Save Lives! Integrate Wearable Health Monitors into Automobiles
Wearable systems that monitor health through vital signs have grabbed the attention of the healthcare, technology
and consumer sectors over the last decade. Motivated by rapidly increasing healthcare costs and propelled by recent
technological advances in ultra-small sensors, low power computation, power sourcing and wireless communication, the
continued advance of wearable, sensor-based systems will transform the future of healthcare. By enabling proactive
personal health management and continuous monitoring of health conditions, healthcare professionals can predetermine
needed care for their patients.¹ Wearable health monitoring systems are becoming one of the fastest growing
consumer markets worldwide.
Hundreds of companies around the world are diligently working to create new wearable health monitoring devices. The
competition is immense, and companies are constantly looking for ways to gain an edge. Designers face many tough
challenges including power consumption, ergonomics, accuracy, RF integration, cost and more.
The most challenging design requirements for wearable devices are size, ergonomics, power consumption and health
monitoring accuracy. This is especially critical in applications where an individual’s health must be monitored
continuously over long periods of time. These wearable devices need to be comfortable, stylish and last at least an
entire day before a recharge is needed. These factors have a direct impact on the product’s real utility.
As wearable health monitoring devices become more widely used in medical platforms rather than just as fitness
monitoring systems, the "on time" or "usable time" before battery recharge becomes much more important. Fitness
users typically only wear the device for short periods of time while exercising. For health monitoring, wearable
devices must be active and usable for very long periods of time. Battery life between charges is one of the most
important criteria for a wearable health monitoring device.
The challenge for power consumption and battery life is balancing battery capacity and size with efficient power
management (i.e. low power modes, efficient designs, etc.).4 A primary method to increase battery life is
to increase the system’s power efficiency. Various load circuits within the system (such as the microcontroller,
radio, sensors, and analog front-ends) must be driven from voltages different from the battery voltage – thus, each
one requires a dedicated DC/DC converter, which brings with it associated losses.
Until recently, the primary focus for voltage regulation DC/DC converters has been the efficiency of power delivery
in active mode, from light to peak to full load. With the power efficiency well understood, and improvement reaching
saturation, the focus is now shifting to improving power savings in passive mode. This shift is demanded by the
popularity of new gadgets that spend a lot of time in a passive state, with only infrequent spurs of activity. It is
clear that if idle and sleep mode are the dominant operational modes, this is where the power savings must come
from.5
For example, a system powered by a 40mAh, 1.55V silver oxide coin cell battery will have a shelf life of one year
before the battery runs out of charge, assuming the current drawn is about 4µA. A current reduction of a single
microamp would then increase the wearable shelf life by approximately three months! With this in mind, looking at a
traditional product portfolio of conventional low power ICs for mobile and hand held devices, which consume tens of
microamps of quiescent current and several microamperes of shut-down current, it’s easy to see that any improvement
in these parasitic currents will be beneficial.5
Companies such as Maxim Integrated are striving to meet these challenges with ICs designed specifically for the
wearable market. The emphasis has been on making ICs smaller in physical size while operating at ultra-low power
levels. As an example, the MAX1722 boost
converter is optimized for low power consumption applications. This device uses aggressive power savings techniques
to reduce current consumption when the system is in sleep mode and the regulator is shutdown. Shutdown currents can
still be costly, so when the MAX1722 is in
shutdown, all the regulator control circuits are switched off, leaving only the unavoidable parasitic
leakages.5
Smart watches and wearable healthcare systems incorporate many "pivot" type ICs, such as biosensors, wireless
transceivers, and microprocessors. The focus on power consumption and savings should not be limited to these parts
within the system, but must include the supporting ICs, as well. Many other ultra-small, low power devices support
the main infrastructure of a wearable device including supervisors, data converters, and RF chips. Maxim offers a
wide selection of such ICs developed with the wearable market in mind.
A variety of system prototypes and commercial products have been produced in recent years which provide real-time
health feedback directly to the user or to a medical center or physician. These systems can alert the individual or
professional in case of imminent, health threatening conditions. Maxim has developed several healthcare reference
designs to help customers quickly get started building, testing and evaluating their own systems. These complete
designs include full schematics, bills of materials (BOM), PCB Gerber files and support software. One design of note
is the MAXREFDES117, Heart Rate and Pulse Oximetry Monitor
(Figure 1). This low power, optical heart rate module integrates red LEDs, IR LEDs, and a power supply. The tiny
board is optimized for wearable applications and may be placed on a finger or earlobe to accurately detect heart
rate. The versatile module works with Arduino® and mbed® platforms for quick testing,
development and system integration. A basic, open-source, heart rate and SpO2 algorithm is included in the example
firmware.
Figure 1: MAXREFDES117
PCB Board
The MAXREFDES117 utilizes a heart-rate/SpO2 sensor
(MAX30102), an efficient, low power step-down converter (MAX1921), and an accurate level translator with I²C
capability (MAX14595). The entire design typically operates at less than 5.5mW when using with the example firmware.
A block diagram of the system is shown in Figure 2.
Figure 2: The MAXREFDES67# reference design block diagram.
Moving forward, how can we use the latest technology in wearable devices while also helping society and possibly
saving people’s lives? The automotive industry is highly motivated in this area. Automobile designers are
enthusiastically adding more electronics into all aspects of automobiles for comfort, efficiency and safety. This
technology has the potential to reduce the likelihood of automobile fatalities by alerting emergency responders to
victims’ vital signs in the event of an accident or medical emergency.
Consider these statistics on driving and traffic related deaths and injuries:
- According to the U.S. National Safety Council, 38,300 people were killed and 4.4 million injured on U.S. roads
in 2015. From January to June 2016, the United States was on track to have its deadliest traffic year since 2007,
with nearly 19,000 people killed as a result of motor vehicle accidents.
- - Nearly 2.3 million "serious injuries," defined as those requiring medical assistance, were sustained during
the same six-month period, up 30 percent when compared with the first half of 2014. In a similar upward trend, the
estimated costs of these crashes—including medical expenses, wage and productivity losses and property
damage—increased 24 percent, to roughly $152 billion.²
The main emphasis until now for wearable health care devices has been in the fitness market, to monitor health
while exercising – such as while biking, running or similar activities. Wearable systems include a variety of
miniature biosensors capable of measuring significant physiological parameters, such as heart rate, blood pressure,
body and skin temperature, oxygen saturation, respiration rate, and electrocardiogram. The measurements obtained are
communicated via a wireless or wired link to a central node (for example, to a personal digital assistant device or
a microcontroller board). The information can then be displayed on a user interface, or the aggregated vital signs
can be transmitted to a medical center.
Automobiles have the ability to act as the central node to deliver this information to health care providers,
emergency responders, or police as needed. Traffic related deaths and injury statistics can be greatly reduced by
implementing current technology into motor vehicles of the future. Through the use of a simple wearable health
monitoring system in conjunction with current alert systems such as OnStar® or Life
Alert®, a person’s vital signs, including heart rate, temperature and blood pressure, could be sent
to a doctor or emergency responder. This would save critical time by allowing them to prepare for or administer
proper care as soon as possible. To accomplish this, everyone within a vehicle would need to sync their wearable
device to the automobile’s on-board alert system. This could happen once the person is within a reasonable vicinity
of the vehicle so that in the case of an ejection the link would remain. For family vehicles, the wearable device
worn by each person in the car would automatically connect every time the device is near the vehicle. Once connected
to the vehicle, the vital signs would be displayed on the on- board screen and also sent directly to the alert
staff, in the case of a catastrophic event. With this system a parent would have the security of knowing that in
such an event, their child’s health status would be available to medical professionals immediately.
Conclusion
For engineering firms and technology companies, the time is now to not only participate in the wearables movement,
but to also lead it by enabling new solutions to promote healthier lifestyles, prevent injuries, and ultimately,
save lives. Maxim Integrated has been working closely with consumer wearable companies in this regard and is well on
the way toward meeting the tough design challenges posed. By integrating sensors, further miniaturizing components,
and developing new wearable designs and technology, Maxim is actively demonstrating a dedication to the wearable
healthcare industry.
References
- A Survey on Wearable Sensor-Based Systems for Health Monitoring and Prognosis
Alexandros Pantelopoulos and Nikolaos G. Bourbakis, Fellow, IEEE
- U.S. Traffic Deaths Injuries and Related Cost up in 2015
BY Stav Ziv; Newsweek; on 8/17/15 at 2:40 PM
- Design Challenges for Wearables
ECN, Wed, 01/07/2015 - 1:36pmby Karen Lightman, Executive Director, MEMS Industry Group
- 5 Challenges in Wearable Product Design You Can’t Afford to Forget
Design News, 5/06/2015, Mitch Maiman, Intelligent Product Solutions
- Correct Voltage Regulator Selection is Key to Battery Life in Wearables
EDN Europe, 6/16/2016, Nazzareno Rossetti and Meng He, Maxim Integrated
