OR with Ultrasound System

Auto Cool Imminent

Error messages such as Auto Cool Imminent, Over Temperature Warning, and Near Thermal Limit can occur with no cause of the probe.

It can be trying for both end-users as well as service engineers when a product, sent-in for repair of a specific issue, is found to have no problems whatsoever.  Repair providers face increasing pressure to resolve problems accurately and quickly yet doing so without valid data for best practices has the potential to have serious consequences. Those that engage in multiple types of and levels of testing are better prepared to solve problems right the first time and achieve optimum outcomes.  Over the years, the Innovatus team has repaired over 25,000 TEE probes and has evaluated over double that amount.  Our engineers have spent thousands of man-hours researching the various models of TEE probes and collecting data to develop profiles and characteristics for the various models we support.

One scenario where we cannot always duplicate the end-user’s issue involves messages received during a TEE study, such as “AUTO COOL IMMINENT“, “OVER TEMPERATURE WARNING” or “NEAR THERMAL LIMIT“.  Messages like these are a result of the distal tip of the TEE probe becoming excessively warm and posing a risk of esophageal burn to the patient.

THEORY:  The continued high-frequency pulsing of the acoustic array within a TEE probe causes its internal temperature to rise. The rise in tip temperature can be transferred to the patient causing thermal damage or even burning of the esophagus. TEE transducers contain a temperature sensor, called a thermistor,  within the tip to sense the temperature (of the tip, not the patient) and disable the ultrasound system if the tip temperature becomes excessively high. During a TEE study, this temperature is displayed on the scanner for end-users to monitor.

What many end-users, as well as veteran service engineers, may not realize is that it’s possible for a factory-new TEE probe to experience an over-temperature issue.

OR with Ultrasound System

APPLICATION: When the TEE transducer is first connected to the scanner and is initially inserted into the patient (while the scanner is frozen and before active imaging has started), the temperature reported will be very close to the patient’s actual core temperature. Once the scanner has been unfrozen (and is actively imaging), the tip temperature can rise 1 – 2 °C above the patient’s core temperature. Once color Doppler or 3D mode is enabled, the tip temperature can rise an additional 1 – 2 °C. The use of harmonic imaging, which is extremely common, can also have an effect on the tip temperature. Depending upon the physiological conditions of the patient, the length of time that the probe is actively scanning and the particular scanning mode in-use, a TEE tip temperature of 41 – 43 °C could be possible. Our engineers have been able to induce an over-temperature condition on factory-new TEE probes.

SOLUTIONS:  OEM’s specifically address thermal heating in their user manuals, and it’s suggested that end-users and service engineers consult OEM manuals for the most up-to-date information for their particular scanner. In general, OEM’s recommend the following when over-temperature messages are encountered.

  • Reducing the acoustic output of the transducer: This is a very seldomly used secondary control that is often hidden on a sub-menu on most scanner user interfaces. According to our data, this has the greatest effect on reducing thermal heating.
  • Limiting the time spent in color Doppler and/or 3D mode:  Although color imaging is one of the primary modes used during TEE studies, limiting its use (and ultimately its power) can greatly affect tip temperature. Also, 3D volumetric imaging utilizes thousands of acoustic elements within the array versus the amount (traditionally <100) used during traditional 2D imaging.
  • Freezing the scanner, when active imaging in not required:  Freezing the scanner, if only occasionally for a minute or two, allows the tip to cool.
  • Disabling harmonic imaging: Although highly popular, disabling harmonic imaging can help to reduce TEE tip temperature according to one OEM.

One scenario which can intensify over-temperature errors is performing a TEE study on a patient with an elevated body temperature. Remember that the patient’s core temperature is the baseline.  A patient with a core temperature of 38° versus 37°, only allows for 3° of variance before an over-temperature message is displayed. End-users, performing TEE studies on patients with elevated core temperatures, may need to slightly adjust their scanner settings or modify their practices.

Innovatus Imaging has the expertise, the tools, and proprietary testing capabilities to thoroughly assess TEE probe performance. Our data shows that of all the probes being reported as having an issue with temperature sensing, over-temperature errors or overheating, less than 1% actually presented with a problem. In the event that you have a probe reported to have temperature issues, we can help. We have a team to walk you (or your customer) through the steps listed above as well as welcome the opportunity to assess your probe’s performance.

Taking time to explain the theory behind, the potential applications and possible solutions to end-users can really go a long way in building a strong rapport with the professionals you support.

For more information on the level of testing and engineering that is performed in our Centers of Excellence, click here. You’ll take a video tour of our Center of Excellence for Design and Manufacturing as well as our Center of Excellence for Ultrasound Repair

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