Validation of steam sterilisers means that the efficiency of the steam sterilisation procedure is checked in accordance with valid standards. The basis for safe operation, as also set forth in the Medical Devices Operator Ordinance (MPBetreibV), is REPRODUCIBLE PROCESS SEQUENCES which can be proven during validation. Hence validation of OLDER DEVICES is particularly recommended, i.e. of those devices manufactured prior to EN 285 and which do not have a CE mark with a number (as per the German Medical Devices Act - MPG). In the case of older systems a number of special points have to be borne in mind here when making preparations for validation.1
Unlike sterilisers manufactured as per DIN EN 285, in the case of older systems a check must be carried out first of all to establish whether they lend themselves at all to validation. It must be assumed that the original technical fittings do not meet the quality required for successful validation. Mandatory prerequisites for a validable sterilisation process are ONE OR SEVERAL PREVACUUM PHASES for removing air prior to sterilisation from the item to be sterilised. If these prerequisites are not met, the system no longer complies with the state of the art. Is such cases the German Society for Hospital Hygiene (DGKH) recommends that the respective steriliser be upgraded or taken out of service.1
Further REQUIREMENTS FOR A VALIDABLE STERILISER as defined by the DGKH, include:
- Pressure control in the chamber by means of an absolute pressure gauge
- Execution of measurements in the chamber as per DIN EN 285
- Monitoring of temperature limit values
- Own programme for Bowie-Dick test
- Programme for testing for vacuum tightness
- Recorder for recording chamber pressure and temperature
- Separate control and recording of pressure and temperature
- Reproducible process sequence
If only some or none of this equipment is available, validation cannot be performed as per DIN EN 554. Therefore such systems, in line with another DGKH recommendation, should only be operated with the 121°C STERILISATION PROGRAMME and for a minimum plateau time of 15 minutes. In such a case, microbiological tests (spore samples) should be carried out at short intervals in order to check efficiency. Based on past experience, older systems are unable to meet the majority of the DGKH requirements. But so as to, nonetheless, be able to operate validable sterilisers, the hospital should look into the possibility of purchasing new devices or upgrading.
When upgrading or newly purchasing a steriliser it is recommended that, in addition to the general equipment specifications as per EN 285, the future requirements addressed by the hospital to the CSSD in respect of documentation of the sterile items and processes be taken into consideration at the planning stage. Moreover, ancillary equipment used in the immediate surroundings of the sterilisers should as far as possible be adapted to DIN EN 285. This includes, inter alia, the choice of materials for the incoming steam as well as the steam quality. Equally important is quality assurance in the CSSD. Therefore when planning validation such aspects of previous and future CSSD tasks should also be borne in mind.
If the conditions prevailing in the surroundings of the steriliser are in line with the standards and hospital-specific requirements, plans for validation itself can now commence. An orientational guide to this effect is DIN EN 554 because validation must always be carried out according to the same specifications irrespective of the age of the system. The first step is commissioning during which a test is conducted to establish whether all preconditions are met for operation of the steriliser as per the applicable regulations.
When planning validation it should be elucidated or defined which CONFIGURATIONS are used in the hospital or are required for sterile supply. Therefore it is useful to get a prior idea of the sterile supplies encountered in order to be able to classify the sterile supplies and form sterile supply groups. These groups are a good basis for definition of configurations and of the actual extent of validation.
The equipment used for measurement and control technology should always be calibrated before conducting the tests specified for validation. After this a test for vacuum tightness is required because only with a vacuum- and pressureproof system can reproducible process sequences be obtained and guaranteed. Further validation steps include measurement of temperature distribution in the empty chamber as well performance assessment with a standardised load and with reference loads specific to the respective hospital. This determines the temperature distribution in the chamber and load for all the previously defined configurations (combination of sterilisation procedure, load and loading pattern).
Planning and carrying out validation are complex tasks. Preparations for validation are inevitably more onerous in the case of older systems. The operators of such sterilisers can rely neither on their manufacture as per DIN EN 285 nor can they invoke the provisions of MPG. Rather, they themselves must furnish proof of the quality of their systems. Hence validation of older sterilisers above all poses an organisational challenge for the operator, with technical implementation ranking only second. Despite all difficulties validation of sterilisation procedures is an important and rewarding challenge aimed at quality assurance in the hospital.
1 For the main validation procedure please consult the Recommendations by the Quality Task Group (3 and 4) (Part 1 and 2) in Central Service 1999; 7 (1 and 2): 59 and 129.