Human Pulse Quantification through Photoplethysmography

Project Title

Human Pulse Quantification through Photoplethysmography

Project Area of Specialization Biomedical EngineeringProject Summary

In this project, a medical device based on the principle of photoplethysmography (PPG) is developed for human pulse quantification. The purpose of this device is to assist the eastern medical practitioner. The device uses non-invasive optical technique for detecting cardio-vascular pulse wave from the fingertip. The quantification of important parameters from the acquired human pulse signal includes measuring voltage difference, amplitude / pressure, time-period, and pulse frequency. To implement PPG, there are two types: transmittance and reflectance. We use TCRT5000, a reflective optical sensor to sense the blood variation in the finger tissue and outputs a digital waveform for pulse which is synchronous with the heartbeat. In TCRT5000, the light source and the light detector are both placed on the same side of a body part. The light is emitted into the tissue and the reflected light is measured by the detector. As the light does not have to penetrate the body, the reflectance PPG can be applied to any parts of human body. To compare the results, we may contrast with a robust sensor, HRM-2511E that operates in transmission mode and fits tight around the fingertip, thereby it is less prone to motion artifacts. The TCRT5000 sensor works on the reflective mode, whereas HRM 2511E works on transmission mode. The MCP6004 operational amplifier is used with rail-to-rail output capability for maximum signal swing where potentiometer plays role in gain controlling for the analog output. The medical device is developed in house to support eastern practitioner focus. 
 

Project Objectives

•    To design a photoplethysmography modality for the quantification of the human pulse. The vital signs to measure are time duration, heart rate, pulse pressure, and blood volume. 
•    To realize the designed medical device in an embedded system for implementation in a healthcare setup.

Project Implementation Method

In this project, a medical device is developed. The photoplethysmography (PPG) principle is used to acquire the human pulse data (Figure 1). Important parameters are extracted from the pulse data and displayed on the liquid crystal display. Eastern medicine concepts are used to implement the required computations on an embedded platform. A reflective infrared sensor TCRT5000 is used for the data acquisition. A signal conditioning circuit is used to get a noise free version of the data. Four parameters are extracted from the filtered PPG signal. These parameters include maximum voltage level for amplitude measure, peak-to-peak measure for the time period, computation of the area under the curve for pressure / volume, and the pulse frequency. 
The final year project team consists of three members. One team member takes care of hardware design including the power supply for the medical device. The second team member takes care of software design. The third team member designs the medical device enclosure for safe use by the medical expert. The project supervisor and co-supervisor review the progress and guide the team to resolve the project related matters in a timely manner. A medical expert onboard helps to align the function of the medical device according to the eastern medicine practice. 
Once the prototype of the device is ready, it has to go through the evaluation phase by the expert. The expert may suggest modifications towards a production ready unit. The team works to incorporate changes suggested by the expert. Once, the prototype gets approval from the medical expert, the team creates workable final project/product deliverables in the form of complete operating units.

Figure 1. PPG modality.

Benefits of the Project

•    Low-cost
•    Easy-to-handle
•    Medical device
•    User friendly
•    Low weight
•    Portable
•    Noninvasive
•    Assistive technology
•    Potential to scale as IoT
•    Vital signs measurement

Technical Details of Final Deliverable

The final deliverable is in the form of a medical device (Figure 2). Two units are made as a ready-to-use product. Each working device contains the following major components. 
•    Power supply 
•    Sensor 
•    Signal conditioning circuit 
•    Embedded system 
•    LCD 
•    Casing
The power supply unit provides 5 volts output with optional 3.3 volts are available through the embedded platform. The power supply follows the standards to meet the specifications of a medical device.
The optical reflex sensor TCRT5000 is used. This sensor is selected based on better strength of optical coupling, low cost, and availability. The sensor is mounted on a printed circuit board and protected by appropriate shielding to avoid direct contact. 
The signal conditioning circuit removes noise from the acquired signal towards accurate measurements. An MCP6004 Low Power 1MHz Op-Amp integrated circuit is used for signal amplification. 
Arduino is used as an embedded platform. The signal processing is implemented through Arduino IDE and C language is used for writing the program code.

Figure 2. Medical device outlook.

Final Deliverable of the Project HW/SW integrated systemCore Industry HealthOther Industries Medical Core Technology Wearables and ImplantablesOther TechnologiesSustainable Development Goals Good Health and Well-Being for PeopleRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	80000
Pulse Module	Equipment	1	21000	21000
IR Sensor	Equipment	8	450	3600
Operational Amplifier	Equipment	4	500	2000
Arduino	Equipment	3	5000	15000
Miscellaneous	Miscellaneous	1	10000	10000
Battery Module	Equipment	5	1200	6000
TFT Display	Equipment	3	2500	7500
Casing	Equipment	3	1750	5250
PCB	Equipment	3	1700	5100
Transistor	Equipment	10	350	3500
Probe	Equipment	3	350	1050