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Health Services on Wearable Devices   Leave a comment

Healthcare systems around the world are facing a ‘perfect storm’, contending with rising costs, changing demographics and growing consumer expectations.  PA Consulting in the UK concluded that a vital component in helping to solve these problems could be the use of ultra-low-power wearable technology. Wearable technology, increasingly enabled by miniaturised ultra-low-power electronics, is said to be used by 8million people in the UK already, with many of those devices being healthcare related.

The benefits of wearable devices are threefold,  they can act as a ‘digital lifestyle coach’; provide unobtrusive monitoring of patient data; and drive efficiencies in the delivery of treatments.  People are voluntarily embracing consumer products ranging from heart rate and sleep monitors to pedometers. Unobtrusive sensors, when combined with the connectivity enabled by the Internet of Things, are making it possible to deliver on-going care, as well as allowing clinicians to collect long-term data and make more informed decisions as a result. The advent of wearable appliances and ubiquitous connectivity could provide the impetus needed to finally make such initiatives a reality.

A ‘wearable’ can be defined as a product that is worn by the user for an extended period of time and which enhances their experience as a result of the product being worn. But add connectivity and independent data processing capabilities, and you have a ‘smart’ wearable device. Bio-stats, for example, are vital signs that measure the human body’s basic functions and can be used to indicate an individual’s state of health. These can include body temperature, pulse/heart rate, respiratory rate and
blood pressure.

Traditional patient monitoring has usually required a trip to the doctor or hospital; wearable solutions, by contrast, can offer an efficient and inexpensive alternative enabling these stats to be measured in the home or at work. As a result lifestyle and behaviour modifications could be suggested and made in real time.

Semiconductor manufacturer Ams has developed a new optical heart rate sensor for use in wrist wearables. The device, the AS7000, has been designed to measure a person’s heart rate by shining light into blood vessels, using a technique known as photoplethysmography (PPG), which works by analysing scattered reflections. The device includes two green LEDs and a photosensing signal processing IC based around an ARM Cortex-M0, the module has been paired with an external accelerometer which allows internal algorithms to handle several potential causes of interference and
distortion.

The main challenges for measuring PPG on a wrist-worn device are the impact of ambient light, cross talk and motor-generated artefacts.  But light from fluorescent and energy saving lamps carry frequency components that can cause AC errors. Analog Devices, which has developed the ADPD142 optical module, uses two structures to reject this type of interference. After the analogue signal conditioning, a 14bit,
successive approximation A/D converter digitises the signal, which is transmitted via an I2C interface to a microcontroller for final post processing. The device includes a synchronised transmit path that is integrated in parallel with the optical receiver. Its independent current sources can drive two separate LEDs with current levels programmable up to 250mA. The LED currents are pulsed, their lengths being in the microsecond range, so the average power dissipation is kept low.

Sensor technology and falling device costs means that wearable technology is becoming increasingly practical, whether as simple ‘single vital sign’ unit that can be attached to the body, such as the AS7000, or in more sophisticated full body sensor filled exoskeletons. The core architecture of a smart wearable has to be a combination of parts such as a microprocessor or microcontroller; some sort of micro-electromechanical sensors (MEMS); mechanical actuators; Bluetooth/cellular/Wi-Ficonnectivity to collect/process and synchronise data; imaging electronics, LEDs; computing resources; a battery pack and support electronics.

 

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