Simultaneous acquisition of functional magnetic resonance images and impedance cardiography

While simultaneous acquisition of electrocardiography (ECG) data during MRI is a widely used clinical technique, the effects of the MRI environment on impedance cardiography (ICG) data have not been characterized. We collected echo planar MRI scans while simultaneously recording ECG and thoracic impedance using carbon fiber electrodes and customized amplifiers. Here, we show that the key changes in impedance (dZ/dt) and features of the ECG waveforms are not obstructed during MRI. We present a method for ensemble averaging ICG/ECG signals collected during MRI and show that it performs comparably with signals collected outside the MRI environment. These results indicate that ICG can be used during MRI to measure stroke volume, cardiac output, preejection period, and left ventricular ejection time.     

基于Android系统的生理数据蓝牙传输技术

目的：本文建立基于Android智能系统的生理参数移动监护系统,实现生理数据从监测模块向智能手机端传输。方法：在生理参数检测端增加蓝牙传输模块．将检测端采集到的心电等生理数据发送至Android系统智能手机端,智能手机端利用Android蓝牙API开发类,对手机端蓝牙实现打开蓝牙、搜索附近蓝牙设备等基本操作,再利用Socket连接,实现数据传输。同时手机端利用界面编程类,实现心电图界面显示,利用文件操作类实现数据存储和初步的心率计算,最终实现心电等生理参数的接收、显示、心率分析以及传输。结果：Android系统智能手机端接收蓝牙模块发送的心电数据,绘成实时心电图表,绘制在手机屏幕上,并对心电数据进行初步分析,计算得到心率值,显示在手机屏幕顶端,若心率值偏高或偏低,则发出语音报警信息。该系统演示了生理数据的传输过程,实现了蓝牙接口的数据传输控制技术。结论：本文立足于移动医疗监护系统,实现了多生理参数在Android系统中的蓝牙接口传输控制方法,该技术应用前景广泛。     

基于体表生理信号的呼吸功能监测仪研制

目的：研制一款基于体表心电、膈肌电和胸阻抗信号的呼吸功能监测仪原理样机,可在家庭、医疗急救等场合实现对呼吸功能的持续监测。方法：以STM32F411VET6单片机开发系统为平台,用一对Ag/AgCl电极作为高频激励信号的输出和心电、胸阻抗信号的检测电极,另一对Ag/AgCl电极作为膈肌电信号检测电极,两对电极同时检测心电、膈肌电和胸阻抗信号。系统硬件主要包括心电信号检测电路、胸阻抗信号检测电路、膈肌电信号检测电路、恒流源激励电路以及微控制器。系统采用12 V可充电锂电池供电,模拟信号通过单片机A/D转换成数字信号,通过SDIO接口存储于SD卡。在完成样机制作和性能测试之后,采集13例因呼吸功能障碍实施机械通气患者和13例健康成年人的信号,计算15个与呼吸功能相关的参数,比较机械通气患者与健康对照组参数之间的差异,验证了呼吸功能监测仪的可靠性。结果：样机采集信号的信噪比>10 dB、共模抑制比>80 dB,样机漏电流<30μA。机械通气患者的吸气时间、呼气时间、潮气量、胸阻抗峰峰值、胸阻抗1 s变化量、膈肌电低频功率、膈肌电高频功率、高频比低频、膈肌放电面积、膈肌放电时...     

Portable Wireless ECG Monitor with Fabric Electrodes

A portable and comfortable wireless ECG monitoring system composed of fabric electrodes and a monitoring terminal was proposed,which is essential to continuous ECG monitoring. The ECG signal acquired could be processed and stored in the monitoring terminal. The HR was got and transmitted to any devices through a Bluetooth interface. The experimental results in resting and walking showed that the ECG monitoring system could acquire the ECG signal steadily,continuously and precisely.     

一种基于胸阻抗法的心功能无创检测分析仪

目的为了经济、快捷、全面地实现心功能的无创检测,基于胸阻抗法成功研发了一种心功能无创检测分析仪,可方便地实现胸阻抗信号、心电信号、心音信号的同步检测分析,从而实现对患者心功能的无创综合评价。该方法无毒无创,操作简单,完全可以实现家用化普及。方法本文首先描述了系统的硬件模块构成,说明了胸阻抗信号的采集过程。其次,使用FPGA芯片与DDS芯片构成系统的控制与信号发生核心,指出了恒流源的精度等性能指标。再次,指出了胸阻抗信号处理的要点,运用互感原理实现干扰信号的隔离。最后,介绍了仪器软件功能,并展示了仪器软件实测结果。结果通过临床试验,对胸阻抗法与超声多普勒法检测的数据结果进行t检验,结果表明二者具有一致性。结论由于采用了先进的特征点判别方法,该设备具有较高的临床检测精度和较好的临床适用性,可满足临床心功能无创检测和评估的要求。     

A SiC microdevice for the minimally invasive monitoring of ischemia in living tissues

Monitoring of ischemia in living tissues is a field of increasing interest in many clinical settings. In this work we report for the first time anywhere the development of needle-shaped, minimally-invasive impedance probes based on silicon carbide (SiC) substrates. An in-vitro comparison of these new devices with Si-based impedance probes demonstrates that their effective operation range extends up to the 100 kHz range, thus allowing a wide-spectrum multi-frequency analysis of impedance modulus and phase angle. Furthermore, we show that, when applied to in-vivo settings, this kind of analysis yields to an accurate monitoring of ischemia, while making possible the application of more robust mathematical methods for the study of impedance in living tissues.     

适用于智能听诊的心肺音、心电同步采集设备设计与研制

基于现有听诊器不具备心肺音、心电同时采集的功能,设计一款完备的新型双模心肺音、心电同步采集设备。采用精密微弱信号放大技术实现音频的无损放大,采用高输入阻抗设计实现心电的单电极采集,采用高保真SJR-BTM870-B蓝牙模块实现双模音频无损传输。最后实验结果表明,该研制设备具有重要的临床应用价值和科研价值。     

基于Android平台的心电监护仪设计

目的：设计一种基于Android平台的心电监护系统,可以将数据发送至手机界面,并显示心电波形和心率。方法：系统基于Android平台,结合飞思卡尔单片机9SXSl28和蓝牙模块设计,完成了心电信号的获取、放大和滤波、A／D转换和蓝牙发送的功能。系统包含电源模块、心电获取硬件模块、数据采样单片机系统、蓝牙发送模块、Android手机及软件五大部分组成。结果：通过肢体导联获取心电信号,之后经单片机AD采样,通过串口转蓝牙将数据发送至手机界面,并显示心电波形和心率。结论：本文设计并实现了心电采集模块的硬件电路和软件程序,编写了Android系统手机上的简单心电监护应用程序,心电采集模块与手机之间运用蓝牙无线方式传输心电数据。系统通过肢体导联获取人体心电信号并最终实时显示在手机上。该系统轻便小巧、低功耗、操作简单。经调试,系统运行稳定,心电信号可实时显示在手机界面,心率测量准确。通过这种设计有效缓解了就医难的问题,在医疗资源相对集中的国情下,基于Android手机的健康监护有着较大前景。     

基于G-sensor有运动情景动态心电监护系统

基于移动设备的心电监护设备越来越多,但大多数仅显示心电图,没有考虑到对应的用户运动情景。使用Android手机内置的G-sensor采集三轴加速度,设计一种有运动情景的动态心电监护系统。充分利用目前Android手机提供的功能,降低医疗成本,是面向家庭和社区医院的新型医疗系统,用户家属和医务人员可以通过客户端对用户进行实时监护,随时掌握其心电和运动状态信息,有利于医生做出准确的诊断,实现远程的、有运动情景的动态心电监护。     

基于DSP的家庭健康监护仪的设计

目的 设计一种新型的适合家庭使用的便携式监护系统.方法 系统以数字信号处理器(TMS320F2812)为核心控制芯片,主要实现对系统中其它模块的控制功能,完成MD采样及LCD液晶显示;采用蓝牙通汛模块,实现了系统与PC机之间数据的实时快速传输.结果 该监护仪能正确完成人体心电、呼吸频率、脉搏以及体温等多项人体生命参数的监测,且性能稳定.结论 充分利用DSP与蓝牙模块的优势,设计体积小、功耗低、使用简单方便、面向家庭的新型多功能监护仪,具有广阔的应用与市场前景. Abstract： Objective To design a new portable vital signs monitor for family use. Methods TMS320F2812, a kind of digital signal processor, was applied as the main processor to control the functional mod-ules including A/D convertor, LCD display. Bluetooth communication module was introduced to achieve real-time fast transfer of data between the system and the PC. Results Not only can the system monitor electrocardiogram (ECG), breath rate, pulse rate, body temperature and other vital signs accurately, but also it runs stably. Conclusion The features of DSP and Bluetooth were well combined in the design of the family-oriented, easy to use, multi-functional monitor with small size, low power consumption and convenience. A broad application and market prospects can be predicted.     

应用阻抗心动图测量脉搏波传导时间

为了研究射血前时间对用脉搏波传导时间进行连续血压测量的影响,本文设计并实现一种用阻抗心动图确定脉搏波起始点计算脉搏波传导时间的方法,在深呼使血压产生波动的过程中,采用此方法与心电R波峰值作起始点的方法进行对比实验.实验结果表明,用这种方法测量脉搏波传导时间随呼吸的变化曲线与血压变化的规律相一致.与用心电R波法相比,阻抗心电图法可以有效避免射血前时间变化对PWTT测量结果的影响,是一种准确测量脉搏波传导时间的方法.     

Mechanism of the Formation for Thoracic Impedance Change

The purpose of this study is to investigate the mechanism of the formation for thoracic impedance change. On the basis of Ohm’s law and the electrical field distribution in the cylindrical volume conductor, the formula about the thoracic impedance change are deduced, and they are demonstrated with the model experiment. The results indicate that the thoracic impedance change caused by single blood vessel is directly proportional to the ratio of the impedance change to the basal impedance of the blood vessel itself, to the length of the blood vessel appearing between the current electrodes, and to the basal impedance between two detective electrodes on the chest surface, while it is inversely proportional to the distance between the blood vessel and the line joining two detective electrodes. The thoracic impedance change caused by multiple blood vessels together is equal to the algebraic addition of all thoracic impedance changes resulting from the individual blood vessels. That is, the impedance changes obey the principle of adding scalars in the measurement of the electrical impedance graph. The present study can offer the theoretical basis for the waveform reconstruction of Impedance cardiography (ICG).     

Single prediction equation for bioelectrical impedance analysis in adults aged 22-59 years

The purpose of this study was to validate a single bioelectrical impedance analysis (BIA) equation in healthy Indian subjects aged 22-59 years with a body mass index (BMI) between 16.8 and 47.3 kg m?2. Healthy subjects (34 men and 30 women) were measured by two methods: bone mineral content (BMC) was measured by a commercial body composition analyser and bioelectrical impedance at various frequencies was measured by a newly developed bioelectrical impedance measurement system. As correlations were high and prediction error was low, a single equation was developed using all subjects as follows: BMC?=?-3.5268?+?(0.0279 x h)?+?(0.0145 x w)?+?(184 x (h2/Z(body50)))-(1.08 x (w x h2/Z(body6.25)))-(0.0032 x (age))-(0.103 x (sex); men?=?1, women?=?0). BMC measured from commercial instrument InBody720 was 2.552?±?0.457 kg. BMC predicted by equation was 2.554?±?0.447 kg (R?=?0.976, adjusted R2?=?0.948, standard error of estimate?=?0.104 kg, total error?=?0.09987 kg). The results of this study show that the newly developed multi-frequency bioelectrical impedance measurement system with the single prediction BIA equation can be used in screening the subjects suspected with osteoporosis and for follow-up study of the patient under the therapy for osteoporosis. For validation of commercial instrument InBody720, BMC of 22 healthy subjects was measured by InBody720 and dual-energy X-ray absorptiometry. High correlation (R?=?0.9531) and low error (total error?=?0.0913 kg) was found between these two methods.     

Development of a fully implantable wireless pressure monitoring system

A fully implantable wireless pressure sensor system was developed to monitor bladder pressures in vivo. The system comprises a small commercial pressure die connected via catheter to amplifying electronics, a microcontroller, wireless transmitter, battery, and a personal digital assistant (PDA) or computer to receive the wireless data. The sensor is fully implantable and transmits pressure data once every second with a pressure detection range of 1.5 psi gauge and a resolution of 0.02 psi. In vitro calibration measurements of the device showed a high degree of linearity and excellent temporal response. The implanted device performed continuously in vivo in several porcine studies lasting over 3 days. This system can be adapted for other pressure readings, as well as other vital sign measurements; it represents the first step in developing a ubiquitous sensing platform for telemedicine and remote patient monitoring.     

A portable battery powered microfluidic impedance cytometer with smartphone readout: towards personal health monitoring

We present a portable system for personalized blood cell counting consisting of a microfluidic impedance cytometer and portable analog readout electronics, feeding into an analog-to-digital converter (ADC), and being transmitted via Bluetooth to a user-accessible mobile application. We fabricated a microfluidic impedance cytometer with a novel portable analog readout. The novel design of the analog readout, which consists of a lock-in-amplifier followed by a high-pass filter stage for subtraction of drift and DC offset, and a post-subtraction high gain stage, enables detection of particles and cells as small as 1 μm in diameter, despite using a low-end 8-bit ADC. The lock-in-amplifier and the ADC were set up to receive and transmit data from a Bluetooth module. In order to initiate the system, as well as to transmit all of the data, a user friendly mobile application was developed, and a proof-of-concept trial was run on a blood sample. Applications such as personalized health monitoring require robust device operation and resilience to clogging. It is desirable to avoid using channels comparable in size to the particles being detected thus requiring high levels of sensitivity. Despite using low-end off-the-shelf hardware, our sensing platform was capable of detecting changes in impedance as small as 0.032%, allowing detection of 3 μm diameter particles in a 300 μm wide channel. The sensitivity of our system is comparable to that of a high-end bench-top impedance spectrometer when tested using the same sensors. The novel analog design allowed for an instrument with a footprint of less than 80 cm². The aim of this work is to demonstrate the potential of using microfluidic impedance spectroscopy for low cost health monitoring. We demonstrated the utility of the platform technology towards cell counting, however, our platform is broadly applicable to assaying wide panels of biomarkers including proteins, nucleic acids, and various cell types.     

A portable system for the assessment of neuromuscular diseases with electrical impedance myography

Primary objective:?To create a system for the acquisition of multi-angle, multifrequency muscle impedance data.

Research design:?Device development and preliminary testing.

Methods and procedures:?The system presented here employs an interrogating signal composed of multiple tones with frequencies between 10 kHz and 300 kHz. The use of a composite signal makes possible measurement of impedance at multiple frequencies simultaneously. In addition, this system takes impedance measurements at multiple orientations with respect to the muscle fibres by means of an electronically reconfigurable electrode array. The required measurement time is reduced by taking advantage of muscle's linearity with respect to the flow of electrical current.

Main outcomes and results:?The system was tested in normal subjects, a patient with amyotrophic lateral sclerosis, and one with inclusion body myositis; unique impedance signatures were identified the two patients.

Conclusions:?Early data suggest that this system is capable of high-quality data collection and may detect changes in neuromuscular disease; study of additional normal subjects and patients with a variety of neuromuscular diseases is warranted.     

Beat-to-beat estimation of stroke volume using impedance cardiography and artificial neural network

Impedance cardiography is a low-cost noninvasive technique, based on monitoring of the thoracic impedance, for estimation of stroke volume (SV). Impedance cardiogram (ICG) is the negative of the first derivative of the impedance signal. A technique for beat-to-beat SV estimation using impedance cardiography and artificial neural network (ANN) is proposed. A three-layer feed-forward ANN with error back-propagation algorithm is optimized by examining the effects of number of neurons in the hidden layer, activation function, training algorithm, and set of input parameters. The input parameters are obtained by automatic detection of the ICG characteristic points, and the target values are obtained by beat-to-beat SV measurements from time-aligned Doppler echocardiogram. The technique is evaluated using an ICG-echocardiography database with recordings from subjects with normal health in the under-rest and post-exercise conditions and from subjects with cardiovascular disorders in the under-rest condition. The proposed technique performed much better than the earlier established equation-based estimations, and it resulted in correlation coefficient of 0.93 for recordings from subjects with cardiovascular disorders. It may be helpful in improving the acceptability of impedance cardiography in clinical practice.

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Graphical abstract ?

     

Contactless respiratory and heart rate monitoring: validation of an innovative tool

Primary objective:?To assess the accuracy of the EverOn? piezoelectric sensor based contactless heart rate and respiration rate monitoring system.

Methods:?Measurements of the Everon? and reference devices were performed in a sleep lab and an intensive care unit (ICU) setting. One minute measurements by both the reference device and the EverOn? were averaged and compared. Accuracy was defined in accordance with industry criteria.

Results:?Respiration rate (RR) accuracy in the 41 children and 16 adults evaluated in the sleep lab was 93.1% and 90.6% respectively, and heart rate (HR) accuracy was 94.4% and 91.5% respectively. For the 42 ICU patients RR accuracy was 82.0% and 75% (versus end-tidal CO₂ and manual respectively), while accuracy of HR was 94.0%. The EverOn? was found to be superior to the impedance technique in measuring RR.

Conclusions:?The system described was found to be accurate in accordance with regulatory and industry criteria.     

Thoracic percussion yields reversible mechanical changes in healthy subjects

In order to characterize the mechanical effects of thoracic percussion per se in lung parenchyma, we analyzed respiratory impedance parameters by impulse oscillometry (12 healthy subjects) and lung mechanics by the least square method (6 healthy subjects) before (PRE-TP) and after (POS-TP) thoracic percussion, and after a deep-breath-maneuver (POS-DB). Pulmonary resistance was similar among PRE-TP, POS-TP and POS-DB while pulmonary dynamic compliance showed a significant reduction after TP (mean ± SEM: from 0.15 ± 0.018 L/cmH₂O to 0.12 ± 0.016 L/cmH₂O; P = 0.001), returning to basal values (mean ± SEM: 0.15 ± 0.021; P = 0.004) after DB. Reactance parameters (AX and f ₀) evaluated by oscillometry increased significantly after TP, returning to previous values after DB. Total impedance (Z5) and respiratory system resistance at 5 Hz (R5) did not differ significantly among experimental conditions. Our data strongly suggest that thoracic percussion can promote changes in respiratory mechanics compatible with lung collapse and/or pneumoconstriction, which are, however, reversible by deep inspirations.     

A non-contact vital sign monitoring system for ambulances using dual-frequency microwave radars

We developed a novel non-contact monitoring system to measure the vital signs of casualties inside a moving ambulance. This system was designed to prevent exposure of patients to infectious organisms under biochemical hazard conditions. The system consists of two microwave radars: a 10-GHz respiratory-monitoring radar is positioned 20 cm away from the surface of the isolator. The 24-GHz cardiac-monitoring radar is positioned below the stretcher underneath the isolator. The subject (22.13 ± 0.99 years) was placed inside the isolator on a stretcher in the simulated ambulance. While the ambulance was in motion at a speed of approximately 10 km/h, the heart rates determined by the cardiac-monitoring radar correlated significantly with those measured by ECG (r = 0.69, p < 0.01), and the respiratory rates derived from the respiratory-monitoring radar correlated with those measured by the respiration curves (r = 0.97, p < 0.0001). The proposed system appears promising for future on-ambulance monitoring of the vital sign of casualties exposed to toxins.