Defibrillation Process Research Articles

Design of Multifunctional Automated External Defibrillator Based on STM32

This paper presents a design of multifunctional portable automated external defibrillator based on STM32F103VC SCM. The defibrillator mainly realizes the defibrillation and ECG analysis function, and according to the clinical actual need, increases information storage and transmission function, query of local records, the function of synchronous LCD display and voice prompt in the defibrillation process. The device uses the defibrillating electrodes to measure body resistance, ECG and so on. We detailedly researched and achieved the discharge module of biphasic defibrillation apparatus based on the damping of two order discharge circuit, and finished the real-time LCD display and voice prompt modules of defibrillation information based on the control of PIC24FJ256DA210 chip.

A new quality index for benchmarking of different cellulose nanofibrils

From a single plant source, a wide range of mechanically-deconstructed cellulose nanomaterials can be obtained due to the large number of possible combinations of pre-treatments, mechanical disintegration process, and post-treatments. It leads to the existence of a variety of cellulose nanofibrils with different shapes, morphologies, and properties on the market. The resulting material is actually a complex mixture of nanoscale particles, microfibrillated fibers, and residual fibers on the millimeter scale. Defining a “degree of fibrillation” for determining the final cellulose nanofibril quality is a challenging issue. This study proposes a multi-criteria method to obtain the quality index of cellulose nanofibril suspensions under the form of a unique quantitative grade. According to this method, the influence of different parameters such as pulp conditioning, refining, and hemicellulose content on the defibrillation process is highlighted. This method also allows for the benchmarking of different commercial nanocellulose products.

Isolation of lignocellulose nanofibrils (LCNF) and application as adhesive replacement in wood composites: example of fiberboard

Thermomechanical pulp (TMP) produced using atmospheric refining was ground to isolate lignocellulose nanofibrils (LCNF). Forty minutes and a specific energy of about 1300 kWh/t were necessary to reach the end-point of the process defined by the presence of 95% fines in the slurry. 100% fines were reached after 90 min and 5800 kWh/t. The similarity in structure between pilot-scale produced reference cellulose nanofibrils (CNF) and LCNF with an average fibril diameter of 12 nm confirmed the negligible effect of residual lignin on the defibrillation process. The thermal stability of LCNF was found to be 30 °C lower compared to that of CNF due to the lignin influence, but it was in the range of processing temperatures used for wood composite materials. The effect of using LCNF as adhesive replacement in fiberboard has been assessed. A maximum modulus of rupture of 12.1 MPa comparable to that of commercial fiberboards and high modulus of elasticity, was obtained at 20% LCNF content for panels produced at 180 °C. The binding ability of LCNF and its effect on the mechanical properties of fiberboards were more perceptible when a less refined TMP with lower fine content and longer fibers was used in the process.

Preparation and property assessment of neat lignocellulose nanofibrils (LCNF) and their composite films

Lignocellulose nanofibrils (LCNF) were produced from thermo-mechanical pulp (TMP) using a micro-grinder and were characterized with respect to fiber diameter and thermal stability. The initial water content in the TMP affected the defibrillation process and longer grinding time was necessary for the air-dried TMP, resulting in LCNF with higher fibril diameter. As compared to the reference cellulose nanofibrils (CNF) produced through a refining process, LCNF was less thermally stable and started to degrade at a temperature that was 30 °C lower than that of CNF. LCNF obtained from the never-dried TMP was combined with various additives (10 wt%) to produce composite films. The neat LCNF and composite films did not reach the mechanical properties of the neat CNF film that was evaluated as reference. However, the addition of poly(vinyl alcohol) (PVA) at 10 wt% on a dry basis did cause a 46 and 25% increase in tensile strength and elastic modulus, respectively. Other additives including cellulose nanocrystals, bentonite and CNF were also found to increase to some extent the Young’s modulus and ductility of the LCNF composite films whereas the addition of talc did not improve the film performance. Water absorption of neat LCNF films was lower than the reference CNF and was negatively affected by the addition of PVA.

Structural and morphological characterization of bacterial cellulose nano-reinforcements prepared by mechanical route

Bacterial cellulose (BC) is a very promising material due to its high purity, good mechanical properties and thermal stability. Bacterial cellulose nanofibers (BCNF) in dry form could be used as reinforcements in hydrophobic polymer matrices like polylactic acid (PLA) or polyhydroxyalkanoates for biomedical applications. In this work, BCNF were obtained by simple eco-friendly mechanical treatments applied to BC pellicles, consisting in successive wet and dry mechanical disintegration steps or only wet mechanical disintegration followed by freeze drying. The defibrillation processes did not modify the allomorph composition of BC, characterized by the preponderance of Iα compared to Iβ form, but determined an increase of crystallinity, from 81% to 84–85%. Morphological investigations revealed that the pellicles were entirely disintegrated by the mechanical treatments. AFM Peak-Force Quantitative-Nanomechanical-Mapping revealed unexpected detachment of small fibers from the BC ribbons at regular intervals, which was proved so far only for cellulose nanofibers from plants. PLA composites obtained with these BCNF showed higher modulus with almost 30% compared to the matrix. Dried BCNF prepared by these eco-friendly approaches are good reinforcements for bionanocomposites for “in vivo” or “ex vivo” application, due to their high purity.

Cationic nanofibrillar cellulose with high antibacterial properties

Cationic nanofibrillar cellulose (C-NFC) has been prepared via a high pressure homogenization using quaternized cellulose fibers with glycidyltrimethylammonium chloride. It has been shown that the quaternization of dried softwood pulp facilitated the defibrillation processes and prevented clogging of the homogenizer. The effects of the trimethylammonium chloride content on the fibrillation yield, the transparency degree of the gel, the rheological behavior of the NFC suspension and their electrokinetic properties were investigated. AFM observation showed that the NFC suspension consisted of individualized cellulose I nanofibrils 4–5nm in width and length in the micronic scale. In addition to their strong reinforcing potential, the inclusion of C-NFC into a polymer matrix was shown to efficiently enhance the antibacterial activity. The reinforcing potential of C-NFC, studied by dynamic mechanical analysis (DMA), was compared to anionic NFC and the difference was explained in terms of the nanofibrils capacities to build up a strong networks held by hydrogen bonding.

New insights into defibrillation of the heart from realistic simulation studies.

Cardiac defibrillation, as accomplished nowadays by automatic, implantable devices, constitutes the most important means of combating sudden cardiac death. Advancing our understanding towards a full appreciation of the mechanisms by which a shock interacts with the heart, particularly under diseased conditions, is a promising approach to achieve an optimal therapy. The aim of this article is to assess the current state-of-the-art in whole-heart defibrillation modelling, focusing on major insights that have been obtained using defibrillation models, primarily those of realistic heart geometry and disease remodelling. The article showcases the contributions that modelling and simulation have made to our understanding of the defibrillation process. The review thus provides an example of biophysically based computational modelling of the heart (i.e. cardiac defibrillation) that has advanced the understanding of cardiac electrophysiological interaction at the organ level, and has the potential to contribute to the betterment of the clinical practice of defibrillation.

Virtual 3D Heart Models to Aid Pacemaker Implantation in Children

Virtual 3D Heart Models to Aid Pacemaker Implantation in Children

Lung injury and pneumothorax after defibrillation as demonstrated with computed tomography

Many patients present for emergency services after electric injuries or require defibrillation during emergency services. Although the defibrillation process is safe, skin burns and myocardial injuries are reported after defibrillation procedures. There are limited data about the complications of defibrillation. In the case reported here, a lung injury and a small pneumothorax were observed after defibrillation. To the best of our knowledge, this is the first reported case in which computed tomography is used to demonstrate that a trace of electric current passed through the lung. Computed tomography may be an excellent diagnostic modality to demonstrate the severity and extent of electric injuries to the lung.

Numerical Solution for PDE-Constrained Optimization Problem in Cardiac Electrophysiology

paper, we present the numerical solution for the PDE- constrained optimization problem arises in cardiac electrophysiology. The monodomain model, which is a well- established model for simulating electrical behavior of the cardiac tissue, appears as the constraint in our problem. Our objective is to search for the optimal applied current, which is able to dampen out the excitation wavefront of the transmembrane potential during defibrillation process. The modified Dai-Yuan nonlinear conjugate gradient method is employed for computing the optimal applied current, and our numerical results show that the excitation wavefront is successfully dampened out by the optimal applied current.

The Effects of Control Domain Position on Optimal Control of Cardiac Arrhythmia

We study the effects of control domain position on optimal control problem of cardiac arrhythmia. The well‐established mathematical model, namely, the monodomain model, is used to represent the electrical behavior of the cardiac tissue. Two test cases are considered in this paper: the control domain for Test Case 1 is close to the excitation domain, while the control domain for Test Case 2 is a little bit far away from the excitation domain. The modified Dai‐Yuan nonlinear conjugate gradient method is employed for computing the optimal applied extracellular current. Our experiment results show that the excitation wavefronts are successfully dampened out for both test cases. Also, experiment results show that the position of the control domain for Test Case 1 is preferable than that of Test Case 2 during the defibrillation process.

Modeling Defibrillation of the Heart: Approaches and Insights

Cardiac defibrillation, as accomplished nowadays by automatic, implantable devices (ICDs), constitutes the most important means of combating sudden cardiac death. While ICD therapy has proved to be efficient and reliable, defibrillation is a traumatic experience. Thus, research on defibrillation mechanisms, particularly aimed at lowering defibrillation voltage, remains an important topic. Advancing our understanding towards a full appreciation of the mechanisms by which a shock interacts with the heart is the most promising approach to achieve this goal. The aim of this paper is to assess the current state-of-the-art in ventricular defibrillation modeling, focusing on both numerical modeling approaches and major insights that have been obtained using defibrillation models, primarily those of realistic ventricular geometry. The paper showcases the contributions that modeling and simulation have made to our understanding of the defibrillation process. The review thus provides an example of biophysically based computational modeling of the heart (i.e., cardiac defibrillation) that has advanced the understanding of cardiac electrophysiological interaction at the organ level and has the potential to contribute to the betterment of the clinical practice of defibrillation.

Nanofibrillated cellulose from TEMPO-oxidized eucalyptus fibres: Effect of the carboxyl content

In the present work the effect of the carboxyl content on the high pressure defibrillation of oxidized eucalyptus from micro to nanoscale size was investigated. It has been shown that TEMPO-mediated oxidation of dried softwood pulp not only facilitates the defibrillation process, but also reduces the number of passes necessary to get the gel, as well as preventing the clogging of the homogenizer. In fact, these effects became apparent up to a carboxyl content about 300 μmol/g, and over 500 μmol/g, the yield in the nanofibrillated cellulose exceeded 90%, at a defibrillation pressure of 600 bar. The morphology of the ensuing nanofibrillated cellulose (NFC) and its crystalline degree were characterised by FE-SEM and DRX measurement, respectively. The evolution of the transparency degree and the viscosity according to the oxidation degree and defibrillation pressure were also analysed by UV–vis transmittance and rheological measurement. The reinforcing potential of the ensuing NFC was explored by means of dynamic mechanical analysis (DMA) carried on nanocomposite film prepared from a suspension of NFC as the reinforcing phase and an acrylic latex dispersion as the matrix.

Optimization of Bipolar Pulses of External Defibrillators Based on the Repolarization Hypothesis

The defibrillation process is simulated using a wide spectrum of spatial models [1]. It is difficult to use most spatial models to simulate and select the optimal bipolar electric defibrillation pulse. In practice, simpler spatial models are used [2, 3]. In this work, bipolar pulses of external defibrillators were optimized based on the repolarization hypothesis. The algorithm of the optimization is based on a simple model of defibrillation pulse effect on myocardium cell membrane (Fig. 1) [2, 3]. The defibrillation pulse is applied to resistor Rs (the patient’s chest resistance). The signal from resistor Rs is applied to the model of myocardium cell membrane response to an external effector. This model consists of serially connected resistor Rm (cell membrane resistance) and capacitor Cm (cell membrane capacitance). The time constant of cell mem brane reaction to the defibrillation pulse τm is a quantita tive parameter of the myocardium cell reaction to the defibrillation pulse:

Evaluation of Impact of Some Pulse Parameters on the Efficiency of Electric Cardiac Defibrillation

Objective: to test the hypothesis of the resonance pattern of an electric cardiac defibrillation process and to study the impact of the frequency spectrum of pulses of various shape on the efficiency of defibrillation. Material and methods. The frequency spectrum of pulses the efficiency of which during defibrillation was known was examined. Delta pulses with a steep anterior and flat posterior front; a pulse with a flat anterior and steep posterior front, a bipolar asymmetric trapezoidal pulse from a DKI-H-15 St BIFASIK+ defibrillator, and its returning pulse were considered. The pulse spectra were calculated and plotted using the Mathematica program (Wolfram Research Inc.). Results. The different pattern of a relationship of the efficiency of defibrillation to the duration of pulses with a damping increment or decrement is shown to be contradictory to the hypothesis of the resonance pattern of an electric cardiac defibrillation process. The pulses with the equal frequency spectrum may have a great efficiency difference during defibrillation. The efficiency may be affected by the pulse phase interval. Conclusion. The value of a spectrum module at the zero frequency of pulse phases may be regarded as one of the parameters characterizing the efficiency and safety of defibrillation exposure.

Construction of a Computer Model to Investigate Sawtooth Effects in the Purkinje System

The sawtooth effect refers to how one end of a cardiac cell is depolarized, while the opposite end is hyperpolarized, upon exposure to an exogenous electric field. Although hypothesized, it has not been observed in tissue. The Purkinje system is a one-dimensional (1-D) cable-like system residing on the endocardial surface of the heart and is the most obvious candidate for the manifestation of this phenomenon. This paper describes a computer modeling study of the effect of electric fields on the Purkinje system. Starting with a three-dimensional geometrically realistic, finite element, ventricular description, a Purkinje system is constructed which adheres to general physiological principles. Electrical activity in the Purkinje is described by use of 1-D cubic Hermite finite elements. Such a formulation allows for accurate modeling of loading effects at the Purkinje-myocyte junctions, and for preserving the discrete nature of the system. The response of a strand of Purkinje cells to defibrillation strength shocks is computed under several conditions. Also, the response of the isolated Purkinje network is illustrated. Results indicate that the geometry of the Purkinje system is the greatest determinant for far field excitation of the system. Given parameters within the plausible physiological range, the 1-D nature of the Purkinje system may lead to sawtooth potentials which are large enough to affect excitation. Thus, the Purkinje system is capable of affecting the defibrillation process, and warrants further experimentation to elucidate its role.

Defibrillation of the heart: insights into mechanisms from modelling studies

Despite its critical role in restoring cardiac rhythm and thus in saving human life, cardiac defibrillation remains poorly understood. Further mechanistic inquiry is hampered by the inability of presently available experimental techniques to resolve, with sufficient accuracy, electrical behaviour confined to the depth of the ventricles. The objective of this review article is to demonstrate that realistic 3-D simulations of the ventricular defibrillation process in close conjunction with experimental observations are capable of bringing a new level of understanding of the electrical events that ensue from the interaction between fibrillating myocardium and applied shock. The article does this by reviewing the results of two studies, one on vulnerability to electric shocks and another on defibrillation. An overview of the modelling tools used in these studies is also provided.

A Finite Volume Method for Modeling Discontinuous Electrical Activation in Cardiac Tissue

This paper describes a finite volume method for modeling electrical activation in a sample of cardiac tissue using the bidomain equations. Microstructural features to the level of cleavage planes between sheets of myocardial fibers in the tissue are explicitly represented. The key features of this implementation compared to previous modeling are that it represents physical discontinuities without the implicit removal of intracellular volume and it generates linear systems of equations that are computationally efficient to construct and solve. Results obtained using this method highlight how the understanding of discontinuous activation in cardiac tissue can form a basis for better understanding defibrillation processes and experimental recordings.

Success and Failure of the Defibrillation Shock:

This simulation study presents a further inquiry into the mechanisms by which a strong electric shock fails to halt life-threatening cardiac arrhythmias. The research uses a model of the defibrillation process that represents a sheet of myocardium as a bidomain. The tissue consists of nonuniformly curved fibers in which spiral wave reentry is initiated. Monophasic defibrillation shocks are delivered via two line electrodes that occupy opposite tissue boundaries. In some simulation experiments, the polarity of the shock is reversed. Electrical activity in the sheet is compared for failed and successful shocks under controlled conditions. The maps of transmembrane potential and activation times calculated during and after the shock demonstrate that weak shocks fail to terminate the reentrant activity via two major mechanisms. As compared with strong shocks, weak shocks result in (1) smaller extension of refractoriness in the areas depolarized by the shock, and (2) slower or incomplete activation of the excitable gap created by deexcitation of the negatively polarized areas. In its turn, mechanism 2 is associated with one or more of the following events: (a) lack of some break excitations, (b) latency in the occurrence of the break excitations, and (c) slower propagation through deexcited areas. Reversal of shock polarity results in a change of the extent of the regions of deexcitation, and thus, in a change in defibrillation threshold. The results of this study indicate the paramount importance of shock-induced deexcitation in both defibrillation and postshock arrhythmogenesis.

Automatic adjustment of biphasic pulse duration in transthoracic defibrillation

Many studies have proven that biphasic defibrillation pulses are more efficient than the damped sinusoid monopolar waveform. Transthoracic resistance was shown to change during the two phases. On the other hand, it was proven that transthoracic resistance plays an important role in the defibrillation process, yielding the current for selected energy or voltage. Pre-shock measurement of the resistance may lead to improved selection. Stabilized current defibrillators are of low stored-to-delivered energy ratio. Therefore, automatic dynamic adjustment of some defibrillator parameters with respect to transthoracic resistance changes seems rational. An approach is known for modifying the pulse duration, in order to deliver a selected energy. A method is proposed here and an experimental defibrillator is developed for dynamic pulse duration adjustment with the purpose of obtaining a desired optimal timecourse of the cardiac cell transmembrane potential.