We’ve got a new toy and we want to share it with you! Introducing the new GEN5 Electronic Bowie Dick type test. It’s an inbuilt self-test performed with each sterilization cycle that (in conjunction with annual calibration) remains highly accurate all year-round with no need to purchase indicators, manually store results or replace any component on a routine basis. When used as part of the Sterilizers start of day sequence, the test will be performed automatically prior to the start of a shift resulting in no time wasted carrying out the old-style testing, freeing staff up for other all-important tasks. It’s basically a better way to free up scarce resources and streamline workflow while maintaining effective sterilization protocols.
Effective sterilization dictates that the steam critically penetrates all surfaces of the devices being processed. Therefore, several tests must be performed to ensure that cycle parameters, steam and the sterilizer itself are all within specification. The efficiency of steam sterilization is achieved when steam gives up its latent heat, changing from steam to liquid when contacting items, thereby accomplishing microbial kill. An equivalent dry heat cycle requires a substantially higher temperature to produce the same lethal effect.
The Bowie-Dick test is utilized to determine the air removing efficiency of a pre-vacuum steam sterilizer; an insulating or shielding pocket of air surrounding an object may prevent sterilization of that object. The original test pack was developed in England by Dr. J. Bowie and Mr. J. Dick in 1963. Since that time, the ‘Bowie-Dick’ type test pack was widely used and was recognized as a valuable means of monitoring the air removal efficiency of pre-vacuum and vacuum pressure pulse Steam sterilizers. The original test consisted of 29-36 huckaback type towels, each folded and stacked to a height of 10 -11 inches. A sheet of paper with chemical indicator tape (applied in the pattern of a St. Andrew’s cross) was placed in the centre of the towel stack. The towel stack was then placed inside a metal dressing casket or equivalent container.
Due to the lack of available materials originally specified for the Bowie-Dick type test pack, alternate configurations evolved in the 1970’s. 100% cotton surgical towels were substituted for the huckaback towels; pre-printed chemical indicator sheets replaced the St. Andrews’ cross pattern of indicator tape; muslin, and eventually non-woven surgical wrap material replaced the metal casket.
The 1980’s brought the first single-use, disposable Bowie-Dick test pack. This was a significant development in that for the first time, a convenient, yet reproducible test pack could be used, which was also less expensive. This innovation eliminated the cost of securing huckaback type towels, the time-consuming task of laundering the towels between tests, the labour involved in pack assembly, and the storage space needed for the towel test packs.
Despite these advantages over the original test, the disposable Bowie Dick often requires the user to dismantle the test device to retrieve the indicator. The results on the indicator are often not be easily visible and interpretation can change amongst users. Difficulties with chemical indicator storage over long time periods are an issue. As the bulk of these products are disposable, environmental factors should also be considered.
Although a breakthrough in its time, the disposable Bowie Dick still has some drawbacks. It often requires the user to dismantle the test device to retrieve the indicator. The results on the indicator are not be easily visible, and interpretation can change amongst users. As the bulk of these products are disposable, environmental factors are also a major concern.
To overcome these issues, electronic alternatives have been available since the late 1990’s. Electronic Bowie Dick type tests assess the important physical parameters of the sterilization process with far more accuracy than the disposable Bowie Dick. Objective
Responding to environmental, economic and standards compliance, Atherton has introduced an Electronic Bowie Dick type test. Game-changing, the GEN5 Electronic Bowie Dick type test;
• does not use disposable indicators,
• does not require the operator to manually store results
• does not need to cool down between cycles,
• does not need stand-alone software,
• does not use an interchangeable process challenge device.
An inbuilt self-test is performed with each cycle. In conjunction with annual calibration the system remains highly accurate all year round.
The result is that operators do not have to purchase indicators, manually store results, or replace any component on a routine basis. When used as part of the Sterilizers start of day sequence, the test will be performed automatically prior to the start of a shift resulting in no staff time wasted carrying out the old-style testing.
In a standard Bowie-Dick test pack, steam penetrates the pack from all six sides. As pressure forces steam into the pack, the steam gives up its latent heat to the towels at a lower energy level (heat sink) and condenses into water. If there is air associated with the steam upon its condensation, the residual air is forced into the pack via external pressure. However, due to inconsistencies in towels and pack preparation, the steam may not penetrate with equal force from all six sides and the air may not be concentrated at the exact centre of the pack. The air may be concentrated into two or more diffuse pockets or it may gather above or below the indicator sheet.
With THE GEN5 Electronic Bowie Dick type test, steam can enter only from the bottom of the hermetically sealed challenge system. As pressure forces steam into the unit, the steam gives up its latent heat to the cooler challenge system and condenses into water. If there is any air or other non-condensable gasses retained due to either insufficient air removal or introduced due to a leak during the air removal, or associated with the steam during the steam admission stages, the residual air or other non-condensable gasses, after condensation, are retained in the hermetically sealed unit. This air pocket is cooler than steam at the same pressure. A highly accurate temperature sensor (challenge system RTD) monitors the temperature at the closed end of the challenge system. In an efficiently operating sterilizer, with no air leaks and sufficient vacuum, the temperature measured by the challenge system RTD will not be >2.0°C lower than the chamber reference RTD. If air is present in a sufficient amount to effect sterilization, the temperature measured by the challenge system RTD will be >2.0°C lower than the chamber reference RTD.
Insert Diagram of Challenge System (including challenge system and chamber reference RTD’s) here with an example of air and an example of steam inside the device and one showing an example of air inside the device
The GEN5 Electronic Bowie Dick type test’s detection limits are set to meet the requirements of ISO 11140-4, Sterilization of health care products – Class 2 indicators as an alternative to the Bowie and Dick-type test for detection of steam penetration.
