According to the U.S. Food and Drug Administration (FDA), home healthcare is the fastest-growing segment of the medical device industry. Longer life spans, an increasing number of patients with chronic medical conditions, and rising health costs are the main forces behind the trend of immersing the consumer home market with “smarter” and “friendlier” medical devices (Fig. 1).
What kinds of medical care products are turning up in the home? Blood glucose meters, digital blood-pressure meters, blood gas meters, digital pulse and heart-rate monitors, digital thermometers, pregnancy testers, iontophoresis transdermal drug-delivery systems, dialysis systems, and oxygen concentrators. Many can be interconnected via the Internet, often wirelessly, to the offices of healthcare providers for constant on-the-spot monitoring of vital signs and diagnostics.
As technological medical product developments become more complicated, so do the requirements for their design—many of which can be conflicting—to ensure that they can be used safely and effectively by everyone, including healthcare providers and patients, and most importantly, the home user. For the design engineering community, all of this has meant doing more on the chip or circuit board in a given amount of space while dissipating the least amount of power.
“The biggest problem for a designer of ICs for home healthcare products is knowing how to properly balance issues like small size, lower power, costs, reliability, lifetime, processing power, and safety,” explains Steve Kennelly, senior manger of the Medical Products Group of Microchip Technology. “The amount of processing power needed is influenced by who the user of the medical device is.”
Many medical devices aren’t produced in very large quantities, making it difficult to automate their manufacture and achieve low market costs. One positive note on this front is that prices for individual electronic components within these products (sensors, MCUs, displays, memory, etc.) are sliding.
Yet another roadblock is achieving hermetic levels well beyond those required for non-medical applications. Across-the-board miniaturization makes hermeticity even harder to attain.
Get To Know Your Device
Operating medical equipment is more intuitive for doctors and clinicians since they’re trained to use such tools. For a home patient, however, operational simplicity is much more important. Fortunately, the latest highly integrated ICs, sophisticated DSPs and microcontrollers, high-density flash memories, and advanced microelectromechanical systems (MEMS) sensors help to achieve that goal.
“We welcome conflicting requirements since they represent an opportunity for us to innovate,” explains Todd Schneider, vice president in the Medical Business Unit of AMI Semiconductor, which largely uses application-specific standard products (ASSPs) and application-specific ICs (ASICs) in its medical designs. “We’ve been in the medical device business for over 20 years and understand the technical challenges posed.”
Every healthcare medical product requires a different set of performance priorities, depending on the application. For example, low cost is one of the top parameters for something like portable glucose meters, which often use disposable chemical strips. A portable home dialysis system, on the other hand, must have reliability and long life as top-of-the-list requirements in a design, with cost being a secondary factor. Implantable devices like automated pacemakers primarily must be highly reliable and small with a long life and as little power dissipation as possible. Cost isn’t a factor in this case.
Size Does Matter
As a result of the large number of performance requirements for medical products, engineers face various design tradeoffs. This means they must carefully balance what kind of sensor, analog-to-digital conversion, amplification and filtering, control and data-processing, power supply, display, and wireless transceiver circuits to use.
Size often is a major design constraint, particularly for medical implants, where minimal invasiveness is an absolute must. Such implants typically contain a sensor, some signal-processing circuitry, and possibly a transmitter, all designed to fit into a tiny catheter or probe that’s inserted into the human body. Small size also makes it easier for the physician or healthcare provider to place the implant in the body.
For example, some smart pills contain sensors, cameras, and RF transmitters that provide a clear and non-invasive view of internal organs. Similarly, DexCon Inc. uses an ultra-low-power ASIC system-on-achip (SoC) from AMI Semiconductor in its implantable glucose monitor, which continuously monitors diabetics using RF transmissions in the 402- to 405-MHz range.
Continue on Page 2
Reprints
