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After implementing all of our design solutions, we proceeded to testing the flow loop with our sponsor, Dr. Barleben.
Throughout the procedure, we monitored the pressure in the aortic branches using Honeywell board-mounted pressure sensors, which relayed pressure signals via Arduino to a laptop running a MATLAB script which plotted the pressure in real time.
Key results from the surgery
Key results from the surgery
Baseline Pressure Readings
Baseline Pressure Readings
For the majority of the procedure, pressure was maintained at about 120/80 mmHg as shown to the left. This gives us a baseline from which to compare any changes to the pressure that may occur during specific parts of the surgery. There were only two instances of significant pressure change, which both happened during ballooning steps.
Ballooning of Main Stent
Ballooning of Main Stent
During the ballooning of the main stent, pressure increased across the board, peaking at around 200/170 mmHg, and returned to baseline after about 10 seconds. This was expected because during this step, a balloon is inflated inside the main body of the stent, restricting flow through the descending aorta, and thus redirecting flow to the branching arteries.
Ballooning of Branching Stent
Ballooning of Branching Stent
During the ballooning of the branching stent in the left subclavian artery, we saw pressure decrease in the stented artery and increase in the other three, returning to baseline after about 10 seconds. Again, this was expected because during this step, a balloon is inflated in the branching stent, effectively temporarily blocking flow through that artery, and diverting flow to the others.
Conclusions
Conclusions
Based on these results, Dr. Barleben found both our flow loop and his fenestration procedure a success. Since our loop simulated baseline pressure correctly and responded as expected to the ballooning steps, we considered it a valid model for the purposes of the project. Dr. Barleben also considered his fenestration technique a success since at the end of the stenting, pressure was not significantly impacted. The short term spikes are not an issue, since he can temporarily slow or stop the patient's heart using cardioplegia.
Future Directions
Future Directions
One of the main future directions of the project will be to use the results from these tests to inform computational fluid dynamic simulations in order to further support our conclusions. Additionally, Dr. Barleben would like to explore other methods of creating fenestrations, such as laser or heat, as opposed to using a simple sharp-tipped catheter. Finally, certain parts of the system, namely connections to the 3D printed patient aorta model, should be standardized to facilitate changing between different patient anatomies.
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