PS-BPC01-4: NONINVASIVE CONTINUOUS BLOOD PRESSURE MONITORING BASED ON WEARABLE RADAR SENSOR WITH PRELIMINARY CLINICAL VALIDATION

Abstract

This paper proposes a novel sensing system for noninvasive and continuous estimation of blood pressure (BP), which is based on a custom designed wearable 120 GHz Doppler radar sensor. With radar signals detected from brachial artery at the elbow, the moving trajectory of the pulses can be accurately demodulated with micrometer accuracy, and thus the reflective pulse transit time(RPTT) can be obtained for the prediction model to estimate blood pressure. Clinical trials have been launched with invasive blood pressure as reference. Patients keep their arms straight with palms facing upward, and a transducer set for medical invasive blood pressure measurement called DTXPlus is set up. DTXPlus has one end connected to a monitor, and the other end connected to the arterial catheter that reaches the brachial artery. The blood pressure signals for reference standard are collected by a data acquisition card (DAQ) from the transmission wire between DTXPlus and monitor. Meanwhile, the 120 GHz radar sensor with concentrated energy and high frequency is used to obtain the pulse wave signals from the brachial artery at the elbow, which is almost the same place detected by both invasive and noninvasive methods. The radar sensor continuously transmits electromagnetic signals to the human body, and the throb of the artery modulates the electromagnetic waves in the phase and the backscattered signals return to the radar receiver. For comparison later, the radar outputs are acquired by the DAQ in synchronization with the blood pressure signals. Experiments were carried out in the operating room with permission, patients with cardiovascular diseases were tested for several minutes after operations. The experimental results show a great performance of the designed wearable radar sensor in the detection of weak pulse signatures. Compared to the ground truth of the invasive blood pressure, the estimated blood pressures by radar have mean errors below 3mmHg for most subjects. The results reveal the possibility for the proposed radar-based BP estimation technique to be employed inside and outside the clinic, such as applications in the vast internet-of-things (IoT) and in-home health monitoring.