Electrocardiogram (ECG) or photoplethysmograph (PPG) wearable monitoring systems have become increasingly popular in recent years. Heart-rate monitors, pulse oximeters and activity trackers are commercially available and already play an important role in everyday life. A wearable monitor significantly improves patient comfort by replacing long, cumbersome cords with much less obtrusive dry electrodes that enhance mobility.
The wearable monitor market is experiencing rapid growth, fueled by an increase in health awareness and the advent of improved monitoring services. Of specific importance is the Internet of Things (IoT) concept of tracking vital signs via mobile apps, with data transmission through the cloud to a doctor or health service. This concept, combined with machine learning and artificial intelligence, is expected to take fitness tracking and health monitoring to the next level by contributing to predictive analytics (and thus preventive care) to improve health and reduce health care costs.
A PPG takes optical measurements of an organ’s volume to estimate the oxygen saturation level in the blood (SpO2). There are two types of optical arrangements: transmissive and reflective. The transmissive case uses a bulky finger clip to transmit light through a light-emitting diode (LED) on one side of the finger and measures the absorption by placing a sensitive photodiode on the other side. The finger clip applies some pressure, which causes discomfort over time. In the reflective arrangement, the photodiode and LED are on the same side and the photodiode collects the light reflected from various depths underneath the skin without using the finger clip. This type of mechanism is easily incorporated into watches and other wearable devices that touch the body and do not cause any discomfort.
Conventional ECG monitoring uses a coupling gel on the sensing electrodes, which must be placed correctly on the patient’s body by a professional. Some patients develop allergic reactions and skin irritation when these electrodes are used for long-term ambulatory monitoring. Moreover, the gel also dries out over time, reducing signal quality and performance. In recent years, there has been a growing interest in using dry or ungelled electrodes for long-term physiological monitoring.
TI’s extensive portfolio supports emerging market trends. For example, the Wearable, Wireless, Multi-Parameter Patient Monitor Reference Design uses the AFE4900 single-chip bio-sensing front end for synchronized ECG and PPG measurements (see Figure 1). It integrates flexible LED drivers with complete receiver chains for the photo diodes. It communicates with the CC2640R2F SimpleLink Bluetooth® low energy Wireless MCU, which has an integrated Arm® Cortex-M3 and 2.4GHz radio-frequency (RF) transceiver, over Serial Peripheral Interface (SPI) (or I2C). The design supports wired data capture using a Joint Test Action Group (JTAG) connection, as well as wireless data capture, by sending it over Bluetooth® 5.
Figure 1: Patient monitor reference design block diagram
The key components of the design are:
A LabVIEW-based graphical user interface (GUI) is implemented for testing the reference design. Figure 2 shows measured ECG and PPG data on a remote terminal.
Figure 2: Heart-rate monitor data (using SFH 7072 sensor from OSRAM) and ECG data
The reference design was created for medical, personal health care and fitness applications, and comes with a design guide, schematic, layout and bill-of-materials files to help you quickly evaluate and accelerate product development. It facilitates real-time monitoring and data-logging capabilities and supports optimization for different configurations.
Are you designing a wireless patient monitor? What are your biggest challenges? Tell us in the comments.
a very impressive design, well done.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.