Manikins with human-like chest properties--a new tool for chest compression research

Commercially available training manikins for cardiopulmonary resuscitation (CPR) do not accurately mimic the mechanical properties of human chests. This may limit the usefulness of CPR research performed on such manikins. This paper presents the construction of manikins with chest properties matching those measured in patients during an ongoing CPR. The chest stiffness and damping of 59 cardiac arrest patients was measured during out-of-hospital CPR, using a defibrillator with a compression sensor with built-in force sensor and accelerometer. A manikin with eight interchangeable chest force–depth profiles, representing the measured range of chest stiffness and the average damping of these patients, was then specified and constructed. The stiffness and damping of the manikins were verified using the same equipment and method as was used during data collection. Between 30 and 50 mm compression depth, the force–depth relationship of all eight manikins were found to be within ±30 N of force or ±2 mm of depth from the reference specifications derived from measurements on patients’ chests. The average damping was also found to closely match the specified value.      

Canine sternal force-displacement relationship duringcardiopulmonary resuscitation

A viscoelastic model developed to model human sternal response to the cyclic loading of manual cardiopulmonary resuscitation (CPR) [8] was used to evaluate the properties of canine chests during CPR. Sternal compressions with ventilations after every fifth compression were applied to supine canines (n = 7) with a mechanical resuscitation device. The compressions were applied at a nominal rate of 90/min with a peak force near 400 N. From measurements of sternal force, sternal displacement, and tracheal airflow, model parameters were estimated and their dependence on time and lung volume evaluated. The position to which the chest recoiled between compressions changed with time at a mean rate of 1.0 mm/min. Within each ventilation cycle (five compressions) the sternal recoil position decreased by 2.0 cm for each liter of decrease in lung volume. The elastic force and damping decreased with time and decreasing lung volume. Canine and human [8] model parameters were found to be similar despite the notable differences in thoracic anatomy between the species, supporting the continued use of canines as models for human CPR. These parameters may be useful in the development of a model relating sternal compression forces to blood flow during CPR.     

System for mechanical measurements during cardiopulmonaryresuscitation in humans

Effective study of CPR requires measurement of the mechanical properties of the human chest and the resultant vascular pressures. A computer-based mobile data acquisition system was designed and built for this purpose. During manual CPR a short cylindrical module was placed between the rescuer's hands and the patient's chest. This module, which was attached to an easily manipulated position-sensing arm, measured force and acceleration at the sternum. Three-dimensional position and orientation of the module were measured, as well as the component of the applied force which was perpendicular to the sternum. The central venous and aortic pressures were measured by high fidelity pressure transducers. All transducer signals were recorded by digital computer. Real-time feedback of sternal force and displacement, and vascular pressures was provided to the rescue team via chart recordings. An audible signal was produced as an aid in maintaining desired compression rate and duration. The system's mobility permitted rapid implementation at any hospital location. In conclusion, this system was capable of measuring, recording, and displaying multiple physical quantities during manual CPR in humans.     

A Least Mean-Square Filter for the Estimation of the Cardiopulmonary Resuscitation Artifact Based on the Frequency of the Compressions

Cardiopulmonary resuscitation (CPR) artifacts caused by chest compressions and ventilations interfere with the rhythm diagnosis of automated external defibrillators (AED). CPR must be interrupted for a reliable diagnosis. However, pauses in chest compressions compromise the defibrillation success rate and reduce perfusion of vital organs. The removal of the CPR artifacts would enable compressions to continue during AED rhythm analysis, thereby increasing the likelihood of resuscitation success. We have estimated the CPR artifact using only the frequency of the compressions as additional information to model it. Our model of the artifact is adaptively estimated using a least mean-square (LMS) filter. It was tested on 89 shockable and 292 nonshockable ECG samples from real out-of-hospital sudden cardiac arrest episodes. We evaluated the results using the shock advice algorithm of a commercial AED. The sensitivity and specificity were above 95% and 85%, respectively, for a wide range of working conditions of the LMS filter. Our results show that the CPR artifact can be accurately modeled using only the frequency of the compressions. These can be easily registered after small changes in the hardware of the CPR compression pads.      

Design and Development of a Medical Parallel Robot for Cardiopulmonary Resuscitation

The concept of a medical parallel robot applicable to chest compression in the process of cardiopulmonary resuscitation (CPR) is proposed in this paper. According to the requirement of CPR action, a three-prismatic-universal-universal (3-PUU) translational parallel manipulator (TPM) is designed and developed for such applications, and a detailed analysis has been performed for the 3-PUU TPM involving the issues of kinematics, dynamics, and control. In view of the physical constraints imposed by mechanical joints, both the robot-reachable workspace and the maximum inscribed cylinder-usable workspace are determined. Moreover, the singularity analysis is carried out via the screw theory, and the robot architecture is optimized to obtain a large well-conditioning usable workspace. Based on the principle of virtual work with a simplifying hypothesis adopted, the dynamic model is established, and dynamic control utilizing computed torque method is implemented. At last, the experimental results made for the prototype illustrate the performance of the control algorithm well. This research will lay a good foundation for the development of a medical robot to assist in CPR operation.     

An algorithm used for ventricular fibrillation detection without interrupting chest compression

Ventricular fibrillation (VF) is the primary arrhythmic event in the majority of patients suffering from sudden cardiac arrest. Attention has been focused on this particular rhythm since it is recognized that prompt therapy, especially electrical defibrillation, may lead to a successful outcome. However, current versions of automated external defibrillators (AEDs) mandate repetitive interruptions of chest compression for rhythm analyses since artifacts produced by chest compression during cardiopulmonary resuscitation (CPR) preclude reliable electrocardiographic (ECG) rhythm analysis. Yet, repetitive interruptions in chest compression are detrimental to the success of defibrillation. The capability for rhythm analysis without requiring "hands-off" intervals will allow for more effective resuscitation. In this paper, a novel continuous-wavelet-transformation-based morphology consistency evaluation algorithm was developed for the detection of disorganized VF from organized sinus rhythm (SR) without interrupting the ongoing chest compression. The performance of this method was evaluated on both uncorrupted and corrupted ECG signals recorded from AEDs obtained from out-of-hospital victims of cardiac arrest. A total of 232 patients and 31,092 episodes of either VF or SR were accessed, in which 8195 episodes were corrupted by artifacts produced by chest compressions. We also compared the performance of this method with three other established algorithms, including VF filter, spectrum analysis, and complexity measurement. Even though there was a modest decrease in specificity and accuracy when chest compression artifact was present, the performance of this method was still superior to other reported methods for VF detection during uninterrupted CPR.     

A computer controller for vest cardiopulmonary resuscitation (CPR)

The authors recently developed a cardiopulmonary resuscitation (CPR) technique in which the airways are obstructed automatically during each chest wall compression. Energy loss accompanying air convection from the lungs during chest wall compression is limited so lung volume and intrathoracic pressures are increased. This technique required the development of a simple controller device to govern the pressure applied to ribcage and abdominal vests together with controller airflow at the airway opening. Experiments with the controller device on eight mongrel dogs showed that cardiac output increased obstructed expiratory cardiopulmonary resuscitation (OECPR) by 19% relative to the cardiac output during standard vest CPR (61% of the prearrest cardiac output relative to 24%, respectively). Furthermore, the OECPR technique without adjunct ventilation resolved the hypocapnic respiratory alkalosis that developed during the standard vest CPR with no ventilatory support. The authors give background information on the obstructed expiratory vest CPR and describe the controller device for delivering this CPR method     

用基波平衡原理分析非线性电子网络的稳定性

对于一个非线性非保守的电子网络,根据等效推力理论,可以求出变阻尼力在一周期中贡献能量的等效平均值Df.文中在等效推力的基础上,提出基波平衡原理.若在适当端口施加正弦电压源,则网络的稳定性取决于进入端口基波电流的实功与虚功成份的符号值.这种原理适用于含几个非线性器件的三阶电子网络.     

Active damping of drive train oscillations for an electrically driven vehicle

A problem encountered with electrically driven vehicles are resonances in the drive train caused by elasticity and gear play. Disadvantageous effects caused by this are noticeable vibrations and high mechanical stresses due to torque oscillations. The oscillations can be damped using a control structure consisting of a nonlinear observer to estimate the torque in the gear and a controller, which computes a damping torque signal that is added to the driver's demand. The control algorithm was implemented in the existing motor control unit without any additional hardware cost. The controller was successfully tested in a test vehicle. The resonances can essentially be eliminated. The controller copes satisfactorily with the backlash problem.     

T型压电变摩擦阻尼器性能试验与分析

结合压电陶瓷驱动器和T型金属摩擦阻尼器的特点，提出了T型压电变摩擦阻尼器及其三种阻尼力模型。其次，设计并制作了最大阻尼力450N、阻尼力可调倍数2．5～3倍的T型压电变摩擦阻尼器模型，并进行了可调阻尼力性能实验，得到了输入电压分别为常电压、位移和速度相关形变电压的阻尼力滞回曲线，试验结果与理论分析较吻合。     

Presliding hysteresis damping of LuGre and Maxwell-slip friction models

In this paper, the damping properties of presliding hysteresis are explored for the LuGre and Maxwell-slip friction models. Taking out of consideration the classical linear viscous damping and Stribeck effect, the nonlinear damping of force–displacement hysteresis is analyzed, in Lyapunov sense, for the motion dynamics. Based thereupon the simple but straightforward criteria of model’s parametrization are derived for kinetic friction to be dissipative. Further we show a related experimental example of presliding hysteresis friction response in vicinity to zero velocity.     

Optimization of Coronary Blood Flow During Cardiopulmonary Resuscitation (CPR)

In order to improve coronary blood flow during cardiopulmonary resuscitation (CPR), it is necessary to increase the aortic-right atrial pressure gradient. In the closed cardiovascular system, this gradient should be primarily determined by the level of cardiac output. Alternating simultaneous compression and decompression of the thorax and abdomen should result in improved cardiac output and coronary blood flow over present methods. Based on computer simulation results, this previously untried method was found to improve coronary flow three times the level predicted for standard CPR. Other recently proposed CPR strategies were also evaluated but resulted in significantly lower coronary perfusion levels. In all cases, coronary blood flow varied directly with cardiac output. The use of simultaneous compression and decompression appears to be a promising CPR procedure which warrants further consideration.     

基于原子力显微镜技术的单个生物大分子压弹性研究

单个生物大分子力学性质已经成为一个新兴的研究领域,近几年来由于单分子技术的不断发展,这个领域取得了很多突破性的进展。本文介绍了基于原子力显微镜技术的几种单分子压弹性测量技术及这些技术的具体应用,同时也简要阐述了这些技术的局限性。另外对这个领域的发展也进行了初步地探讨。     

Interfacial Sliding and Buckling of Monolayer Graphene on a Stretchable Substrate

The nonlinear mechanical response of monolayer graphene on polyethylene terephthalate (PET) is characterised using in‐situ Raman spectroscopy and atomic force microscopy. While interfacial stress transfer leads to tension in graphene as the PET substrate is stretched, retraction of the substrate during unloading imposes compression in the graphene. Two interfacial failure mechanisms, shear sliding under tension and buckling under compression, are identified. Using a nonlinear shear‐lag model, the interfacial shear strength is found to range between 0.46 and 0.69 MPa. The critical strain for onset of interfacial sliding is ～0.3%, while the maximum strain that can be transferred to graphene ranges from 1.2% to 1.6% depending on the interfacial shear strength and graphene size. Beyond a critical compressive strain of around ?0.7%, buckling ridges are observed after unloading. The results from this work provide valuable insight and design guidelines for a broad spectrum of applications of graphene and other 2D nanomaterials, such as flexible and stretchable electronics, strain sensing, and nanocomposites.     

Compression depth estimation for CPR quality assessment using DSP on accelerometer signals

Chest compression is a vital part of cardiopulmonary resuscitation (CPR). This paper demonstrates how the compression depth can be estimated using the principles of inertia navigation. The proposed method uses accelerometer sensors, one placed on the patient's chest, the other beside the patient. The acceleration-to-position conversion is performed using discrete-time digital signal processing (DSP). Instability problems due to integration are combated using a set of boundary conditions. The proposed algorithm is tested on a mannequin in harsh environments, where the patient is exposed to external forces as in a boat or car, as well as improper sensor/patient alignment. The overall performance is an estimation depth error of 4.3 mm in these environments, which is reduced to 1.6 mm in a regular, flat-floor controlled environment.     

基于模态试验的PCB板结构动态性能的等效建模

PCB因其基板内部结构的复杂性以及元器件种类众多且分布无规律性导致有限元模型建立困难,为此本文针对某车载热像仪主处理板上元器件的分布及结构特点,提出了一种基于自由模态试验数据的PCB板动态性能等效建模的方法.该方法对基板采用其原几何尺寸建立,对元器件的处理方式根据其物理属性以及在基板上分布特点按不同方法处理,最终需保持...     

Predicting tumor location by modeling the deformation of the breast

Breast cancer is one of the biggest killers in the western world, and early diagnosis is essential for improved prognosis. The shape of the breast varies hugely between the scenarios of magnetic resonance (MR) imaging (patient lies prone, breast hanging down under gravity), X-ray mammography (breast strongly compressed) and ultrasound or biopsy/surgery (patient lies supine), rendering image fusion an extremely difficult task. This paper is concerned with the use of the finite-element method and nonlinear elasticity to build a 3-D, patient-specific, anatomically accurate model of the breast. The model is constructed from MR images and can be deformed to simulate breast shape and predict tumor location during mammography or biopsy/surgery. Two extensions of the standard elasticity problem need to be solved: an inverse elasticity problem (arising from the fact that only a deformed, stressed, state is known initially), and the contact problem of modeling compression. The model is used for craniocaudal mediolateral oblique mammographic image matching, and a number of numerical experiments are performed.     

基于原子力显微镜的细胞弹性测量及分析方法

原子力显微镜作为纳米压痕工具已被广泛应用于测量细胞等生物材料的力学性能.然而,由于研究目的实验方法和数据处理方法的不同,造成实验结果差异大,数据提取方式不准确,结果分析解释不清等问题.本文以细胞为例,对实验数据获取和处理方法的适用范围、优缺点、可靠性及结果的分析方法进行讨论,并与其他力学性能测量方法相比较,以期提高实验结果的可靠性,为细胞力学性能实验的开展提供参考.     

机敏约束层阻尼结构动态模型辨识

针对机敏约束层阻尼(SCLD)非线性系统的动力学建模问题,系统辨识是一种简便有效的方法.该文以NARX网络表征待辨识模型,并采用串并联与并联相结合的方法训练网络,根据实验数据辨识出非线性系统的动力学模型.通过对SCLD薄板结构外扰通道和控制通道的建模研究,证明了NARX网络良好的辨识性能及该文研究方法的正确性.为进一步验证该文建模方法的有效性和可行性,将NARX网络用于SCLD复杂车厢结构的动态模型辨识,并取得了较满意的效果.     

Dynamic behaviour of pneumatic linear actuators

The use of pneumatic linear actuators is generalised in engineering applications because of their many advantages, but modelling the force they supply may become more of a challenge due to their nonlinear behaviour and the hysteresis their energy losses cause. The authors propose a straightforward model to accurately predict force–displacement behaviour using as a basis experimental observations for several pressures and harmonic displacements of the rod. The model proposed includes two dissipative terms: one due to Coulomb friction and another due to structural damping. The force is proportional to relative pressure when acting as an actuator but nonlinear (modelled as a polytropic transformation) when acting as a pneumatic spring (with a closed pressurised chamber). The model accurately reproduces experimental results (Normalised Root Mean Square Errors lower than 2.5%) and may be used in control systems as well as in adaptive stiffness systems.