Electronic Design
Medical Devices Get Ready To Make House Calls

Medical Devices Get Ready To Make House Calls

The population is aging and medical costs are soaring, creating a greater need for home-based healthcare solutions. These pressures have led to an increase in the number of healthcare devices on the market as smaller, portable, and less expensive homecare technologies replace larger, costlier equipment.

The numbers are daunting. According to the World Health Organization (WHO), the worldwide number of people age 50 and older was 650 million in 2006. WHO expects this total to reach 1.2 billion by 2025. In the U.S. alone, those age 65 or older now constitute an increasing share of the population, a number that is expected to rise steadily in the future.

The healthcare market is big business. According to the U.S. government, the U.S. spends $2.5 trillion on healthcare, representing 18% of the nation’s gross domestic product (GDP). ABI Research forecasts that 59 million wearable home health devices will be used by 2014 and that the total number of wearable devices will be 420 million by then, when devices for sports and fitness applications are counted.

The Freedonia Group puts the present market value of home healthcare medical equipment at well over $7 billion, when technologies for respiratory therapy, intravenous (IV) injections, dialysis, patient monitoring, wheelchairs, walking assistance, medical furniture, and safety devices are considered.

Today’s devices give patients a lower-cost and hassle-free option for monitoring and in some cases treating their health conditions right in their own homes. There’s less of a need to have them travel to a hospital, medical clinic, or doctor’s office. Healthcare is becoming more decentralized.

Portable home healthcare medical gadgets include blood glucose, blood pressure, and heart rate monitors, digital thermometers, pulse oximeters, wheezometers for patients with asthma and other respiratory disorders, fall and movement detection devices for the elderly and disabled, and digital scales for weight monitoring and management. Therapeutic devices for sleep apnea are available as well. And, many home fitness devices are being updated to include health measurement and management functions.

IC ADVANCES

Facilitated by Internet connectivity, advances in semiconductor IC performance and integration levels are driving innovations in home healthcare. Paradoxically, these semiconductor IC advances are saving thousands of lives and pushing the number of people living longer even higher, placing still greater demands on healthcare and increasing the need for more medical innovation.

Designers can take advantage of sensors, microcontroller units (MCUs), microprocessors, DSPs, analog front ends, memory devices, power ICs, and transmitters and receivers. FPGAs also are implementing many functions. These solutions all achieve a high level of functional integration.

Many IC functions are driving the home healthcare trend, particularly processors and advanced sensors. For example, DSPs are enabling a new class of monitoring products thanks to their high computational performance levels.

Advanced accelerometers like the Analog Devices ADXL345 iMEMS tri-axis digital accelerometer, found in millions of games, navigation devices, cell phones, automotive applications, and other consumer products, ensure the accuracy of home digital blood pressure meters. They sense and ensure the correct position of the arm (where the cuff is placed) relative to the patient’s heart for maximum accuracy.

Pulse oximetry is one of the more recent functions to invade the home healthcare monitoring scene. It’s considered the fifth vital sign after blood pressure, heart rate, respiratory rate, and temperature. It measures the amount of oxygen bound to hemoglobin, an essential part of the red blood cells that deliver oxygen from the lungs to the tissues.

A pulse oximeter (Fig. 1) can be designed using a number of conventional ICs, according to ON Semiconductor. The company purchased AMI Semiconductor, a leading manufacturer of advanced custom ICs for medical applications, three years ago. Some semiconductor IC manufacturers supply the entire signal chain of functions needed for home healthcare applications.

“We developed the AD5933 impedance analyzer chip for measuring parameters such as body fat and blood coagulation. Its output can be linked to a home telehealth terminal for communications with a physician,” explains Paul Errico, worldwide strategic marketing manager for the Analog Devices Healthcare Group. “This is just one of the ICs needed for an entire signal chain (Fig. 2) in portable home healthcare products that we can supply.”

“We’re trying to enable the solutions for present and future home healthcare applications needs, which include not only the data measurement part of the signal chain, but also the connectivity part between home patients and their medical providers,” says Steve Dean, medical marketing director at Texas Instruments.

DESIGN CHALLENGES

The home healthcare equipment market poses challenging requirements to design engineers. These include the need for low power and thus longer battery life, robust and powerful data processing, friendlier and simpler user operation, wireless connectivity, and low end-user costs. And, semiconductor IC manufacturers are rising to these challenges.

The integrated Texas Instruments CC430 platform (Fig. 3) includes the MSP430 MCU, the CC1101 RF transceiver system-on-a-chip (SoC) IC, and intelligent peripherals, all within a 9.1- by 9.1-mm, 64-pin, quad-flat no-lead (QFN) package. The unit features 128-bit security encryption and 433-, 865-, and 915-MHz communications, the last two of which are user-selectable. TI also says that the MSP430 is the industry’s lowest power-dissipation MCU. It operates from 2.2 to 5.5 V and dissipates a mere 330 µA (at 3 V and 1 MHz). In the standby mode, current drain is a measly 0.1 µA.

The most recent development based on the CC430 is TI’s eZ430-Chronos sports watch (Fig. 4), which is designed to enable many applications beyond athletics. “We have shipped 110,000 eZ430 development kits,” says Adrian Valenzuela, the MSP430 marketing manager (see “Low-Cost Kits Make Evaluation Faster”). “With this development platform, we are trying to enable many more applications like medical (e.g., heart rate, pulse rate, blood glucose level, and temperature monitoring), home automation, hobbies, etc.”

Microchip Technology has tweaked its nanoWatt XLP extremely low-power technology (Fig. 5) in its PIC microcontrollers for use in home healthcare devices like blood glucose meters. Its PIC16, 18, and 24F microcontrollers draw just 100 nA in power-down mode and feature 800-nA watchdog timers and real-time clocks and calendars.

Some companies use flash memory microcontroller units optimized for low power dissipation for handheld home healthcare equipment like blood glucose monitors. The 16-bit all-flash MCUs from NEC Electronics are based on the company’s 78k0R CPU core and operate from 3.3 to 5 V. They feature an integrated LCD driver, 12-bit analog-to-digital and digital-to-analog converters (ADCs and DACs), op amps, and a voltage reference. Their 1.2-µA standby current was achieved by de-activating the CPU when the LCD is enabled in that mode.

“We’ve been in the blood glucose meter business since the early 1990s and understand the low-power requirements of such medical equipment,” says Michael Clodfelter, principal technical marketing engineer at NEC. “The low-power standby mode specifications in the nA range being bandied about by some MCU manufacturers are a bit of overkill. In reality, about 1 µA is more than enough, for the standby mode, for long battery life in a blood glucose meter.”

Clodfelter also sees a trend toward using 32-bit MCUs in portable medical home equipment to provide even higher levels of accuracy. In fact, NEC offers its 32-bit all-flash V850ES (Fig. 6), which consumes just 900 mW of power/Dhrystone, for blood glucose meters. The microcontroller’s pipelined architecture executes up to 43 Dhrystone MIPS (1.1) at clock speeds from 5 to 20 MHz.

RESPIRATORY MONITORING

Portable instruments for respiratory monitoring are among the more recent healthcare products finding their way into the home. Some of the more notable respiratory ailments include chronic pulmonary compulsive disorder (COPD), asthma, and sleep apnea. More than 300 million people worldwide suffer from asthma.

For asthma patients, KarmelSonix has introduced the Wheezometer. This personal asthmatic assessment device is based on Analog Devices’ 400-MHz BF524 Blackfin DSP. The handheld unit is placed against a patient’s throat. Piezoelectric sensors then pick up air flow irregularity data from the patient’s breathing and feed it to the DSP. The processor determines the patient’s wheeze rate, which is defined as the respiratory cycle duration occupied by wheezing. KarmelSonix says that the wheeze rate is a dynamic and significant asthma attack measure of an asthma patient.

KarmelSonix’s patented software algorithms apply strict criteria to determine the presence of wheezing. The company says that guidelines supplied by computerized respiratory sound analysis (CORSA) define these criteria.

“Having a wheezometer is a real convenience even beyond the home. Such a portable piece of equipment can be carried in one’s backpack. The meter’s output data can then be downloaded, via a USB port on a laptop computer, to a physician or medical provider, from just about anywhere,” explains Tony Zarola, strategic marketing manager at Analog Devices. “We’re looking to use the Blackfin DSP in EKG wireless monitoring applications, via USB ports.”

To expedite the development of portable home healthcare medical equipment, TI is offering development kits based on the TMS320VC5505 DSP. TI says the kits  accelerate time-to-market by up to eight months. Each kit includes hardware and software design tools, including schematics, sample application code, medical-specific algorithms, and collateral support.

Royal Philips Electronics offers an intelligent sleep apnea therapy system for home healthcare. About the size of clock radio (7 by 5.5 by 4 in.), the Reprionics Sleep Therapy System provides of therapy options for patients with mild to severe forms of sleep apnea. The unit works on the Philips-developed positive airway pressure principle by delivering a gentle flow of pressurized air through a face mask to keep the patient’s airway open.

“This is our most sophisticated offering to date, in sleep apnea therapy, and it comes at a time when patient compliance matters most,” says Donald Spence, CEO of Philips’ home healthcare solutions.
Philips also supplies the Trilogy 100 portable at-home life-support ventilator for adult and pediatric use. It is designed to help caregivers and clinicians administer patient care in the home as well in skilled nursing facilities.

Additionally, Philips is promoting home healthcare medical platform display terminals that will facilitate remote patient management delivered through the patient’s home TV or the Internet. That’s what the company’s Motiva interactive platform does. In addition to monitoring vital signs, it can deliver educational information and motivational messages. It can be used for health-related surveys as well.

Intel recently released for testing its Health Guide, a type of PC for medical information monitoring and communication (see “Electronics Helps Foster Decentralized Healthcare” ). It monitors the vital signs of elderly patients with chronic conditions and provides details via the Web to a remotely located medical provider.

Intel and GE, both heavyweight members of the Continua Health Alliance, recently joined forces to focus on healthcare issues for the home as well as assisted-living facilities. Formed in 2006, the organization aims to address the lifestyles, health, and demographic trends contributing to the skyrocketing costs of healthcare.

The Continua Health Alliance consists of leading healthcare providers, insurance companies, hospitals, pharmaceutical companies, semiconductor IC companies, and sports gear and medical equipment manufacturers. It is trying to standardize wireless and wired communications protocols, enabling many IC and medical equipment providers to actively participate in the portable home healthcare monitoring equipment market. 

THE ROLE OF INTEROPERABILITY

Interoperability is a key goal for home healthcare equipment. The medical equipment and IC communities recognize that for home healthcare devices to proliferate, they must be able to cost-effectively, securely, and rapidly communicate with each other and other sources of patient information.

“Interoperability is a major issue that will enable the portable home healthcare market to grow further,” says Rajesh Verma, TI’s business development manager for MCU medical solutions. “As part of that effort, we’re involved with the Continua Health Alliance to standardize on all workable communications protocols.”

The Continua Health Alliance recently selected the 2.4-GHz Bluetooth Low Energy (BLE) and ZigBee Healthcare protocols for Version Two of its Interoperability Design Guidelines. Because of its popularity in mobile phones, BLE likely will become the norm for home healthcare applications. On the other hand, Steve Dean of TI says, ZigBee is likely to dominate some clinical settings for patient and asset tracking.

Then there are proprietary protocols like ANT from ANT Wireless, a division of Dynastream Innovations. ANT is an ultra-low-power wireless 2.4-GHz protocol for healthcare and fitness monitoring applications. The company says that ANT-power nodes can operate for years running on coin-cell batteries compared to months for other types of batteries. Designed for reliable and flexible data communications, ANT is immune to cross-talk interference.

Interference-free medical monitoring is a major issue for design engineers and medical equipment OEMs. Medical monitors and transceivers must be designed to emit low energy levels without interfering with other ambient signals. Wireless and wired transmissions must meet stringent U.S. Food and Drug Administration (FDA) safety and reliability requirements. Moreover, transmitted data must meet strict privacy requirements for both patients and medical providers.

Nordic Semiconductor employs the ANT protocol in its nRF24AP2 eight-channel wireless transceivers. More recently, the company has begun sampling its nRF8001 BLE chip (Fig. 7).

According to ABI Research, just over 2.5 billion BLE chip sets will be shipped by 2014 in a market that will grow at compound annual growth rate (CAGR) of 78%. The growth of the chip sets will mirror BLE’s two different implementations, dual mode and single mode, with single-mode chips implemented first. 

Freescale Semiconductor has endorsed the ZigBee Healthcare protocol. With a market share around 60%, Freescale is the leading provider of ZigBee-based transceiver chips, which conform to the IEEE 802.14.5 standard. It also is a leading supplier of sensors, embedded processors, and power-management devices, all used extensively in home healthcare applications. These include pulse oximeters, blood glucose meters, insulin pumps, infusion pumps, blood pressure monitors, and personal monitoring products, such as activity monitors, gait sensors, and wearable panic alarms.

BODY-WORN NETWORKS

Efforts like those of the Continua Health Alliance are giving rise to the development of body-worn wireless sensor networks, also known as body-area networks (BANs) and personal-area networks (PANs). Such networks use inexpensive, very low-power, interoperable, and interference-free wireless sensors that connect to a real-time display like a watch and then to a home computer. From there, medical information can be sent over the Internet or even wirelessly to a medical provider.

“Wireless monitoring would allow healthcare authorities to maintain a high level of vigilance over the elderly while allowing them to remain in their homes as long as possible. This is a recipe for a dramatic reduction in costs and a happier patient,” says Alf Helge Omre, business development manager at Nordic Semiconductor.

At the IMEC Holst Centre in Lueven, Belgium, scientists are developing a BAN for arousal monitoring by measuring four physiological body parameters to assess a person’s emotional state. The BAN is being developed within the Centre’s Human++ program. It uses sensors attached to a strap that goes around the person’s body.

Detected body data is wirelessly transmitted to a PC acting as a basestation for further analysis by medical or other personnel in the medical and gaming fields. IMEC’s scientists believe this can be of great value for a variety of applications in the entertainment and medical fields.

A mix of hardware and software built into everyday items such as clothing and bedding to monitor and alert cardiac patients about their conditions is part of the European Union’s 14-million Euro HeartCycle project. While such a system of networked sensors and monitors would not be a substitute for face-to-face meetings between patients and doctors, it would alleviate that need by requiring fewer such meetings.

The system detects and remotely monitors small changes in the heart’s behavior that can be addressed in due time before these changes become more serious. Led by Philips Research in Germany, the project involves 17 other academic and industry organizations, including Finland’s Clothing Plus Oy, Philips Electronics NV in the Netherlands, and Medtronics Iberica SA in Spain.

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