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Heart Rate Detection from Plantar Bioimpedance Measurements
... Another example is related to bioimpedance measurements, where the basal impedance of some tissues is AM by the dynamic activity of some physiological functions, for example, from the arterial blood circulation [1]. Variations of 500 m have been reported, which demanded a fully differential (FD) demodulation in order to reduce the contribution of common-mode (CM) errors caused by the electrode impedance imbalances and the finite CM rejection ratio (CMRR) of the measurement system [2]. ...
... Analog synchronous demodulation has demonstrated to be a technique, not only cheap and robust but also effective [4]. They have demonstrated a good performance when the AM signals come from high-impedance sensors (capacitive) [4] or dry electrodes in bioimpedance measurements [2], also in high-resolution measurements in order to detect the cardiac activity [11], [12]. Different analog demodulator circuits have been proposed. ...
... The output stage in Fig. 6(a) and (b) was implemented by an IA INA111 (Texas Instruments) with a gain of 10, followed by a first-order lowpass filter with a cutoff frequency of 15 Hz. This bandwidth was selected thinking of applications related to detect cardiac signals using synchronous demodulation, like those obtained in [2], [11], and [12], where a high-resolution measurement system was needed to detect low-amplitude signals buried in noise. All the measurements were obtained by a 6 ½ digits multimeter DMM4050 from Tektronix, which was configured to measure dc voltages at 1 power line cycle. ...
A novel fully differential (FD) demodulator is presented. Using different design strategies, the circuit can be used for processing amplitude-modulated (AM) signals obtained from impedance measurements or coming from modulating sensors with differential outputs where a high common-mode rejection ration (CMRR) and low noise are demanded. The circuit multiplies the AM input signal by a square wave with the same frequency and phase of the carrier of the input signal. This kind of wave is simpler to generate than a sine wave (homodyne detection) and narrow unit-amplitude pulses (synchronous sampling). The proposed circuit is not a perfect floating system, but yields a high CMRR if matched op-amps are used and does not depend on matched resistors. The system has been tested with off-the-shelf amplifiers; at 100 kHz, the CMRR is about 65 dB when fast and wide-bandwidth amplifiers are used. The spectral density of noise voltage obtained is lower than 55 nV/√ Hz at 1 kHz; for a bandwidth of 15 Hz, this results in a noise voltage (rms) of 213 nV. Provided the circuit is implemented with low value resistors, the main contribution of noise comes from the noise voltage of the op-amps used to implement the demodulator.
... In this method, a check for the agreement between the data of the peak and time integral of the velocity in the context of clinical measurement will be conducted. Rafael et al. [9] designed a bio-impedance system to check for heart variations based on feet impedance. The design is validated via Bland-Altman method by comparing the result of the bio-impedance with the ECG of the interval time and heart rates [9]. ...
... Rafael et al. [9] designed a bio-impedance system to check for heart variations based on feet impedance. The design is validated via Bland-Altman method by comparing the result of the bio-impedance with the ECG of the interval time and heart rates [9]. Chan Yang et al. [10] tinkered with low-cost signal systems to capture human physical movements. ...
... This method is based on the mean difference between the validated systems and the developed system or instrument. The mean difference value will limit the accepted area of the data that it is created via the addition or subtraction of the standard deviation (SD) [9]. The formula of Mean and SD used are as written in (1) and (2) ...
... In this method, a check for the agreement between the data of the peak and time integral of the velocity in the context of clinical measurement will be conducted. Rafael et al. [9] designed a bio-impedance system to check for heart variations based on feet impedance. The design is validated via Bland-Altman method by comparing the result of the bio-impedance with the ECG of the interval time and heart rates [9]. ...
... Rafael et al. [9] designed a bio-impedance system to check for heart variations based on feet impedance. The design is validated via Bland-Altman method by comparing the result of the bio-impedance with the ECG of the interval time and heart rates [9]. Chan Yang et al. [10] tinkered with low-cost signal systems to capture human physical movements. ...
... This method is based on the mean difference between the validated systems and the developed system or instrument. The mean difference value will limit the accepted area of the data that it is created via the addition or subtraction of the standard deviation (SD) [9]. The formula of Mean and SD used are as written in (1) ...
Wireless Sensors (WS) are utilized in industries, medical, greenhouses, and other applications to sense and monitor parameters required to control and utilize data. There are many challenges to implement WS networks such as collision, end-to-end delay, dead nodes and power consumption to name a few; however, the main challenge that face the implementation of WS are the sensing and transferring the data between the sensor and the system and the time taken. The time taken of a wired sensor to transfer data is undoubtedly slightly shorter than the time taken in WS. This paper intends to design WS that could reduce the data transfer time and compare the amount of transferred data and the time taken by the wired system. The WS design will be validated first by Bland-Altman method and data will be collected using MATLAB and the PLX-DAQ program. The results show that the amount and time taken to transfer data in WS is comparable to the wired system. The validated results suggested by this work are more than 95% in similarity to Bland-Altman. This led us to conclude that WS can be utilized with a multitude of applications in place of wired sensors.
... Impedance plethysmography (IPG) is a technique to detect variations in electrical impedance related to changes in volume such as the vascular sector or other body parts. A tetra-polar bioimpedance measurement can detect volume changes due to blood flow [14] powered by the heart [15]. This paper aims to study the feasibility of using standard force sensors as plantar bioimpedance electrodes.This intermediate requirement during the design of the new DIAPODAL device stems from the necessity to reduce as much as possible the number of sensors in the diabetic person's shoe. ...
... First, we have tested IPG and ECG simultaneous recordings with standard electrodes, namely AG-AgCl and Al-pads described in previous work [15]. Having obtained satisfactory IPG signals using conventional electrodes, we set ourselves the goal of substituting them with FSRs. ...
Diabetic foot ulcers (DFUs) are an ominous consequence of diabetic foot. To develop a multidimensional lesion warning device, several variables must be considered, among which vascular parameters. To minimize the number of sensors, we investigate the use of standard flexible force sensing resistors (FSRs), FSR402 and FSR406, to detect not only plantar pressure but also bioimpedance plethysmography. Since FSRs include conductive electrodes covered by polymer film, the interface with the subject can be considered a capacitive electrode. We present a special impedance plethysmography (IPG) circuit to inject current using FSRs and measuring the resulting voltage from other FSRs contacts. IPG simulations with two modeled FSRs, two contacts each, were not successful, but using four FSRs, one capacitive contact each, shows a precision within 4% of the expected FSR resistor value. The IPG system was verified with simultaneously matching ECG-lead I, Ag–AgCl, and capacitive electrode signals alongside power spectra. For the first time, four sole pressure sensors are used also as bioimpedance electrodes to detect cardiac activity with standard components at frequencies up to 50 kHz and simulated as well as experimentally verified on one healthy subject.
... Impedance plethysmography (IPG) is a bioimpedance measurement technique that allows us to obtain arterial volume variations of the arterial circulation [10]. IPG could be an additional measurement to be included in multivariable approaches to the monitoring of diabetic foot during gait as it adds cardiac activity. ...
... To measure the voltage, an alternating-coupled front end suppresses the contribution of mains interference and the contribution of 1/f noise from the instrumentation amplifier (IA). Figure 2a shows a configuration used in [7] and [10], applied in electronic weighing scales that have dry electrodes to perform Bioimpedance Analysis (BIA). For this set-up, Al square plates (4 cm x 4 cm) were used as skin contact electrodes, soldered to 1 mm 2 section insulated wires. ...
Foot impedance plethysmography was implemented using two types of electrodes (dry and capacitive) and sole force sensors. The latter are commonly used for assessing diabetic foot ulcers (DFU). For impedance plethysmography, a tetrapolar configuration has been used with three different plantar setups: four skin contact electrodes, four capacitive contact electrodes and two Force Sensing Resistors (FSRs). In this work, FSRs have been considered as possible capacitive electrodes because the top substrate contains interdigitating conductive electrodes and a semiconductive polymer. All the measurements have been performed using a 1 mA/10 kHz excitation current and have been tried under the feet of a standing person to detect impedance plethysmography signals. Contact electrodes allow a good cardiac pulse signal while capacitive contact through the socks features mains interferences. Force sensing resistors with their force-dependent resistance in parallel to the capacitive coupling, were not able to detect cardiac pulse. But promising results can be anticipated from these findings provided higher frequencies are used and larger sensor areas to help detect altered skin states in diabetic foot.
... Impedance plethysmography (IPG) is a technique to detect variations in electrical impedance related to changes in volume such as the vascular sector or other body parts. A tetra-polar bioimpedance measurement can detect volume changes due to blood flow [14] powered by the heart [15]. This paper aims to study the feasibility of using standard force sensors as plantar bioimpedance electrodes.This intermediate requirement during the design of the new DIAPODAL device stems from the necessity to reduce as much as possible the number of sensors in the diabetic person's shoe. ...
... First, we have tested IPG and ECG simultaneous recordings with standard electrodes, namely AG-AgCl and Al-pads described in previous work [15]. Having obtained satisfactory IPG signals using conventional electrodes, we set ourselves the goal of substituting them with FSRs. ...
... Skin characteristics refer to the physiological stratification and biological characteristics of the skin, while bioimpedance analysis is a simple non-invasive and fast assessment method in the field of biomedical engineering as compared to other technologies [10]. Skin impedance finds extensive applications in health care technologies like determination of heart rate [11], investigation of body components like water, fat tissue and muscles [12], glucose level monitoring [13], dermatological research like performance evaluation of drugs and cosmetics [14], measurement of skin moisture level or content [15]. ...
... SS res (9) and SS tot (10) are the residual sum of squares and the total sum of squares, respectively. The goodness of fit is represented by (11) ...
The skin is a complex biological tissue whose impedance varies with frequency. The properties and structure of skin changes with the location on the body, age, geographical location and other factors. Considering these factors, skin impedance analysis is a sophisticated data analysis. However, despite all these variations, various researchers have always worked to develop an equivalent electrical model of the skin. The two most important categories of electrical models are RC-based model and CPE-based model which focus on the physiological stratification and biological properties of skin, respectively. In this work, experimental skin impedance data is acquired from ten sites on the body to find the fitting model. It is observed that a hybrid of fractional-order CPE-based model and higher-order RC layered-based model can provide the best fitting electrical model of skin. A new model is developed with this hybrid orders. Genetic algorithm is used for the extraction of parameter components. Least error of fitting has been observed for the proposed model as compared with the other models. This model can be used in correlating many skin problems and in the development of diagnostic tools. It will offer an additional supportive tool in-vitro to the medical specialist.
... In early plastic straps, water or liquid was required to get good performance [4,5]. Later units have used conductive smart fabric with built-in microprocessors which analyze the EKG signal to determine heart rate [6]. ...
... Newer versions include a microprocessor which is continuously monitoring the EKG and calculating the heart rate, and other parameters [6]. These may include accelerometers which can detect speed and distance eliminating the need for foot worn devices. ...
This study presents the design of photo-induced heart beat monitor that uses cheap and readily available materials unlike most of all the rather sophisticated heart beat monitoring devices that uses complicated designs and therefore needs the help of an expert to carry out the exercise and also to do the interpretation for users, this device is simple, portable, affordable and easy to operate. This is based on principle and
technique of measuring the heart beat with the method of photo induction, through a fingertip using a PIC16F877A Microcontroller interface to a Digital Display for data logging and further analysis of signals generated as a result of such activities. The circuit designed is made up of different stages which involve sensing the Finger Tip through Infrared Receiver; Filtering the Signal, thereby measuring the Heartbeat with the PIC16F877A Microcontroller; calculating through the connected Local Clock Signal
and displaying the Result through the 2 X 16 Liquid Crystal Display (LCD) Output. It is therefore a useful design for everyone that wishes to stay healthy and monitor their heart rate for early detection of hypertension and heart-related ailments. This design is highly versatile and economical. It can be used everywhere at any time. It is safe, convenient and easy to use.
... Based on the activities that in daily such as, walking, standing, sitting, sleeping, and effect on the state of stress. As well as the overall health of our people [1]. Traditionally studied about heart rate typically, during relaxes time a heart rate at 72 times per minute or about 60-80 times per minute, infants and young children have a heart rate 90-140 time per minute. ...
... This fluctuation of blood can be detected through an optical sensing mechanism placed around the fingertip. The signal can be amplified further for the microcontroller to count the rate of fluctuation, which is actually the heart rate [1]. Figure 1shows the block diagram of heart rate system consists, fist block describe an infrared light emitting diode and a photo diode and placed fingertip, Second block is filter and gain amplifier circuit, this little alteration in the amplitude of the reflected light can be converted into a pulse, Third is microcontroller for calculation and processing, fourth block is heart rate display monitoring in beat per minute. ...
The problem shortage of medical devices in rural Thailand, cause a budget to limit and constrain. Therefore a development the medical device with low cost as one solution. This paper proposes an improvement the heart rate device to applied in the rural local medical in Nakhon Phanom province. The hardware circuit consist the instrument amplifier, low pass filter, auto adjust zero and microcontroller processing, acquisition signal parameter of heart rate. First step the detection heart rate in the pulse signal and count the pulse in the one minute to get the beat per minute (BMP) detection pulse with a finger and measure the intensive light. The pulse signal to amplified with the instrument amplifier and send to the microcontroller. The count value of pulses per minute and show heart rate in BMP digital. Results show that compared with experimental commercial device and low cost device base on medical criterion, the average error results approximation 1.31%, it is confirm that the medical low cost device could work in the target areas.
... Bio-impedance sensors check the resistance of body tissue to the tiny pulses of electrical current which helps in capturing physiological signals like heartbeat. Bio-impedance sensors measure tiny changes in the impedance of the user's body , to measure the heart rate the amount of blood flowing in the arteries is used to create an impedance change, bio-impedance sensors also capture the respiration rate and hydration by measuring the oxygen level in the blood [12]. Bio impedance sensors work by using 4 electrodes which send a pulse of electric signal to one another then the impedance level of the readings are evaluated to calculate the heart rate. ...
... At very high frequencies, the capacitance of the cell membrane will be low, allowing the current to pass through. The equivalent circuit of high frequency will be R = (RE×RI) / (RE+RI) [6]. At intermediate frequencies (0 < f < ∞), in the two extremes of zero or infinite frequencies, the mathematical model circuit behaves as a pure resistance. ...
The impedance plethysmography (IPG) is considered one of
the useful bioimpedance applications. It is a non-invasive
assessment of pulsatile blood volume changes in the veins of
limbs by measuring the changes of their bioimpedance at the
skin surface. The tissue's electrical conductivity and hence its
bioimpedance (Z) can vary because of the breathing rate and
consequently the changes of blood flow in the vessels
according to the changes in the cardiac output and circulating
blood volume. In this paper, we present one of the IPG
applications for real-time measurement of cardiac output and
the circulating blood volume flow in the lower limbs of
humans. The method is based on pushing a low amplitude
A.C. current through the limb skin, which produces a bio
voltage drop across this part of the limb. An electronic circuit
has been designed, implemented, and applied for real-time
measurement of the dv/dt rate of the bio voltage. The signal
of each electronic part of the circuit was verified and followed
up along all the stages of the circuit. Kubicek's equation
was used to find out the blood flow rate. All the obtained and
calculated data were close to the expected medical finding
which concern human parameters.
... In many existing works, for instance, in Huynh et al. [7] similar setups are used to measure both, pulse-wave velocity and the heart rate. In other works, for example, in Gonzalez-Landaeta et al. [8] heart rate detection algorithms are applied to bioimpedance measurements performed with a tetrapolar electrode connection with feet as the contact surface. Compared to the studies mentioned above, the current study utilizes a bipolar electrode setup in contrast to the typical tetrapolar one. ...
... Landaeta, et al, portrayed the detection of heart rate from plantar bioimpedance measurements. 19 They have proposed a technique for measuring heart rate and it also relies on electrical impedance variations which are detected by a plantar interface with both feet, such as those in some bathroom weighing scales for the analysis of body composition. The Heart-related impedance variations that arise in the legs come from arterial blood circulation and are below 500 m Omega. ...
Introduction: According to World Health Organisation (WHO), Heart Disease is the leading cause of Population Death. The World Health Organization survey says that heart disease is the common cause of population death in the world. The heart’s main function is to pump blood into the circulatory system of human beings; if one of its ventricles fails to work, the heart gets attacked, and in due course, leads to death if not resuscitated on time. Most of the time, a heart attack results in abrupt death before the patients get any consideration from a medical professional.
Objective: This paper proposes an Electro Cardiogram (ECG) monitoring system which detects the heart problem using IoT (Internet of Things) applications.
Methods: It is about the IoT Based ECG Monitoring with AD8232 ECG Sensor and ESP-32 developing kit using an online IoT platform called Ubidots, which captures the sensor data and turn it into useful information. It also measures an ECG signal and transmits it to a smartphone via WiFi for data analysis.
Results: The ECG signal from a patient is viewed by the doctor using their smartphone. The system utilizes the user’s smartphone for data processing, and the built-in communication is used to generate an ECG waveform. By analysing the ECG waveform, it detects the heart problem, if any. If the heartbeat rate is under abnormal condition, then the Ubidots platform sends a message to the doctor stating that the patient condition is abnormal. At the same time, the Buzzer and Light Emitting Diode (LED) also make an alert to notify the condition of the patient of the caretaker.
Conclusion: Since the last few decades, heart diseases are becoming a greater issue and many people lost their lives because of such health problems. Hence, heart disease cannot be taken lightly. By analyzing and continuously monitoring the ECG signal at the initial stage, heart disease would be prevented.
Key Words: WHO (World Health Organization), ECG (Electro Cardio Gram), IoT (Internet of Things), WBAN (Wireless Body Area Network), GSM (Global System for Mobile Communications), (SMS) Short Message Service.
... Landaeta, et al, portrayed the detection of heart rate from plantar bioimpedance measurements. 19 They have proposed a technique for measuring heart rate and it also relies on electrical impedance variations which are detected by a plantar interface with both feet, such as those in some bathroom weighing scales for the analysis of body composition. The Heart-related impedance variations that arise in the legs come from arterial blood circulation and are below 500 m Omega. ...
Introduction: According to World Health Organisation (WHO), Heart Disease is the leading cause of Population Death. The World Health Organization survey says that heart disease is the common cause of population death in the world. The heart’s main function is to pump blood into the circulatory system of human beings; if one of its ventricles fails to work, the heart gets attacked, and in due course, leads to death if not resuscitated on time. Most of the time, a heart attack results in abrupt death before the patients get any consideration from a medical professional.
Objective: This paper proposes an Electro Cardiogram (ECG) monitoring system which detects the heart problem using IoT (Internet of Things) applications.
Methods: It is about the IoT Based ECG Monitoring with AD8232 ECG Sensor and ESP-32 developing kit using an online IoT platform called Ubidots, which captures the sensor data and turn it into useful information. It also measures an ECG signal and transmits it to a smartphone via WiFi for data analysis.
Results: The ECG signal from a patient is viewed by the doctor using their smartphone. The system utilizes the user’s smartphone for data processing, and the built-in communication is used to generate an ECG waveform. By analysing the ECG waveform, it detects the heart problem, if any. If the heartbeat rate is under abnormal condition, then the Ubidots platform sends a message to the doctor stating that the patient condition is abnormal. At the same time, the Buzzer and Light Emitting Diode (LED) also make an alert to notify the condition of the patient of the caretaker.
Conclusion: Since the last few decades, heart diseases are becoming a greater issue and many people lost their lives because of such health problems. Hence, heart disease cannot be taken lightly. By analyzing and continuously monitoring the ECG signal at the initial stage, heart disease would be prevented.
... Contact-based heart monitoring remains a vast topic that many emerging technological solutions have been explored, such as photoplethysmography (PPG) [5], bio-impedance analysis (BIA) [6], which detect accurate heart rate readings in a wearable device. Radar-based cardiac monitoring in the contact-mode, however, is still a relatively open topic. ...
... found in almost all commercial available EIS instru due to its implementation simplicity, is the fixed frequency sinusoidal signal. Here the measurements are carried out at a specific frequency, as is the case for these full designs [10,11], or in a small set of frequencies such as it is found in the commercial instrument xCELLigence [ which measures the impedance at three discrete frequencies. ...
Fibrosis represents an open issue for medium to long-term active implants, such as pacemakers, given that this biological medium surrounds the stimulation electrodes and can impact or modify the perfor- mances of the system. For this reason, Embedded Impedance Spectroscopy (EIS) techniques have been investigated these last years to sense the fibrosis. The following article introduces a new technique for EIS derived from multi-carrier digital communication methods. Due to its properties of flat spectrum and fast generation the Orthogonal-Frequency Division Multiplexing (OFDM) technique for EIS represents an efficient and a low foot-print alternative compared to the classical sweep frequency technique. This article focuses on this approach and also proposes a solution that reduces the effect of high crest factor typi- cally found in OFDM systems. An embedded implementation is also presented. This designed prototype is used here to characterize the impedance spectrum of a pacemaker’s electrode achieving an accuracy of 99% when measuring with 64 OFDM subcarriers and with a sampling frequency of 12 kHz.
... found in almost all commercial available EIS instruments, due to its implementation simplicity, is the fixed frequency sinusoidal signal. Here the measurements are carried out at a specific frequency, as is the case for these full designs [10,11], or in a small set of frequencies such as it is found in the commercia which measures the impedance at three discrete frequencies. ...
Fibrosis represents an open issue for mid- to long-term active implants, like pacemakers, given that this biological tissue surrounds the stimulation electrodes and can impact or modify the performances of the system. For this reason, we present a strategy for the continuous sensing of fibrosis induced by cardiac implants, based on the use of the same set of electrodes involved in the implant stimulation process and whose implementation can be integrated into the pacing and sensing circuitry of pacemakers. To do this, the proposed measurement system complies with certain requirements for its integration, such as rapid measurement time, flexibility, low power consumption, and low use of resources. This was achieved through the use of an orthogonal multitone stimulation signal and the design of an Orthogonal Frequency Division Multiplexing (OFDM) architecture that are the bases of the system. As a proof of concept, we implemented this technique within a FPGA. Initial tests of this system have been performed through in vitro measurements of cell cultures related to fibrosis, which, once validated, have allowed us to advance to ex vivo measurements of inhibited and perfused cardiac tissue; these are the conditions that offer a first view of in vivo measurements. This article describes the measurement system implemented and also discusses the results of its validation and of the in vitro and ex vivo measurements, comparing them with results obtained by a reference instrument.
... Various measuring agents, such as current, impedance [42], and capacitance, suffer from low signal-to-noise (S/N) ratio. Heart-correlated impedance changes in the legs are measured for pulse rate, and a comparative result has been obtained under well-controlled conditions [43]. The bathroom weighing scale concept has been applied and an unobtrusive impedance monitor has been developed for cardiovascular health [44]. ...
Biological and medical diagnoses depend on high-quality measurements. A wearable device based on Internet of Things (IoT) must be unobtrusive to the human body to encourage users to accept continuous monitoring. However, unobtrusive IoT devices are usually of low quality and unreliable because of the limitation of technology progress that has slowed down at high peak. Therefore, advanced inference techniques must be developed to address the limitations of IoT devices. This review proposes that IoT technology in biological and medical applications should be based on a new data assimilation process that fuses multiple data scales from several sources to provide diagnoses. Moreover, the required technologies are ready to support the desired disease diagnosis levels, such as hypothesis test, multiple evidence fusion, machine learning, data assimilation, and systems biology. Furthermore, cross-disciplinary integration has emerged with advancements in IoT. For example, the multiscale modeling of systems biology from proteins and cells to organs integrates current developments in biology, medicine, mathematics, engineering, artificial intelligence, and semiconductor technologies. Based on the monitoring objectives of IoT devices, researchers have gradually developed ambulant, wearable, noninvasive, unobtrusive, low-cost, and pervasive monitoring devices with data assimilation methods that can overcome the limitations of devices in terms of quality measurement. In the future, the novel features of data assimilation in systems biology and ubiquitous sensory development can describe patients’ physical conditions based on few but long-term measurements.
... Compared with many other complex technologies in the biomedical engineering field, bioimpedance detection is a fast, simple, non-invasive, and cost-effective method for assessing the condition of the human body [1]. So far, it has been applied to many fields, such as heart rate measurement [2], fake finger detection in security systems [3], dermatological research [4], and so on. However, only a few applications have been realized after six decades of development. ...
Due to advances in telemedicine, mobile medical care, wearable health monitoring, and electronic skin, great efforts have been directed to non-invasive monitoring and treatment of disease. These processes generally involve disease detection from interstitial fluid (ISF) instead of blood, and transdermal drug delivery. However, the quantitative extraction of ISF and the level of drug absorption are greatly affected by the individual’s skin permeability, which is closely related to the properties of the stratum corneum (SC). Therefore, measurement of SC impedance has been proposed as an appropriate way for assessing individual skin differences. In order to figure out the current status and research direction of human SC impedance detection, investigations regarding skin impedance measurement have been reviewed in this paper. Future directions are concluded after a review of impedance models, electrodes, measurement methods and systems, and their applications in treatment. It is believed that a well-matched skin impedance model and measurement method will be established for clinical and point-of care applications in the near future.
... In 2011, Poh and McDuff paved a way for heart rate acquisition by detecting the video image from facial exposed region [16,17]. Alternatively, Rafael González-Landaeta et al. describes the methodology by measuring plantar bio-impedance when standing without attaching any electrodes [18]. In 2012, Kwon et al. proposed a method of heart rate detection via mobile phone camera, which processes pixel average based on RGB channels in time domain and therefore get the heart rate information [19]. ...
Non-contact detection of heart rate has been addressed by researchers from very different fields. However, the low accuracy of measuring results in the difficulties in methodology deployment. This paper introduces the principle of heartbeat detection. A detection scheme by using Kinect is proposed. Further, the signal processing approach based on JADE algorithm is developed to efficiently remove the clutter in mixture signals, and it enables accurate transforming via Z-score normalization. Due to the significances presented in this work, the detection error is 1.79%, when processed with the proposed algorithm. Experimental results are statistically analyzed, which makes it a promising basis for the realization of heart rate detection.
... The result of the shielding is shown in the S 21 and S 12 coefficients in Fig. 4E 3B-D. The ECG and ICG are based on the bio-impedance readout circuit in [39]. The ICG is calculated from the thorax impedance signal by differentiating it at 70Hz. ...
Motivation:
In the state of the art, typically bioimpedance, heart sounds and / or ultrasound is used to measure STIs. All three methods suffer from insufficient accuracy of STI estimation due to various reasons. CW radar is investigated for its ability to overcome the deficiencies in the state of the art.
Methods:
Ten healthy male subjects aged 25-45 were asked to lie down at a 30 degree incline. 60 second recordings were taken without breathing and with paced breathing. Heart Sounds, Electrocardiogram, respiration and Impedance cardiogram were measured simultaneously as reference. The radar antennas were placed at three positions on the chest. The antennas were placed directly on the body as well as with cotton textile in-between. The beat to beat STIs have been determined from the reference signals as well as CW radar signals.
Results:
The results indicate that CW radar can be used to estimate STIs in ambulatory monitoring.
Significance:
The results can be used for a potentially more compact method of estimating STIs in an ambulatory setting, which can be integrated into a wearable device.
... In 2005, Kristiansen et.al using an handheld impedance plethysmograph to measure impedance heart rate, with a Pearson's of 1.00, the mean difference compare to the gold standard is -x beats/min, show no significance systemic error [7]. 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]. ...
. As a basic health indicator, heart rate has been widely used in clinical measurement and daily health care.
Electrical bio-impedance (EBI) measurement provides non-invasive method for heart rate detection. therefore, this paper proposed a method to detect heart rate based on EBI. With the BIOPAC EBI module, the signal can be de-noised in real-time. Finally, the de-noised EBI signal is used to compute heart rate. Four electrodes are located at radial artery of left upper limb in this method. The result proves that this method has high accuracy on heart rate measurement.
... The hardware contains readouts for reference signals i.e. the radial artery pulse wave using a piezoelectric sensor [16], the ECG and impedance cardiogram (ICG) (4mA rms current at 10kHz) based partly on [17]. These are used to measure the PAT and the pre-ejection period (PEP) respectively. ...
Ambulatory blood pressure monitors based on pulse transit time are limited by the challenge of changing vascular tone. This study focuses on the use of the carotid artery as an alternative location for arterial pulse acquisition. We use continuous wave radio frequency (RF) radar coupled directly to the body to detect the pulse wave signal. We have shown that the blood pressure-pulse transit time calibration using the carotid pulse is as accurate as that of the radial arterial pulse. The results of this investigation may be useful in developing wearable sensors for long-term monitoring of the pulse wave signal at the carotid artery.
... The resulting voltage carrier signal is amplified differentially. The carrier signal is demodulated synchronously by a clock signal of 50% duty cycle and zero phase difference with respect to the sine wave [41]. The baseband signal is then amplified and converted to a single ended signal using a 3-opamp instrument amplifier (INA333), followed by an anti-aliasing lowpass RC filter. ...
Objective:
We have developed and tested a new architecture for pulse transit time (PTT) estimation at the central arteries using electrical bioimpedance, electrocardiogram and continuous wave radar to estimate cuffless blood pressure.
Methods:
A transmitter and receiver antenna is placed at the sternum to acquire the arterial pulsation at the aortic arch. A four-electrode arrangement across the shoulders acquires arterial pulse across the carotid and subclavian arteries from bioimpedance as well as a bipolar lead I electrocardiogram. The PTT and pulse arrival times (PAT) are measured on six healthy male subjects during exercise on a bicycle ergometer. Using linear regression, the estimated PAT and PTT values are calibrated to the systolic and mean as well as diastolic blood pressure from an oscillometric device.
Results:
For all subjects, the Pearson correlation coefficients for PAT-SBP and PTT-SBP are -0.66(p=0.001) and -0.48 (p=0.0029). Correlation coefficients for individual subjects ranged from -0.54 to -0.9 and -0.37 to -0.95 respectively.
Conclusion:
The proposed system architecture is promising in estimating cuffless arterial blood pressure at the central, proximal arteries, which obey the Moens-Korteweg equation more closely when compared to peripheral arteries.
Significance:
An important advantage of PTT from the carotid and subclavian arteries is that the PTT over the central, elastic arteries is measured instead of the peripheral arteries, which potentially reduces the changes in PTT due to vasomotion. Furthermore, the sensors can be completely hidden under a patients clothes, making them more acceptable by the patient for ambulatory monitoring.
... Design of a contact less measurement of heart rate in home environment has also been proposed [16]. Heart rate monitoring utilizing acceleration sensor [17] and planter bio-impedance measurement [18] are also studied in the same year. Some recent studies also include detecting heart rate from electronic weighing scale [19], air pressure sensor [20] non-contact ECG measure [21], body sound [22], ZigBee wireless link [23] and finger tips [24], Kim et al. reported about the nonintrusive measurement of heart rate using a flexible sensor array [25]. ...
The heart rate is one of the significant physiological parameters of the human cardiovascular system. Heart rate is the number of times the heart beats per minute. Heart rate data reflects various physiological states such as biological workload, stress at work and concentration on tasks, drowsiness and the active state of the autonomic nervous system. Human cardiac
dynamics are driven by the complex nonlinear interactions of two competing forces: sympathetic regulation increases and parasympathetic regulation decreases the heart rate. Thus, monitoring of heart rate plays a significant role in providing the status of cardiovascular system and clinically correlated information to medical professionals. Heart rate measurement is also regarded as an essential parameter in patient care monitoring system.
Heart rate can be measured either by the ECG waveform or by sensing the pulse - the rhythmic expansion and contraction of an artery as blood is forced through it by the regular contractions of the heart. The pulse can be felt from those areas where the artery is close to the skin. This paper highlights on the design of a microcontroller (PIC series) based heart rate counter that is able to capture the pulse from finger tip by sensing the change in blood volume. The heart rates of fifteen healthy normal subjects (students of age 21-22 yrs.) both in relaxed and excited states were measured using the designed device and a standard heart rate measuring device. The outputs of the measured device were satisfactory. Also, the designed device, being noninvasive one, can easily find its place in health care monitoring system.
... However, the method proposed in [12] requires the exposure of four recording sites and the placement of six electrodes, which is still unpractical for fast screenings or regular self-administrated health status checks. Alternatively, the IPG can be measured from hand to hand [13] and from foot to foot [14], which only requires the exposure of two measurement sites. Since the current injected in limb-to-limb measurements travels through proximal and distal arteries, it is reasonable to assume that certain features of the recorded waveform will reflect volume changes in arteries more proximal to the torso than the recording site, analogously to whole-body impedance measurements. ...
We present a novel method to detect proximal volume changes based on the impedance plethysmogram (IPG) measured from limb to limb with two electrode pairs symmetrically placed at distal areas of the upper or the lower limbs. Since the measurement is sensitive to changes along the whole current path, this method allows us to detect changes in arteries that are more proximal to the torso than the measurement sites. Our results show that the Pulse Arrival Time (PAT) measured from the R peak of the ECG to the hand-to-hand IPG is close to the PAT to the elbow whereas the PAT measured from the R peak of the ECG to the foot-to-foot IPG is close to the PAT to the knee. This opens new avenues for noninvasive cardiovascular measurements based only on electrodes in contact with hands or feet.
... Una limitación de estos métodos es que no se pueden aplicar en personas que tengan una sola pierna o que no puedan mantenerse de pie. También se han usado básculas de baño destinadas al análisis de la impedancia bioeléctrica (BIA) para obtener el ritmo cardiaco [13], pero no sirven para personas con una sola pierna o que lleven calcetines. La salida del desmodulador se amplifica (G 2 = 300) y filtra con un filtro activo pasabanda de segundo orden (0,5 Hz -10 Hz) para quitar el offset y limitar el ancho de banda del ruido. ...
Las básculas de baño electrónicas son un medio sencillo y asequible para medir, además del peso corporal, el balistocardiograma (BCG) y a partir de él extraer el ritmo cardíaco, y estimar variaciones en el gasto cardíaco y la presión arterial sistólica. Las básculas para el análisis de bioimpedancia (BIA) también han sido propuestas para obtener el ritmo cardíaco mediante la amplificación de la componente de impedancia pulsante (pletismograma de impedancia, IPG) superpuesta a la impedancia basal. Sin embargo, las básculas electrónicas no pueden obtener fácilmente el BCG de personas incapaces de mantenerse de pie, o el IPG de personas que tienen una sola pierna o usen calcetines. En este trabajo proponemos un método para detectar el ritmo cardíaco (HR) a partir de la bioimpedancia plantar capacitiva adquirida en un solo pie o entre ambos pies de un sujeto en dos situaciones distintas: de pie sobre una báscula de baño comercial y sentado, con los pies apoyados en los electrodos de la báscula.
... In previous works, we have proposed two different methods to obtain the heart rate using an electronic weighing scale. The first method is based on plantar bioimpedance measurements, which detects impedance variations from arterial blood flow in the legs, using the electrodes intended for body composition estimation [8]. Coherent demodulation based on synchronous sampling and a high gain amplifier allowed us to sense impedance variations below 500 mΩ and obtain a pulse signal with a signal-to-noise ratio (SNR) around 54 dB. ...
Background and objective:
Transdermal delivery of a therapeutic drug is a non-invasive method of drug administration. For a controlled delivery of the maximum number of drugs, several external enhancement mechanisms are used in the domain of transdermal drug delivery (TDD). Iontophoresis is one of the processes which uses a weak electric current to increase drug delivery and electrically control its penetration into the body. This method is governed by the Nernst-Planck equation, which gives the total flux of administering drugs due to iontophoresis. In this work, an effort has been made to simulate iontophoresis to predict transdermal drugs in the dermal layers using electrical equivalent skin models.
Methods:
As the executable route of drug administration is skin, the electrical impedance value of the dermal layers can be utilized in predicting the amount of iontophoretic drug flux by introducing impedance parameters of skin in the Nernst-Planck equation. Researchers have developed electrical equivalent models of skin that explain the skin's physiological stratification and biological properties.
Results:
Numerical simulation of iontophoresis is performed using the human skin impedance values with these impedance models of skin to predict drug concentrations in the dermal layers. For the computation and analysis of drug delivery using simulations, boundary conditions were developed based on the descriptions of the electrical impedance models and the morphology of human skin.
Conclusions:
This proposed method establishes a clear relationship between TDD and skin impedance. It could be used in in-silico prediction before experimentation of any drugs on live animals or humans. The adopted methodology could be implemented in programming to develop software for real-time prediction of transdermal drugs in dermal layers using instantaneous skin impedance values. Further researchers can work upon this idea to include more natural constraints that identify complex biological features of the skin and physio-chemical properties of drugs.
IoT plays a vital role in critical patient care remote monitoring anywhere around the globe. Cardiac patients in remote areas in specific aged patients have to visit physician for diagnosing their health state regularly. In our proposed system critical cardiac patient heath was diagnosed using electrical bioimpedance technique and the same diagnosed impedance cardiograph signal was make available in live to the physician through IoT. Before designing hardware, simulation circuits are designed to obtain the required specifications in order to avoid hardware damage during testing.
In addition to the electrochemical sensors discussed in Chap. 2, a range of other sensing modalities are also important for biomedical and implantable applications. The frequency-dependent electrical properties of tissues are essential for assessing various physiological parameters. This, for example, can be quantified via electrical bioimpedance measurements, which can be combined and corroborated with electrochemical sensors. The human body is a dynamic system in constant motion; therefore, sensors for the measurement of physical properties such as strain and pressure are also important. Sensors for these applications rely on the measurement of resistance, capacitance, and sometimes inductance, and these will also be discussed in this chapter for completeness. Temperature is an important health marker for various applications, and consequently the current state of the art in temperature sensors is also discussed, in terms of both monolithic integration and discrete sensor solutions. Monitoring of the electrical response of the nervous system and the delivery of stimuli represent an important family of applications for neuroscience research and neuroprosthetic devices. These will be addressed in this chapter, along with various application scenarios. Other aspects to be discussed include sensor metrics, such as sensitivity, limit of detection, stability, linear range, selectivity, and specificity.
The measurement of aortic pulse transit time (PTT), the time for the arterial pulse wave to travel from the carotid to the femoral artery, can provide valuable insight into cardiovascular health, specifically regarding arterial stiffness and blood pressure (BP). To measure aortic PTT, both proximal and distal arterial pulse timings are required. Recently, our group has demonstrated that the ballistocardiogram signal measured on a modified weighing scale can provide an unobtrusive, yet accurate, means of obtaining a proximal timing reference; however, there are no convenient, reliable methods to extract the distal timing from a subject standing on the modified weighing scale. It is common to use a photoplethysmograph (PPG) attached to a toe to measure this distal pulse, but we discovered that this signal is greatly deteriorated as the subject stands on the scale. In this paper, we propose a novel method to measure the distal pulse using a custom reflective PPG array attached to the dorsum side of the foot (D-PPG). A total of 12 subjects of varying skin tones were recruited to assess the preliminary validation of this approach. Pulse measurements using the D-PPG were taken from seated and standing subjects, and the commercially available PPG were measured for facilitating comparison of timing measurements. We show that the D-PPG was the only sensor to retain the high detection rate of feasible timing values. To further test and optimize the system, various factors such as applied pressure, measurement location, and LED/photodiode configuration were tested.
A reference design of an EIT (electrical impedance tomography) belt using the AFE4300 IC, with supplemental amplifying buffers, is presented. The experimental results are promising, recommending it for practical implementation. The paper also indicates the possibility to develop other EIT belts variants based on AFE4300, using multiple impedance measuring pairs, suitable for wireless wearable EIT belts. Lung function monitoring with tidal volume estimation using EIT, aims at the application area of sports medicine. The ECG sensor module of the AFE4300 was also explored as a supplementary bio sensor channel use-full in applications. In all, the reference design outlines a digital SPI bio-impedance and ECG sensing modules, with low total power and cost and ready of application in practice.
Most health measurement equipment at present can only obtain a single type of physiological data from users and are non-continuous static devices, resulting in the inability of users to continuously monitor their physiological conditions throughout the day. This paper presents the design and development of an integrated heart rate (HR), hydration level (HL) and blood glucose concentration (BGC) sensor system within a continuous monitoring wearable watch. The three identified physiological parameters are measured based on a single multi-frequency bio impedance modality in the watch. A parallel signal processing approach is implemented to identify the HR, HL and BGC components from the bio impedance signal and the results are demonstrated in this paper. This highly portable and wearable prototype demonstrates the potential of continuous real-time tracking for health-conscious or diabetic individuals, as well as athletics, who needs to closely monitor their HR, HL and BGC throughout the day.
In this paper, we presented the novel design and development of a non-invasive new integrated device for measuring calories burnt from the heart rate in Arduino environment. By using the heart rate, a relation for calories burnt will be calculated. As obese people are most concerned about losing their weight, they regularly need to check the weight they lose during exercises. This calorie estimator helps in calculating calories burnt by using raise in heartbeat during am exercise. In this project, heart rate is measured using Heartbeat sensor (IR sensor). However, most heart rate measuring tools and environments are expensive and do not follow ergonomics. Our proposed IR sensor is economical and user friendly and uses optical technology to detect the flow of blood through index finger. In this project, Arduino is used in which microcontroller ATmega328 is embedded into it, suitable codes have been written to detect and count the heartbeat and also to calculate the calories burnt.
An integrated portable device for continuous heart rate and body temperature monitoring system development is presented in this paper. Heart related diseases are increasing day by day; therefore, an accurate, affordable and portable heart rate and body temperature measuring device is essential for taking action in proper time. Such a device is more essential in a situation where there is no doctor or clinic nearby (e.g., rural area) and patients are unable not recognize their actual condition. The developed system of this study consists of Arduino UNO microcontroller system, transmission system and Android based application. The system gives information of heart rate and body temperature simultaneously acquired on the portable device in real time and shows it through the connected Android application instantly. The developed system is more affordable with low price compared to other developed devices due to use of easy available Arduino UNO and smart phone as Android device. The developed device is shown acceptable outcomes when compared with other measuring devices.
Heart rate, or pulse, is one of the vital signs used to measure basic functions of human body. Heart rate is the number of times one's heart beats per minute. The method that has been used to measure heart rate in this project is widely known as photoplethysmography (PPG). The constructed device can be used to find out the heart rate of a person and to analyze readings using existing software. Theoretically, any body part can be used to measure heart rate through the sensor of the device, although fingertips and earlobes are commonly targeted.
The instrument which is used in home or in clinics should be cost effective and provide quality of health services. The medical industry is growing in terms of integration. Individual instruments are very costly so the need arises of making a device which has low cost and it measures some of physiological parameters of the body in a single device. This paper describes the design and development of a device which combines three physiological parameters of body i.e. heart rate, arterial blood oxygen concentration and body temperature. The output is displayed on LCD using low cost microcontroller.
We describe and analyze passive and active analog filters with differential input and differential output. They are implemented by coupling single-ended filters and provide very high common-mode rejection ratios. This makes it possible to place these filters before differential amplifiers, thus improving interference rejection and noise reduction.
This paper provides an outline of methods used for the implementation of a computer reliant diagnostic aid in the medical specialty of Ophthalmology. Some problems have been associated with many previous diagnostic models. A careful review indicates that the most serious problems were:
This paper analyzes the advantages and limitations of using the floating- (or flying-) capacitor technique as a building block with differential input and either differential or single-ended output to implement voltage amplifiers, multiplexers, and coherent amplitude demodulators. Theoretical analysis, supported by experimental results, shows that the fully differential configuration has a better common-mode rejection ratio (CMRR). However, if the output signal, once amplified, must be single ended, then it may be better to have a floating capacitor with single-ended output in amplifiers and some multiplexers whereas in demodulators a floating capacitor with differential output yields a better CMRR. Peer reviewed
We have applied synchronous sampling to the demodulation of bioelectric impedance signals. This overcomes the need for analog demodulators in bioimpedance measurements. The sampling rate is determined by signal bandwidth, rather than by the highest frequency component before demodulation.
AC coupling is essential in biopotential measurements. Electrode offset potentials can be several orders of magnitude larger than the amplitudes of the biological signals of interest, thus limiting the admissible gain of a dc-coupled front end to prevent amplifier saturation. A high-gain input stage needs ac input coupling. This can be achieved by series capacitors, but in order to provide a bias path, grounded resistors are usually included, which degrade the common mode rejection ratio (CMRR). This paper proposes a novel balanced input ac-coupling network that provides a bias path without any connection to ground, thus resulting in a high CMRR. The circuit being passive, it does not limit the differential dc input voltage. Furthermore, differential signals are ac coupled, whereas common-mode voltages are dc coupled, thus allowing the closed-loop control of the dc common mode voltage by means of a driven-right-leg circuit. This makes the circuit compatible with common-mode dc shifting strategies intended for single-supply biopotential amplifiers. The proposed circuit allows the implementation of high-gain biopotential amplifiers with a reduced number of parts, thus resulting in low power consumption. An electrocardiogram amplifier built according to the proposed design achieves a CMRR of 123 dB at 50 Hz.
This paper describes the development of an optophysiological model
of a finger in conjunction with a ring-type photoplethysmography device
(the ring sensor). It describes the photoplethysmographic effects due to
the relative displacement and rotation of a finger to a ring-type
optoelectric device that monitors the arterial pulsation noninvasively
and continuously. Numerical simulations and experiments were conducted
to verify and evaluate this model
This paper analyzes the advantages and limitations of using the
floating(or flying-) capacitor technique as fully differential or
differential input but single-ended output building block to implement
voltage amplifiers, multiplexers and coherent amplitude demodulators.
Theoretical analysis supported by experimental results show that the
fully differential configuration has a better common mode rejection
ratio (CMRR). However, if the signal, once amplified, must be single
ended, then in amplifiers and some multiplexers it may be better to have
a floating capacitor with single-ended output whilst in demodulators a
floating capacitor with differential output yields a better CMRR
We describe a new analog differential synchronous demodulator for AC signals where: (i) the signal is synchronously demodulated using the floating capacitor technique after being amplified, if necessary, by a low-gain AC amplifier with differential input and differential output, thus yielding a very high CMRR; and (ii) the differential-to-single ended signal conversion is performed after demodulation, that is, on a low-frequency signal that can be amplified by low-cost, high-performance circuits. We prevent the possible signal-to-noise ratio degradation because of synchronous sampling by using bandpass differential filters
When a current is injected into a body, in addition to the voltage profile developed on the surface, a common-mode voltage (CMV) which produces errors in the measurement also appears. The great accuracy needed to reconstruct images in electrical impedance tomography (EIT) requires the use of differential amplifiers with a high common-mode rejection ratio (CMRR) to avoid this error. Nevertheless, the effective CMRR is lower than the differential amplifier ratio due to mismatches in the electrode impedances and other circuits in the measurement channel. The use of common-mode feedback (CMFB) is an alternative to reducing the error produced by the CMV. The stability of the feedback loop is analysed for a broadband system. Simulation and experimental results show that it is possible to obtain an improvement of 40 dB in the measurements at frequencies of up to 10 kHz.
The impedance cardiograph is a new device capable of providing information concerning the mechanical function of the heart without penetrating the skin. Its use is as simple and easy as recording the electrocardiogram. Use of the instrument creates no hazard or discomfort to the subject. The procedure to obtain the impedance information is simple, convenient, and inexpensive, suitable for any clinical or research application.
The authors previously developed an unconstrained and noninvasive measurement system of heartbeat and respiration using an acoustic sensor enclosed in an air pillow (or an air mat). Although the continuous trends of the instantaneous heartbeat and respiration periods were accurately measured with the system, these periods originally should be discretely obtained. The paper improves the pre-proposed measurement system such that the heartbeat and respiration periods are discretely outputted, like the conventional sensors as the electrocardiograph and the thermistor type respiration pick-up.
The following topics are dealt with: the next era of examination and management of the patient with cardiovascular disease; the importance of technology in rehabilitation; wearable technology applications in Parkinson's disease; wearable sensor technology for functional assessment after stroke.
An impedance pulse, recorded noninvasively, has contributions due to both the change in blood volume of the arteries and to the change in the blood resistivity. Other researchers have tried to quantify the relative contributions and have either underestimated or overestimated the contributions since they did not simulate the physiological conditions. We have used an in vitro flow circulation system to more closely simulate the physiological conditions and quantify the two contributions. We find that the blood resistivity change contribution is strong enough (21.5 percent of the arterial volume change contribution) to change the morphology of the impedance pulse. There is, however, a phase difference between the two contributions. As a result of this, the blood resistivity change contribution to the height of the impedance pulse will be less than 5.5 percent.
Body weight scales equipped with body fat meter
- K Oguma
K. Oguma, "Body weight scales equipped with body fat meter,"
TANITA CORP, WO9920175-A, Apr. 29, 1999.
Metthod and apparatus to obtain the heart rate from electrical impedance variations measured between the feet Patent application to the Spanish Patent Office
- R O Pallàs-Areny
- R Casas
- Gonzalez Landaeta
Wireless Heart Rate Monitor with Infrared Detecting Module
- Y Chen
Y. Chen, "Wireless Heart Rate Monitor with Infrared Detecting
Module," US2005075577-A1, Apr. 7, 2005.
- B H Brown
- R H Smallwood
- D C Barber
- D R Hose
B. H. Brown, R. H. Smallwood, D. C. Barber, L. P.V., and D. R.
Hose, Medical Physics and Biomedical Engineering, UK: IoP, 1999,
pp. 613-615.
Metthod and apparatus to obtain the heart rate from electrical impedance variations measured between the feet
- R Pallàs-Areny
- . O Casas
- R González Landaeta
R. Pallàs-Areny. O. Casas and R. González Landaeta, "Metthod and
apparatus to obtain the heart rate from electrical impedance
variations measured between the feet." Patent application to the
Spanish Patent Office, October 28, 2005. [In Spanish].