Ethylene Oxide Sterilisation

Question 1

when would you use EtO sterilisayion?

Answer 1

difficult to monitor

- used for disposbale items and around 50% of medical devices

Question 2

what are the targets sites for EtO sterilisation?

Answer 2

• Alkylation of sulphhydryl, amino, hydroxyl and carboxyl groups on Prt and NA – multiple target binding sites

Question 3

what are toxic residues/

Answer 3

can be produced during process and will cause serious harm to the human body. We need to ensure we removal all toxic residues after sterilisation

Question 4

what are the parameters for EtO?

Answer 4

•	Time 
- 1-24 hours (not standardised)
•	Temperature
- 25-65 degrees
•	Humidity
- 40-85% moisture needs to be present., this also helps kill microorganism as it is more lethal is the presence of moisture.
•	EtO Concentration
- 250-1200mg/L EtO
- EtO distribution and penetration issues

Question 5

what is the process flow for EtO sterlisation?

Answer 5

1. pre-conditioning
2. sterliser
3. aeration

Question 6

what equipment is needed for EtO sterilisation?

Answer 6

• Pre-conditioning area (room/chamber) these could all take place in one big chamber but they usually have 3 distinct chambers
• Sterliser
• Aeration area (room/chamber)
• Preconditioning

Question 7

what is the sterilisation cycle?1

Answer 7

1. Evacuation – removal of air from chamber and the product. EtO is explosive in air so you may introduce CO2
2. Vacuum hold (leak test) – no air getting in
3. Conditioning – to the air levels to get back to where they should be and started to heat the product
4. Sterilant injection – little cannisters which you insert and pierce at the EtO vaporises at around 10 degrees.
5. Exposure
6. Sterilant removal – catalytic convertors are used which convert EtO into CO2 and water.
7. Flushing – introducing sterile air into the chamber and onto the product. Vacuum is also pulled to actively remove air and remaining EtO. Often the air is mixed with nitrogen usually to ensure there is no small explosions likely to happen.
8. Aeration – products pulled and are exposed to nitrogen between 12 hours and seven days. Safe guarding to make sure to EtO residuals left as they are toxic to human tissue.