Human vs. Machine: Which Ensures Devices Are Clean?

May 25, 2023
Comparing, contrasting automated instrument washer/disinfectors and manual cleaning efforts

Protecting patients from contaminated surgical instruments is the No. 1 priority for everyone involved in instrument processing. The most efficient and effective way to reduce the risk of patient harm caused by a surgical instrument that remains contaminated after processing is to use an automated washer/disinfector. Manual cleaning of surgical instruments is a time-consuming, labor-intensive activity that often does not ensure a clean, safe instrument after processing.

Automated washer/disinfectors are designed to clean and decontaminate surgical instruments so that they can be safely handled during processing and sterilization. Instruments that are contaminated with hepatitis, CJD or HIV present an obvious hazard to processing personnel. In addition to reducing the risk to processing personnel, automated washer/disinfectors provide the added advantages of:

·      Ensuring reliable, validated and repeatable results on every processing cycle

·       Providing optimal disinfection, cleaning and removal of contamination on instruments

·       Significantly reducing decontamination, cleaning and processing time

·       Reducing labor time, effort and expense

·       Eliminating the human variability of results 

One of the most rigorous decontamination and cleaning validation studies of an automated washer/disinfector was designed and conducted by Jahan Azizi BS, CBET, and Amanda Simonsen, BA, at Midbrook BioMedical.1 The study was designed to create a “worst case” decontamination and cleaning scenario utilizing Midbrook’s Tempest Washer2 and flushable, one-piece Clear Flush Kerrisons.3 The test was designed specifically to see if the Clear Flush Kerrisons could be completely decontaminated and cleaned with the Tempest Washer after the Kerrisons had been thoroughly contaminated with Artificial Test Soil (ATS) and allowed to air dry for 24 hours4 without manual pre-flushing, pre-soaking, or manual pre-washing. 

According to the CDC, the FDA and AAMI, the only way to ensure clean surgical instruments on every processing cycle is to use instruments whose cleaning Instructions for Use (IFUs) have been validated using AAMI and FDA validation testing protocols.5 The Midbrook study was designed to validate the cleaning efficacy of the Tempest Washer under a “worst case” scenario (the cleaning IFU for the Clear Flush Kerrisons had previously been validated by Nelson Laboratories and is available at 

At the start of the test, the Kerrisons were seeded both inside and out with Healthmark’s Artificial Test Soil (ATS)6 containing hemoglobin, protein and carbohydrate to simulate the types of bioburden most frequently encountered in surgical cases. Following the guidelines outlined in AAMI TIR#12,7 the ATS serves as the inorganic/organic challenge for this test protocol. 

The Kerrisons were then left for twenty-four (24) hours to allow the ATS to dry and harden on the outsides and insides of the instruments to replicate a “worst case” scenario from the start of a surgical procedure, the duration of a procedure (which can be up to 14 hours for a liver transplant), transport to decontamination, and the eventual start of the cleaning process. The instruments were then put into the Tempest Washer and run through the standard, automatic cannulated cycle. 

Test Results: The Tempest Washer removed one-hundred percent (100%) of the inoculated Artificial Test Soil (ATS) containing hemoglobin, protein, and carbohydrate after drying for twenty-four (24) hours from all six Clear Flush Kerrisons. 

For a cleaning test to be clinically valid, it must be repeatable by anyone at any time. With the automated Tempest Washer and the flushable Clear Flush Kerrisons, these extraordinary test results can be repeated in any hospital, by any reprocessing personnel, at any time. 

By utilizing this unique, validated technology, hospitals can eliminate the “human variable” in instrument reprocessing and have the guaranteed assurance of thoroughly decontaminated, surgically clean Kerrisons with a minimum of effort for every patient, every time. 

Conclusion: This “worst case” validation testing confirms that a Midbrook Tempest Washer combined with Clear Flush Kerrisons is the new standard for instrument reprocessing. More importantly, this combination virtually eliminates a patient’s risk of contracting a surgical infection from a contaminated instrument.8 

As this “worst case” validation study* shows, automated washer/disinfectors are clearly superior to manual cleaning. The study also demonstrates why it is crucial to patient safety that hospitals only use automated washer/disinfectors and instruments whose cleaning IFUs have been validated using AAMI and FDA testing protocols. Without validation, processing personnel have no way of knowing if all the organic bioburden, including blood and bacteria, have been removed. In the absence of validated IFUs, processing personnel can be following a manufacturer’s non-validated IFU perfectly and still not be assured of sending clean, sterile, moisture-free instruments back to surgery. 

To learn more about validated IFUs, IFU validation studies and their impact on patient safety visit #IFUcan, an online community that examines and explores the world of manufacturers’ IFUs. 

Prior to his retirement in December 2018, James Schneiter had been the founder, owner and president of America’s MedSource Inc., which designed, developed, licensed and marketed a variety of implantable vascular devices, laparoscopic devices and neurosurgical instruments. Schneiter has nearly five decades of experience in medical device design and production, is a recognized expert in instructions for use (IFU) and independent laboratory IFU validation studies and is a co-founder of #IFUcan, an online community that examines and explores the world of manufacturer IFUs. Schneiter can be reached at [email protected]. 

*To receive a copy of the complete Midbrook Biomedical validation test with before-and-after photos of the test Kerrisons please email the author at [email protected]


2 The Midbrook Tempest Washer is now marketed by Skytron as the Flex Ultrasonic Washer-Disinfector,
3 The patented, flushable Clear Flush Kerrisons are available from Elmed Inc.,
4 By way of comparison, instead of the 24-hour contamination used in the Midbrook Biomedical cleaning validation study, the FDA only requires a 30-minute contamination for a validation study. Accordingly, the Midbrook Biomedical validation study was 48 times more rigorous than the FDA’s validation study requirement.
5 FDA publication, “Reprocessing Medical Devices in Health Care Settings: Validation Methods and Labeling. Guidance for Industry and Food and Drug Administration Staff,” updated June 9, 2017
6 Healthmark Industries, Fraser, MI., 2010
7 Association for the Advancement of Medical Instrumentation, Technical Information Report #12,, September 2010