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Spatial mapping of skin perfusion provides essential information about physiological processes that are often hidden from the eyes of the examining physician. The perfusion map quality depends on several key factors, such as the camera system type, frame rate, sensitivity, or signal-to-noise ratio. When investigating physiological parameters, the reference signal allows for increasing the spatial resolution of the photoplethysmography imaging (PPGI) system. On the other hand, it increases the system complexity and the synchronization prerequisites. Our solution is a hardware device that modulates the reference biosignal into the audio frequency band. This signal is connected to the mic input of a digital camera or a smartphone, enabling the transformation of such a device into a PPGI measurement system even in the case of compressed video recording using lock-in amplification technique. It also brings the possibility of synchronous recording of PPGI and another reference signal such as conventional photoplethysmogram or electrocardiogram.

Distributed cutaneous tissue blood volume oscillations contain information on autonomic nervous system (ANS) regulation of cardiorespiratory activity as well as dominating thermoregulation. ANS associated with low-frequency oscillations can be quantified in terms of frequencies, amplitudes, and phase shifts. The relative order between these faculties may be disturbed by conditions colloquially termed 'stress'. Photoplethysmography imaging, an optical non-invasive diagnostic technique provides information on cutaneous tissue perfusion in the temporal and spatial domains. Using the cold pressure test (CPT) in thirteen healthy volunteers as a well-studied experimental intervention, we present a method for evaluating phase shifts in low- and intermediate frequency bands in forehead cutaneous perfusion mapping. Phase shift changes were analysed in low- and intermediate frequency ranges from 0.05 Hz to 0.18 Hz. We observed that time waveforms increasingly desynchronised in various areas of the scanned area throughout measurements. An increase of IM band phase desynchronization observed throughout measurements was comparable in experimental and control group, suggesting a time effect possibly due to overshooting the optimal relaxation duration. CPT triggered an increase in the number of points phase-shifted to the reference that was specific to the low frequency range for phase-shift thresholds defined as π/4, 3π/8, and π/2 rad, respectively. Phase shifts in forehead blood oscillations may infer changes of vascular tone due to activity of various neural systems. We present an innovative method for the phase shift analysis of cutaneous tissue perfusion that appears promising to assess ANS change processes related to physical or psychological stress. More comprehensive studies are needed to further investigate the reliability and physiological significance of findings.

The presented system for non-contact examination of tissue perfusion is one of the tools for complex examination of human body tissues (skin, subcutaneous) and their mutual interactions, including blood flow and activity under various external stimuli. In our system, optical radiation, with wavelengths of 525 nm, 625 nm, and 940 nm, was used to investigate the perfusion and properties of skin tissue. Our work presents that it is possible to obtain comprehensive information about the cardiovascular system and skin tissue perfusion by a suitable combination of wavelengths, light intensity, and homogeneous illumination distribution with a properly chosen sensing device—a camera. The proposed system consists of an illumination device that emits light of the three wavelengths mentioned above and thus makes it possible to investigate the skin tissue structures and their interrelationships in terms of their blood supply and interactions with each other.

Measurement of fingers and hand kinematics during the grasping activities and manipulation with various objects play an essential role in ergonomics, sport science, occupational medicine, and rehabilitation, as it is an indicator of hand function. That is why the design and realization of a device for finger flexion and extension and forearm motion became the main objective of this article. The work deals with designing and implementing the system prototype, its calibration, and testing under laboratory conditions. The designed device is promising to be used in occupational medicine and rehabilitation applications such as the device to assess the hand function impairment and track patient hand function disability recovery progress.

This paper describes a distance measurement process, tracking the environment, and determining the presence of space obstacles. The ultrasonic module HC-SR04 is used to measure the distance. This module is complemented by a servo motor, which allows gradual monitoring of the surroundings. The way of signaling obstacles in the space is realized via the vibrating motor. All information about the measured distance is then transmitted to the computer via the Bluetooth module, where is created graphical user interface in the MATLAB program. The system is designed to enable orientation in space for people with visual impairments.

The proposed article introduces a design of low-cost and low-energy home health-care monitoring system. The developed prototype is capable of measuring the three primary diagnostic modalities: electrocardiogram, photoplethysmogram, and body temperature. During the bio-signals acquisition, the data are visualized on the screen in the real-time and simultaneously transmitted to the computer for the subsequent processing.

The topic of the article is analysis of circuits for active electrodes used at capacitively coupled measurements. The work compares differences between wet and insulate electrode. There is analyzed circuit for active electrode which uses integrated voltage follower and there are also presented and simulated improvements for proper using this kind of active electrode for capacitively coupled electrode. Each of these simulations was performed in TINA SPICE - based analog simulation program by Texas Instruments. Finally, the article presents a solution for an operational amplifier integrated into the active electrode to prevent saturation of its inputs. This solution ensures to ground operational amplifier input in the case of overrunning threshold value.

OBJECTIVE Photoplethysmography imaging (PPGI) is a promising contactless camera-based method of non-invasive cardiovascular diagnostics. To achieve the best results, it is important to choose the most suitable camera for a specific application. The settings of the camera influence the quality of the detected signal. APPROACH The standard (European Machine Vision Association 2016 EMVA Standard 1288-Standard for Characterization of Image Sensors and Cameras pp 1-39 (available at: https://www.emva.org/wp-content/uploads/EMVA1288-3.1a.pdf)) for evaluating the imaging performance of machine vision cameras (MVC) helps at the initial decision of the sensor, but the camera should always be tested in terms of usability for a specific application. So far, PPGI lacks a standardized measurement scenario for evaluating the performance of individual cameras. For this, we realized a controllable optoelectronic phantom with artificial silicone skin allowing reproducible tests of cameras to verify their suitability for PPGI. The entire system is housed in a light-tight box. We tested an MVC, a digital single-lens reflex camera (DSLR) camera and a webcam. Each camera varies in used technology and price. MAIN RESULTS We simulated real PPGI measurement conditions simulating the ratio of pulse (AC) and non-pulse (DC) component of the photoplethysmographic signal and achieved AC/DC ratios of 0.5 % on average. An additional OLED panel ensures proper DC providing reproducible measurement conditions. We evaluated the signal morphological features, amplitude spectrum, signal-to-noise ratio (SNR) and spatially dependent changes of simulated subcutaneous perfusion. Here, the MVC proved to be the most suitable device. A DSLR is also suitable for PPGI, but a larger smoothing kernel is required to obtain a perfusion map. The webcam, as the weakest contender, proved to be very susceptible to any inhomogeneous illumination of the examined artificial skin surface. However, it is still able to detect cardiac rhythm. SIGNIFICANCE The result of our work is an optoelectronic phantom for reproducible testing of PPGI camera performance in terms of signal quality and measurement equipment costs.

This article introduces a capacitive measurement method for objective examination of textile sensor sensitivity within the frequency range associated with various biosignals. The proposed evaluation method is subsequently used to investigate biosignal sensing properties of a basic copper surface sensor and two selected textile sensors made from commercially available and commonly used conductive Shieldex and Elitex fibres. Experiment results indicate that the Elitex-based electrode is more suitable than Shieldex and copper surface electrodes. The signal attenuation of the Elitex electrode is lower by approx. 1–2 dB in comparison to the Shieldex electrode in the 0.5 Hz to 10 kHz frequency range. The copper surface electrode has slightly better signal transmission properties within low frequencies (

The article deals with the design of an electrical model of variable segments of a non-symmetrical tree of small arteries This model can be used to simulate the blood pressure and flow. Peripheral arterial resistance changes are modelled by an exponentially dependent resistor. By modulating the capacitor value, we can model the arterial wall properties which depend on the arterial pressure. Simulations are performed in which vasoconstriction and vasodilation were modelled by varying the transmural pressure. As a result, we can observe the changes in the blood pressure for each arterial generation.

This article is focused on the design and the construction of the simple low-cost wireless ECG system for university education practices. The system is split into functional blocks performing particular functions. In separated sections, these blocks are described in detail. The paper presents analog circuit for acquisition and filtration of the ECG signal in detail. ATmega328p embedded in the Arduino Nano board is the primary component of the hardware dealing with signal digitalization. The wireless transmission of the digitalized signal is made by the HC-06 Bluetooth module. The end of the article deals with experimental measurements and the device's capacity to measure the ECG signal. The usage of our tool for educational purposes is also presented.

Measurement of forces exerted by hand during contact and manipulation with various objects has its importance in the field of ergonomics, sports, occupational medicine and in rehabilitation too, because it is an indicator of hand functionality. That is, why the design and realization of device for hand press force became the main goal of this article. A part of the work is devoted to sensors and methods of force and pressure measurement. We are focusing on the design and development of the device measuring the grip forces based on the knowledge from technical and medical areas. The work deals with the calibration and the testing of the device under simulated industrial conditions. The designed device is promising to be used in applications such as the force measurement during work activities and the assessment of risks related to the excessive physical load.

The proposed article introduces a low-cost and ultra-low-energy wireless sensor design that forms part of a wireless network consisting of one central node and several peripheral sensor nodes. The nRF24L01+ transceiver modules operating in unlicensed 2.4 GHz band are used as a wireless technology. The main effort is focused on the optimal selection of wireless communication parameters to ensure reliability and data transmission range between central and sensor nodes. In addition, a design and implementation of wireless sensor node to monitor humidity and temperature environmental data is discussed. A conducted series of experiments to assess the power efficiency and communication reliability have shown that the proposed wireless sensor network is suitable for Smart Home applications. Developed sensor node’s transmission power is approx. 3.5 mA, operating up to 225 days in standby mode while driving a single coin battery.

The topic of the article is the design and construction of the device usable in various types of capacitance measurement. The AD7745 chip presents the main part of the created device. The system contains auxiliary circuits for extension of CDC range and multiplexors to measure one from connected capacitances. The device functionality is described in detail. The ability of the device to be used in various types of the biomedical application was proved by measurements. The article presents measurements of liquid level, breathing and it also presents a way how to use the AD7745 with multiplexors to reliably map a position of pressure applied to the sensor matrix.

The proposed article introduces a design of smart bed sheet for contactless electrocardiogram (ECG) measurement. As a sensor part, active capacitively coupled textile electrodes sewn into the bed sheet were designed. A measuring part represents a developed control unit for data preprocessing and acquisition utilizing the ADS1198 front-end chip. Design and implementation of the sensor part as well as measuring part are discussed in detail. A pilot prototype was fabricated to evaluate the feasibility of the design and reliability of contactless ECG measurement. The present prototype appears promising for application to bedding as an unconstrained method for ECG monitoring.

A capacitive measurement of the biosignals is a very comfortable and unobtrusive way suitable for long-term and wearable monitoring of health conditions. This type of sensing is very susceptible to noise from the surroundings. One of the main noise sources is power-line noise, which acts as a common-mode voltage at the input terminals of the acquisition unit. The origin and methods of noise reduction are described on electric models. Two methods of noise removal are modeled and experimentally verified in the paper. The first method uses a passive capacitive grounding electrode, and the second uses an active capacitive Driven Right Leg (DRL) electrode. The effect of grounding electrode size on noise suppression is experimentally investigated. The increasing electrode area reduces power-line noise: the power of power-line frequency within the measured signal is 70.96 dB, 59.13 dB, and 43.44 dB for a grounding electrode area of 1650 cm2, 3300 cm2, and 4950 cm2, respectively. The capacitive DRL electrode shows better efficiency in common-mode noise rejection than the grounding electrode. When using an electrode area of 1650 cm2, the DRL achieved 46.3 dB better attenuation than the grounding electrode at power-line frequency. In contrast to the grounding electrode, the DRL electrode reduces a capacitive measurement system’s financial costs due to the smaller electrode area made of the costly conductive textile.

This article presents an analysis of active electrode design for capacitively coupled measurement of bioelectrical signals. It deals with constructing an active electrode using a guard layer to decrease its input's parasitic capacitance. Three dielectric materials (cotton, polyester, wool) were examined under different pressure (1.23 kPa, 3.07 kPa) of the active electrodes. The Common Mode Rejection Ratio (CMRR) analysis of the system using guarded and unguarded electrodes is also investigated. The results show that the guard layer increases the active electrode's gain in the whole measured frequency range for all insulation materials and pressures. An unguarded active electrode reaches a gain of −7.45 dB while using cotton as dielectric material under the pressure of 1.23 kPa compared to the guarded active electrode, which reaches the gain value of −0.47 dB at the same conditions. The measurements of the CMRR prove that the guard layer increases the system CMRR.

wireless communication eliminates obtrusive cables associated with wearable sensors and considerably increases patient comfort during measurement and collection of medical data. Wireless communication is very popular in recent years and plays a significant role in telemedicine and homecare applications. Bluetooth technology is one of the most commonly used wireless communication types in medicine. This paper describes the design of a universal wireless communication device with excellent price/performance ratio. The said device is based on the low-cost RN4020 Bluetooth module with Microchip Low-energy Data Profile (MLDP) and due to low-power consumption is especially suitable for the transmission of biological signals (ECG, EMG, PPG, etc.) from wearable medical/personal health devices. A unique USB dongle adaptor was developed for wireless communication via UART interface and power consumption was evaluated under various conditions.

Heart rate variability (HRV) reflects the physical health and ability of the organism to handle stress situations. HRV biofeedback is a real-time training process which helps reduce stress and asthma severity. The most important prerequisite for the HRV biofeedback is the detection of R peaks in the ECG signal. This article describes in detail a real-time algorithm capable of R peaks detection. The algorithm is implemented within a standalone C# application and functionality thereof is demonstrated. The results indicate that the proposed algorithm is immune against various types of artefacts.

The article deals with principle of the heart activity measurement using a piezoelectric sensor. There is an information about design of the device serving for arterial pulse wave measurement. The device allows conversion of an electrical charge from the piezoelectric sensor and offers analog signal preprocessing. The signal is later digital processed to achieve a heart rate of the measured subject.

The presented article deals with the topic of monitoring CO 2 absorption in a closed loop diving apparatus. While partial pressure is monitored in the closed-circuit breathing loop using oxygen sensors, carbon dioxide is not monitored at all. However, higher carbon dioxide or oxygen content in the breathing medium has toxic effects on the organism. CO 2 absorber composition, manufacturing thereof and chemical reactions occurring during CO 2 absorption are discussed - based on this a device for monitoring the exothermic absorber chemical reaction is constructed. The proposed device estimates the time to CO 2 absorber depletion based on the displacement of the chemical reaction zone.

The objective of this study was to explore the possibility of combining the theoretical human arterial model based on electromechanical analogy with real impedance cardiography measurements - the fusion of which would create a per-person adaptable model. Cardiac activity was modeled based on two different sources – the first model (Model No.1) included real-life hemodynamic parameters based on variation of universal aortic pressure, while the second model (Model No.2) was based on real-life aortic flow derived from measurements. Simulated blood pressure propagation in proximal aortic segment was compared with reference pressure values measured by an electronic sphygmomanometer. Model No. 2 was found to be more accurate and better representative of real behavior of the arterial system under normal conditions. Additionally, the blood pressure and blood flow curves directly reflected the variability of the cardiac activity.

Human arterial system simulation models represents a helpful tool for investigating blood pressure and blood flow propagating from the aorta towards upper and lower peripheral vessels. Real-life hemodynamic parameters are used as input for the arterial model based on electromechanical analogy. The mentioned parameters are determined from impedance cardiography measurements carried out on five human subjects. The theoretical model is thus individually adapted using real-life hemodynamic parameter values and the impact of stroke volume and heart rate changes on blood pressure and blood flow waveforms are investigated. We can conclude that the stroke volume influences especially the amplitude of the said curves, whereas the heart rate modifies shape thereof.

Impedance measurements are gaining importance in wide field of research. This paper presents the design and construction of an impedance measurement device based on the AD5933 integrated circuit. Our low-cost system can be used in many areas of bioresearch. For the purpose of this paper, the device was used as impedance cardiography (ICG) analyzer for human thoracic impedance measurements. The measured raw data from impedance recordings were processed in order to extract specific features and several important hemodynamic parameters were calculated from the ICG curve.

The article deals with design and description of a graphical user interface (GUI) which represents a support tool for accelerometer and gyroscope measurements. First of all, the GUI serves for data acquisition from realized module consisting of integrated accelerometer and gyroscope. From the acquired data, it is possible to calculate rotation angle of device or when it is needed, calibration of device or moving average filtering can be performed. Within the article there are described the algorithms serving for data acquisition, device calibration and data filtering using of moving average filter routine.

Within this work, the analysis of the selected arterial system segments were performed regarding to various hematocrit values. Properties of arteries were transformed to electrical quantities by using electromechanical analogy. There is theory of two port electrical circuits, which was used for analysis of the selected arterial segments. The characteristic voltage and current transfers were calculated in order determine the atrial properties as function of frequency for the various hematocrit values. The work deals with model of blood viscosity assuming non — Newtonian flow and then combines it with Newtonian blood flow, which is characteristic for the used arterial system model. The impact of different hematocrit values on the selected arterial segments is evaluated.

Wireless communication is very popular in medicine in recent years. It eliminates obtrusive cables of wearable sensors and considerably increases patient comfort during measurement and collection of medical data. Wireless communication plays a significant role in telemedicine and homecare applications. Bluetooth technology is one of the most commonly used wireless communication types in medicine. The aim of this paper is introduce a low energy Bluetooth module for medical/health devices — the low-cost RN4020 module with Microchip Low-energy Data Profile (MLDP). Unique USB dongle adaptor was developed for wireless communication via UART interface. The power consumption tests in different configurations were performed and results are presented in this paper. The declared low power consumption of module was confirmed by measurements in different modes of module — deep sleep, discoverable, connected and sending data.

The cardiovascular disease is a serious problem in the world. The early diagnosis of heart disease leads to minimization of deaths. The analysis of electrocardiogram (ECG) patterns and cardiac frequency is used for detecting arrhythmias and discovering the nature of disease.. In many cases patients encounter heart problems (pain, sudden change of heart beat) but no longer have an ECG device and/or equipment for measurement. These drawbacks can be overcome using an ECG logger. In this paper it is described hardware design of one-lead ECG data logger. The designed ECG logger is small and compact device without any cables - it is a miniature, hand-held device with fixed electrodes for fingers. Measured data are stored on built-in microSD memory card and then transferred to PC via USB connection.

A model of the nonsymmetrical arterial tree was analyzed. The arterial branching model was based on the principle of the electromechanical analogy. The nonsymmetrical arterial tree was divided to 7 arterial generations, starting from larger arteries towards small arteries and arterioles. For each generation the transfer function was calculated and there is presented the pressure simulation results for each arterial generation. Outflow conditions were determined regarding to calculation of the transfer functions and simulation results.