Routine Control of Autoclaves with Bowie Dick Testing

Making sure that procedural and surgical hospital utentils are totally sterile and clean is vital in order to protect patients against contagious diseases and infections. To achieve this, Central Sterilization Service Departments (CSSD’s) wash equipment in washing disinfectors before sterilizing them in large steam sterilizers called autoclaves.

These autoclaves are tested daily to ensure that they operate and sterilize as intended, as patient safety is at stake. Most hospitals utilize large autoclaves (above 60L) and so, are required to perform daily steam penetration tests as a routine control according to the standards ISO 17665 and EN 285.

A Bowie Dick Test is the most frequently utilized steam penetration test. It was originally developed in 1963 by Dr. J. Bowie and J. Dick to monitor the air removal efficiency in steam sterilizers.

Their test was made up of a large volume of folded towels containing a sheet of paper equipped with chemical indicator tape. The test result would be considered a pass if the heated steam within the autoclave passed through the towels successfully and caused all of the tape to react.

The aim of the Bowie Dick test is to assess if the air-removal system within the autoclave removed any excess air and other non-condensable gasses (NCG’s) successfully – thus ensuring that saturated steam reaches, and properly sterilizes all elements of the equipment.

Since applying a large bundle of towels in their autoclaves, the industry has come a long way, normally settling for modern electronic tests or traditional chemical indicators. Yet, the original Bowie Dick test remains the reference technique for compliance testing of alternative Bowie Dick test techniques.

Bowie Dick Testing

Image Credit: Ellab

Chemical Indicators

As previously discussed, chemical indicators have been employed to establish whether the autoclave has reached saturated steam. Chemical indicators are made up of layers of paper and a special test sheet that changes color if the steam successfully reaches it.

Next, the change in color is determined subjectively to either mean pass or fail. This can cause a problem because, if read incorrectly, a slight alteration in color can be detrimental.

Further to this, the accuracy of these indicators has come into question recently, as a number of studies have shown them to give false positives, which can jeopardize patient safety.

Electronic Bowie Dick Tests

Electronic alternatives have been available on the market for some time now, this is because of the aforementioned issues and storage difficulties associated with chemical indicators. Electronic alternatives perform routine and batch control of autoclaves to test their capabilities daily.

Electronic Bowie Dick tests objectively measure and assess critical physical parameters of the sterilization process, eliminating any guess work by supplying more accurate results.

Bowie Dick Testing

Image Credit: Ellab

Batch Control and Parametric Release

Batch control is employed to prove that loads are sterilized according to the Safety Assurance Level (SAL), whereas the daily routine control of autoclaves is performed to “release” autoclaves in the morning. Historically, biological indicators have been the go-to technique for carrying out batch control of steam sterilizers.

These indicators are made up of an ampule which contains a specified amount of microbiological spores in suspension, which are counted after sterilization to identify the survival rate, which is quite a time-consuming process. Yet, electronic test units have also now been introduced for carrying out fast and efficient batch controls.

These devices are introduced alongside the batch and read post sterilization, giving instant results and permitting parametric release. Parametric release is a principle that requires measured data of critical physical parameters using an independent electronic device.

When compared to traditional indicators and techniques, electronic devices and the parametric release techniques carry some distinct benefits:

  • The result is presented straight after the test, permitting the batch/load to be released immediately. Whereas biological indicators require incubation and resource dependent assessments before a batch/load can be released for use
  • Data is shown with a clear pass/fail result, removing any subjective assessment and the risk of misreading
  • Electronic solutions also lead to fewer waste products, supplying a more environmentally friendly process
  • Electronic devices are economically efficient with high test volumes, so data is easy to store, retrieve and compare as it is all located conveniently in a database for safe operation

Choosing the Ultimate Electronic Bowie Dick Test Device

Ellab has recently launched a new and innovative product for electronic Bowie Dick testing and batch control, the ISO 11140-4 compliant SteriSense® system, which is unrivaled in terms of size, user-friendliness, performance, accuracy, and reliability.

By identifying potentially faulty sterilizers that could otherwise have passed less reliable methods, the extremely compact device ensures patient safety – and with annual calibrations, the SteriSense sensors stay highly accurate all year round.

What really sets it aside from other electronic Bowie Dick testing devices is that SteriSense is equipped with a game changing interchangeable Process Challenge Device (PCD).

The interchangeability means that operators do not have to purchase additional backup devices for subsequent runs, or wait for equipment to cool, instead, before running another cycle they can simply unscrew the PCD and replace it with a spare.

The SteriSense software is very user-friendly and next to no training is required to use it. The measuring unit is started and ready to be placed in the process with just one click. Once the program is complete, the device is read, assessing the data instantly and providing a clear Passed or Failed result.

If more detailed information is necessary, reports may be produced, assessed and saved, ensuring full electronic documentation of the process.

Bowie Dick Testing

Image Credit: Ellab

This information has been sourced, reviewed and adapted from materials provided by Ellab.

For more information on this source, please visit Ellab.


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