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"Please give blood!" is a cry heard constantly around the world. The need is never-ending. Fortunately, many people are motivated to donate blood in response to large-scale disasters such as hurricanes or earthquakes, but the need is no less great in calmer times when people may not be so generous.
Patients undergoing treatment for leukemia or certain other types of cancer, from the existing blood supply, however, is limited both by the number of donors and by the frequency with which they can donate. While unable to do anything to increase the number of donors, Gambro BCT of Lakewood, Colo., has found a way to dramatically increase the frequency with which donors can donate blood.
"Our Trima™ Automated Blood Component Collection System separates blood into platelets, plasma and red cells by a process known apheresis," says James Ladtkow, a Gambro BCT senior engineer. "It automatically harvests only the needed components and reinfuses the unneeded ones back into the donor. Since it takes the body longer to replenish its supply of red cells than to regenerate platelets or plasma, returning the red cells to the donor shortens the time required between donations."
The effect can be quite dramatic. Through apheresis, a single blood donor can provide six to eight times the amount of platelets found in a unit of whole blood. In addition, when the red cells are reinfused, a person can donate blood up to 24 times a year. Normally, blood can be donated only five times a year. The Trima™ Automated Blood component Collection System can also be programmed to harvest any combination of blood components, depending on what is needed. The system allows a blood center to fulfill its blood collection needs with 25% fewer donations, reducing its costs and increasing its blood supply.
At the heart of the Trima™ Automated Blood Component Collection System is a plastic cassette molded of Eastman Chemical Company's Eastar™ copolyester. The cassette measures approximately 9 ½" (24.13 cm) x 4 ½" (11.43 cm) with a wall thickness of 0.080" (2mm). The cassettes are molded and assembled in-house.
"We evaluated both polycarbonate and Eastar™ copolyester for this application," notes Ladtkow. "We selected the copolyester for several reasons. One, of course, was cost. It also compares quite favorably in impact resistance. But more importantly, we selected the copolyester for its solvent compatibility. We use cyclohexane to bond PVC tubing to the cassette, and the copolyester is compatible with it while the polycarbonate is not."
Sterilization of the cassette was another consideration. "The cassette must maintain its optical clarity," Ladtkow explains. "It cannot yellow when exposed to gamma radiation or ethylene oxide (EtO). We originally intended to use gamma radiation but eventually decided that EtO was a superior process, and the copolyester is unaffected by either."
While Gambro BCT engineers designed the cassette, Eastman provided assistance with the mold design. "They provided extremely valuable mold flow data that allowed us to improve the mold design by reducing its cost and complexity," says Ladtkow.
Eastar™ copolyester is available in a variety of grades, each with a slightly different balance of properties designed to meet the need of different applications. All offer superior ease of processing and chemical resistance compared with polycarbonate and, because of their low heat-deflection temperature, can be easily thermoformed into complex shapes.
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