During July and August of 2008, I did a brief research experience with Dr. Steven Day, a Mechanical Engineering professor at Rochester Institute of Technology. His research is focused on improving artificial heart pumps (constant axial flow pumps like the Jarvik 2000) by replacing mechanical bearings with magnetic bearings. The purpose of this is to eliminate maintenance on the pump due to wear and tear. This way, the pump will outlast the user – not the other way around.
He had me contribute to the project by helping design and construct a frame to simulate the chest cavity were the pump will be implanted. This was upon request from several doctors at Duke University who want to train people to perform the surgery on something artificial before moving to a pig or calf, then ultimately a person.
Right now, the doctors are training people for performing the surgery using a pig heart sitting in a baking tin. It is our job to present them with something a little more realistic and practical that will incorporate the use of rib spreaders, and simulate the confined space they have to work with.
Attached at the bottom of the page, you can find the word document of this web page.
Phase I was supposed to be simple. It targeted a few main ideas: the rib spreaders must be able to be used, and the pig heart should be contained in something easily cleanable that approximates the size of the chest cavity. I was told a basic idea for the frame and that we were on a short timeline (the simulated chest had to be completed in a few days).
We used a Rubberware container to replicate the chest cavity. It was supposed to be close to 6” wide, 6” deep, and 10” long – about the size of the area the doctors have to work with inside the body. I drilled 2 holes in the container and lined them with rubber tubing for the hoses for the pump to go through. The bottom wall (closest to our feet as if it were our body) served as the diaphragm for the hosing to go through.
The container itself sits inside the framework. The frame simulates the sternum and ribcage. The frame was built out of aluminum angle and aluminum flat bar. I made all the necessary cuts on the band saw, filed it, and had somebody from the machine shop weld it together for us. I then drilled holes in the frame and attached the 4 hinges. We lined the “sternum” (aluminum flat bar) with rubber so it would sit better at rest. Springs were also attached to the frame to provide tension as a ribcage would.
Phase I was given to the doctors, and they liked the design when they initially received it.
The design process of Phase II was based on ideas from me, some graduate students working on the heart pump, and Dr. Day. I didn’t get a chance to hear the feedback from the doctors on how they liked the initial simulated chest cavity we gave them. In turn, I unfortunately could not incorporate any ideas or improvements from the doctors. Additionally, phase II will not be completed by me due to lack of time. I will however present some ideas for the next step in the process.
I. Better alignment of “ribs” at “sternum” and when spread
a. Attach tabs near “sternum” so it rests aligned
b. Add bars to keep it centered during motion
II. More solid foundation for ribs to sit on when closed
a. Add bars to the length of the base of the frame
b. Add square beam
III. Hold Tupperware box in place
a. Add aluminum bars and line with rubber or foam padding
· Length bars slide on rods, width bars lock into length bars with slots that are in both length and width bars
IV. Tension providing options
a. Spring or rubber tubing – desired force
b. Across ribs or incorporate with potential centering bars
Below are some drawings of the frame I created using SolidWorks for the next phase. These are all rough ideas and subject to change upon further review.
I. Create a “sternum” to cut
a. 2” X 4” that bolts into frame
II. Cover frame so can close off when done
a. Put rubber on outside of frame
I. Increase dimensions to fit pump inside
II. Create “diaphragm” to cut through
a. Thick rubber for “diaphragm”
b. Create slot in box for “diaphragm” to sit in
III. Other organs?
I. A manikin
II. A torso used for CPR practice
III. Stitch rubber on outside when finishing “surgery”
IV. Lungs made from some sort of inflated ball that will deflate if cut
V. Liver beneath diaphragm
Overall, I feel this whole experience was quite beneficial. I learned about some new technologies and ideas that are being applied to the human heart to help us live longer, healthier lives. I was able to see what kind of work is done in Dr. Day’s lab, and watch videos of the actual surgery people have when getting heart pumps implanted. This allowed me to understand the final destination of the heart pump, and what kind of confined space the surgeons are working with. Keeping all of this in mind, I was able to help construct a simulated rib cage and chest cavity for the doctors at Duke University to practice the implantation of the artificial heart pump.