A bio-impedance measurement system for portable monitoring of heart rate and pulse wave velocity using small body area

A 3.9 mW 25-Electrode Reconfigured Sensor for Wearable Cardiac Monitoring System

“…The proposed 4-layer compact plaster sensor detects ECG and TIV signals concurrently with 16 different electrode configurations. The maximum impedance detection sensitivity is 3.17 V which is more sensitive than [12] by 5 times, and consumes only 2.4 mW which is far lower than [6], [11]. Moreover, two versatile wireless communication channels are provided for W-BSN either by using cm-range 13.56 MHz inductive coupling, or 20-40 MHz BCC.…”

“…The reason for scanning through the measurement sites is because the TIV measurement signal is highly dependent on the location of the electrodes along the blood vessels. A higher impedance change ( ) can be observed when the electrodes are located along or close to the blood vessel [11]. With reconfiguration of electrodes for TIV measurement, the optimum TIV sensing point can be determined by considering the linearity and SNR of the extracted TIV signal.…”

“…6 is one of the key building blocks in the proposed SoC which enables the high SNR TIV measurement, since a pure sinusoidal current source is difficult to realize with low power consumption and low harmonic distortion. As a result, most previous approaches were implemented either by using an external bulky sinusoidal signal generator [11], [12], or with a power consuming FPGA-based direct digital synthesizer (DDS) with low accuracy [13], [20]. To achieve both low power consumption and high signal quality, two Fully Differential Amplifiers (FDA) and an RC frequency selective network ( 120 k , 14 pF) are used to generate a 90 kHz (determined by RC time constant ) balanced sinusoidal voltage signal ( -) as shown in Fig.…”

“…As a result, the Amplitude Modulated (AM) TIV signal obtained is very small, typically several tens of V, with a modulation depth below 3%. The low noise requirements for detecting such a small signal mean that to date only high power consuming and bulky implementations [11]- [13] have been available.…”

A method to detect heart rate based on electrical bio-impedance

“…In 2008, Rafael et.al present a method from plantar bio-impedance measurement, compare with gold standard ECG derived RR, the mean bias of RR intervals was -0.2ms and the 95% confidence interval was about ±36ms, through the Bland-Altman analysis, there is only one point out of the 95% consistency limit [8]. In 2009, Cho et.al compared different measuring position of arm artery and find an appropriate position with the Pearson's correlation coefficient of 0.982 to the gold standard, and the RMSE (RootMean Square Error) is 1.817 beats/min [9].…”