[SPONSORED] 20/20 Imaging Insights: Troubleshooting TEE Probe Leakage Failures

By Ted Lucidi, CBET

Last month, we presented some background content on leakage testing of TEE probes. The process can seem overwhelming and confusing, and it definitely continues to challenge even the most well-experienced HTM professionals. Allow me to begin by firmly stating that routine TEE probe leakage testing is NOT the responsibility of the HTM team. That being said, they should have a clear understanding of the process, the equipment needed to perform the test, and how to help end-users troubleshoot leakage test failures. Simply put, TEE probe leakage testing involves assessing IF a break in the probe’s physical integrity exists (on the distal tip, bending section, or insertion tube).

Unlike flexible endoscopes, TEE probe leakage testing REQUIRES the probe be immersed in a test liquid, typically tap/sterile water or a chemical disinfectant. This poses a challenge, especially if there actually IS a break or opening somewhere on the probe. As soon as the probe would be immersed in the test liquid, the liquid would enter, and begin flooding, the probe.  

Even though facilities and end-users may be performing TEE leakage testing, they may not be following a process that yields the best outcomes. It’s crucial for end-users to perform a thorough visual inspection of the probe PRIOR TO performing a leakage test. Think of it this way … if a hole or opening can be visualized, then there’s no need to perform a leakage test. Departments need to have a comprehensive process for performing TEE leakage testing, answering the questions, “What if I see an area of concern?”, and “What if the leakage test fails?” Merely following the same process every time despite changes in a probe’s physical condition is what leads to costly catastrophic failures. 

Additionally, if the probe fails the visual inspection, or the leakage test, it is going to be removed from service. In this scenario, there is no need to immerse the probe in high-level disinfectant. Ideally, upon seeing an area of concern, an end-user would perform a low-level disinfection (cleaning the probe with an approved disinfectant wipe) and remove it from service. 

From a comprehensive perspective, TEE leakage testing is designed to identify holes or openings on the probe that CANNOT BE VISUALIZED. 

Whether your end-users are using a Fluke ULT800 or BC Group ULT2020 (the two most common meters in-use), it’s possible for them to encounter false-positive leakage test failures. TEE leakage meters perform two tests as part of the full testing protocol: a bath (or conductivity) test and the leakage test.

A bath (or conductivity) test confirms that 1) the proper test lead of the leakage meter is immersed in a test liquid and 2) that the test liquid has enough particulates to adequately conduct electricity. If this test fails, or an error message occurs during this test, the issue IS NOT PROBE-RELATED.

To successfully pass the leakage test, the value of leakage, in microamps (uA), must be both, above a lower threshold and below an upper threshold. The lower threshold confirms that 1) the probe is PROPERLY connected to the meter’s test adaptor(s), and 2) that the probe is immersed deeply enough in the test liquid. If end-users encounter a “Leakage Too Low” error message, while using the BC Group meter, the issue IS NOT PROBE-RELATED. The Fluke meter uses a very slowly flashing red “fail” LED to indicate the same.  

In this scenario, problems with the set up or connectivity are indicated. Possible sources could be failed or intermittent lead wires, poor connectivity between the probe and the meter’s test adaptors, as well as the probe not being immersed, or immersed deeply enough, in the test liquid. Recently, we’ve seen a rise in false positives from customers who use GE TEE probes. Typically, TEE probes are connected to the leakage meter using a single connection. In 2018, GE began requiring the use of two probe adaptors, versus one. Without the use of the additional adaptor, users WILL intermittently encounter “Leakage Too Low” messages. 

The higher threshold is maximum leakage current permissible (as defined by the meter, not international standards). The Fluke ULT800 uses an upper limit of 185 uA, while the BC Group ULT2020 can be programed with a user-defined value. If end-users encounter a “Leakage Too High” error message, the issue MAY be probe related.

As of 2018 GE, along with requiring the second probe adaptor, raised their allowable leakage current limit to 350uA. Most GE 6VT-D probes have nominal leakage at or above 185uA. Using the Fluke meter or setting the BC Group meter’s user-defined limit to less than 350uA could result in false positive test results.

Typically, those performing routine TEE probe leakage testing are following a documented procedure. They may not have a good, or solid, understanding of the science behind the leakage testing process or how best to troubleshoot error messages or failures. HTM professionals can assist their customers by not only helping them understand the testing process, but also potentially eliminating having to remove a probe from service that has falsely failed a leakage test. 

Innovatus provides technical support on the products that we service (ultrasound probes and MRI coils), and many tech support calls are related to TEE probe leakage testing. We’re here to assist you and your customers with this topic and others. We have visual inspection guides on our website that can be posted or used for training end-users. We can also assist with troubleshooting leakage test failures. For questions, assistance, or more information, please reach out to info@innovatusimaging.com If you have a TEE probe that has failed the leakage test, we can help! We have comprehensive repair capabilities on standard and 3D TEE probe models.  

For more information, email at
TedL@innovatusimaging.com or visit
www.innovatusimaging.com/ultrasound.

– Ted Lucidi, CBET, is a clinical, technical and commercial specialist at Innovatus Imaging.