External Factors that Affect the Photoplethysmography Waveforms

TL;DR

This study investigates how external factors like touch force and temperature significantly influence PPG waveform accuracy, emphasizing the need to account for these factors to improve cardiovascular monitoring reliability in smart devices.

Contribution

The paper identifies and quantifies the impact of external factors on PPG signals, providing insights for enhancing measurement accuracy in wearable health monitoring devices.

Findings

Touch force greatly affects PPG waveform shape.

Temperature variations significantly alter PPG signals.

External factors must be considered for reliable cardiovascular measurements.

Abstract

Photoplethysmography (PPG) is a simple and inexpensive technology used in many smart devices to monitor cardiovascular health. The PPG sensors use LED lights to penetrate into the bloodstream to detect the different blood volume changes in the tissue through skin contact by sensing the amount of light that hits the sensor. Typically the data is displayed on a graph and it forms the pulse waveform. The information from the produced pulse waveform can be useful in calculating measurements that help monitor cardiovascular health, such as blood pressure. With many more people beginning to monitor their health status on their smart devices, it is extremely important that the PPG signal is accurate. Designing a simple experiment with standard lab equipment and commercial sensors, we wanted to find how external factors influence the results. In this study, it was found that external factors, touch force and temperature, can have a large impact on the resulting waveform so the effects of those factors need to be considered in order for the information to become more reliable.