Magnetic sensor for arterial distension and blood pressure monitoring

A novel sensor for measuring arterial distension, pulse and pressure waveform is developed and evaluated. The system consists of a magnetic sensor which is applied and fixed to arterial vessels without any blood vessel constriction, hence avoiding stenosis. The measurement principle could be validated by in vitro experiments on silicone tubes, and by in vivo experiments in an animal model, thereby indicating the non-linear viscoelastic characteristics of real blood vessels. The sensor is capable to provide absolute measurements of the dynamically varying arterial diameter. By calibrating the sensor, a long-term monitoring system for continuously measuring blood pressure and other cardiovascular parameters could be developed based on the method described. This will improve diagnostics for high risk patients and enable a better, specific treatment.     

Long-term pressure monitoring with arterial applanation tonometry: a non-invasive alternative during clinical intervention?

Arterial tonometry is a non-invasive technique for continuous registration of arterial pressure waveforms. This study aims to assess tonometric blood pressure recording (TBP) as an alternative for invasive long-term bedside monitoring. A prospective study was set up where patients undergoing neurosurgical intervention were subjected to both invasive (IBP) and non-invasive (TBP) blood pressure monitoring during the entire procedure. A single-element tonometric pressure transducer was used to better investigate different inherent error sources of TBP measurement. A total of 5.7 hours of combined IBP and TBP were recorded from three patients. Although TBP performed fairly well as an alternative for IBP in steady state scenarios and some short-term variations, it could not detect relevant long-term pressure variations at all times. These findings are discussed in comparison to existing work. Physiological alterations at the site of TBP measurement are highlighted as a potentially important source of artifacts. It is concluded that at this point arterial tonometry remains not enough understood for long-term use during a delicate operative procedure. Physiological changes at the TBP measurement site deserve further investigation before tonometry technology is to be considered as an non-invasive alternative for long-term clinical monitoring.     

Photoacoustic determination of blood vessel diameter

A double-ring sensor was applied in photoacoustic tomographic imaging of artificial blood vessels as well as blood vessels in a rabbit ear. The peak-to-peak time (tau(pp)) of the laser (1064 nm) induced pressure transient was used to estimate the axial vessel diameter. Comparison with the actual vessel diameter showed that the diameter could be approximated by 2ctau(pp), with c the speed of sound in blood. Using this relation, the lateral diameter could also precisely be determined. In vivo imaging and monitoring of changes in vessel diameters was feasible. Finally, acoustic time traces were recorded while flushing a vessel in the rabbit ear with saline, which proved that the main contribution to the laser-induced pressure transient is caused by blood inside the vessel and that the vessel wall gives only a minor contribution.     

基于脉搏波传导时间的血压测量方法

目的:设计一种连续血压测量方法,在无创的条件下能够实时监测受试者的血压。方法:对耳后动脉和趾背动脉的脉搏波进行特征识别,计算两个脉搏波之间的传播时间,并根据受试者的血液密度、血管内径、血管壁厚度等参数计算脉搏波传导速度,然后在传统脉搏波传导时间算法的基础上,增加受试者身高和体重,计算出人体的血压。结果:该算法得到的血压结果与真实值较为接近,并且实时性较好。结论:改进后的基于脉搏波传导时间的血压测量方法可用于血压的实时测量,为临床诊断提供帮助。     

Continuous estimation of systolic blood pressure using the pulse arrival time and intermittent calibration

A continuous noninvasive method of systolic blood pressure estimation is described. Systolic blood pressure is estimated by combining two separately obtained components: a higher frequency component obtained by extracting a specific frequency band of pulse arrival time and a lower frequency component obtained from the intermittently acquired systolic blood pressure measurements with an auscultatory or oscillometric system. The pulse arrival time was determined by the time interval from QRS apex in electrocardiogram to the onset of photoplethysmogram in a fingertip beat-by-beat via an oximetric sensor. The method was examined in 20 patients during cardiovascular surgery. The estimated values of systolic blood pressure were compared with those measured invasively using a radial arterial catheter. The results showed that the correlation coefficients between estimated values and invasively obtained systolic blood pressure reached 0.97±0.02 (mean±SD), and the error remained within ±10% in 97.8% of the monitoring period. By using a system with automatic cuff inflation and deflation to acquire intermittent systolic blood pressure values, this method can be applicable for the continuous noninvasive monitoring of systolic blood pressure.     

Thermal method for continuous measurement of cerebral perfusion

A new thermal system using constant heating power for continuous measurement of cerebral perfusion is presented. It is designed and implemented for optimal perfusion sensitivity and dynamic response based on heat-transfer analysis of perfused brain tissue with thermistors on the cortical surface. Two matched thermistors are used, one to serve as a perfusion sensor and the other to compensate for the base-line temperature changes. To improve the signal-to-noise ratio of the measurement system, lock-in amplifiers are used to minimise long-term drift and low-frequency noise. Errors in the measurement caused by electrical and thermal fluctuations are tested and analysed. In vitro tests show that the measurement accuracy of temperature change is better than 10⁻³°C, and the temperature resolution is even greater. In vivo evaluation confirms that the system is responsive to cerebral perfusion changes associated with sudden changes in mean arterial blood pressure caused by bolus injection of norepinephrine, blood withdrawal and blood infusion. The dynamic response of the system is sufficient to detect the autoregulatory perfusion changes in response to arterial blood pressure alteration and the oscillations of cerebral blood flow.     

The Research on Absorption of Pressure-induced Near-infrared though Tissue in Vivo

INTRODUCTION Itisnowwell-recognizedthatangiogenesis,thegrowthofnewbloodvessels,is aturnkeyeventforthegrowth,invasionandmetastasesofsolidtumors.Overthe pastthreedecades,majorcellularandmolecularpathwaysoftumorangiogenesishavebeenelucidated.Clinicalstudiesh…     

An adjunctive preventive treatment for heart disease and a set of diagnostic tests to detect it: insulin-like growth factor-1 deficiency and cell membrane pathology are an inevitable cause of heart disease

Coronary heart disease (CHD) is a preventable disease with high morbidity and mortality. Largely omitted from the efforts at detection and treatment are the contributions of the lungs, the skeletal muscles and the arteries to heart disease pathology. Also omitted are the effects of the age-related decline in insulin-like growth factor-1 (IGF-1) and the age-related increase in cell membrane pathology. The hypothesis on which this model is based postulates that growing older, over time, necessarily results in pathological changes in the heart, the lungs, the skeletal muscles and the arteries. Additionally, the age-related decline in (IGF-1) that occurs in the otherwise healthy aged population also causes similar pathological changes. The drug portion of the proposed treatment includes the use of the drug acetyl-l-carnitine (ALC) to increase the age-related decreased IGF-1 levels. The drug centrophenoxine (CPH) is used to reverse the age-related pathological changes that inevitably occur in the heart, the lungs, the skeletal muscles and the arteries. A testing procedure is included to improve the detection of heart disease and to monitor the results. It consists of five tests: the monitoring of plasma IGF-1 levels; the monitoring of blood pressure, and in particular elevated systolic blood pressure; the monitoring of blood pressure variability over time; a heart rate recovery time test and a heart rate reserve test. Heart rate reserve is defined as the difference between maximal heart rate and resting heart rate, after treadmill exercise. The changes in test results noted during treatment are an indicator of progress or deterioration in the prevention of heart disease, whatever the case may be.     

An Implantable Microsystem for Tonometric Blood Pressure Measurement

This paper presents an implantable microsystem for tonometric blood pressure measurement in small animals. The microsystem consists of four major components: (1) a titanium base for supporting a pressure sensor and an interface chip, (2) a micromachined capacitive pressure sensor array, (3) a switched-capacitor interface chip, and (4) a titanium cap. A new micromachining fabrication process has been developed to create capacitive pressure transducers with a flat surface necessary for tonometric pressure measurement. An array of three capacitive sensors is used to increase signal output and improve stability. A custom-designed switched-capacitor CMOS interface circuit is used to measure changes in capacitance. In vitro calibration tests have been performed on the complete cuff using a silastic tube to mimic a pliable blood vessel. A sensitivity of 2 mV/mmHg @ 100 mmHg and a resolution of 0.5 mmHg (based on 1 mV RMS interface chip noise floor) has been obtained. The dimensions of the cuff system 10(L)×6.5(W)×3(H) mm³.     

Continuous cardiac output monitoring system

A continuous cardiac output monitoring system has been developed in the laboratory to allow the real-time measurement of the cardiac output. This form of continous cardiac output measurement allows the doctor to view the beat-to-beat cardiac output and can be employed to measure artery constrictions as well. The sensor comprises a laser Doppler velocimeter and an impedance measurement unit. The laser Doppler velocimeter is capable of measuring bi-directional blood flow within the vessel while the impedance measurement unit determines the cross-sectional area of the vessel. In laboratory tests, it was demonstrated on a heart-lung machine that the product of the two parameters measured is proportional to the actual flow volume of up to 6l min⁻¹ with a mean percentage error of 12.4% and a mean square error of 0.09 (using the l min⁻¹ scale) were obtained. This is significantly more accurate than the measurement made using the thermodilution cathether.     

基于脉搏波信号和血管弹性腔模型的动脉血压连续测量方法

目的为满足健康监护中的连续测量血压的要求,研究并实现一种基于脉搏波信号和血管弹性腔模型的动脉血压拟合计算方法。方法利用自制的穿戴式人体生理参数监测系统收集测试对象的脉搏波信号、心电信号以及血压数据。根据心电信号与脉搏波信号的时间关系,推导出收缩压和脉搏波传导时间的回归分析方程,而舒张压的测量,则是通过脉搏波的波形系数分析以及血管单弹性腔模型的参数计算完成。结果试验结果表明,该方法血压测量结果的平均偏差和标准偏差为(0.51±0.74)kPa([384±5.54)mmHg],达到了美国医疗仪器促进协会建议的(0.665±1.064)kPa([5±8)mmHg]标准。结论结合脉搏波信号和弹性腔模型可以估算人体血压值,为连续血压测量提供了新的实现方法。     

Sensor packaging design for continuous underfoot load monitoring

Continuous force measurement can provide valuable insight to the efficacy of limb loading regimes during fracture rehabilitation. Currently there is no load monitoring device that is capable of more than 1 h of continuous recording. To enable continuous underfoot load monitoring a piezoresistive pressure sensor was encapsulated in a non-compressible silicone gel. This basic approach to signal transduction was implemented in three continuous underfoot load sensor designs. Design I constrained the gel in a rigid urethane housing. Design II constrained the gel in a silicone elastomer bladder. Design III utilized a hybrid approach by constraining the gel with a rigid upperplate inside of an elastomeric bladder. All three designs were subjected to bench and human testing. Design I outperformed the other two designs showing high linearity (correlation coefficient of 1), low static drift (<1%) and low dynamic drift (<3%) and captured the largest percentage of weight during human testing (35%). The sensor was designed, tested and shown to be durable and accurate for a 2 week window of time. This sensor has the low cost and high performance required for large scale clinical tests to correlate limb loading and fracture healing rates.     

Microflotronic Arterial Tonometry for Continuous Wearable Non-Invasive Hemodynamic Monitoring

Personalized mobile medicine will continue to advance through the development of wearable sensors that can wirelessly provide pertinent health information while remaining unobtrusive, comfortable, low cost, and easy to operate and interpret. It is the intention that the sensor presented hereafter can contribute to such innovation. By applying a combination of emerging microfluidic and electronic technologies, a miniature, flexible, transparent, highly sensitive and wearable pressure sensor with microfluidic elements has been implemented, referred to as a microflotronic device. High sensitivity of 0.1 kPa^?1 and fast response time on the order of tens of milliseconds has been achieved on the microflotronic sensor design. Its sensitivity is among the highest in impedance-based flexible pressure sensors. Once configured into an array, the transparent device can be easily aligned over the target artery to measure blood pressure noninvasively and continuously. In addition, the ultraflexible and thin plastic construct of the microflotronic sensor (of 270 µm in height) can be worn comfortably for extended periods of time. Importantly, the proposed microflotronic sensor has been utilized to perform arterial tonometry with the capability of noninvasive monitoring of arterial blood pressure waveforms in a real-time and continuous fashion.     

Telemetric analysis of haemodynamic regulation during voluntary exercise training in mouse models

Regular physical exercise reduces the risk of cardiovascular disease and improves outcome in patients with cardiovascular diseases. The dynamic changes in blood pressure and heart rate with acute exercise are independently predictive of prognosis. Quantification of the haemodynamic response to exercise training in genetically modified mouse models may provide insight into the molecular mechanisms underlying the beneficial effects of exercise. We describe, for the first time, the use of radiotelemetry to provide continuous blood pressure monitoring in C57BL/6J mice during a programme of voluntary wheel exercise with continuous simultaneous recording and analysis of wheel rotations and beat-by-beat haemodynamic parameters. We define distinct haemodynamic profiles at rest, during normal cage activity and during episodes of voluntary wheel running. We show that whilst cage activity is associated with significant rises both in blood pressure and in heart rate, voluntary wheel running leads to a further substantial rise in heart rate with only a small increment in blood pressure. With 5 weeks of chronic exercise training, resting heart rate progressively falls, but heart rate during episodes of wheel running initially increases. In contrast, there are minimal changes in blood pressure in response to chronic exercise training. Finally, we have quantified the acute changes in heart rate at the onset of and recovery from individual episodes of wheel running, revealing that changes in heart rate are extremely rapid and that the peak rate of change of heart rate increases with chronic exercise training. The results of this study have important implications for the use of genetically modified mouse models to investigate the beneficial haemodynamic effects of chronic exercise on blood pressure and cardiovascular diseases.     

Microwave sensor for the investigation of glucose-dependent reflection properties in aqueous samples

Abstract

The reported paper presents the development of a microwave sensor with a resonant frequency 2.4?GHz. The sensor is also demonstrated in vitro to investigate the variation in its response as a function of glucose concentration. The sensor could be used for the monitoring of blood glucose level in diabetics through non-invasive technology. The approach followed is based on the notion that, change in glucose concentration in the blood affects dielectric properties of blood which in turn produce an impact on reflection properties of the sensor. This effect on response of sensor will be ultimately used to estimate blood glucose concentration. The design specifications considered for the development of sensor are defined in the paper. The experimental setup for in vitro experiment and procedure employed for the investigation of the reflection properties of the sensor as a function of glucose concentration are also discussed in detail. The shift in resonance frequency and the change in the magnitude of the reflection coefficient of proposed sensor have been observed. The reported measurement results are the preliminary results in exploring the implementation of proposed sensor for non-invasive blood glucose monitoring.     

Prediction method for decreases in blood pressure during hemocatharsis therapy by arteriolar blood flow measurement

In clinical practice, the prediction of changes in blood pressure during hemocatharsis therapy depends on invasive monitoring, the physician's experience, or blood pressure measurement when patients ask for it. It is extremely difficult to predict blood pressure variation in patients under general anesthesia or with disturbance of consciousness. Therefore, the prediction of blood pressure variation during hemocatharsis therapy is an important issue. To address this issue, we invented a new noninvasive continuous blood flow monitor using arteriolar blood flow measurement by laser Doppler flowmetry. Then we examined and determined some extremely important phenomena, including the relationship between rapid blood pressure change and arteriolar blood flow, and failures of the cerebral blood flow autoregulatory mechanism, through measurements in clinical practice of hemodialysis, specific hemocatharsis therapy, and drug monitoring. The results suggest that blood pressure variation during hemocatharsis therapy is highly predictable by arteriolar blood flow measurement. Therefore, this new method for arteriolar blood flow measurement might be widely useful for patients under anesthesia, anesthesia monitoring in neonatal infants and animals (no conversation ability), as well as for hemocatharsis therapy.     

A new thermal sensor for surface-based measurement of local myocardial perfusion

The transient response of a new thermal sensor for continuous surface-based measurement of local tissue blood flow was evaluated in the beating dog heart. The sensor is 2.5 mm square, tests on the heart, and responds to flow changes only within a region of tissue 3-4 mm below its location on the epicardial surface. Initial studies demonstrate excellent sensitivity, good frequency response with a time constant of the order of 10-11 s, and an ability to continuously monitor changes in local myocardial blood flow during a variety of well-understood interventions, including coronary artery occlusion, reactive hyperemia, and intravenous administration of nitroglycerin and dipyridamole.     

Development of a transcutaneous blood-constituent monitoring method using a suction effusion fluid collection technique and an ion-sensitive field-effect transistor glucose sensor

The paper describes a method for the transcutaneous monitoring of blood constituents. It combines the use of a suction effusion fluid (SEF) collecting technique with a silicon on sapphire/ion-sensitive field-effect transistor (SOS/ISFET) biosensor. SEF is directly collected by a weak evacuation through skin from which the stratum corneum has been removed. An SEF collecting cell with a stainless-steel mesh at the bottom is kept in a weak vacuum condition, and SEF is sucked up through the mesh and deposited in a reservoir above. An ISFET glucose sensor is able to detect glucose concentrations in very small SEF samples through the use of two small ISFETs and an immobilised enzyme membrane. The reliability of transcutaneously obtained SEF was first confirmed in an experiment using rabbits. A clinical analyser was used to determine levels of glucose, urea nitrogen and creatinine in SEF obtained transcutaneously; these results are compared with results obtained by the same analyser directly from sera. The ISFET glucose sensor was successfully tested on human subjects for the monitoring of blood glucose levels. During these tests, glucose level changes in the SEF followed acutal blood glucose level changes with a slight time delay. Results suggest the feasibility of non-invasive, transcutaneous monitoring of low molecular weight substances in the blood without the use of ordinary blood sampling.     

In vivo measurement of dye concentration using an evanescent-wave optical sensor

A miniaturised evanescent-wave optical sensor is proposed for in vivo measurement of dye concentrations. It enables a continuous monitoring of the optical-dye attenuation or fluorescence spectra between 380 and 650 nm. The sensor is constructed with polished fibres: the cladding of a single-mode fibre is removed by longitudinal polishing. The proximity of the core to the medium favours penetration of the evanescent part of the modal field into the bio fluid. The dimensions of the probe permit several potential applications: for example, insertion into hypodermic needles for spectroscopic analysis of tissues and blood. In the paper, a gastro-enterologic application of the sensor introduced into a catheter is reported. In vivo tests demonstrate the feasibility of quantitative measurement of dye clearance in the gastro-oesophageal tract.