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1.
In this study, we developed a new miniature motor-driven pulsatile left ventricular assist device (LVAD) for implantation into a Japanese patient of average build by means of computer-aided design and manufacturing (CAD/CAM) technology. A specially designed miniature ball-screw and a high-performance brushless DC motor were used in an artificial heart actuator to allow miniaturization. A blood pump chamber (stroke volume 55ml) and an inflow and outflow port were designed by computational fluid dynamics (CFD) analysis. The geometry of the blood pump was evaluated using the value of index of pump geometry (IPG) = (Reynolds shear stress) × (occupied volume) as a quantitative index for optimization. The calculated value of IPG varied from 20.6Nm to 49.1Nm, depending on small variations in pump geometry. We determined the optimum pump geometry based on the results of quantitative evaluation using IPG and qualitative evaluation using the flow velocity distribution with blood flow tracking. The geometry of the blood pump that gave lower shear stress had more optimum spiral flow around the diaphragm-housing (D-H) junction. The volume and weight of the new LVAD, made of epoxy resin, is 309ml and 378g, but further miniaturization will be possible by improving the geometry of both the blood pump and the back casing. Our results show that our new design method for an implantable LVAD using CAD/CAM promises to improve blood compatibility with greater miniaturization.  相似文献   

2.
During the final development of a unique Magnetically Actuated Left Ventricle Assist Device (MALVAD), three of the most widely used clinical prosthetic valves were evaluated to determine their suitability for the stringent requirements for LVAD use, in both the inflow and outflow positions. The three valves (St. Jude Medical-SJM; Medtronic Hall-MH; Bjork-Shiley Convex-Concave-BSCC), with lumen size of 25 mm, were tested in the same appropriate mock loop to the following set of hydraulic parameters: 1) after-load systemic pressure = constant 100 mmHg; 2) preload pressure ranged from 3 mm to 18 mmHg; 3) beat rate ranged from 60 bpm to 80 bpm. Pump actuator power was held constant, correspondent with specific bpm rate, for all valves tested. Results from a series of 10 bench tests per valve showed that the SJM was significantly better, on a statistical basis, than both the MH and BSCC valves, at fill pressures of 5 mmHg. At 10-mm fill pressure, however, the statistical flow rates for both the SJM and the MH valves were significantly superior to the BSCC valve, so that the BSCC valve was classified as a marginal candidate for LVAD use. The SJM and MH valves had bench test flow-rate values whose numerical difference was too small to serve conclusively as an arbitrary basis for valve choice. Because of this, the two valves were further evaluated in terms of two widely recognized, mandatory LVAD valve design criteria: (1) comparative mechanical ruggedness, and (2) relative ease and simplicity of LVAD design inclusion.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
To investigate the feasibility of a long-term left ventricular assist device (LVAD) placed in the aortic valve annulus, an implantable aortic valve pump (21 mm outer diameter, weighing 27 g) was developed. The device consists of a central rotor and a stator. The rotor assembly incorporates driven magnets and an impeller. The stator assembly has a motor coil with an iron core and outflow guide vanes. The device is to be implanted identically to an aortic valve replacement, occupying no additional anatomic space. The pump delivers the blood directly from left ventricle to the aortic root, like a natural ventricle, therefore causing less physiologic disturbance to the natural circulation. Neither connecting conduits nor ‘bypass’ circuits are necessary. The pump is designed to cycle between a peak flow and zero net flow to approximate systole and diastole. Bench testing indicates that the pump can produce a blood flow of 5 l min?1 with 50 mmHg pressure increase at 17 500 rpm. At zero net flow rate, the pump can maintain a diastole aortic pressure against 80 mmHg at the same rotating speed.  相似文献   

4.
To investigate the feasibility of a long-term left ventricular assist device (LVAD) placed in the aortic valve annulus, an implantable aortic valve pump (21 mm outer diameter, weighing 27 g) was developed. The device consists of a central rotor and a stator. The rotor assembly incorporates driven magnets and an impeller. The stator assembly has a motor coil with an iron core and outflow guide vanes. The device is to be implanted identically to an aortic valve replacement, occupying no additional anatomic space. The pump delivers the blood directly from left ventricle to the aortic root, like a natural ventricle, therefore causing less physiologic disturbance to the natural circulation. Neither connecting conduits nor 'bypass' circuits are necessary. The pump is designed to cycle between a peak flow and zero net flow to approximate systole and diastole. Bench testing indicates that the pump can produce a blood flow of 5 l min(-1) with 50 mmHg pressure increase at 17,500 rpm. At zero net flow rate, the pump can maintain a diastole aortic pressure against 80 mmHg at the same rotating speed.  相似文献   

5.
The purpose of this study was to develop a compact wearable pneumatic drive unit for a ventricular assist device (VAD). This newly developed drive unit, 20 × 8.5 × 20 cm in size and weighing approximately 1.8 kg, consists of a brushless DC motor, noncircular gears, a crankshaft, a cylinder-piston, and air pressure regulation valves. The driving air pressure is generated by the reciprocating motion of the piston and is controlled by the air pressure regulation valves. The systolic ratio is determined by the noncircular gears, and so is fixed for a given configuration. As a result of an overflow-type mock circulation test, a drive unit with a 44% systolic ratio connected to a Toyobo VAD blood pump with a 70-ml stroke volume achieved a pump output of more than 7 l/min at 100 bpm against a 120 mmHg afterload. Long-term animal tests were also performed using drive units with systolic ratios of 45% and 53% in two Holstein calves weighing 62 kg and 74 kg; the tests were terminated on days 30 and 39, respectively, without any malfunction. The mean aortic pressure, bypass flow, and power consumption for the first calf were maintained at 90 × 13 mmHg, 3.9 × 0.9 l/min, and 12 × 1 W, and those for the second calf were maintained at 88 × 13 mmHg, 5.0 × 0.5 l/min, and 16 × 2 W, respectively. These results indicate that the newly developed drive unit may be used as a wearable pneumatic drive unit for the Toyobo VAD blood pump.  相似文献   

6.
Hemodynamic and ventricular energetic parameters were measured in calves implanted with the air driven Utah Ventricular Assist Device (UVAD). Uptake site was varied to determine the effect of control mode and vacuum augmentation of filing. Uptake was drawn solely from the left atrium or combined with a left ventricular apical vent. LVAD outflow returned to the descending, thoracic aorta. Control modes examined included asynchronous pumping as well as 1:1 and 1:2 synchronous diastolic counterpulsation. The 85cc LVAD, vacuum formed from PELLETHANE, was implanted acutely in four animals and chronically in six (7, 49 and 116 days paracorporeally, 1, 28 and 32 days intrathoracically). Instantaneous blood pressures, intramyocardial pressure, aortic outflow, oxygen consumption, LVAD output and drive parameters were recorded. LVAD output was independent of control mode when the natural heart rate was greater than or equal to 80 beats per minute. Intrathoracically positioned LVADs pumped a mean flow of approximately equal to 5 liters/min without vacuum augmentation of filling. Paracorporeally positioned LVADs pumped approximately equal to 3 liters/min mean flow without vacuum augmentation and up to approximately equal to 6 liters/min with 38 mm Hg of vacuum augmentation of filling. Instantaneous ascending aortic pressure and flow showed distinct beat-to-beat variation depending on LVAD control mode. Lower average ventricular afterload was observed when pumping the LVAD asynchronously or 1:2 synchronously. In one acute preparation, left ventricular myocardial oxygen consumption was reduced from the unassisted average control level by 37% for the asynchronous and 1:1 synchronous control modes with left atrial uptake.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
 Nowadays, left ventricular assist devices are usually designed as high-speed, electric, rotary blood pumps. The pump drains blood from the left ventricular apex via an inlet cannula and ejects into the aortic root via an outlet conduit. To develop a high-performance pump, the present study utilizes partial differential equations to generate a surface representation of the impeller of the blood pump. Flow analysis around the impeller is performed by using the finite volume method to solve the fully incompressible three-dimensional Navier–Stokes equations along with the k-ε turbulence model. The numerical results highlight flow features in the end-wall region of the pump, namely the clearance leakage cross-flow, and the vortex associated with this leakage. These secondary flows induce major energy losses in the pumping device. On the test study, a test loop was proposed to measure the performance characteristics. It was shown that the design would provide a flow rate of 4.4 l/min with a pressure head of 122 mmHg. The DC motor power under these conditions was about 6 W and the rotational speed was 4500 rpm. Both the flow rate and head can satisfy the demand for the left artificial heart to work normally. Received: September 25, 2002 / Accepted: January 23, 2003 Acknowledgments National Science Council, R.O.C., grant number NSC 91-2213-E-218-018 supported this work.  相似文献   

8.
We present a novel concept to process human blood on a spinning polymer disk for the determination of the hematocrit level by simple visual inspection. The microfluidic disk which is spun by a macroscopic drive unit features an upstream metering structure and a downstream blind channel where the centrifugally enforced sedimentation of the blood is performed. The bubble-free priming of the blind channel is governed by centrifugally assisted capillary filling along the sloped hydrophilic side-wall and the lid as well as the special shape of the dead end of the two-layer channel. The hematocrit is indicated at the sharp phase boundary between the plasma and the segregated cellular pellet on a disk-imprinted calibrated scale. This way, we conduct the hematocrit determination of human blood within 5 min at a high degree of linearity (R 2 = 0.999) and at a high accuracy (CV = 4.7%) spanning over the physiological to pathological working range. As all processing steps including the priming, the metering to a defined volume as well as the centrifugation are executed automatically during rotation, the concept is successfully demonstrated in a conventional PC-CDROM drive while delivering the same performance (R 2 = 0.999, CV = 4.3%).  相似文献   

9.
 The undulation pump is a unique continuous-flow displacement-type blood pump with high performance. However, the undulation pump has limited mechanical durability. To eliminate this limitation, the principle of the rotary undulation pump was developed. The rotary undulation pump is composed of a disk having a pair of convex shapes on both side and pump housing having a shape such that one side is narrow and the other side is wide. The disk nutates and at the same time rotates at half the speed of nutation. With this movement of the disk, the disk can rotate through the narrow part of the pump housing and pump mechanism occurs. Between the disk and the pump housing, four pump rooms are created. The four outputs are added at the outlet port, and continuous flow is generated. The practical shape was designed with computer graphics. The motion of the disk was calculated accurately with the computer, and the principle was confirmed. The inlet and outlet port areas were also calculated. Models were developed to demonstrate the principle. With the magnetic coupling method, up to about 6 l/min of output could be measured against 100 mmHg of pressure load, and the principle was demonstrated to work. An experimental model to study an electromagnetic drive method, including a magnetically suspended drive, is being developed for the next step. Although many objectives remain, the basic principle of the rotary undulation pump was confirmed. Received: October 11, 2000 / Accepted: October 31, 2001  相似文献   

10.
It has been widely acknowledged that permanent maglev cannot achieve stability; however, the authors have discovered that stable permanent maglev is possible under the effect of a combination of passive magnetic and nonmagnetic forces. In addition, a rotary left ventricular assist device (LVAD) with passive magnetic bearings has been developed. It is a radially driven impeller pump, having a rotor and a stator. The rotor consists of driven magnets and impeller; the motor coil and pump housing form the stator. Two passive magnetic bearings counteract the attractive force between motor coil iron core and rotor magnets; the rotor thereafter can be disaffiliated from the stator and become levitated under the action of passive magnetic and haemodynamic forces. Because of the pressure difference between the outlet and the inlet of the pump, there is a small flow passing through the gap of rotor and stator, and then entering the lower pressure area along the central hole of the rotor. This small flow comes to a full washout of all blood contacting surfaces in the motor. Moreover, a decreased Bernoulli force in the larger gap with faster flow produces a centring force that leads to stable levitation of the rotor. Resultantly, neither mechanical wear nor thrombosis will occur in the pump. The rotor position detection reveals that the precondition of levitation is a high rotating speed (over 3250 rpm) and a high flow rate (over 1 l min(-1)). Haemodynamic tests with porcine blood indicate that the device as a LVAD requires a rotating speed between 3500 and 4000 rpm for producing a blood flow of 4 - 6 l min(-1) against 100 mmHg mean pressure head. The egg-sized device has a weight of 200 g and an O.D. of 40 mm at its largest point.  相似文献   

11.
Peristaltic piezoelectric micropump system for biomedical applications   总被引:3,自引:0,他引:3  
This study presents a peristaltic piezoelectric micropump system to transport deionized water and whole blood, and deliver phosphated buffered saline (PBS) into the vein of a rat, thus simulating insulin injections for diabetes. The proposed system comprises a micropump, a 12 V battery, an ATmega 8535 microprocessor, a 12–180 V DC-to-DC converter based on transformerless technology, three differential amplifiers, an IC 7805, a phase controller, an A/D converter, a keyboard and an LCD module. The system can generate step-function signals of the 3-, 4-, and 6-phase actuation sequences with voltages of up to 228 Vpp (± 114 V) and frequencies ranging from 10 Hz to 100 kHz, as the inputs for the pump. It is portable and programmable with a package size of 22 × 12.8 × 9 cm. Additionally, a protocol of the PEOU (N-(triethosilylpropyl)-O-polyethylene oxide urethane) coating is developed to form a self-assembly monolayer, thus increasing the hemocompatibility of the micropump, and keeping blood flowing smoothly through the micropump without blocking. This study performs the circuit testing and fluid pumping, and reveals the effects of actuation sequences and liquid on pump performance. The flow rates for pumping DI water and whole blood are 16.6–121.6 μl/min and 8.6–50.2 μl/min, respectively when the voltages are changed from 80 Vpp (± 40 V) to 140Vpp (± 70 V). And the maximum backpressures are 3.2 and 1.8 kPa for DI water and whole blood at 150 Vpp (± 75 V), respectively. The mean artery pressure (MAP) and heart rates of the rate are 63–69 mmHg and 266–279 beats/min, respectively, throughout the injection process, indicating an insignificant change in physiological reactions of rats.  相似文献   

12.
It has been widely acknowledged that permanent maglev cannot achieve stability; however, the authors have discovered that stable permanent maglev is possible under the effect of a combination of passive magnetic and nonmagnetic forces. In addition, a rotary left ventricular assist device (LVAD) with passive magnetic bearings has been developed. It is a radially driven impeller pump, having a rotor and a stator. The rotor consists of driven magnets and impeller; the motor coil and pump housing form the stator. Two passive magnetic bearings counteract the attractive force between motor coil iron core and rotor magnets; the rotor thereafter can be disaffiliated from the stator and become levitated under the action of passive magnetic and haemodynamic forces. Because of the pressure difference between the outlet and the inlet of the pump, there is a small flow passing through the gap of rotor and stator, and then entering the lower pressure area along the central hole of the rotor. This small flow comes to a full washout of all blood contacting surfaces in the motor. Moreover, a decreased Bernoulli force in the larger gap with faster flow produces a centring force that leads to stable levitation of the rotor. Resultantly, neither mechanical wear nor thrombosis will occur in the pump. The rotor position detection reveals that the precondition of levitation is a high rotating speed (over 3250 rpm) and a high flow rate (over 1?l min?1). Haemodynamic tests with porcine blood indicate that the device as a LVAD requires a rotating speed between 3500 and 4000 rpm for producing a blood flow of 4?–?6?l min?1 against 100?mmHg mean pressure head. The egg-sized device has a weight of 200?g and an O.D. of 40?mm at its largest point.  相似文献   

13.
We sought to determine whether the cardiovascular deconditioning that occurs in exercising men after prolonged (42 days) bedrest in the head-down tilt (HDT) position is primarily related to mechanical changes in the heart or to an impaired arterial-cardiac-chronotropic baroreflex. Seven subjects were studied before (C, control) and repeatedly after HDT with rapid tilting between the upright and supine positions during steady-state 50-W dynamic leg exercise. Ventricular interdependence was assumed to be an index of cardiac size; it was assessed on the basis of the initial dip of arterial pulse pressure (PP) induced by a sudden tilt from the upright to the supine position (down-tilt). Arterial-cardiac-chronotropic baroreflex sensitivity (ABS) was assessed as the ratio between tilt-induced heart rate transients and the preceding (and reciprocal) transient in arterial pressure. On the first day of recovery, the initial PP dip was −4 (2) mmHg (where 1 mmHg is 0.13 kPa), less than half of the control value; on subsequent recovery days, the initial PP dip was not significantly different from the control value. When tilting from the upright to the supine position, mean ABS ranged from 1.02 to 1.06 bpm/mmHg during three separate control sessions. Tilts in the opposite direction gave lower ABS values because of the more sluggish HR response and ranged from 0.43 to 0.45 bpm/mmHg in the control situations. ABS did not change after HDT. Our results indicate that impairments of the cardiovascular system after long-term bedrest are of haemodynamic rather than baroreflex origin. Accepted: 8 March 2000  相似文献   

14.
For better anatomic and physiologic fitting, a novel implantable aortic valvo-pump (IAVP) has been developed. A valvo-pump is a micro axial flow impeller pump, which has the same dimensions and function, as well as the same location, of a valve. Therefore, IAVP needs no inlet and outlet tubes, no additional anatomic occupation, and has less physiologic disturbance to natural circulation compared with the traditional bypass left ventricular assist device (LVAD). The device has a stator and a rotor. The stator consists of a motor coil with an iron core and an outflow guide vane; the rotor includes driven magnets and impeller. There is neither bearing nor strut in both the pump and the motor. In order to reduce the attractive force between the rotor and the stator, so as to enhance the durability of the performance, the rotor magnets were minimized without reducing the driving torque and efficiency of the motor. The impeller vane was designed according to a three-dimensional and analytical method, for preventing stasis and turbulence. The largest outer diameter is 24.7 mm and the length at this point is 12.4 mm. The total weight is 40 g (including the rotor of 11 g). The consumed power is 7 W (14 V x 0.5 A) at 15 000 rpm. This rotating speed stays unchanged during haemodynamic testing together with a pulsatile centrifugal pump, which imitates a failing ventricle. The maximal flow cross IAVP reaches over 10 l min(-1) and the pressure head at 0 l min(-1) can be as large as 80 mmHg. At flow rate of 4 - 8 l min(-1), IAVP enlarges the flow c. 1 l min(-1) and meanwhile increases the pressure about 10 mmHg. The pressure pulsatility generated by the pulsatile centrifugal pump remains 40 mmHg after passing IAVP. By first animal experimental trial the device was sewed in aortic position of an 80 kg pig without harm to adjacent tissue and organs. IAVP promises to be a viable alternative to natural donor heart for heart transplantation in the future.  相似文献   

15.
For better anatomic and physiologic fitting, a novel implantable aortic valvo-pump (IAVP) has been developed. A valvo-pump is a micro axial flow impeller pump, which has the same dimensions and function, as well as the same location, of a valve. Therefore, IAVP needs no inlet and outlet tubes, no additional anatomic occupation, and has less physiologic disturbance to natural circulation compared with the traditional bypass left ventricular assist device (LVAD). The device has a stator and a rotor. The stator consists of a motor coil with an iron core and an outflow guide vane; the rotor includes driven magnets and impeller. There is neither bearing nor strut in both the pump and the motor. In order to reduce the attractive force between the rotor and the stator, so as to enhance the durability of the performance, the rotor magnets were minimized without reducing the driving torque and efficiency of the motor. The impeller vane was designed according to a three-dimensional and analytical method, for preventing stasis and turbulence. The largest outer diameter is 24.7 mm and the length at this point is 12.4 mm. The total weight is 40 g (including the rotor of 11 g). The consumed power is 7 W (14 V?×?0.5 A) at 15?000 rpm. This rotating speed stays unchanged during haemodynamic testing together with a pulsatile centrifugal pump, which imitates a failing ventricle. The maximal flow cross IAVP reaches over 10 l min?1 and the pressure head at 0 l min?1 can be as large as 80 mmHg. At flow rate of 4?–?8 l min?1, IAVP enlarges the flow c. 1 l min?1 and meanwhile increases the pressure about 10 mmHg. The pressure pulsatility generated by the pulsatile centrifugal pump remains 40 mmHg after passing IAVP. By first animal experimental trial the device was sewed in aortic position of an 80 kg pig without harm to adjacent tissue and organs. IAVP promises to be a viable alternative to natural donor heart for heart transplantation in the future.  相似文献   

16.
The main purpose of this study was to develop an implantable direct-electromagnetic left ventricular assist system driven by a linear actuator (linear LVAS). The linear LVAS is a pulsatile pump with a pusher plate that is driven directly by a linear oscillatory actuator (LOA) without any movement converters. This prototype pump unit with a LOA was 100 mm in diameter, 50 mm in thickness, and weighed 740 g. The full-fill/full-eject driving method was applied to the control algorithm. In addition, a mechanism to detect and release sucking was realized to overcome this problem that accompanies the active-filling type of VAS. The performance of the linear LVAS was evaluated in a long-term animal experiment using a goat (56 kg). The goat survived for 42 days. The reason why we terminated this experiment was that thrombus was found in the pump. There was no frictional debris found around the LOA. The linear LVAS did not exhibit electrical or mechanical problems during the first animal experiment.  相似文献   

17.
Our objective was to characterize the responses of heart rate (HR) and arterial blood pressure (BP) to changes in posture during concomitant dynamic leg exercise. Ten men performed dynamic leg exercise at 50, 100, and 150 W and were rapidly and repeatedly tilted between supine (0°) and upright (80°) positions at 2-min intervals. Continuous recordings of BP and HR were made, and changes in central blood volume were estimated from transthoracic impedance. Short-lasting increases in BP were observed immediately upon tilting from the upright to the supine position (down-tilt), averaging +18 mmHg (50 W) to +31 mmHg (150 W), and there were equally short-lasting decreases in BP, ranging from −26 to −38 mmHg upon tilting from supine to upright (up-tilt). These components occurred for all pressure parameters (systolic, mean, diastolic, and pulse pressures). We propose that these transients reflect mainly tilt-induced changes in total peripheral resistance resulting from decreases and increases of the efficiency of the venous muscle pump. After 3–4 s (down-tilt) and 7–11 s (up-tilt) there were large HR transients in a direction opposite to the pressure transients. These HR transients were larger during the down-tilt (−15 to −26 beats · min−1) than during the up-tilt (+13 to +17 beats · min−1), and increased in amplitude with work intensity during the down-tilt. The tilt-induced HR fluctuations could be modelled as a basically linear function of an arterial baroreflex input from a site half-way between the heart and the carotid sinus, and with varying contributions of fast vagal and slow sympathetic HR responses resulting in attenuated tachycardic responses to hypotensive stimuli during exercise. Accepted: 24 August 1999  相似文献   

18.
The purpose of this article is to present test results for a second generation, high efficiency, nonpulsatile centrifugal blood pump that is being developed for use as a left ventricular assist device (LVAD). The LVAD pump uses a hybrid passive-active magnetic bearing support system that exhibits extremely low power loss, low vibration, and high reliability under transient conditions and varying pump orientations. A unique feature of the second generation design configuration is the very simple and direct flow path for both main and washing blood flows. The pump was tested in both vertical and horizontal orientations using a standard flow loop to demonstrate the performance and durability of the second generation LVAD. Steady state and transient orientation pump operating characteristics including pressure, flow, speed, temperatures, vibration, and rotor orientation were measured. During the tests, pump performance was mapped at several operating conditions including points above and below the nominal design of 5 L/min at 100 mm Hg pressure rise. Flow rates from 2 to 7 L/min and pressure rises from 50 to 150 mm Hg were measured. Pump speeds were varied during these tests from 2,500 to 3,500 rpm. The nominal design flow of 5 L/min at 100 mm Hg pressure rise was successfully achieved at the design speed of 3,000 rpm. After LVAD performance testing, both 28 day continuous duty and 5 day transient orientation durability tests were completed without incident. A hydrodynamic backup bearing design feasibility study was also conducted. Results from this design study indicate that an integral hydrodynamic backup bearing may be readily incorporated into the second generation LVAD and other magnetically levitated pump rotors.  相似文献   

19.
 We have been using the Gyro centrifugal pump C1E3 for cardiopulmonary bypass in anticipation of high efficiency, low hemolysis, and antithrombogenicity of this pump. However, the clinical evaluation of this pump remains to be clarified, because it has been a short time since the pump appeared in clinical situations. The aim of the present study is to inspect and analyze the Gyro pumps morphologically after clinical use. We examined 80 consecutive pumps after cardiopulmonary bypass for 186 ± 67 min with a mean flow rate of 2.52 ± 0.22 l/min/m2 at a mean rotational speed of 2485 ± 81.1 rpm. Although no abnormal findings were present in 79 pumps, one pump was found to contain effusion at the connection between the impeller body and the shaft. The extudate was supposed to be blood, based upon the results of X-ray spectrometer analysis. The cause was determined to be the upward deviation of the shaft off the impeller body. Scanning electron microscopy showed scratches on a part of the bottom housing and a smooth surface of both the male and female pivots of the pump. Surface profile measurement revealed that the deformity of the female pivots was 0.14 mm (top) and 0.05 mm (bottom). These observations suggest that the floating force and vibration by the rotating impeller acted on the joint zone between the alumina ceramic shaft and the polycarbonate impeller body, resulting in dissection of the adhesive agent from the polycarbonate. Although this abnormality may be rare, the structural design still may need to be improved. Received: November 9, 2001 / Accepted: February 4, 2002  相似文献   

20.
We have been developing a pneumatic ventricular assist device (PVAD) system consisting of a diaphragm-type blood pump. The objective of the present study was to evaluate the flow pattern inside the PVAD, which may greatly affect thrombus formation, with respect to the inflow valve-mount orientation. To analyze the change of flow behavior caused by the orifice direction (OD) of the valve, the flow pattern in this pump was visualized. Particle image velocimetry was used as a measurement technique to visualize the flow dynamics. A monoleaflet mechanical valve was mounted in the inlet and outlet ports of the PVAD, which was connected to a mock circulatory loop tester. The OD of the inlet valve was set at six different angles (OD = 0°, 45°, 90°, 135°, 180°, and 270°, where the OD opening toward the diaphragm was defined as 0°) and the pump rate was fixed at 80 bpm to create a 5.0 l/min flow rate. The main circular flow in the blood pump was affected by the OD of the inlet valve. The observed regional flow velocity was relatively low in the area between the inlet and outlet port roots, and was lowest at an OD of 90°. In contrast, the regional flow velocity in this area was highest at an OD of 135°. The OD is an important factor in optimizing the flow condition in our PVAD in terms of preventing flow stagnation, and the best flow behavior was realized at an OD of 135°.  相似文献   

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