Sep. 23, 1998 Little did one Case Western Reserve University engineering professor know when he had open heart surgery and an aortic valve replacement in 1994 that it would have a major impact on his research. Nor did he realize that his graduate student would put him on a track that could one day help others suffering from heart disease.
Jaikrishnan Kadambi, CWRU professor of mechanical and aerospace engineering, became interested in the way blood flows through the circulatory system when former student Chip Davies was doing work on the artificial heart. Davies piqued his professor's interest in how laser diagnostic techniques Kadambi developed to study coal slurries might be applied to blood flow in an artificial heart.
What do coal water slurries and blood have in common? Both are a mixture of liquids and solid particles.
"Blood basically is a slurry," Kadambi explained. "It has plasma, which is liquid, and red blood cells and platelets, which are particles."
If the cells and platelets collect on artery walls or mechanical heart valve surfaces, they can cause blood clots, resulting in stroke and death.
Nature is perfect and does not allow ridges or discontinuities to form along the heart's surfaces, or on the surfaces of arteries and blood vessels, Kadambi said. The blood-flow patterns through the heart valves are perfect. The mechanical heart and its components have surface flaws. Imperfect flow patterns in the valves can leave platelets on these surfaces, resulting in blood clots and other problems.
Researchers have traditionally focused on how liquid flows through the circulatory system, not how a solid-liquid mixture flows, Kadambi said.
He began studying coal slurries in 1986 through research funded by the U.S. Department of Energy. Over the next five years, he learned how to obtain information about the velocity and behavior of particles in the slurry by a technique that matches the refraction index of particles and liquids in a slurry. The refraction index is a property which controls the degree of bending of a light ray.
Although slurries are usually opaque, Kadambi developed a method to make the slurry transparent. He does this by matching the refraction index of the solid -- glass beads -- with the liquid. This allows him to use laser diagnostic techniques to track the flow of particles in the slurry.
"By using this method, we can follow the motion of the simulated platelets and cells through artificial heart components," he said.
Kadambi and Stefan Baumann, a CWRU graduate student in mechanical engineering, are working with Hiroaki Harasaki, a researcher from the Cleveland Clinic Foundation, to study blood flow through artificial heart components. Harasaki is an adjunct associate professor of biomedical engineering at CWRU. The Cleveland Clinic is funding the project, which will hopefully lead to better designs for artificial hearts.
The team has set up a pulsating heart loop in the Laser Flow Diagnostics laboratory in the Glennan Building that mechanically simulates how the blood flows through the heart. The pulsating heart loop represents how the real heart works when it pumps blood. It is linked to a computer that measures the systolic and diastolic cycles.
During the systolic cycle, the heart contracts, forcing blood into the heart chambers, and during the diastolic cycle, these chambers are filled with blood. The researchers can change the systolic and diastolic cycle timing to reflect the heart rate during periods of rest or exercise.
The researchers use a particle imaging technique known as Particle Image Velocimetry to follow the particle movement and velocity through the slurry.
"We can see the concentration and distribution of the particles in the flow and how they behave," Kadambi said.
This aspect of heart research would have been impossible without looking at coal slurries first, he believes.
"We would not know how to obtain the information about the velocity of the particles without matching the refractive index of the simulated plasma and the cells and platelets."
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