Blood Flow Sensor Research Articles

Simulation and fabrication of blood filtration system for patients with kidney diseases

Here the authors present the new design of blood filtration system for patients with kidney diseases. The proposed system consists of electronic module, drug delivery part, blood extraction and blood insertion part, blood filtration part, flow sensors and blood pressure sensor. Electronic module provides necessary functionalities and control to other components of system. Using inductively coupled plasma etching technology hollow silicon microneedles have been developed for drug delivery part. Nano porous aluminium membrane has been fabricated for blood filtration part. Ultra-sharp tip polymeric dual radii microneedles have been proposed for blood extraction and insertion part. Using ANSYS, strength modelling, microfluidic static and multifield analyses have been conducted. Water, ethanol and blood have been used as working fluid in microfluidic analysis to foresee the flow rate and viscosity effect through microneedles. Fluidic analysis shows that the proposed design is suitable for blood transport because two different lumens radii in microneedles are useful to avoid the clogging effect because of pressure difference in the lumen regions.

Useful method to monitor the physiological effects of alcohol ingestion by combination of micro-integrated laser Doppler blood flow meter and arm-raising test

Alcohol has a variety of effects on the human body, affecting both the sympathetic and parasympathetic nervous system. We examined the peripheral blood flow of alcohol drinkers using a micro-integrated laser Doppler blood flow meter (micro-electromechanical system blood flow sensor). An increased heart rate and blood flow was recorded at the earlobe after alcohol ingestion, and we observed strong correlation between blood flow, heart rate, and breath alcohol content in light drinkers; but not heavy drinkers. We also found that the amplitude of pulse waves measured at the fingertip during an arm-raising test significantly decreased on alcohol consumption, regardless of the individual's alcohol tolerance. Our micro-electromechanical system blood flow sensor successfully detected various physiological changes in peripheral blood circulation induced by alcohol consumption.

An Inductively Powered Implantable Blood Flow Sensor Microsystem for Vascular Grafts

Monitoring blood flow rate inside prosthetic vascular grafts enables an early detection of the graft degradation, followed by the timely intervention and prevention of the graft failure. This paper presents an inductively powered implantable blood flow sensor microsystem with bidirectional telemetry. The microsystem integrates silicon nanowire (SiNW) sensors with tunable piezoresistivity, an ultralow-power application-specific integrated circuit (ASIC), and two miniature coils that are coupled with a larger coil in an external monitoring unit to form a passive wireless link. Operating at 13.56-MHz carrier frequency, the implantable microsystem receives power and command from the external unit and backscatters digitized sensor readout through the coupling coils. The ASIC fabricated in 0.18-μm CMOS process occupies an active area of 1.5 × 1.78 mm (2) and consumes 21.6 μW only. The sensors based on the SiNW and diaphragm structure provide a gauge factor higher than 300 when a small negative tuning voltage (-0.5-0 V) is applied. The measured performance of the pressure sensor and ASIC has demonstrated 0.176 mmHg/√Hz sensing resolution.

On the Anatomy of a Modern Biotelemetry System: A Cell phone Paradigm

Totally implantable biotelemetry systems are becoming very useful tools in both academic and pharmaceutical research laboratories. In the past 30 years, implantable biotelemetry systems have made possible a number of studies that required the use remote measurements of parameters such as ECG, blood pressure and temperature. Current and future medical research measurements, however, demand more advanced features and functions from the biotelemetry systems currently available. In the past, biotelemetry implants were very much like the cell phones of that era. Inflexible, unchangeable, preset, analog. Our recently introduced EndoGear modern biotelemetry system, is a powerful, flexible, user configurable, programmable and digital, much like the smartphones of today. The advantages of our biotelemetry implants are the harnessing of demanding applications by incorporating new and advanced sensors, such as blood flow sensors, solid‐state pressure sensors, and modern RF communication protocols. Users can attach and control a variety of add‐on modules that can perform new functions without the need for a completely new implant; i.e., run a new application (app). Commands and data using digital RF communication protocols minimize signal noise and improve signal accuracy. In general, the advancement of modern biotelemetry systems was a direct result of the advancement of modern smartphone technologies. The drive to produce smaller, more advanced electronic parts and more powerful smartphones helped the development of smaller, more advanced and more powerful biotelemetry systems that have the capacity and new capabilities to assist medical researchers to exciting new discoveries.

Physiological Control of Intraaorta Pump Based on Heart Rate

Because of the special structures of intraaorta pump, the pressure and blood flow sensors cannot be implanted in the blood pump. Moreover, the cardiovascular pump is a very complex system that has no accurate model but much uncertainty and disturbance. Hence, the conventional control algorithm cannot achieve good performance. To overcome this problem, on one hand, a cardiovascular pump model is established. The heart rate in this model is chosen as a controlled variable that is a nonlinear function of the mean arterial pressure. On the other hand, a fuzzy logic feedback control algorithm, which maintains the actual heart rate tracking the desired heart rate, is designed. Computer simulations are performed to verify the robustness and dynamic characters of the controller. The simulation results demonstrate that the controller can maintain the actual heart rate tracking the desired one without static error. When the desired heart rate changed from 100 to 80 bpm, the settling time is <10 seconds. When the peripheral resistance increases from 1.0 to 0.7 mm Hg/ml, the settling time is <10 seconds.

32×32 pixel array complementary metal-oxide semiconductor imaging sensor for laser Doppler blood-flow measurement

A 32×32 pixel array has been fabricated in a 0.35-μm complementary metal-oxide semiconductor process with the aim of producing two-dimensional laser Doppler blood-flow images. In the design, each pixel contains five basic elements: a photodiode, a front-end consisting of a current to voltage converter, voltage amplifier, antialiasing filter, and buffer. The analog design is optimized for the detection of laser Doppler blood-flow signals and thus offers advantages over conventional sensors. The analog outputs are passed through an on-chip multiplexer and digitized by an external analog-to-digital converter. The sensor has been fully characterized electrically and optically using modulated electrical and optical signals. A calibration process for fixed pattern noise reduces the standard deviation of the ac gain by a factor of 2. The imaging response is tested by imaging a vibrating test structure and a rotating diffuser. Blood-flow measurements on a finger before and after occlusion demonstrate that the sensor array is capable of detecting blood-flow signals from tissue. The knowledge gained from the characterization of the design can be used to develop a fully integrated laser Doppler blood-flow sensors with a higher number of pixels.

Miniaturization of a Laser Doppler Blood Flow Sensor by System‐in‐Package Technology: Fusion of an Optical Microelectromechanical Systems Chip and Integrated Circuits

AbstractWe have developed the first and the smallest blood flow sensor composed of integrated circuits (ICs) fused with an optical microelectromechanical systems (MEMS) chip using system‐in‐package (SiP) technologies for application in a healthcare monitoring system. The probe of this blood flow sensor consists of three layers, and the optical MEMS chip is stacked as the top layer. Through silicon via (TSV), vertical‐cavity surface‐emitting laser (VCSEL) and cavities enable wafer‐level packaging of the optical MEMS chip. The other two layers consisting of ICs are highly densified by SiP technology, and the volume of the probe is miniaturized to about one‐sixth of our previously reported integrated laser Doppler blood flowmeter, an MEMS blood flow sensor to which SiP technology was not applied. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Micro‐Optical Blood Flow Sensor Based on System in Package (SiP) Technology that Fuses Optical MEMS and Intergrated Circuit to Detect Avian Influenza

As a fusion of micro‐electro‐mechanical systems (MEMS) and system in package (SiP) technologies, a very small wireless blood‐flow sensor to be attached to birds was fabricated. Pulse frequencies are output as Fourier‐transformed signals from a sensor that detects blood flow. Although blood flow fluctuates with the bird's movement, the minimum (resting) value detected is stable enough for comparison against a normal index value for healthy birds. The combination of blood flow (monitored remotely by this miniature blood‐flow sensor) and body temperature is expected to be effective for early detection of infection.

Blood flow sensor susceptibility to lipoproteins in early arteriosclerosis and its clinical improvement by statin therapy — a nanoplaque study

Blood flow sensor susceptibility to lipoproteins in early arteriosclerosis and its clinical improvement by statin therapy - A nanoplaque study

3E1-03 褥瘡防止振動シートの開発 : 加振周波数と波形の血流への影響(OS 身体機能・活動力の維持と向上)

In this study, blood flow inhibition which is generated by the continuous oppression as a factor of the bed sore generation has been noticed. Vibration stimulation from the outside to the skin surface is proposed as the technique which eases the blood flow inhibition. Using the blood flow sensor, excitation frequency and waveform, both effects to the blood flow are evaluated, and the usefulness of external stimulation effect for prevention bedsore is shown.

First experimental results with the oxygen electrode as a local blood flow sensor in canine colon.

A modified oxygen electrode was tested against the electromagnetic flowmeter to see if its reading indicated blood flow to the canine colon. Although gross inflow was compared with local flow, the correlation was good in each of seven individuals (r ranged from 0.86 to 0.97). The closeness of the relative values gives the instrument potential for cheap, fast, repeatable and non-invasive estimation of regional blood flow, in colon and other exposed tissues.

Evaluation of the behaviour of a thermal diffusion sensor in a high field strength magnetic resonance system: an experimental study.

Patients with acute brain pathology requiring ferromagnetic bio-medical implants for on-going invasive monitoring are largely excluded from the benefits of MRI scanning. We evaluated the behaviour of a thermal diffusion cortical blood flow (TD-CBF) sensor both in vitro (phantom gelatin model) and in vivo environments in a high field strength MRI system. Two baboons underwent cranial subdural implantation of 2 TD-CBF sensors/hemisphere and a single left parietal sensor was implanted subcortically to determine any deleterious effects. Using standard MRI sequences, artefact size, thermal effects, current generation, movement and reliability of recordings were assessed during scanning. The deflection forces were negligible, no observable thermal effects were demonstrated, while wide fluctuations in cerebral blood flow recordings were recorded. Mean image artefact size for implanted sensors was 6 times larger than in vitro. Patients with an implanted TD-CBF sensor may be safely imaged provided the device is disconnected. The MRI images obtained are of an acceptable quality.

Development of built-in type and noninvasive sensor systems for smart artificial heart.

It is very important to grasp the artificial heart condition and the physiologic conditions for the implantable artificial heart. In our laboratory, a smart artificial heart (SAH) has been proposed and developed. An SAH is an artificial heart with a noninvasive sensor; it is a sensorized and intelligent artificial heart for safe and effective treatment. In this study, the following sensor systems for SAH are described: noninvasive blood temperature sensor system, noninvasive blood pressure sensor system, and noninvasive small blood flow sensor system. These noninvasive sensor systems are integrated and included around the artificial heart to evaluate these sensor systems for SAH by the mockup experiments and the animal experiments. The blood temperature could be measured stably by the temperature sensor system. Aortic pressure was estimated, and sucking condition was detected by the pressure sensor system. The blood flow was measured by the flow meter system within 10% error. As a result of these experiments, we confirmed the effectiveness of the sensor systems for SAH.

Effects of 12 days exposure to simulated microgravity on central circulatory hemodynamics in the rhesus monkey

Central circulatory hemodynamic responses were measured before and during the initial 9 days of a 12-day 10 ° head-down tilt (HDT) in 4 flight-sized juvenile rhesus monkeys who were surgically instrumented with a variety of intrathoracic catheters and blood flow sensors to assess the effects of simulated microgravity on central circulatory hemodynamics. Each subject underwent measurements of aortic and left ventricular pressures, and aortic flow before and during HDT as well as during a passive head-up postural test before and after HDT. Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure were measured, and dP/dt and left ventricular elastance was calculated from hemodynamic measurements. The postural test consisted of 5 min of supine baseline control followed by 5 minutes of 90 ° upright tilt (HUT). Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure showed no consistent alterations during HDT. Left ventricular elastance was reduced in all animals throughout HDT, indicating that cardiac compliance was increased. HDT did not consistently alter left ventricular +dP/dt, indicating no change in cardiac contractility. Heart rate during the post-HDT HUT postural test was elevated compared to pre-HDT while post-HDT cardiac output was decreased by 52% as a result of a 54% reduction in stroke volume throughout HUT. Results from this study using an instrumented rhesus monkey suggest that exposure to microgravity may increase ventricular compliance without alterating cardiac contractility. Our project supported the notion that an invasively-instrumented animal model should be viable for use in spaceflight cardiovascular experiments to assess potential changes in myocardial function and cardiac compliance.

Vascular smooth muscle, a multiply feedback-coupled system of high versatility, modulation and cell-signaling variability.

Under normal conditions, the various vascular regulatory effector influences are interwoven in a dynamic, and not a static, circulatory system. The reaction of a smooth muscle cell is thus reflected only incompletely by the stationary activation curve 'developed tension versus membrane potential'. The missing time domain in this relationship is a reflection of our as yet limited understanding of the system's behavior in space and time. It should be emphasized that the rhythmogenic properties of vascular smooth muscle are closely coupled to a functioning circulation. The electrical and mechanical oscillations, which can be traced back to rhythmic activity of the active, electrogenic Na+/K+ pump, could originate in the allosteric qualities of the enzyme phosphofructokinase (PFK). Thus, PFK represents a rhythmogenic enzyme which may serve as an example of the connection between the biological properties on a molecular level and the spatiotemporal system's behavior. The cardiovascular system and its rhythmicity may be dominated by only a few control points, one of which is distinguished by the viscoelastic properties of a blood flow sensor macromolecule. Therefore, the three prominent control points - PFK, (Na+ + K+)-ATPase and flow sensor conformation - acting as negatively feedback-coupled, nonlinear synergetic order parameters, are sufficient to initiate the periodic events in the cardiovascular system and to provide a plausible explanation for their causal origin.

5520190 Cardiac blood flow sensor and method

5520190 Cardiac blood flow sensor and method

Anionic biopolymers as blood flow sensors

The finding of flow-dependent vasodilatation rests on the basic observation that with an increase in blood flow the vessels become wider, with a decrease the vascular smooth muscle cells contract. Proteoheparan sulphate could be the sensor macromolecule at the endothelial cell membrane-blood interface, that reacts on the shear stress generated by the flowing blood, and that informs and regulates the vascular smooth muscle cells via a signal transduction chain. This anionic biopolyelectrolyte possesses viscoelastic and specific ion binding properties which allow a change of its configuration in dependence on shear stress and electrostatic charge density. The blood flow sensor undergoes a conformational transition from a random coil to an extended filamentous state with increasing flow, whereby Na + ions from the blood are bound. Owing to the intramolecular elastic recoil forces of proteoheparan sulphate the slowing of a flow rate causes an entropic coiling, the expulsion of Na + ions and thus an interruption of the signal chain. Under physiological conditions, the conformation and Na + binding proved to be extremely Ca 2+-sensitive while K + and Mg 2+ ions play a minor role for the susceptibility of the sensor. Via counterion migration of the bound Na + ions along the sensor glycosaminoglycan side chains and following Na + passage through an unspecific ion channel in the endothelial cell membrane, the signal transduction chain leads to a membrane depolarization with Ca 2+ influx into the cells. This stimulates the EDRF/NO production and release from the endothelial cells. The consequence is vasodilatation.

Fabrication and testing of a microdynamic rotor for blood flow measurements

Flow studies have been conducted, in vitro, on prototype microfabricated blood flow sensors. The envisioned measurement principle is the detection of the rotation of a micromachined polysilicon rotor of diameter 300 mu m. Repeatable rotation rates as a function of media velocity were obtained for both nitrogen and water. Fluid flow asymmetries, necessary to produce a torque on the rotor, were created by integrating a 2 mu m thick polysilicon cap over half the rotor. Blade deflection, due to intrinsic stress in the polysilicon films, was eliminated by thermal annealing. This allows the rotor, 2 mu m thick, to rotate in the 7 mu m gap between the substrate and the polysilicon cap. Operation of the device in heparinized dog blood resulted in considerable numbers of erythrocytes sticking to the polysilicon elements.

Thermal clearance blood flow sensor—sensitivity, linearity and flow depth discrimination

A thermal clearance blood flow sensor has been designed which incorporates four separate sensing elements, permitting flow changes at four differing depths to be measured. Static and dynamic laboratory tests have confirmed the differing flow depth response of the sensor and demonstrated a linear response to flow over the physiological skin blood flow range. Flow depth response has been shown to be dependent upon sensor geometry. Response should also in theory be dependent on the thermal conductivity of the sensor body material. However, using conventional encapsulation materials, it does not seem possible to obtain a depth sensitivity of less than 0.2 mm.

A new constrictor device for external induction of a long-term stable and irreversible renal artery stenosis in the dog.

A new externally adjustable constrictor device for renal artery stenosis in the dog is described. The constrictor combines hydraulic and mechanical characteristics, and is connected to the exterior of the animal by a thin catheter. Applying hydraulic pressure via the catheter causes the plunger in the device to compress the renal artery to any desired degree of stenosis. A mechanical catch prevents backward movement of the plunger, thus ensuring a stable, irreversible renal artery constriction. This constrictor was implanted in 13 dogs, together with an electromagnetic blood flow sensor around a renal artery. In twelve dogs the constriction procedure was performed 3-12 weeks after implantation, and in all 12 cases the intended degree of stenosis [defined as percentage renal blood flow reduction (RBF)] was achieved within a range of 10%. In 5 dogs the long-term stability of the stenosis was studied and the RBF reduction appeared to be stable up to at least 6 weeks after constriction. In conclusion, the presented constrictor device is easily externally adjustable, and allows induction of a stable renal artery stenosis of various degrees in the conscious dog.