To fully answer why this test is still important today, we must first understand why it is important to remove air from the sterilizer. Air within a steam sterilizer is often referred to as a non-condensable gas (NCG). As the name indicates, non-condensable gases do not condense when touching a colder item. These gases act like a shield between the steam and the item, potentially shielding bacteria and preventing proper sterilization.
Even today’s sterilizers are not capable of detecting NCG because it could be hiding anywhere in the chamber. Sensors would need to be placed within the packs exactly where the NCG would either be trapped or collected in order to detect it. This is not possible and supports why air-removal tests are still very relevant to today’s modern sterilizers for autoclave testing. The Vacuum Leak Test programmed on your autoclaved only measures the integrity of the sealed pressure vessel and associated piping to assure air is not being admitted to the sterilizer during the vacuum draw downs.
In addition to air-removal, modern Bowie-Dick Tests such as the VERIFY® Bowie-Dick Test Pack provide a critical control for sterilizer performance and verification of steam quality. It ensures the sterilizer can provide the validated preconditioning required, and aid in detection of steam quality that could interfere with sterilization of complex instrumentation.
The Bowie-Dick Test procedure is the same for both qualification and routine testing.
Step 1: Perform a warm-up cycle. This is a critical step needed to properly heat up the sterilizer and can result in false failed Bowie-Dick Test results when not performed. It is the most common step missed, resulting in unnecessary downtime.Step 2: Place the test pack. A Bowie-Dick Test pack must be placed on the bottom rack of the sterilizer, or sterilizer cart, directly over the chamber drain. The drain is where the vacuum is drawn, and any residual air in the chamber will naturally migrate to the test pack.
Step 3: Ensure the chamber is empty. Only the sterilizer cart (on medium and floor loader sterilizers) should be present for a proper test. If the cart is not included, the result could be superheated steam and a failed test.
Step 4: Run the cycle. ANSI/AAMI ST79 does not provide specific guidance on cycle parameters for the test. However, it does indicate that the programmed exposure time should be between 3.5 and 4 minutes. Always follow the sterilizer and Bowie-Dick Test pack's instructions for use on cycle parameters for testing.
Step 5: Open the test pack and interpret results.
Interpreting a Bowie-Dick Test pack varies by manufacturer and can show you more than just air leaks. It can also provide information including moisture presence, steam quality issues, and the presence of NCG in plumbing lines outside of the sterilizer. To assist, STERIS has developed A Bowie-Dick Troubleshooting Guide. Review the Bowie-Dick interpretation guide to better understand what a failed Bowie-Dick Test look like to understand what needs to be done to avoid downtime.