• After the exposure phase all gas must
be removed from the chamber to
facilitate safe handling of the product
after processing (Sterilization)
• Any residue or byproduct of EO gas
must not present in the product or
chamber to avoid undesirable effect
from it.

12. Variables that Impact Lethality
The four primary variables in the EO sterilization
process are:
1. Temperature
2. Humidity
3. Gas Concentration
4. Time

13. 1. Temperature
• The higher the temperature, the higher the
lethality of the cycle.
• Q10 Effect: For every 10 °C temperature
increase, lethality doubles.
• Heat is transferred to the sterilization load
during preconditioning and conditioning via
a controlled steam process.
• The sterilization vessel temperature setting
will also affect the heat transfer to the
sterilization load.

14. 2. Humidity
• Moisture is not only helpful in the
transfer of heat to the product, but it
also aids in the absorption and
desorption of EO into and out of the
product/packaging.
• Moisture is transferred to the
sterilization load during preconditioning
(if utilized) and conditioning via a
controlled steam process.

15. 3. Gas Concentration
• The gas concentration should be enough
to sterilize the product, but not enough
to create EO and ECH residual problems.
• The concentration of gas may be
calculated using the ideal gas law
(PV=nRT)

16. 4. Time
• The exposure time should consider the
time it takes for the gas to penetrate into
all areas of the devices and the
microbiological kill time.
• The duration is determined at the cycle
design/development stage.
• It can be based on a D-value study or on
the experience of the sterilization
specialist.

17. Chamber Monitoring Requirements
• Temperature and Pressure levels throughout
cycle
• Conditioning Humidity levels
• Conditioning Time
• Evidence of gaseous EO
• Gas circulation during exposure
• Exposure time
• EO pressure and volume
• Chemical Indicator (3M)

18. Sterility Test
• To further ensure the product is properly sterilized
• Two methods
 Direct Immersion
 Culturing of Eluent
• Media Used
 TSB (Tryptone Soya Broth)
 For Yeast and Mold
 Temperature 22.5 °C
 Incubation period 14 days
 FTM (Fluid Thioglycolate Medium)
 For Bacteria
 Temperature 32.5 °C
 Incubation period 14 days