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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.
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