Sensors Have Expanding Opportunities for Use in Wearable Devices for Health Monitoring

This content is excerpted from Sensor Technology Alert and Newsletter, a sensor intelligence service published by the Technical Insights unit of Frost & Sullivan.


As the population ages, and there is increasing concern about maintaining one's health, sensors are expected to have increasing opportunities for use in wearable systems to provide real-time information about vital signs and other physiological indicators of health and fitness, such as energy expenditure. Such wearable body monitoring systems are expected to find greater use in such applications as home health monitoring, fitness centers, elderly care facilities, as well as in physicians offices, health research studies, and potentially corporate wellness programs.

Compared to using cumbersome, expensive equipment in a clinical setting, body monitoring technologies can streamline the process of collecting physiological body data. Wearable body monitoring techniques can, moreover, provide very timely health-related data to an individual, as well as to physicians or fitness professionals--who are thereby able to make more informed health decisions.

BodyMedia, incorporated in June 1999, is focused on designing and building wearable body monitoring technologies and products that allow for conveniently collecting, processing, and presenting key information about an individual's health and health-related behavior outside of a clinical environment. Such physiological and life style information can include, for example, energy expenditure, caloric intake, sleeping patterns, adherence to exercise, and healthy lifestyle programs. Moreover, other third-party devices, such as, for example, a blood glucose monitor, digital weight scale, or a digital blood pressure meter, could wirelessly transmit information using BodyMedia's SenseWear biotransceiver.

BodyMedia, which has thus far raised about US $27 million in funding from venture and strategic sources, develops body monitoring products and technologies in partnership with health care, fitness, and consumer products companies to address diverse markets, such as disease management, club-based fitness, wellness, and home care.

Astro Teller, CEO, told Sensor Technology that BodyMedia focuses on using sensor fusion and sophisticated, proprietary algorithms to collect, process, and integrate data from a series of sensors in order to provide a surrogate for monitoring key, higher-level vital signs at an accuracy and level of performance level that is close to that of 'gold standard' medical equipment. He noted that BodyMedia presently receives about two million minutes worth of data per day from customers and has about 200 million minutes worth data in their servers. BodyMedia uses this data about patient behavior under different levels of activity and in different contexts to continuously refine and enhance its body monitoring devices.

BodyMedia uses the streams of multiparameter, continuous data being collected to create techniques and products that will be able to detect patterns in an individual's behavior and provide one with personalized advice. For example, as the algorithms continue to be refined, the company's products may be able to identify that having a regular exercise time helps one sleep better. BodyMedia envisions that the process of accurate and personalized feedback will be the touchstone of next-generation healthcare technologies.

BodyMedia's products for collecting continuous physiological information from individuals include: the bodybugg calorie management system; the BodyMedia clinical weight management system; the BodyMedia bio-metric monitoring system; and the BodyMedia body monitoring system.

Created in collaboration with the Apex Fitness Group, the bodybugg calorie management system can allow fitness trainers and nutritionists to better manage and motivate their clients. Clients can monitor their own activities throughout the week and share this information with their trainers via the Web or print a variety of easy-to-use reports. The Web-based software accommodates Apex's knowledge base and training methods.

In the weight management system for helping to manage weight loss outside of a hospital environment, patients use the SenseWear Pro2 armband to collect energy expenditure data. They also can monitor their lifestyle activities and nutritional habits and share such data with their healthcare provider for the purposes of evaluation and guidance. The InnerView weight manager Web site helps patients and healthcare professionals identify their daily energy balance based on the difference between calories consumed and calories burned.

The InnerView bio-metric monitoring system, developed initially for CorSolutions to facilitate disease management, includes the wireless SenseWear biotransceiver and the wireless gateway. These products allow companies, such as CorSolutions, to wirelessly collect data emanating from digital healthcare devices, such as a blood pressure monitor, blood glucose monitor, or digital weight scale. The biotransceiver collects data from the device and wirelessly transmits it to a nationwide call center using the wireless gateway modem. Once the data is uploaded, registered nurses at the call center use the information to coordinate interventions or educate patients suffering form chronic disease about how to avoid complications regarding their condition.

The InnerView body monitoring system integrates the SenseWear Pro2 armband with a suite of InnerView software applications to provide data management, analysis, and visualization capabilities designed for researchers.

The SenseWear Pro2 armband--a wireless, wearable body monitor enabling continuous physiological and lifestyle data collection outside of the laboratory--is worn on the back of the upper right arm, and gathers raw physiological data concerning movement, heat flow, skin temperature, ambient temperature, and galvanic skin response. It can be worn up to 14 days continuously without re-charging the battery, stores up to 14 days of physiological and lifestyle data, and allows research subjects to time-stamp their events. The SenseWear Pro2 eliminates the need for researchers and clinicians to administer or apply cumbersome sensors to their research subjects. The bodybugg contains the same hardware--sensors--as that used in SenseWear Pro2.

The SenseWear Pro2 armband uses a two-axis microelectromechanical systems (MEMS) accelerometer, from Analog Devices, to measure motion. The motion--or other parameters--can be mapped to forces exerted on the body and, therefore, to energy expenditure. By taking gravity into account, algorithms can also predict the context in which the armband is being worn.

The proprietary heat flux sensor used in the SenseWear Pro2 armband, made by BodyMedia, measures the amount of heat dissipated in the body. The sensor--which uses very low thermally-resistant material and highly sensitive thermocouple arrays--is placed in a thermally conductive path between the skin and the side of the armband exposed to the environment. A high-gain internal amplifier is used to bring the signal to a level that can be sampled by the microprocessor located in the armband.

The galvanic skin response (GSR) sensor used in the SenseWear Pro2 armband, made by BodyMedia, includes two hypo-allergenic stainless steel electrodes integrated into the underside of the armband connected to a circuit that measures the skin's conductivity between the two electrodes. Skin conductivity is influenced by the sweat from physical activity and by emotional stimuli. GSR can serve as an indicator of evaporative heat loss by identifying the onset, peak, and recovery of maximum sweat rates.

Skin temperature is measured in the SenseWear Pro2 armband using a thermistor sensor located on the back side of the armband near its edges and in contact with the skin. Continuously measured skin temperature is linearly related to the body's core temperature activities.

The near-body ambient temperature sensor used in the SenseWear Pro2 armband measures the air temperature immediately around the wearer's armband. The thermistor-type ambient temperature sensor directly reflects the change in environmental conditions around the armband, such as walking out of an air conditioned building on a hot day.

The use of the aforementioned sensors, in conjunction with simple body measurements including gender, age, height, and weight, can allow for accurate calculations of energy expenditure, duration of physical activity, sleep, and other lifestyle activities.

In 2006, BodyMedia plans to offer a new version of the SenseWear armband, which will include an electrocardiogram (ECG) sensor from which heart rate and beat-to-beat variability can be extracted.

In 'Accuracy and Utility of Multi-Sensor Armband ECG Signal Compared With Holter Monitoring (Preliminary Data)', a study enabled by and published in 2004 by BodyMedia and authored by Amin Al-Ahmad, Michael Homer, and Paul Wang, Cardiac Arrythmia Service, Stanford University Medical Center, Stanford, CA, it is noted that traditional cardiac monitoring involves using a standard holter monitor and placement of multiple chest electrodes and leads. New technology developed by BodyMedia obtains an ECG signal using a wearable armband placed on the upper left arm, without requiring chest electrodes and leads.

The advantages of the new technology cited include ease of long-term wear and the ability to incorporate information about an individual's state during the ECG recording. The study notes that, "The information can be valuable to determine the context of the rhythm in terms of patient activity at the time of the rhythm." In monitoring four patients for a total of 24 hours, analysis of the first 40 minutes during ambulatory activity tasks revealed a correlation coefficient--with respect to holter versus armband monitoring--of 0.9 during nonphysical activity, and a correlation coefficient of 0.72 during physical activity, compared to holter monitoring. The study concluded in part that use of an armband ECG monitor is feasible and may have advantages over the holter for long-term monitoring; and "use of multisensors to add contextual information and ease of long-term wearability may add to the diagnostic utility of the BodyMedia armband ECG monitor."

BodyMedia is also looking at a range of other possible sensors for SenseWear, including a sensor based on pulse oximetry.

BodyMedia is working with healthcare, fitness, and consumer products companies to create opportunities in such areas as--in addition to clinical weight management, cardiac disease management--for patients with, for example, congestive heart failure, sleep disorder management--for monitoring an individual's sleep outside the laboratory, assisted living-- continuous monitoring of elderly individuals, and infant monitoring--such as tracking sleep state, core temperature, and heart rate and transmitting these readings to a concerned parent or baby sitter.

Teller explained that BodyMedia plans to enter the following new markets in 2006: infant monitoring, rehabilitation, elder care, and corporate--and general--wellness. The company is developing a continuous temperature monitoring product for infants. Moreover, a future infant monitoring product will include a heart rate monitor.

Moreover, BodyMedia plans to launch versions of the SenseWear patch in 2006. Eventually, the SenseWear patch, which will include a similar set of sensors, would succeed and replace the SenseWear Pro2 armband.


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