DeBakey Ventricular Assist Device, an axial flow VAD of MicroMed Cardiovascular (Houston, TX), is being perfected with the help of Apple Computer technologies:
Professor Marek Behr of Aachen, Germany, works with this technology everyday. He uses finite element analysis (FEA) techniques and a Xserve cluster and Mac desktops to make blood pumps such as the MicroMed DeBakey VAD even more durable and patient-friendly.
“Implantable blood pumps can last for over a year,” says Behr. “That’s long enough for people to find a transplant donor. But our ambition is to make it viable as a permanent replacement.”
Behr directs the Chair for Computational Analysis of Technical Systems (CATS) at the RWTH Aachen University. His team of engineers receives CAD models of the DeBakey VAD from MicroMed Cardiovascular Inc. of Houston, Texas, and subjects them to engineering analysis. The DeBakey VAD is already a medical and commercial success — it has been implanted in nearly 400 patients. But MicroMed and CATS continue to look for ways to improve it.
The pump that CATS engineers are working on is a titanium tube approximately one inch in diameter and three inches long. It is capable of keeping a cardiac patient alive by pumping 300 liters of blood an hour. It pumps steadily, without a pulse.
The pump may be small, but it takes major computing muscle to run the FEA flow studies that Behr and his team are using to refine its design. CATS chose a 44-processor Xserve cluster to power the program.
“We convert the MicroMed CAD models to a finite element mesh,” says Behr, “and we use the mesh to simulate a fully developed flow field on the Xserve cluster using our own computational fluid dynamics (CFD) software. Each simulation is a series of about a thousand time steps, each step with five to ten million finite elements. We needed massive compute power for this process, and once we made our comparisons it was easy to choose the Apple cluster.”
CATS uses these compute-intensive simulations to explore the potential of each design modification, running a variety of flow profiles, flow rates, and impeller speeds to find the best way to improve the flow pump’s biocompatibility. Could it be reduced in size to make it more suitable for young patients? Would a change in the geometry of the impeller blades or the stators reduce hemolysis?