LINCOLNSHIRE, Ill. -- Companies seeking a slice of the huge medical-electronics market might do well to heed the cautionary tale of Aksys Ltd. The startup has been laboring for six years to bring to market the first home system for blood dialysis for U.S. kidney patients. But because of a welter of technical and regulatory issues, breaking new ground is not easy. Even with the technology basically in place, the company's goal is still at least a year away.

Aksys' challenge brings many of the issues facing designers in the medical portion of the embedded-systems world into high relief: There's huge potential, but the technology is especially difficult when lives are at stake. On top of that is the daunting task of dealing with the Food and Drug Administration, an agency many criticize as slow-moving even by the lumbering standards of a government bureaucracy.

The brass ring is a U.S. market that approaches $1 trillion a year. "In what we classify as electro-medical gear, the 1995 market figures reached $9.5 billion, which is a lot of gear," said a spokesman for the Electronic Industries Association (Arlington, Va.). "The market virtually doubled in size from 1986 to 1995."

In its corner of that burgeoning marketplace, Aksys hopes to move hemodialysis--the purification of blood--from the clinic or hospital to the home. The company's Personal Hemodialysis System uses a real-time operating system (RTOS), multiple processors and a host of sensors to pull blood from a patient with kidney failure, purify it and return it to the body. A patented hot-water cleaning system makes it feasible to set the system up at home, since microprocessors monitor all facets of this sterilization task as well as the actual dialysis process itself.

One non-medical hurdle Aksys has encountered lies in telecommunications. Once seen as a feature that could be put off for a while, remote access is now considered a must-have for the first iteration of the device.

"My focus the last year or so has been on the remote interface," said Frank Naber, manager of PC-based software products at Aksys, here. "Everything has to be verifiable. How you get data out of the instrument to show that the treatment is doing what it's supposed to do is a major concern. We're doing that with TCP/IP going to PC software.'' The Personal Hemodialysis System is now able to transfer data over phone lines, "and clinicians can use Windows 95 to export information to any clinical software they want."

Sending data is complicated by the fact that major kidney-treatment clinics might have 30 or so incoming phone lines, and doctors must monitor data in real-time during dialysis. They monitor the patient before treatment starts, and often want to check vital signs afterwards. Aksys is also considering an e-mail feature so patients and clinicians can share other types of data.

The firm was preparing to take its system to the FDA for testing late this summer, but it recently moved that timetable back nine months. Unlike many programs, there wasn't any one key reason.

"The delay wasn't for technical issues, or anything in our initial production," said Dennis Cavender, vice president at Aksys. "It was simply an understanding of the magnitude of work required to prove all modes of operation, to write the software and do the documentation. There are over 150,000 lines of code to be written and looked at."

Even after the system goes to the FDA, revenues will be a while off. Simply submitting the hardware for testing is only the first step.

"By the middle of next year, we should be ready to submit an Investigational Device Exemption request to the FDA so we can do limited medical trials with living humans," Cavender said. "Then we will collect data and submit it in early 1999. The next step is to submit a 510k approval request, which the FDA generally turns around in 90 days. We've allowed for some questions on that, to be conservative. We feel that we'll get clearance to market the system in the middle of the third quarter of 1999."

Like many medical-system firms, Aksys will be running a parallel approval process in Europe. That process is simpler, so it's likely that the system will get its CE mark late in 1998 or early in 1999, Cavender said, about six months ahead of American approval. The anticipated early European okay will help shorten the time the company has to live off funds from its initial public offering, made in May 1996.

The intricately designed Personal Hemodialysis System is an exercise in redundancy. Like many embedded systems, it must operate flawlessly under sometimes unusual conditions.

"Our system has two 386SX Ampro Little boards," Naber said. "One is for normal operation, such as running the modes of operation and handling the user interface. The other board is dedicated to the safety of the patient, providing redundancy for the monitoring systems and redundant feedback from all transducers."

Safety is an obvious concern for a product that is working with a patient's blood. Home hemodialysis systems that were offered years ago occasionally sent cleaning fluids into the tubes while they were connected to the patient, creating trauma and even fatalities. Aksys does not want to repeat that situation, which for a time put the kibosh on the concept of home hemodialysis.

"If the safety processor decides that things are not in the proper range, it will clamp down immediately, shutting off the valves and putting the system in a safe mode," Naber said.

Sensors make the link between the real world of analog signals and the digital world of the controller boards. There is no shortage of them in the machine.

"There are 40 or 50 sensors in our system, mostly transducers and thermistors," Naber said. "They're checking temperature, pressure and conductivity, which tells you how pure the chemicals are."

These sensors are used in three primary operations: preparing the dialysate (the dialysis liquid), performing the dialysis task itself and cleaning the system for its next use. All three operations are quite demanding. A few grams' difference in preparing the dialysate, pumping blood out of the patient too fast or cleaning the system a few degrees below necessary levels could cause severe medical problems or even death. The system relies heavily on processors and sensors to make these medical/mechanical functions safe.

"The first stage is to produce ultrapure water, which we determine with conductivity sensors. The purer the water is, the less conductive it is," Naber said. "Once the water is pure, we drop in dry chemical. This is done in phases, and we tell when it's ready by monitoring conductivity. The dialysate has to be kept at the right temperature during this whole process."

Once this dialysate is prepared, the patient connects to the machine and the actual dialysis begins. The need for precise monitoring while chemicals are prepared pales in comparison to what's needed when the patient's blood is being purified.

"During this process, there are multitudes of things to watch," Naber said. "We've got to continue to assure that the dialysate is delivered at the proper temperature and pressure. We've got to be very careful in the way we pull blood out and put it back. All these parameters are programmed by the physician, so the system has to be programmable."

The third stage is to clean the system and prepare it for the next usage, and here is where Aksys has developed a key technology. The firm came up with a way to disinfect the system with hot water, which is much safer than using chemical disinfectants, even traces of which can cause major problems if they get into the patient's bloodstream.

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