Modern medicine has been able to transplant human hearts for 35 years. But faced by a severe shortage of donors, many patients resort to artificial hearts-an option which has kept them tethered to heavy machines, with wires and tubes running through their skin.

But the AbioCor Implantable Replacement Heart from Abiomed (Danvers, MA) provides the missing ingredient-mobility. Recent engineering advances have made medicine portable, by making devices smaller, lighter, and more efficient.

Other recently developed, portable medical devices include:

Portable heart. The AbioCor heart has been implanted five times in recent months, on its way to satisfying a Food and Drug Administration trial group of 15 patients. Its two artificial ventricles and three-pound, titanium, hydraulic pump are powered by a rechargeable battery and external antenna. One particular challenge was the design of its one-way valves; stagnant flow causes clots, so engineers had to ensure blood flowed smoothly instead of pooling in eddies.

Designers solved this problem with a combination of materials and software: Angioflex, a proprietary polyurethane plastic, and Pro/ENGINEER CAD from PTC (Needham, MA). After moving their conceptual drawings from 2D to 3D, they used Pro/Engineer's complex surfacing software to model the pumps and valves, and to create the testing equipment that simulated blood flow. Finally, Abiomed engineers developed four prototypes in 18 months, so they could run extensive physical tests.

Soon the design could get even better, since Abiomed has teamed with Penn State Medical School's Gerson Rosenberg, Design News' 15^th Engineer of the Year and the creator of a similar device, the Lionheart LVAD (left ventricle assist device), manufactured by Arrow International (Reading, PA). (see DN, 03.11.02)

Bloodless surgery. As we explore the deeper regions of outer space, portable medicine is an absolute demand for astronauts. Whether they're living on the orbiting space station or traveling on a years-long mission to Mars, calling an ambulance is not an option. So NASA funds the National Space Biomedical Institute (NSBRI), a consortium of 12 universities and research labs.

Their most recent achievement is a portable ultrasound device for performing bloodless surgery. High-intensity focused ultrasound (HIFU) is similar to the ultrasound used to diagnose an internal injury, but its beams are precisely focused, not spread out in a fan-shape. That means the HIFU transducer can destroy unwanted tissue or cauterize a lesion by creating pinpoint heat inside the body. It's also intended for remote use in battlefields and ambulances, but is still in the research phase, far from clinical trials.

Only house-calls. NASA is also developing Robo Doc, an autonomous, automated physician that can diagnose sick space travelers. Astronauts who spend many months in space suffer from unique maladies including bone loss, cardiovascular changes (the lack of gravity weakens the heart), muscle wasting (atrophy), balance and orientation troubles, and radiation exposure.

Robo Doc is an integrated set of diagnostic tools, including: an infrared, needleless blood scanner; a miniature MRI (magnetic resonance imager); a touch-screen eye chart; a hand-held x-ray machine; and an infrared photometer than can detect the heat of blood flow to growing cancer cells. Each of these is integrated with existing spacecraft computer systems to save weight.

Hand-held cure. With the growth of handheld medical technology comes a need to train doctors to use these new tools. AssociaMed and MedsPDA (both in Ormond Beach, FL) now offer sites where doctors can share handheld medical software, discuss its applications, browse medical journals, search databases, and swap advice in a virtual medical convention. And personal digital assistants (PDAs) let doctors take this information and go anywhere. The sites are www.associamed.com and www.medspda.com.