Non-Contact VITAL Signs Monitoring of a Patient Lying on Surgical Bed Using Beamforming FMCW Radar

Abstract

Respiration and heartrates are important information for surgery. When the vital signs of the patient lying prone are monitored using radar installed on the back of the surgical bed, the surgeon’s movements reduce the accuracy of these monitored vital signs. This study proposes a method for enhancing the monitored vital sign accuracies of a patient lying on a surgical bed using a 60 GHz frequency modulated continuous wave (FMCW) radar system with beamforming. The vital sign accuracies were enhanced by applying a fast Fourier transform (FFT) for range and beamforming which suppress the noise generated at different ranges and angles from the patient’s position. The experiment was performed for a patient lying on a surgical bed with or without surgeon. Comparing a continuous-wave (CW) Doppler radar, the FMCW radar with beamforming improved almost 22 dB of signal-to-interference and noise ratio (SINR) for vital signals. More than 90% accuracy of monitoring respiration and heartrates was achieved even though the surgeon was located next to the patient as an interferer. It was analyzed using a proposed vital signal model included in the radar IF equation.

Systematic Literature Review Regarding Heart Rate and Respiratory Rate Measurement by Means of Radar Technology

“…In [16,40,48,52,56,65,68,72,81,115], and in seven studies, with three or more test persons simultaneously [16,48,50,56,59,71,81]. In four studies, persons employed to interfere with the signal (interfering persons) were additionally included [25,40,55,77]. Some studies comprised several experimental parts in which the number of test persons measured simultaneously varied [16,40,48,56,59,65,72,81].…”

“…The test persons' positions relative to the radar were as follows: lying in 36 studies [2,3,5,13,17,23,28,29,[31][32][33][34]44,45,50,51,53,55,58,62,77,82,84,88,91,93,94,99,[104][105][106][107]110,112,114,120]; sitting in 60 studies [3,10,11,14-17,19,20,22,24,25,31,36,40,42,46-49,52-54,56,58-61,63,65,66,68-76, 78-80,83,85,86,88,89,96,97,100-103,109-111,113,117,118]; standing in 14 studies [3,21,26,27,39,57,72,76,81,87,110,113,…”

“…In three further studies, the test persons were behind (acrylic) glass [29,84,104]. In five experiments, the test persons were measured through a mattress in a lying position [28,77,105,106,114], and in one study, they were measured through a chair in a sitting position [54]. In ten studies, it was not possible to obtain any information on the positioning of the test persons [12,18,30,35,41,43,64,67,95,108].…”

“…In 94 studies, the reference measurement was performed using contact electrodes [2,3,[33][34][35][36]38,[40][41][42][43][44][45][46][47][48][49][50][51][53][54][55][57][58][59][61][62][63][64][65][66][68][69][70][73][74][75][76][77]79,80,[82][83][84]86,88,89,[93][94][95][96][97]…”

“…In seven studies, the quantitative evaluation was performed by indicating a root mean square error (RMSE) [17,28,59,80,82,84,113]. In 16 studies, the accuracy was indicated in percentage terms [14,19,30,43,47,57,61,74,77,81,86,90,105,107,108,115]. In 32 studies, the deviation was indicated as a percentage value [10,14,15,19,20,26,36,40,43,46,48,54,55,60,62,64,73,79,84,88,93,[95][96][97]100,102,…”