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DECONTAMINATION


Pressure 1000 100


10 1 0.1


0.01 0.001


Time


Figure 3: The CISA SPS system uses both a lower vacuum (typically less than 1 10-3 vacuum washes which allows air to be drawn out of the load.


The CISA method is very effective in


removing air from long narrow lumens . A practical synonym is the action and forces felt when pulling the plunger of a syringe. Rapidly pulling the plunger creates a vacuum in the barrel as the flow of air through the syringe’s nozzle is restricted, not allowing the pressure to instantaneously equalise and thus creating a vacuum. If the plunger is released it retracts back down the barrel under the force of the vacuum until the pressures equalise. However, if the plunger is held, the pressures slowly equalise negating the force exerted by the vacuum. This is what the CISA unit does in reverse, allowing time for the air to seep out of both the packaging and lumens and as such allows longer and narrower lumens to be processed. Removal of the air from the devices allows


rapid and even penetration of the vapourised H2


H2O2 O2


to process devices with lumens. The outcome of the CISA process is


O2 sterilisers


into all parts of the load. The size of the molecules means the gas needs to track


down the lumen and in the past this has been problematic in the ability of H2


that very small lumens (>1.0mm dia) up to 1,500 mm long can be processed using a shorter hold time than normal. As the chemical supplied by the


manufacturer is diluted with water, which will affect the sterilising process, it needs to be evaporated. In the CISA and Sterrad sterilisers the diluted chemical is drawn or pumped from the cartridge into a vapourising


34


concentrating the solution, once the sterilant is released into the chamber the lower chamber vacuum allows it to flash off as a gas.


chamber which is under vacuum and heated to a temperature where the water is evaporated but H2


O2 remains a liquid


Validation and testing Validation and testing consists of a number of different phases: • Commissioning validation (Installation, operational and performance qualifications).


• Operational validation. • Routine validation.


At present there is no standard for the manufacture, validation or monitoring of these machines. Manufacturers need to develop their own procedures using ISO 14937 Sterilisation of healthcare products – General requirements for characterisation of a sterilising agent and the development, validation and routine control of a


mBar) and a series of


sterilisation process for medical devices. Because of this, each machine will have


different testing protocols dependant on the manufacturer, but all would address the overall requirement of ensuring the machine is performing and sterilising correctly. During commissioning validation the machine will initially be checked to see that the services, safety devices, calibration and basic operation are satisfactory (IQ) before moving to testing that shows the machine is sterilising both generally (OQ) and specifically (PQ) using biological and possibly chemical challenges. When challenging the machine a half cycle is used. To perform this cycle the sterilising hold time is reduced by 50% while the other parameters remain the same. In doing this it can be shown that if the challenge of 106 shows no growth then by doubling the exposure time there is confidence in the machine’s Sterilising Assurance Level (SAL). Studies have shown that Geobacillus stearothermophilus has a high


‘Manufacturers need to develop their own procedures using ISO 14937 Sterilisation of healthcare products – General requirements for characterisation of a sterilising agent and the development, validation and routine control of a sterilisation process for medical devices.’


IFHE DIGEST 2014


Chamber pressure mTorr Prevac


Vacuum Plasma


Gas admission Sterilising Time Air flush Plasma


Gas admission Sterilising


Air flush Plasma Air flush


00:02:00 00:05:30 00:09:00 00:12:30 00:16:00 00:19:30 00:22:00 00:25:30 00:29:00 00:32:30 00:36:00 00:39:30 00:43:00 00:46:30 00:50:00 00:53:30 00:57:00 01:00:30 01:04:00 01:07:30 01:11:00 01:14:30 01:18:00 01:21:30 01:25:00 01:28:30 01:32:00 01:35:30 01:39:00 01:42:30 01:46:00 01:49:30 01:53:00 01:56:30 02:00:00 02:03:30 02:07:00 02:10:30 02:14:00


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