An ultra low power personalizable wrist worn ECG monitor integrated with IoT infrastructure
ABSTRACT
Cardiovascular diseases are the leading cause of death in the UK, motivating the use of long term wearable devices to monitor the heart in out-of-the-clinic settings. While a wide number of heart rate measuring wearable devices are now available, they are principally based upon the photo plethysmo graphy (PPG) rather than the electrocardiogram (ECG) and are stand-alone devices rather than integrated with Internet-of- Things infrastructures which collect and combine information from a wide range of sensors. This paper presents a wrist worn ECG sensor which integrates with the SPHERE IoT platform the UK’s demonstrator platform for health monitoring in the home environment, combining a range of on-person and ambient sensors. The ECG device integrates ultra low power consumption electronics with personalizable 3D printed casings which maintain gold standard Ag/Ag Cl electrodes to provide measurements of the raw ECG waveform, heart rate, and mean NN and SDNN heart rate variability parameters. The end device allows for more than a month of battery life for a weight of <50 g including the watch straps. The design and heart sensing performance of the device are presented in detail, together with the integration with the SPHERE IoT platform.
EXISTING SYSTEM :
Fitness trackers are devices or applications for monitoring and tracking fitness-related metrics such as distance walked or run, calorie consumption, quality of sleep and heart rate. Since accurate heart rate monitoring is essential in fitness training, the objective of this study was to assess the accuracy and precision of the Fitbit Charge 2 for measuring heart rate with respect to a gold standard electrocardiograph. Fifteen healthy participants were asked to ride a stationary bike for 10 minutes and their heart rate was simultaneously recorded from each device. Results showed that the Fitbit Charge 2 underestimates the heart rate. Although the mean bias in measuring heart rate was a modest -5.9 bpm (95% CI: -6.1 to -5.6 bpm), the limits of agreement, which indicate the precision of individual measurements, between the Fitbit Charge 2 and criterion measure were wide (+16.8 to -28.5 bpm) indicating that an individual heart rate measure could plausibly be underestimated by almost 30 bpm.
PROPOSED SYSTEM :
This paper presents a wrist worn wearable for overcoming the above four challenges. We use a 3D printed case with painted Silver/Silver-Chloride (Ag/Ag Cl) electrodes which allows for custom shapes and sizes of electrodes which can be made individually for each user if desired (in addition to a fixed size/shape across all people if this is preferred). This is used to provide ECG monitoring of the heart by asking users to touch the face of the wearable with a finger. A second electrode is present on the back face touching the wrist, allowing the wearable to have contact points on either side of the heart for a large amplitude ECG trace to be recorded. We present a high input impedance, high Common-Mode Rejection Ration(CMRR) front-end circuit which is compatible with gel-free electrodes while consuming less than 10 _W of power and using only off-the-shelf electronic devices. The resulting data is used to find the user’s heart rate and other information on the health of the heart, particularly relating to heart rate variability. Our optimized ECG circuitry offers over a month of battery lifetime and is connected to the SPHERE (a Sensor Platform for Health care in a Residential Environment) IoT infrastructure . SPHERE is an established IoT smart-home health care system demonstrator in the UK, and this integration allows for inter-interoperability and platform building based upon the wearable data.
CONCLUSION :
This paper has proposed a new wrist worn wearable for heart monitoring, that is capable of monitoring the user’s heart rate via the ECG, with some measures of heart rate variability extracted and morphological components of the ECG waveform observable. The device has been optimized for low power consumption, trading-off with noise performance. The results allow over a month of battery life assuming moderate usage which is a step change for a wearable of this size and weight (50 g including the strap). It includes 3D printed elements to allow personalization if desired, and to ensure the best body contact is made in all cases. Further, the device is designed to seamlessly integrate with the SPHERE IoT system, adding wrist ECG as a new sensing modality to this platform which already captures activity, location, water usage and other modalities from IoT sensors.