It’s more than obvious that wearable electronics, particularly those used for health and medical applications, are a quickly growing field with much room for imagination and innovation. Consumers have become quite enamored with fashionable devices that wrap around the wrist, ankle, or hang from the neck that not only sort of look good, but tell them something about their daily physical activities. A lot of these devices can also tell the wearer how their anatomy is reacting to those activities.
Since these devices give out readings of physiological responses, such as heart rate, blood pressure, steps taken, distance of a run, moisture levels, calories burned or consumed, etc., most consumers tend to view all of these wearables as reliable medical devices. It is important, however to know the differences between wearable sensors for health and fitness and those for medical applications.
Health & Fitness vs. Medical
Basic health and fitness devices are generally designed for use by those who are physically active. These devices measure the results of activity such as number of steps taken, distance walked or ran, amount of sleep time, heart rate, and several other parameters. One example is the Fitbit Flex, a wrist-wearable or clip-on device that tracks/measures motion, steps, distance, calories, sleep, and provides fitness analytics and goal tracking. Smartphone apps for the Flex are compatible with Windows, Mac, and iOS/Android operating systems. Similar devices include the Jawbone Up24, Misfit Shine, and the Withing Pulse, all of which may have an extra function or two or less.
Most of these fitness trackers range in price from $100 to $200. Pricewise, not a major budget buster, but not so small as to warrant a lack of basic quality. In terms of accuracy, these consumer trackers are essentially accurate enough for their designated users. These are people who, allegedly, have no major medical conditions and are using the devices for tracking their exercise routines, calorie intake, and mileage for getting in better shape and/or for losing a few pounds.
If the accuracy of readings in these devices is, say ±10%, not much harm would be done. These devices are often thought of as being more motivational in function than being precise barometers of health. If someone ran one mile and the wristband reads 0.9 mile or 1.05 mile, the runner may be a little disappointed or elated, respectively, but neither error will have any impact on his or her health.
However, if a person with diabetes were using a consumer wearable to check blood glucose levels, a ±10% accuracy could be dangerously misleading. If the device also dispensed insulin, the inaccuracy could prove fatal.
Wearables for true medical applications should be operationally defined as:
- Devices intended to monitor a critical health parameter or parameters related to a chronic condition and/or illness. A few examples would be blood pressure, temperature, heart rate, galvanic skin responses, skin moisture, and blood sugar/glucose levels.
- Devices that treat a condition by injecting medication, applying stimulation via heat, cold, vibration, or electrical charge, or issue an alarm that medical attention is required soon or immediately. These devices can also send wireless communication to a remote medical practitioner or service.
- Any wearable device ordered by a physician that is not purchased over the counter and requires a prescription.
Of course, if an exercise regimen is prescribed for a patient, an over-the-counter fitness tracker may be safely recommended. But if the activity of a patient with a pacemaker needs to be monitored, a more accurate device should be prescribed.
Any device that functions by measuring the contents of blood via the use of a puncturing implement (needle or other), should be highly accurate and would most likely not be available without a valid prescription. If the device also regulates levels such as insulin or other enzymes, the same considerations should apply.
Another area for critical examination is implantable sensor-based medical devices. That will be a subject for a future article.
Dedicated Medical Wearables
There are some common wearable types that monitor parameters ranging from basic to critical. One example, the VitalPatch made by Vital Connect, employs a biosensor to measure heart and respiratory rates, skin temperature, and posture.
It also provides fall detection, making it viable for use in hospitals, rehab centers, and at home. Importantly, as we’ll see later, VitalPatch carries the necessary regulatory approvals for sale and use in the US.
Some believe there is a diabetes epidemic in the US and elsewhere, due to a variety of genetic dietetic phenomena. Whether diabetes is of an epidemic level or not may be debatable, either way, a lot of people are diagnosed with either Type 1 or 2 diabetes with a good portion having what is known as uncontrollable diabetes. Many require their blood-glucose levels monitored constantly and many also require an automated insulin-delivery system to ensure glucose levels are kept at normal levels.
One of several companies that specialize in diabetic wearable devices is Abbott. Recently approved by the Food and Drug Administration (FDA), the company's FreeStyle Libre Pro system continuously monitors glucose levels.
A small, round sensor is applied on the back of a patient's upper arm via a self-adhesive pad and remains on the arm for up to 14 days. It does not require patient interaction or the need to draw blood for sensor calibration. The sensor records glucose levels every 15 minutes, capturing up to 1,340 glucose results over 14 days, after which a doctor uses a reader to scan the sensor and download the 14-days' worth of glucose results stored in the sensor.
Also addressing diabetic-related events, Medtronic’s MiniMed 530G system with Enlite sensor is described as an artificial pancreas. The FDA-approved wearable device monitors glucose levels and, similar to the pancreas, automatically dispenses insulin as needed.
It must be noted that the title “artificial pancreas” is not quite accurate. Glucose monitor and insulin pump would be more in tune with what the device does. MiniMed 530G monitors blood sugar and administers insulin, but it does not perform any of the other pancreatic functions, such as provide digestive enzymes (amylase, protease, lipase, etc.).
Unique & Esoteric
Currently, there are a wide range of unique medical wearables that are more application-specific than the aforementioned devices. As time goes by, more will emerge to treat patients who suffer various injuries and some less common and emerging illnesses.
One such device that catches the eye is a wearable robot mask to support rehabilitation of facial paralysis. Presented in a paper at the fourth IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, Rome, Italy, June 24-27, 2012, the Robot Mask supports expressiveness for facial-paralyzed patients. One of the more common causes of facial paralysis is Bell’s palsy, followed by other virus infections, stroke, trauma, tumor, and neonatal conditions.
Very briefly, the Robot Mask is a wearable device that provides physical support by pulling the facial skin via flexible wires attached to the face. Shape memory alloy (SMA) based linear actuators pull the wires and a head supporter is used to mount them and other necessary peripherals. The system employs bio-robotic control that relies on bioelectrical signals from the healthy side of the face. Essentially, the actuators are controlled according to reactions of the wearer. As this I too complex to go into further here, and if this intrigues you, the full paper is available for free download.
ACCURACY: A Common Challenge For All Wearable Types
A topic that has been the focus of many articles in the mainstream media surrounding medical and healthcare/fitness wearables is accuracy. No matter what the application, accuracy is without question the most important feature of any of these devices offered to monitor, analyze, report, regulate, and/or treat human health.
Stated earlier, a wider latitude of accuracy, or inaccuracy, may be permissible in general fitness applications. That’s okay if the user understands this and is sensible enough to not take the readings from his or her fitness tracker as golden. On the other hand, the person who may have a serious heart condition who forgoes a more expensive and more accurate heart-rate monitor may be playing against the house odds.
Accuracy An Issue Of Focus At Medical Sensors Design Conference
At the recent Medical Sensors Design Conference, held in Newton, MA May 8-9, 2017, several sessions were devoted to the importance of wearables for both health and fitness and genuine medical applications. The shortcomings of several popular products were discussed and several points and a call were made for sensor makers to step up and ensure future products attain higher levels of both accuracy and reliable functionality.
In her opening keynote presentation, Noa Ghersin, an analyst for Lux Research, outlined the transitioning of consumer-based healthcare wearables to reliable medical devices. Ms. Ghersin comprehensively explained and demonstrated the accuracy shortcomings of commercially-available devices like the Fitbit wearables. These devices, she pointed out, are popular with consumers on a number of levels, most of which are viewed as functional novelties and fashion pieces.
The main point was that these simple devices could be the gateway to better, more accurate, and more powerful tools that will help physicians and healthcare professionals to be more proactive and successful in treating, maybe even curing their patients. Of course, they have a ways to go in coming up to the reliability and accuracy levels to do so.
Attending cardiologist and Director of Women’s Heart Health of Northwell Lenox Hill Hospital in New York City, Dr. Suzanne Steinbaum followed with insights into wireless-sensor technologies for current and future medical applications. Taking a cardiologist’s eye view, Dr. Steinbaum addressed the subject of medical grade wearables through personal experiences in her cardiac practice.
One area of emphasis was the possibility of wearable wireless sensors being able to accurately pinpoint the cause of a certain medical event that often presents with a symptom that could indicate numerous causes. For example, the symptoms commonly reported for a heart attack are similar to those reported for gastritis, pancreatitis, gall bladder attacks, dehydration, and maybe a few more. Also, symptoms for a particular medical event, like a heart attack, are different for women than they are for men.
In Dr. Steinbaum’s presentation, there was a clear call to sensor makers. Future medical diagnoses need to be made more accurate in the detection of these fine nuances that differentiate one symptom from another and the root cause. Future wearable sensors, particularly wireless sensors show great promise and need to provide physicians with uncompromised information about their patients.
In summary, the future looks very promising for wearable medical sensors. They need to be made smaller to ensure patient comfort and more accurate to insure physician confidence and competence. As far as can be seen, all of this is well within reach.
There are two other challenges facing medical wearables makers, which were also brought out in the presentations. These are the task of obtaining Food and Drug Administration (FDA) approvals for new devices and patients gaining medical-insurance coverage should such a device be prescribed by their physicians.
Unfortunately, both of these hurdles are political in nature and can cause some heated, if not aggressive debates. In terms of the FDA, it is important that medical devices and drugs pass stringent testing to ensure user safety. It may not always be the case, but for the most part, gaining agency approvals adds layers of credibility and confidence.
At one time, health insurance was a private-sector issue, but in recent years the US government has had its fingers in the pie. Wearable medical devices do present an interesting conundrum for medical insurance companies, actually loophole would be a better description.
Wearable devices may be considered to be cosmetic since they may be made to look unobtrusive on the patient’s body. A good example comes from the dental field. When dentists and patients learned that the old silver fillings they had were not healthy, there was a demand for safer ceramic replacements. Since these ceramic fillings came in various shades to match the patient’s tooth color, the insurance companies claimed the replacements were for cosmetic reasons and would either reduce or refuse coverage. Even then, this would be considered a political move.
But all of this aside, the future of medical wearables is looking good. There will be many new developments and an exciting time will be had by all. ~MD
About the Author
Mat Dirjish is the Executive Editor of Sensors magazine. Before coming on board, he covered the test and measurement and embedded systems market for Electronic Products Magazine, after which he spent thirteen years covering the electronic components market for EE Product News and Electronic Design magazines. He also has an extensive background in high-end audio/video design, modification, servicing, and installation.