Quinton "Exerdop" Exercise Doppler Instrument
The second major project I worked on at Quinton was a brand new device invented by Dr. Dave Albert. He developed the prototype of the device while he was in med school at Duke and Quinton bought the exclusive rights to develop and market it as a product. It uses a "continuous wave" Doppler ultrasound beam to "see" the blood flow coming up out of your heart up the ascending aorta, the primary "exit pipe" of the heart. The device used some patented and sophisticated analog electronics to continuously monitor the speed of the blood flow and calculate, in real time, the velocity of the flow. The Exerdop had a small printer that recorded the peak flow measurements and did some summary calculations on the report. The operator aimed the probe by listening to the "whoosh-whoosh" sound of the blood flow from the Exerdop speaker, aiming the probe for the loudest and clearest signal.
Here's a brochure for the Exerdop. It's the small, short box on top of the big stress test system in the photo. The technician is holding the small Doppler ultrasound probe against the "suprasternal notch" that is just behind the top of you sternum. This is a nice acoustic "window" that lets the ultrasound probe look right down the ascending aorta to measure the blood flow speed.
The idea was that if your heart was healthy, in response to exercise the "peak velocity" of the blood flow would increase. If it stayed the same or dropped, you likely had a malfunctioning heart. Of course, there are conventional "stress tests" that analyze the ECG waveforms of the heart to interpret how well it's working. But first and foremost, the heart is a incredible hydraulic pump, not a electrical generator. Checking how the heart is pumping by looking at the ECGs is somewhat like estimating the horsepower of an engine by looking at the sparkplug waveforms.
Clinical trials demonstrated that the Exerdop was as good or better than the "Gold Standard" Thallium ejection fraction tested on an exercise bike. That test shoots some radioactive dye into your heart and takes a movie of your pumping heart. My measuring the size of the heart compressed and relaxed, the "ejection fraction" is calculated. The higher the better, but more importantly, if it goes up a certain amount with exercise, that's a sure sign of a good heart.
The downfall of the exerdop was the lack of success in getting insurance companies to reimburse doctors for an "exercise Doppler" test. If a Doctor has to pay a chunk of money for a new machine and can't get any incremental revenue for using it, most doctor's can't afford to use it. In the end, only a few states allowed payment for using the Exerdop and it was not a commercial success. That is sad because it was as good as the invasive thallium test, plus it was much cheaper, safer and much more convenient to perform.
I really learned a lot on this project about medicine. Dr. Albert and his colleagues that participated in the clinical trials were a great group of people that always had the time to help educate me about medicine and cardiology. In my next life, I think I'd like to be a surgeon!
My part on this project was the project manager and mechanical design lead. Besides me, there was one software engineer, one mechanical designer/drafter and one electrical engineer. I also did some of the preliminary mechanical layouts of the enclosure (sheet metal and pressure formed parts), managed the clinical trials, trained the sales staff and did the early design and fabrication of the actual Doppler ultrasound transducers in the Quinton engineering lab.
Last updated: November 09, 1996