Differentiated design of home portable medical electronic devices

The number of healthcare products on the market continues to increase as smaller, cheaper, portable home care technologies replace large, expensive equipment, and advances in semiconductor technology are driving the adoption and cost reduction of home healthcare.

According to the World Health Organization (WHO), the number of people over 50 years old in the world was 650 million in 2006, and it is expected that this number will reach 1.2 billion by 2025. In the United States alone, the proportion of people over 65 years old in the population is increasing and is expected to continue to rise in the future.

The healthcare market is huge. According to the US government, the US spends $2.5 trillion on healthcare, which accounts for 18% of the country's GDP. ABI Research predicts that by 2014, there will be 59 million wearable home healthcare devices in use, and the total number of wearable devices will reach 420 million, including those for sports and fitness.

The Freedonia Group believes that the current market value of home healthcare equipment is well over $7 billion, including technologies such as respiratory therapy, intravenous (IV) injections, dialysis, patient monitoring, wheelchairs, walking assistance, medical equipment and safety equipment.

Today's medical devices offer patients lower-cost and safer ways to monitor, and in some cases even manage, their health conditions in their own homes, reducing the need to visit hospitals, clinics or doctors' offices. Healthcare is becoming increasingly decentralized.

Portable home healthcare devices include blood glucose meters, blood pressure monitors, heart rate monitors, digital thermometers, pulse oximeters, asthma monitors for asthma and other respiratory diseases, fall and motion detection devices for the elderly and disabled, digital scales for weight monitoring and management, and devices for treating sleep apnea. Many home fitness devices have also been upgraded to include health measurement and management functions.

Semiconductor technology for medical devices

Driven by internet connectivity, semiconductor IC performance and integration have greatly improved, which in turn has driven innovation in home healthcare devices. Interestingly, the development of these semiconductor ICs has saved thousands of lives and enabled many people to live longer, which has further improved the requirements for healthcare and increased the need for more medical innovation.

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

Many IC functions are driving the home healthcare trend, especially processors and advanced sensors. For example, DSP has high computing power and can be used to realize the next generation of monitoring products.

Advanced accelerometers, such as the ADXL345 iMEMS triaxial digital accelerometer from Analog Devices, are used in millions of gaming consoles, navigation devices, cell phones, automotive applications, and other consumer products. These accelerometers ensure the accuracy of digital blood pressure monitors for home use. They detect and ensure the correct position of the arm relative to the patient's heart during measurement, resulting in maximum measurement accuracy.

Pulse oximeters are one of the latest devices to join the ranks of home healthcare monitoring devices, and blood oxygen saturation is the fifth most important physical symptom after blood pressure, heart rate, respiratory rate and body temperature. Oximeters can be used to measure the amount of oxygen carried by hemoglobin. Hemoglobin is an important part of red blood cells that is used to export oxygen from the lungs to various tissues in the body.

A pulse oximeter (Figure 1) can be designed using many conventional ICs, according to ON Semiconductor, which acquired AMI Semiconductor, a leading manufacturer of advanced custom ICs, three years ago. Several semiconductor IC manufacturers can provide the complete signal chain functions required for home healthcare applications.

Figure 1: Pulse oximeters can be designed using traditional ICs. ON Semiconductor provides the IC in the brown box for pulse oximeter solutions.

"The AD5933 impedance analysis chip we developed can be used to measure parameters such as body fat and blood coagulation, and the output can be linked to a home healthcare terminal that communicates with a doctor," said Paul Errico, global strategic marketing manager for the healthcare division at Analog Devices. "This is just one of the ICs required for a complete signal chain (Figure 2) in portable home healthcare products that we can provide."

The home healthcare equipment market presents many tough challenges to design engineers, including low power consumption and thus longer battery life, robust and powerful data processing capabilities, more user-friendly and simple operation, wireless connectivity, and lower end-user costs. Semiconductor IC manufacturers are also increasingly facing these challenges.

TI's CC430 platform (Figure 3) includes the MSP430 MCU, CC1101 RF transceiver system-on-chip (SoC) and intelligent peripherals, and the entire platform uses a 9.1x9.1mm 64-pin quad flat no-lead (QFN) package. CC430 uses a 128-bit security encryption algorithm and 433, 865, and 915MHz frequency communication, the latter two frequencies are user-selectable. TI also said that the MSP430 is the industry's lowest power MCU, with a power supply voltage ranging from 2.2V to 5.5V, consuming only 330μA (at 3V and 1MHz), and a leakage current of only 0.1μA in standby mode.

Figure 3: TI’s CC430 platform includes the MSP430 MCU, CC1101 RF transceiver, SoC, and smart peripherals.

The latest development based on CC430 is TI's eZ430-Chronos sports watch (Figure 4), which supports many applications beyond sports. "We have delivered 110,000 eZ430 development kits," said Adrian Valenzuela, marketing manager for MSP430. "Through these development platforms, we are trying to support more applications, such as medical (such as heart rate, pulse, blood sugar and body temperature monitoring), home automation, hobbies, etc.

Figure 4: The CC430-based eZ430-Chronos sports watch supports many applications beyond sports.

Microchip Technology uses nanoWatt XLP ultra-low power technology in its PIC microcontrollers (Figure 5), which can be used in home healthcare equipment such as blood glucose meters. Microchip's PIC16, 18 and 24F microcontrollers consume only 100nA current in power-off mode and integrate 800nA watchdog timer, real-time clock and calendar circuits.

Figure 5: Home blood glucose meter circuits require an ultra-low-power microcontroller, such as Microchip's nanoWatt XLP PIC microcontroller.

Some companies use flash microcontroller units optimized for low power consumption to implement handheld home healthcare devices, such as blood glucose monitors. NEC Electronics' 16-bit all-flash MCU is based on the company's 78kOR CPU core and operates from 3.3V to 5V. This MCU integrates an LCD driver, 12-bit analog-to-digital and digital-to-analog converters (ADC and DAC), op amps, and voltage references. In standby mode, the MCU consumes only 1.2μA.

"We have been in the blood glucose meter business since the early 1990s, so we understand the low power requirements of this medical device very well," said Michael Clodfelter, chief technical marketing engineer at NEC. "Some MCU manufacturers advertise nA-level low-power standby mode specifications that are overkill. In fact, about 1μA in standby mode can ensure a long enough battery life for a blood glucose meter.

Clodfelter also sees a trend toward using 32-bit MCUs in portable medical home devices to provide greater precision. In fact, NEC offers the 32-bit all-flash V850ES (Figure 6), which consumes only 90mW/Dhrystone when used in blood glucose meters. The pipelined architecture of this microcontroller can execute at speeds of up to 43 Dhhrystone MIPS (1.1) at clock frequencies between 5MHz and 20MHz.

Figure 6: NEC offers 32-bit all-flash V850ES

Respiratory monitoring

Portable testers for respiratory monitoring are one of the most recent healthcare products to enter the home. Some of the more well-known respiratory diseases include chronic obstructive pulmonary disease (COPD), asthma, and sleep apnea. More than 300 million people worldwide suffer from asthma.

KarmelSonix has launched an asthma meter for asthma patients. This personal asthma assessment device uses ADI's 400MHz BF524 Blackfin DSP and is a handheld device placed in the patient's throat. The piezoelectric sensor first captures the irregular data of air flow from the patient's breathing and feeds it to the DSP. The processor then determines the patient's breathing rate, which is defined as the duration of the breathing cycle occupied by wheezing. KarmelSonix said that wheezing rate is a dynamic and important asthma attack measurement parameter for asthma patients.

KarmelSonix's patented software algorithm applies strict criteria to determine the presence of wheezing, which the company says are determined using guidance provided by computerized respiratory sound analysis (CORSA).

“Asthma meters can also be used outside the home. This portable device can be placed in a person’s backpack, and the output data from the asthma meter can be downloaded from anywhere to a physician or healthcare provider through a USB port on a laptop,” said Tony Zarola, strategic marketing manager at Analog Devices. “We expect to see the use of Blackfin DSPs in wireless EKG monitoring devices through the USB port.”

To advance the development of portable home healthcare devices, TI offers development kits based on the TMS320VC5505 DSP. According to TI, these kits can accelerate time to market by up to eight months. Each kit contains hardware and software design tools, including schematics, sample code, medical-specific algorithms and other indirect support.

Royal Philips Electronics offers a smart sleep apnea therapy system for home healthcare. The Reprionics Sleep Therapy System is about the size of a clock radio (7x5.5x4 inches) and provides treatment options for patients with moderate to severe sleep apnea. The system uses the positive airway pressure principle developed by Philips to provide a gentle flow of compressed air through a mask to keep the patient's airway open.

"This is the most sophisticated sleep apnea treatment product we have ever offered, and it comes at a time when patient compliance is most problematic," said Donald Spence, CEO of Philips Home Healthcare Solutions.

Philips also offers the Trilogy 100 portable home life-support ventilator for use by adults and children, designed to help nurses and clinicians care for patients at home and in quality care centers.

In addition, Philips is also promoting home healthcare platform display terminals, which can easily achieve remote patient management through the patient's home TV or the Internet. This is exactly what the company's Motiva interactive platform provides. In addition to monitoring important physical symptoms, this device can also provide educational information and motivational messages, and can be used for health-related measurements.

Intel recently announced that it is testing Health Guide, a PC for medical information monitoring and communication that can monitor the vital signs of elderly patients with chronic conditions and provide the details to remote medical providers over the Internet.

Intel and GE, both prominent members of the Continua Health Alliance, recently joined forces to tackle healthcare issues for the home and assisted living devices. The Continua Health Alliance was established in 2006 to address lifestyle, health and demographic trends that are driving rapidly rising healthcare costs.

The Continua Health Alliance is comprised of leading healthcare providers, insurance companies, hospitals, pharmaceutical companies, semiconductor IC companies, and sporting goods and medical device manufacturers. The organization is dedicated to the standardization of wireless and wired communication protocols and helps many IC and medical device providers actively participate in the portable home healthcare monitoring device market.

Interoperability

Interoperability is an important goal for home healthcare devices. The medical device and IC communities recognize that for the home healthcare device market to thrive, these devices must be cost-effective, secure, and able to quickly communicate with each other and other patient information resources.

"Interoperability is an important topic that will drive further growth in the portable home healthcare market," said Rajesh Verma, TI's business development manager for MCU medical solutions. "As part of this effort, we are actively assisting the Continua Health Alliance in standardizing all workable communication protocols."

The Continua Health Alliance recently selected the 2.4GHz Bluetooth LE and Zigbee healthcare protocols for the second version of its interoperability design guide. Due to its popularity in mobile phones, Bluetooth LE may become the standard for home healthcare devices. On the other hand, Steve Dean of TI pointed out that ZigBee may dominate in certain clinical devices for patient and asset tracking.

There are also some private protocols, such as ANT from ANT Wireless, a division of Dynastream Innovations. ANT is an ultra-low power wireless 2.4GHz protocol that is mainly used in healthcare and fitness monitoring applications. ANT Wireless says that nodes using the ANT protocol can last for several years on a button battery, compared to months for other batteries. ANT is specifically designed for reliable and flexible data communications and is highly resistant to crosstalk.

Interference-free medical monitoring is an important issue for designers, engineers and medical design OEMs. Medical monitors and transceiver designs must emit signals at low energy levels and not interfere with other signals in the surrounding area. Wireless and wired transmissions must meet the strict safety and reliability requirements of the U.S. Food and Drug Administration (FDA). In addition, the data sent must meet the strict privacy requirements of patients and medical providers.

Nordic Semiconductor uses the ANT protocol in its nRF24AP2 8-channel wireless transceiver. The company recently began sampling its nRF8001 BLE chip (Figure 7).

ABI Research predicts that more than 2.5 billion Bluetooth low energy chipsets will be shipped by 2014, with the market growing at a compound annual growth rate (CAGR) of 78%. The chipset evolution will reflect two different implementations of Bluetooth low energy, dual-mode and single-mode, with single-mode chips being the first to be implemented.

Freescale Semiconductor uses the ZigBee healthcare protocol. With nearly 60% market share, Freescale is the leading supplier of ZigBee-based transceiver chips that fully comply with the IEEE 802.14.5 standard. Freescale is also a leading supplier of sensors, embedded processors and power management devices that are widely used in home healthcare equipment, including pulse oximeters, blood glucose meters, insulin pumps, injection pumps, blood pressure monitors and personal monitoring products such as activity monitors, walking sensors and wearable panic alarms.

Wearable human network

Work like that done by the Continua Health Alliance is actively promoting the development of body-worn wireless sensor networks, also known as body area networks (BANs) and personal area networks (PANs). These networks use low-cost, very low-power, interoperable and interference-free wireless sensors connected to real-time displays like watches, which in turn connect to computers in the home. Medical information will eventually be sent from these computers to medical device providers over the Internet or even wirelessly.

"Wireless monitoring will allow healthcare professionals to maintain a high level of vigilance for older adults while allowing them to remain in their homes as long as possible. This approach can significantly reduce costs and make patients feel more comfortable," said Alf Helge Omre, Business Development Manager at Nordic Semiconductor.

At the IMEC Holsts Center in Lueven, Belgium, scientists are developing a BAN for wake-up monitoring that measures four physiological parameters to assess a person's emotional state. The BAN, developed as part of the center's Human++ program, uses a number of sensors attached to a bandage that is wrapped around the body.

The detected human body data is sent wirelessly to a PC as a base station for further analysis by doctors or others in the medical and gaming fields. IMEC scientists believe that this solution can bring high value to various applications in the entertainment and medical fields.

Embedded in everyday items such as clothing and bedding, the hardware and software that monitors and alerts heart patients to symptoms is part of the EU's €14 million HeartCycle project. While this system of connected sensors and monitors won't replace face-to-face interactions between patients and doctors, it could reduce the need for them. The system can detect and remotely monitor small changes in the heart's motion and address them before they become more serious.