Gaseous sterilisation

Question 1

how can gaseous sterilisation be divided into 2 parts

Answer 1

1. alkylating agents- ethylene oxide
2. oxidising agents- hydrogen peroxide, ozone

Question 2

describe the properties of ethylene oxide

Answer 2

1. C2H4O
2. gas at room temperature
3. maximum safety limit for humans is 5ppm
4. toxicity concerns- potential carcinogen and mutagenic
5. explosive in mixtures with air above 3.6%
6. used either as pure ethylene oxide at sub atmospheric pressure, air evacuated or ethylene oxide gas with a carrier

Question 3

describe the typical sterilising cycle for ethylene oxide

Answer 3

1. no standard cycle
2. typically used at concentrations of 400-1500mg/L
3. air is removed by evacuation
4. humidification and load pre-conditioning with steam
5. evacuation and entry of vaporised ethylene oxide
6. entry of sterile filtered air
7. desorption from articles

Question 4

describe the activity of ethylene oxide

Answer 4

1. broad spectrum
2. activity on viruses, fungi, bacterial endospores, vegetative cells
3. works by alkylation which inhibits metabolic activities

Question 5

what is involved in the product release of ethylene oxide

Answer 5

1. gas concentration, relative humidity, temperature, duration of process should be monitored and recorded
2. biological indicators
3. samples for sterility testing
4. records of pre conditioning
5. sterilisation cycle records

Question 6

what are the applications of ethylene oxide sterilisation

Answer 6

1. reusable surgical instruments and medical equipment
2. disposable medical devices for those sensitive to radiation

Question 7

what is ethylene oxide sterilisation not suitable for

Answer 7

1. ampoules
2. impermeable packaging
3. products/articles sensitive to high humidity
4. soiled products

Question 8

what are the advantages of ethylene oxide as a sterilising agent

Answer 8

1. cycle can be developed for specific products
2. products can be processed in their transit containers
3. automated sterilisers are available
4. highly penetrative
5. repeat sterilisation without damage
6. can process a wide range of materials

Question 9

what are the disadvantages of ethylene oxide as a sterilising agent

Answer 9

1. associated toxicity, mutagenicity, carcinogenicity
2. explosion hazard
3. no standard cycles available
4. residual in product which must be removed
5. requires specialist expertise for operation
6. no depyrogenation