A mathematical study of some biomechanical factors affecting theoscillometric blood pressure measurement

A mathematical lumped parameter model of the oscillometric technique for indirect blood pressure measurement is presented. The model includes cuff compliance, pressure transmission from the cuff to the brachial artery through the soft tissue of the arm, and the biomechanics of the brachial artery both at positive and negative transmural pressure values. The main aspects of oscillometry are simulated i.e., the increase in cuff pressure pulsatility during cuff deflation manoeuvres, the existence of a point of maximum pulsations (about 1.5 mmHg) at a cuff pressure close to mean arterial pressure, and the characteristic ratios for cuff pressure pulsatility at systole and diastole (0.52 and 0.70, respectively, with this model, using basal parameters and an individual set of data for the arterial pressure waveform). Subsequently, the model is used to examine how alterations in some biomechanical factors may prejudice the accuracy of pressure measurement. Numerical simulations indicate that alterations in wall viscoelastic properties and in arterial pressure pulse amplitude may significantly affect the accuracy of pressure estimates, leading to errors as great as 15-20% in the computation of diastolic and systolic arterial pressure. By contrast, changes in arterial pressure mean value and cuff compliance do not seem to have significant influence on the measurement. Evaluation of mean arterial pressure through a characteristic ratio is not robust and may lead to misleading results. Mean arterial pressure may be better evaluated as the lowest pressure at which cuff pulse amplitude reaches a plateau. The obtained results may help to explain the nature of errors which usually limit the reliability of arterial pressure measurement (for instance in the elderly)     

Improved tracking of limb occlusion pressure for surgicaltourniquets

Constant-pressure tourniquets are widely used to occlude blood flow into a patient's limb to facilitate the performance of a wide variety of surgical procedures. Adaptive tourniquets that automatically adjust the cuff pressure to the minimum necessary for occlusion (limb occlusion pressure) as a function of the patient's changing systolic blood pressure are expected to reduce the incidence of tourniquet-related injuries. However, these devices have not been widely used, largely due to problems in tracking the systolic blood pressure safely, accurately, and reliably in clinical environments with noise present. Initial lab trials and clinical trials compared the performance in tracking limb occlusion pressure during varying noise conditions of a typical oscillometric blood pressure monitor with that of a prototype system. The prototype system functions by detecting noise and rapidly estimating limb occlusion pressure using only data uncorrupted by noise. Results showed that the prototype consistently estimated limb occlusion pressure more rapidly, more accurately, and more reliably than the oscillometric monitor in noisy conditions typical of surgical procedures. The results also indicate that the prototype is feasible for incorporation into an adaptive tourniquet     

Noninvasive Measurement of the Volume Elastic Modulus in Finger Arteries Using Photoelectric Plethysmography

A method for the nonivasive measurement of the volume elastic modulus (Ev) in human finger arteries was developed. The volume change ratio and pulse pressure in the arteries were simultaneously determined by a transmittance type infrared photoelectric plethysmograph and a volume oscillometric sphygmomanometer using an occlusive cuff. The Ev values could be obtained at a desired transmural pressure level of the arteries which was controlled by the cuff. A clear difference was revealed between the Ev values obtained in the fingers of two male subjects of 33 and 65 years old. The values determined by this method were compared to those calculated from pulse wave propagation velocity (Evp) obtained simultaneously in the fingers of 11 subjects. The linear regression equation was Ev = 1.31 Evp ?0.117 with a correlation coefficient r = 0.893 (n = 39). These results suggest that this should be a useful and noninvasive method of evaluating changes in arterial elasticity accompanying aging and perhaps influenced by accompanying hypertension or arteriosclerosis.     

Reduction of interference in oscillometric arterial blood pressure measurement using fuzzy logic

In oscillometry, oscillation amplitudes (OAs) embedded in the cuff pressure are drastically affected by a variety of artifacts and cardiovascular diseases, leading to inaccurate arterial blood pressure (ABP) measurement. The purpose of this paper is to improve the accuracy in the arterial pressure measurement by reducing interference in the OAs using a recursive weighted regression algorithm (RWRA). This method includes a fuzzy logic discriminator (FLD) and a recursive regression algorithm. The FLD is used to reduce the effect of artifacts caused by measurement motion disturbance or cardiovascular diseases, and to determine the truthfulness of the oscillation pulse. According to the truth degree, the relationship between the cuff pressure and OA is reconstructed using the regression algorithm. Because the regression method must utilize inverse matrix operation, which will be difficult to implement in an automatic or ambulatory monitor, the recursive regression method is proposed to solve this problem. To test the performance of this RWRA, 47 subjects underwent the ABP measurement using both the auscultation and the oscillometry combined with the RWRA. It was found that the average difference between the pooled blood pressures measured by the auscultation and those by the oscillometry combined with the RWRA was found to be only 4.9 mmHg. Clinical results demonstrated that the proposed RWRA is more robust than the traditional curve fitting algorithm (TCFA). We conclude that the proposed RWRA can be applied to effectively improve the accuracy of the oscillometric blood pressure measurement.     

Electroluminescence Gray Scale Display Driving Method and Circuit

The increasing use of color terminals for personal computers has raised a demand for video graphic adapter（VGA）-format panel displays. Since only monochrome（ZnS ： Mn） electroluminescence（EL） displays of suitable size and speed are available, lack of colors has to be replaced by grayscale in the first place. There are two basic driving methods to achieve grayscale in thin-film EL displays： pulse amplitude modulation（PAM） method and pulse width modulation（PWM） method. But there are serious disadvantages of the two traditional methods. For the former method, the high voltage PAM ICs are too expensive to produce the grayscale EL display in bulks and the driver integrated circuit（IC） is complex. Though the PWM method has good grayscale display quality, the hardware implementation is too complex. A new driving method with which the width and the amplitude of the pulse can be modulated and simultaneously the challenge can be solved efficaciously is presented.     

Noninvasive Determination of Central Blood Pressure by Impedance Plethysmography

A new algorithm based on impedance plethysmography provides reliable determinations, on an experimental basis, of arterial blood pressure. Signals over the brachial artery are picked up by four Velcro-type electrodes attached to the skinward side of a regular blood pressure cuff. Mathematical formulas are used to define those impedance pulses that correspond to systolic, diastolic, and mean arterial blood pressure values. The envelope of the impedance pulses recorded during cuff deflation can be defined by linear regressions, function of just one normalized independent variable, which is the ratio between the amplitude of the pulse with maximum amplitude and of the amplitude of the pulses with constant amplitude. These linear regressions are assumed to be universally applicable, the influence of individual anatomic variations having been eliminated by the use of a normalized variable. The results of this study prove that the variable pulse amplitude obtained during a cuff deflation is a quantifiable reaction of the circulatory system to arterial constriction.     

Recruitment data for nerve cuff electrodes: implications for designof implantable stimulators

Recruitment characteristics of nerve cuff electrodes implanted in four cats for five months were measured. Monopolar, bipolar, and tripolar configurations were considered. Approximately twice the current was required to achieve a given response using the tripolar configuration as compared with monopolar stimulation. Bipolar stimulation also required more current than monopolar stimulation. Using the recruitment data, a number of strategies for modulating muscle tension were considered. It was shown that both pulse amplitude and pulse duration should be software-selectable to achieve adequate control of muscle tension when using either pulse amplitude modulation or pulse duration modulation. When using pulse amplitude modulation, it was found to be desirable to operate at a low pulse duration in the high end of the allowable range for pulse amplitude. For pulse duration modulation, one should operate at a low pulse amplitude in the high end of the allowable range for pulse duration. The effect of pulse amplitude and pulse duration step size on the maximum step change in muscle tension and the linearity of the recruitment curves were examined. The use of logarithmic steps in the modulation parameter was examined and was shown to result in improved controllability and linearity.     

Distributed Waveform Generator: A New Circuit Technique for Ultra-Wideband Pulse Generation, Shaping and Modulation

A new circuit technique, the distributed waveform generator (DWG), is proposed for low-power ultra-wideband pulse generation, shaping and modulation. It time-interleaves multiple impulse generators, and uses distributed circuit techniques to combine generated wideband impulses. Built-in pulse shaping can be realized by programming the delay and amplitude of each impulse similar to an FIR filter. Pulse modulation schemes such as on-off keying (OOK) and pulse position modulation (PPM) can be easily applied in this architecture. Two DWG circuit prototypes were implemented in a standard 0.18 $muhbox{m}$ digital CMOS technology to demonstrate its advantages. A 10-tap, 10 GSample/s, single-polarity DWG prototype achieves a pulse rate of 1 GHz while consuming 50 mW, and demonstrates OOK modulation using 16 Mb/s PRBS data. A 10-tap, 10 GSample/s, dual-polarity DWG prototype was developed to generate UWB pulses compliant with the transmit power emission mask. Based on the latter DWG design, a reconfigurable impulse radio UWB (IR-UWB) transmitter prototype was implemented. The transmitter's pulse rate can be varied from 16 MHz range up to 2.5 GHz. The bandwidth of generated UWB pulses is also variable, and was measured up to 6 GHz (${- 10} {rm dB}$ bandwidth). Both OOK and PPM modulation schemes are successfully demonstrated using 32 Mb/s PRBS data. The IR-UWB transmitter achieves a measured energy efficiency of 45 pJ/pulse, independent of pulse rate.      

正交混频相位式激光测距方法与系统实现

针对传统的二次混频式激光测距仪鉴相精度不高,难于消除系统误差等问题,提出了正交混频相位激光测距法,利用成熟的正交调制技术进行激光光强的幅度调制,提高了基于二次混频原理的激光测距仪的鉴相精度,并且通过改变低频信号相位来获得两个相对很小的频差,易于消除系统附加相移,大大简化了二次混频式激光测距仪的硬件设计。详细阐述了基于正交混频相位测距方法的激光测距原型机设计要点。系统原型机设计方案采用了集成度很高的正交调制芯片完成,结构紧凑没有冗余元件。原型机实验精度达到±1.52mm,在62.5MHz频点下测相精度达到0.042°,并且可以很方便地通过加入多频调制的方法大大提高测量距离,是采用二次混频法进行相位激光测距的优秀解决方案。     

Flexible Piezoresistive Sensor Patch Enabling Ultralow Power Cuffless Blood Pressure Measurement

Noninvasive and real‐time cuffless blood pressure (BP) measurement realizes the idea of unobtrusive and continuous BP monitoring which is essential for diagnosis and prevention of cardiovascular diseases associated with hypertension. In this paper, a wearable sensor patch system that integrates flexible piezoresistive sensor (FPS) and epidermal electrocardiogram (ECG) sensors for cuffless BP measurement is presented. By developing parametric models on the FPS sensing mechanism and optimizing operational conditions, a highly stable epidermal pulse monitoring method is established and beat‐to‐beat BP measurement from the ECG and epidermal pulse signals is demonstrated. In particular, this study highlights the compromise between sensor sensitivity and signal stability. As compared with the current optical‐based cuffless BP measurement devices, the sensing patch requires much lower power consumption (3 nW) and is capable of detecting subtle physiological signal variations, e.g., pre and postexercises, thus providing a promising solution for low‐power, real‐time, and home‐based BP monitoring.     

基于BP神经网络的脉搏触压觉与血压关系分析

本研究旨在探究脉搏触压觉与血压之间的关系,自制的脉搏图像采集系统获得触压觉参数的同时,通过袖带法得到动脉血压值,并进行二者关系预测。首先在不同切脉压力下,采集探头的薄膜搏动视频图像,并从中提取脉搏信号的脉幅最大值、重心频率、功率谱密度最大值等时频域特征。然后采用反向传播神经网络对动脉血压的舒张压和收缩压进行分析。实验结果表明通过以上特征参数可以较准确地预测出血压值。     

ECG recording on a bed during sleep without direct skin-contact

A new indirect contact (IDC) electrocardiogram (ECG) measurement method (IDC-ECG) for monitoring ECG during sleep that is adequate for long-term use is provided. The provided method did not require any direct conductive contact between the instrument and bare skin. This method utilizes an array of high-input-impedance active electrodes fixed on the mattress and an indirect-skin-contact ground made of a large conductive textile sheet. A thin cotton bedcover covered the mattress, electrodes, and conductive textile, and the participants were positioned on the mattress over the bedcover. An ECG was successfully obtained, although the signal quality was lower and the motion artifact was larger than in conventional direct-contact measurements (DC-ECG). The results showed that further studies are required to apply the provided method to an ECG diagnosis of cardiovascular diseases. However, currently the method can be used for HRV assessment with easy discrimination of R-peaks.     

Flexible Weaving Constructed Self‐Powered Pressure Sensor Enabling Continuous Diagnosis of Cardiovascular Disease and Measurement of Cuffless Blood Pressure

Pulse wave carries comprehensive information regarding the human cardiovascular system (CS), which is essential for directly capturing CS parameters. More importantly, cuffless blood pressure (BP) is one of the most critical markers in CS. Accurately measuring BP via the pulse wave for continuous and noninvasive diagnosis of a disease associated with hypertension remains a challenge and highly desirable. Here, a flexible weaving constructed self‐powered pressure sensor (WCSPS) is reported for measurement of the pulse wave and BP in a noninvasive manner. The WCSPS holds an ultrasensitivity of 45.7 mV Pa^?1 with an ultrafast response time of less than 5 ms, and no performance degradation is observed after up to 40 000 motion cycles. Furthermore, a low power consumption sensor system is developed for precisely monitoring pulse wave from the fingertip, wrist, ear, and ankles. A practical measurement is performed with 100 people with ages spanning from 24 to 82 years and different health statuses. The discrepancy between the measured BP results using the WCSPS and that provided by the commercial cuff‐based device is about 0.87–3.65%. This work demonstrates an efficient and cost‐effective way for human health monitoring, which would be a competitive alternative to current complex cardiovascular monitoring systems.     

Microcontroller-based underwater acoustic ECG telemetry system

The paper presents a microcontroller based underwater acoustic telemetry system for digital transmission of the electrocardiogram (ECG). The system is designed for the real time, throughwater transmission of data representing any parameter, and it was used initially for transmitting in multiplexed format the heart rate, breathing rate and depth of a diver using self contained underwater breathing apparatus (SCUBA). Here, it is used to monitor cardiovascular reflexes during diving and swimming. The programmable capability of the system provides an effective solution to the problem of transmitting data in the presence of multipath interference. An important feature of the paper is a comparative performance analysis of two encoding methods: pulse code modulation (PCM) and pulse position modulation (PPM)     

Half-Symbol-Rate-Carrier Offset QPSK Transmitter for Bandwidth-Efficient High-Speed Data Communications

This letter proposes a half-symbol-rate-carrier (HSRC) offset quadrature phase shift keying (OQPSK) modulation for high-speed data communications. A prototype transmitter generating the HSRC-OQPSK signal was designed and built. Measurement results confirm the theory that the proposed HSRC-OQPSK modulation improves spectral efficiency by reducing the second lobe of the signal spectrum by 10 dB. Furthermore, HSRC-OQPSK modulation reduces the first null bandwidth by 25% compared to standard non-return-to-zero (NRZ) modulation. Like NRZ, HSRC-OQPSK uses two-level data decision which enables a simpler transceiver architecture than multilevel pulse amplitude modulations (PAMs), such as 4-PAM and duobinary     

DPCM quantizer adaptation method for efficient ECG signal compression

This paper addresses the problem of electrocardiogram (ECG) signal compression with the goal to provide a simple compression method that outperforms previously proposed methods. Starting with the study of the ECG signal nature, the manner has been found to optimize rate-quality ratio of the ECG signal by means of differential pulse code modulation (DPCM) and subframe after subframe procession. Particularly, the proposed method includes two kinds of adaptations, short-time and long-time adaptations. The switched quantization i.e. the short-time DPCM quantizer range adaptation is performed according to the statistics of the ECG signal within particular subframes. It is ascertained that the short-time adaptation enables a sophisticated compression control as well as a constant quality of the ECG signal in both segments of low amplitude and high amplitude dynamics. In addition, by grouping the subframes of a particular frame into two groups according to their dynamics and performing the long-time DPCM quantizer range adaptation, based on the statistics of the groups, it has been revealed that an important quality gain is achieved with an insignificant rate increase. Moreover, the two iterative approaches proposed in the paper, mainly differ in the fact whether the long-time range adaptations of the used DPCM quantizers are performed according to the maximum amplitudes or according to the average powers of the signal difference determined in all subframes within a certain group. The benefits of both approaches to the above proposed method are shown and discussed in the paper.     

便携式电子血压计连续动态监测的设计

设计了一种能够连续监测动态血压的便携式电子血压计。血压计测量方法采用示波法,以ATmega16单片机为核心,实现A/D转换、定时测量、数据存储、串口通信、LCD显示等功能,可用作偶测血压计,需要时能够连续全天24小时监测动态血压和脉搏。     

基于LiNbO3M-Z调制器的UWB信号PAM调制技术研究

提出一种基于LiNbO3Mach-Zehnde调制器(MZM)实现超宽带(UWB)脉冲幅度调制(PAM)的方案,只利用一个LiNbO3-MZM,实现幅度调制,结构简单,易于实现。利用OptiSys-tem7.0软件对方案进行了仿真,研究了调制信号的传输特性,并分析了光源功率、光源波长、脉冲宽度、调制速率、延迟时间以及传输距离对调制信号的影响。     

An Efficient Low Computational Cost Method of R-Peak Detection

Wireless Personal Communications - Visual inspection of R-peaks in an electrocardiogram (ECG) signal may lead to wrong diagnosis due to physiological variability and the noisy status of the QRS...     

ECG data compression techniques-a unified approach

A broad spectrum of techniques for electrocardiogram (ECG) data compression have been proposed during the last three decades. Such techniques have been vital in reducing the digital ECG data volume for storage and transmission. These techniques are essential to a wide variety of applications ranging from diagnostic to ambulatory ECG's. Due to the diverse procedures that have been employed, comparison of ECG compression methods is a major problem. Present evaluation methods preclude any direct comparison among existing ECG compression techniques. The main purpose of this paper is to address this issue and to establish a unified view of ECG compression techniques. ECG data compression schemes are presented in two major groups: direct data compression and transformation methods. The direct data compression techniques are: ECG differential pulse code modulation and entropy coding, AZTEC, Turning-point, CORTES, Fan and SAPA algorithms, peak-picking, and cycle-to-cycle compression methods. The transformation methods briefly presented, include: Fourier, Walsh, and K-L transforms. The theoretical basis behind the direct ECG data compression schemes are presented and classified into three categories: tolerance-comparison compression, differential pulse code modulation (DPCM), and entropy coding methods. The paper concludes with the presentation of a framework for evaluation and comparison of ECG compression schemes.