A Review on the Design of Non-Contact Vital Signs (NCVS) Biosensors for Long-Term Continuous Monitoring

Abstract

It has been the dream of many scientists and engineers to realize a non-contact remote biosensing system that can perform continuous, accurate, and long-term monitoring of human vital signs as what we saw in some SciFi movies. Having a system that can measure and record key vital signs (such as heart rates and respiration rates) remotely and continuously without touching the patients, for example, can be an invaluable tool for physicians who need to make rapid life-and-death decisions. Such a system would also be an effective tool to help physicians and patients make better informed decisions when viewing a patient’s long-term monitored data. Therefore, there has been a large increase in research activities to develop a system that can monitor a patient’s vital signs and quickly transmit the information to healthcare professionals. Radio-Frequency (RF) Non-contact vital signs (NCVS) monitoring system are particularly attractive for long term vital signs monitoring because there are no wires, electrodes, wearable devices, nor contact-based sensors for the subjects to worry about. Approach: In this paper, we will provide a brief review on some latest development on NCVS sensors, and also compare them against a novel phased-array Doppler-based RF non-contact NCVS biosensor system we have built in our RF-SoC Lab. To determine the accuracy of our NCVS sensor, the heart rate measurements from our NCVS system are compared against an external contact-based piezoelectric finger sensor as a reference. Objective: In some of our previous works, the NCVS sensor performance was tested within a clutter-free anechoic chamber inside our Lab to mitigate the environmental clutters. To examine the performance of our NCVS sensor in a more practical setting, most tests here were performed within the typical Herman-Miller type office cubicle setting, inside a section of our Lab. Additionally, we will detail the measurement data to demonstrate the feasibility of long-term noncontact vital signs monitoring. Conclusion: The measured data strongly suggests that our latest phased array NCVS system should be able to perform long-term vital signs monitoring, especially for situations where the subject is sleeping and there is not expected to have hectic movements nearby. Recommendation: Our phased-array NCVS biosensor system appears to be quite robust and attractive. We will be performing several 24-hours tests to quantitatively analyze the effects of the background noise to long-term vital signs monitoring in office cubicle setting, and report our findings on these important topics in the near future. In the future, we also plan to continue to perform long-term NCVS monitoring on subjects during their sleep next for potential applications on sleep apnea and sudden cardiac arrest (SCA) patients.