Michael Rapin

Electrical impedance tomography (EIT) for quantification of pulmonary edema in acute lung injury.

BackgroundAssessment of pulmonary edema is a key factor in monitoring and guidance of therapy in critically ill patients. To date, methods available at the bedside for estimating the physiologic correlate of pulmonary edema, extravascular lung water, often are unreliable or require invasive measurements. The aim of the present study was to develop a novel approach to reliably assess extravascular lung water by making use of the functional imaging capabilities of electrical impedance tomography.MethodsThirty domestic pigs were anesthetized and randomized to three different groups. Group 1 was a sham group with no lung injury. Group 2 had acute lung injury induced by saline lavage. Group 3 had vascular lung injury induced by intravenous injection of oleic acid. A novel, noninvasive technique using changes in thoracic electrical impedance with lateral body rotation was used to measure a new metric, the lung water ratioEIT, which reflects total extravascular lung water. The lung water ratioEIT was compared with postmortem gravimetric lung water analysis and transcardiopulmonary thermodilution measurements.ResultsA significant correlation was found between extravascular lung water as measured by postmortem gravimetric analysis and electrical impedance tomography (r = 0.80; p < 0.05). Significant changes after lung injury were found in groups 2 and 3 in extravascular lung water derived from transcardiopulmonary thermodilution as well as in measurements derived by lung water ratioEIT.ConclusionsExtravascular lung water could be determined noninvasively by assessing characteristic changes observed on electrical impedance tomograms during lateral body rotation. The novel lung water ratioEIT holds promise to become a noninvasive bedside measure of pulmonary edema.

Design and Optimization of A Blood Pump for A Wearable Artificial Kidney Device

The aim of the European project Nephron+ is the design of a wearable artificial kidney device. This paper is focused on the design of the corresponding ultralow-hemolysis continuous-operation blood pump. Accurate specifications and operating principle of the pump are determined. A first nonoptimal configuration of a linear electromechanical actuator which will be used to pump the blood is designed. Its prototype is presented along with the corresponding driving electronic circuit. Finally, based on the measurements, the actuator is optimized, and the final design and first experimental results are presented.

Electrical and mechanical design of a vest measuring a large set of physiological signals

This paper presents the mechanical and electrical design of a wearable vest with embedded sensors that allows measuring a big number of various physiological signals. The system paves the way for closely monitoring patients with chronic obstructive lung disease in their everyday life.

Synchronization and communication of cooperative sensors

Cooperative sensors are an emerging technology consisting of autonomous sensor units working in concert to measure physiological signals requiring distant sensing points, such as biopotential (e.g., ECG) or bioimpedance (e.g., EIT). Their advantage with respect to the state-of-the-art technology is that they do not require shielded and even insulated cables to measure best quality biopotential or bioimpedance signals. Moreover, as all sensors are simply connected to a single electrical connection (which can be for instance a conductive vest) there is no connecting limitation to the miniaturization of the system or to its extension to large numbers of sensors. This results in an increase of wearability and comfort, as well as in a decrease of costs and integration challenges. However, cooperative sensors must communicate to be synchronized and to centralize the data. This paper presents possible communication strategies and focuses on the implementation of one of them that is particularly well suited for biopotential and bioimpedance measurements.

Cooperative sensors: a new wired body-sensor-network approach for wearable biopotential measurement

Cooperative sensors are a novel measurement architecture based on active dry electrodes that allows the acquisition of biopotential signals (e.g., electrocardiogram, ECG) on patients in a comfortable and easy-to-integrate manner. This paper starts by analyzing the classical methods for measuring multilead ECG signals. Based on these classical methods, we then briefly introduce the concept of cooperative sensors and show how these sensors can be implemented in a wearable and reliable system that measures ECG signals in a real-life scenario. The main focus and innovation presented in this paper is on the duplex communication between the cooperative sensors. In addition, we show a first measurement of an ECG signal with cooperative sensors.

Standalone dry electrode-sensors for multilead ECG monitoring in mobile patients

Nowadays, standalone dry electrode-sensors allow for acquiring ECGs with a signal quality similar to those of standard ECG recorders. Moreover, standalone electrode-sensors are much easier to connect than the usual electrodes and do not require a specific electronic box for the recorder (the measured biopotentials are recorded directly in the electrode-sensors). This results in very high overall integration, and increased comfort and reliability. The main innovation presented in this paper is the circuit and mechanism (patent pending) allowing perfect synchronization of all the attached standalone electrode-sensors.

New biosensors and wearables for cardiorespiratory telemonitoring

Many cardiorespiratory physiological signals can be measured from the chest skin. When measured at many spots, some of them like EIT (Electrical Impedance Tomography) produce images. Classical approaches cannot practically be used to make wearables with a large number of sensors, because the sensing points are connected to a bulky centralized electronics box in a star arrangement. The solution is to use cooperative sensors. A vest embedding 51 multi-signal sensors designed for COPD (Chronic Obstructive Pulmonary Disease) patients is described as example.

Electromagnetic disturbances rejection with single skin contact in the context of ECG measurements with cooperative sensors

Classical approaches to make high-quality measurements of biopotential signals require the use of shielded or multi-wire cables connecting the electrodes to a central unit in a star arrangement. Consequently, increasing the number of leads increases cabling and connector complexity which is not only limiting patient comfort but also anticipated as the main limiting factor for future miniaturization and cost reduction of tomorrows wearables. We have recently introduced a novel sensing architecture that significantly reduces cabling complexity by eliminating shielded or multi-wire cables as well as by allowing simple connectors thanks to a bus arrangement. In this architecture, electrodes are replaced by so-called cooperative sensors. However, in this design, one of the cooperative sensors needs to be equipped with two contacts with the skin for proper common mode rejection, thus making its miniaturization problematic. This paper presents a novel common mode rejection principle which overcomes this limitation. When compared to others, the suggested approach is advantageous as it keeps the cabling complexity to its minimum. First measurements demonstrated in a real-life scenario the feasibility of this common mode rejection principle for a wearable 12-lead electrocardiogram monitoring system.

Design of a blood pump for a wearable artificial kidney device

The aim of a European project Nephron+ is design of a wearable artificial kidney device (WAKD). This paper is focused on design of the corresponding ultralow-hemolysis continuous-operation blood pump. Accurate specifications and operating principle of the pump are determined; a first, non-optimal configuration of an electro-mechanical actuator which will be used to pump the blood is designed; its prototype is presented along with the corresponding driving electronic circuit; finally, based on the measurements, the actuator is optimized, and the final design and first results are presented.