Public health services are under increasing pressure with a rapidly expanding population, government cuts and a shortage in qualified staff. Against this backdrop, wearable technology has made serious waves in the last year as the government and health services recognise the potential of self-monitoring in healthcare. Last year The Huffington Post called wearable technology “The Coming Revolution in Healthcare,” whilst the Guardian predicted that 2015 would see healthcare become the central focus for the wearable technology market.
The most common factors measured by medical wearables include heart rate, body temperature, oxygen saturation, blood-pressure, activity and calorie burning. The boom for these kind of devices has triggered a manufacturing drive for sensors that are capable of monitoring this kind of complex, real time information. Yet the design of these sensors represents a host of new challenges to design engineers.
Heart tracking is usually collected by bio-potential measurement, also known as ECG measurement. Electrodes are connected to the body which measure electric signals from the cardiac tissue. Wearable heart tracking devices usually take the form of a chest strap with two electrodes, however, as this is not particularly comfortable, alternative methods such as integrating the electrodes directly into a sports shirt are increasingly popular.
A newer trend in heart-rate monitoring is using a small watch or wrist worn device. This is not possible using ECG methods but requires photoplethysmogram (PPG), technology which also frequently to measure the oxygen saturation level in the blood. With PPG, light is being sent to the surface of the skin and absorption of the light by blood-flow is being measured with a photo sensor. In the case of a wrist worn device, you need to pick up pulsatile components from veins and capillaries just under the surface of the skin.
The main challenges for measuring PPG in a wrist worn device are dealing with ambient light and interference generated by motion. Independent environmental conditions like ambient light, the tint of the person’s skin, or even hairs or sweat between sensor and skin might impact the sensitivity at the receiving side. Ambient light can be incredibly disruptive to measurement. Meanwhile, sport watches and devices worn during exercise have a hard time cancelling out motion interference to the optical system.
To tackle all these issues ADI has developed the ADUCM350, a high performance, flexible analog front-end (AFE) and M3 microprocessor. This can be combined with an optical sensor, a motion sensor and software algorithms to make it a complete optical system. Various power modes make the chip ideal for portable- and wearable- application.
Jan-Hein Broeders, healthcare business development manager, Europe at ADI