Ultrasonic Blood Flowmeter Research Articles

Prediction of Cross-Clamp-Induced Cerebral Ischemia During Carotid Endarterectomy Using Arterial Blood Flow Assessment

BackgroundCross-clamping during carotid endarterectomy (CEA) is associated with the risk of cerebral ischemia. Various studies have evaluated different criteria for detecting cerebral ischemia, but difficulties arise when ischemic changes appear after the carotid artery is cross-clamped and incised. Here, we explored a parameter that can predict cerebral ischemia prior to cross-clamping during CEA using a blood-flow meter. MethodsThe carotid arterial blood flow was measured directly (direct ABF) in the common carotid artery prior to cross-clamping. The anatomical information in preoperative magnetic resonance imaging, cerebral blood flow in xenon-enhanced computed tomography, and carotid peak systolic flow velocity by carotid echo from the skin surface were also evaluated. A decrease in the short-latency somatosensory evoked potentials (SSEP) during cross-clamping to insert a shunt was assessed, and a decrease in amplitude of ≥ 50% was considered an indicator for cerebral ischemia. Surgery was performed under general anesthesia, and a shunt was inserted in all cases. ResultsOf 156 CEA patients between April 2013 and March 2020, 30 had decreased SSEP during cross-clamping. The baseline characteristics and intra- and postoperative findings were not significantly different between patients with and without a decrease in SSEP. Among the evaluated parameters, only the direct-ABF ratio (ABF-internal carotid artery/ABF-common carotid artery) differed significantly between the 2 groups (P = 0.011). The direct-ABF ratio ≤ 0.58 was predictive of cerebral ischemia during CEA. ConclusionsDirect-ABF measurement with an ultrasonic blood-flow meter can be useful for predicting cerebral ischemia prior to carotid artery cross-clamping during CEA.

Ultrasonic blood flowmeter with a novel Xero algorithm for a mechanical circulatory support system

Mechanical circulatory support systems (MCSSs) are crucial devices for transplants in patients with heart failure. The blood flowing through the MCSS can be recirculated or even stagnated in the event of critical blood flow issues. To avoid emergencies due to abnormal changes in the flow, continuous changes of the flowrate should be measured with high accuracy and robustness. For better flowrate measurements, a more advanced ultrasonic blood flowmeter (UFM), which is a noninvasive measurement tool, is needed. In this paper, we propose a novel UFM sensor module using a novel algorithm (Xero) that can exploit the advantages of both conventional cross-correlation (Xcorr) and zero-crossing (Zero) algorithms, using only the zero-crossing-based algorithm. To ensure the capability of our own developed and optimized ultrasonic sensor module for MCSSs, the accuracy, robustness, and continuous monitoring performance of the proposed algorithm were compared to those of conventional algorithms after application to the developed sensor module. The results show that Xero is superior to other algorithms for flowrate measurements under different environments and offers an error rate of at least 0.92%, higher robustness for changing fluid temperatures than conventional algorithms, and sensitive responses to sudden changes in flowrates. Thus, the proposed UFM system with Xero has a great potential for flowrate measurements in MCSSs.

Outflow monitoring of a pneumatic ventricular assist device using external pressure sensors.

BackgroundIn this study, a new algorithm was developed for estimating the pump outflow of a pneumatic ventricular assist device (p-VAD). The pump outflow estimation algorithm was derived from the ideal gas equation and determined the change in blood-sac volume of a p-VAD using two external pressure sensors.ObjectivesBased on in vitro experiments, the algorithm was revised to consider the effects of structural compliance caused by volume changes in an implanted unit, an air driveline, and the pressure difference between the sensors and the implanted unit.MethodsIn animal experiments, p-VADs were connected to the left ventricles and the descending aorta of three calves (70–100 kg). Their outflows were estimated using the new algorithm and compared to the results obtained using an ultrasonic blood flow meter (UBF) (TS-410, Transonic Systems Inc., Ithaca, NY, USA).ResultsThe estimated and measured values had a Pearson’s correlation coefficient of 0.864. The pressure sensors were installed at the external controller and connected to the air driveline on the same side as the external actuator, which made the sensors easy to manage.

Middle meningeal arteries with and without transdural anastomosis in Moyamoya disease can be distinguished using intraoperative Doppler sonography

Abstract Transdural anastomosis (TA) from the middle meningeal arteries (MMAs) to the brain is important in maintaining cerebral blood flow in patients with Moyamoya disease. A 16-year-old adolescent girl presented with a transient ischemic attack. Preoperative cerebral angiography revealed TA from the MMA. During surgery, the MMA was exposed on the dural surface directly under the burr hole. Measurement of flow velocity in the MMA with an ultrasonic blood flowmeter revealed increased diastolic flow velocity. As the MMA was assumed to contribute to TA, a new burr hole was made to preserve the MMA, and a bone flap was prepared. Direct and indirect bypass surgeries were performed. Electrocoagulation was not applied to the MMA associated with TA, but the artery was compressed with gelfoam containing fibrin glue to achieve hemostasis. Postoperatively, no evidence of cerebral infarction was detected. Determining which of several MMAs exposed in the surgical field is associated with TA can be difficult. However, measurement of flow velocity with an ultrasonic blood flowmeter to confirm increased flow velocity in the diastolic phase is useful for confirming the presence or absence of TA from the extracranial arteries including the MMA.

もやもや病に対するSTA-MCA bypass術における局所脳血流量の定量的評価システムの開発

Transient neurological deterioration is relatively common after superficial temporal artery-middle cerebral artery bypass surgery for the treatment of moyamoya disease. Evaluation of postoperative cerebral blood flow (CBF) indicated that these symptoms could be associated with hemodynamic alteration. To prevent permanent neurological damage, timely and adequate management of this status is required. However, there is currently no intraoperative evaluation system to predict transient neurological deterioration in the postoperative period. Therefore, in this preliminary study, we evaluated quantitative cortical blood flow using indocyanine green videoangiography, ultrasonic blood flowmeter, and a dedicated software in a case of moyamoya disease. As a result, substantial increase of focal cortical blood flow was calculated by the software. However, no postoperative neurological deterioration was observed, and the postoperative CBF evaluation showed no hyperemia or ischemic status. This system might be useful; however, further evaluation is essential.

Changes of renal hemodynamics in dogs with endotoxemic shock

To explore the changes of renal hemodynamic in dogs with endotoxemic shock (ES) and their potential roles in acute kidney injury (AKI). Canine endotoxic shock model was induced by an infusion of lipopolysaccharide of Escherichia coli through pulmonary artery catheter (PAC). Systemic hemodynamics and left renal blood flow (RBF) was monitored by PAC, pulse index continuous cardiac output (PiCCO) and ultrasonic blood flow meter. Blood and urine specimens were harvested timely for blood gas analysis, renal function tests and biochemical detection. Hemodynamics: CO and RBF fluctuated widely but without any significance (P > 0.05). The values of mean arterial pressure (MAP), systemic vascular resistance (SVR), renal vascular resistance (RVR) and 2-hour urine volume significantly decreased (all P < 0.05) while extravascular lung water (EVLW) increased markedly (P < 0.05). Renal function: There was a drop in CCr, urine osmotic pressure and an elevation in SCr and NAG. RBF was correlated positively with CO (R(2) = 0.630, P = 0.001) .However, it had no correlation with MAP (R(2) = 0.009, P = 0.758) . CCr was correlated positively with MAP (R(2) = 0.415, P = 0.003) . However, it had no correlation with RBF or CO (P > 0.05 ). The auto-regulation curve of GFR had a shift to the right. RBF is positively correlated with cardiac output in endotoxin shock. Renal pressure perfusion may decrease obviously without any noticeable change of renal flow perfusion. The shift of renal auto-regulation under pressure perfusion occurs at the early stage of septic shock.

Tissue Blood Flow Reductions Induced by Remifentanil in Rabbits and the Effect of Naloxone and Phentolamine on These Changes

The purpose of this study was to investigate the effects of naloxone and phentolamine on the blood flow changes in rabbit oral tissue induced by remifentanil during sevoflurane anesthesia. Male Japan White rabbits were anesthetized with sevoflurane under mechanical ventilation. Remifentanil was continuously infused at a rate of 0.4 μg/kg/min. Naloxone 0.01 mg/kg or phentolamine 0.01 mg/kg was administered during remifentanil infusion. Observed variables were systolic and diastolic blood pressures, mean arterial pressure, heart rate, common carotid artery blood flow, tongue mucosal blood flow, mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows. The common carotid artery blood flow was monitored continuously using an ultrasonic blood flowmeter. Tongue mucosal blood flow was monitored continuously using a laser Doppler blood flowmeter. Mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows were measured using a hydrogen clearance tissue blood flowmeter. One-way analysis of variance for repeated measurements followed by the Student-Newman-Keuls test was used. Remifentanil produced decreases in the heart rate, systolic blood pressure, and common carotid artery blood flow by about 15% and mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows by about 30%. In the naloxone group, all variables recovered after naloxone administration. In contrast, in the phentolamine group, tissue blood flow recovered, whereas heart rate, systolic blood pressure, and common carotid artery blood flow did not recover after phentolamine administration. Remifentanil deceased oral tissue blood flow and systemic hemodynamic variables. Naloxone and phentolamine produced a recovery of oral tissue blood flow with and without systemic hemodynamic recovery, respectively.

1522: Pre-Clinical Studies of the Measurement of Volumetric Blood Flow

Verify a previously reported non–invasive, angle independent, 3-D Doppler ultrasound method for measurement of volumetric blood flow in vivo with comparison to an accepted, but invasive, standard method. A GE Logiq 9 with a 4D10L probe acquired 3D Doppler of the femoral and carotid arteries in a canine model. Color flow volume spanned a 6 by 4 cm axial-lateral field of view with a 29° elevational sweep, encompassing the vessel in <7 s. Constant depth planes were used to integrate color flow pixels and power Doppler data was used to correct partial volume effects. An artificial stenosis varied the ambient volume flow by restricting the vessel using a pneumatic cuff. An ultrasonic blood flowmeter with flow probe around the vessel served as the invasive gold standard. Unrestricted, bidirectional, flow was measured as high as 400 mL/min with flow restrictions as low as 20 mL/min. All flow rate estimates (N=23 from 4 animals) were plotted against the gold standard yielding a general line fit of y=0.926x-0.87 (R2=0.95). The percent-error distribution was computed and fitted to a gaussian function with a mean=-7.04% and sigma=9.52%. A secondary curve fit with the slope = 1 and the intercept = 0 yielded R2=0.93. Direct comparison of volume flow rate estimates using volumetric color Doppler and an independent standard showed good accuracy under in vivo pulsatile blood flow conditions. Subsequent comparisons under clinical conditions will demonstrate possible applications.

Technical note: An improved surgical model for the long-term studies of kinetics and quantification of nutrient absorption in swine1,2

An improved technique to study kinetics and quantitative absorption of nutrients in pigs is described. Three female pigs (35 kg of BW) were surgically modified with catheters in the hepatic portal vein and carotid artery and an ultrasonic flow probe around the portal vein. Catheter placement and patency was secured using distal modifications (rings and holes) and nonabsorbable suture. Catheters and flow probe cable were tunneled subcutaneously after exteriorization for further protection. Fibrosis and adhesions in the body cavity were minimized by avoiding excessive manipulation and drying of viscera. Pigs were supported during recovery by intravenous fluid therapy of AA and electrolytes until regular feeding resumed. Catheters were flushed daily with heparinized saline (200 IU/L). After 10 d, pigs were fed a diet based on wheat and soybean meal for 6 consecutive 7-d periods. On d 7, blood was collected postprandially every 15 min from -15 to 60 min, 30 to 240 min, 60 to 480 min, and 120 to 720 min. Blood flow was measured simultaneously. Plasma was analyzed for glucose, and net glucose absorption was calculated from plasma portal-arterial differences x plasma flow [blood flow x (1 - hematocrit)]. The specific improvements for long-term use of this model are distal modifications of the catheters, postoperative treatment using parental nutrition and gut motility drug, prevention of infection of body cavity by further tunneling of catheters and blood flow probe cable, and use of ultrasonic blood flow probes and meter. Blood flow measurements using an ultrasonic blood flow probe was not changed after 52 d compared with 10 d post-surgery, indicating the reliability of this model. This catheterized pig model, thus, will allow the long-term study of the kinetics of nutrient absorption.

Clinical significance of ultrasonic umbilical artery flow analysis in pregnancy with gestational diabetes mellitus

objective To investigate the clinical significance of ultrasonic umbilical artery flow analysis in pregnaney with gestational diabetes mellitus(GDM).Methods Ultrasonic Doppler umbilical artery blood flowmeter was used to detect the systolic/diastolic blood pressure(S/D)ratio,pulse index,and resistance index of umbilical artery in 102 GDM women,aged(29±4),and 105 aged-matched normal pregnant women.The delivering and pefinatal outcomes were observed. Results The S/D ratio,pulse index.and resistance index of the GDM women were 2.55±0.52,1.03±0.23,and 0.59±0.68respectively,all significantly higher than those of the control group(2.11±0.22,0.81±0.13,and 0.52±0.47 respectively.all P＜0.01.The rates of premature rupture of fetal membrane,postpartum hemerrhage,fetal macrosomia,and bad outcome of perinatal infant in the GDM group were 12.7%,7.8%,17.7%,and 12.7%respectively,all significantly higher than those in the control group(1.9%,1.9%,6.7%,and 1.9%,all P＜0.05).The rates of premature labor,premature rupture of fetal membrane,postpartum hemorrhage,fetal macrosomia,and bad outcome of pefinatal infant of the GDM women with the S/D.S/D≥2.5(n=47)were 36.2%,21.3%,17.0%,55.3%,and 21.3%respectively,all significantly higher than those of the GDM women with the S/D＜2.5(n=55)12.7%,3.6%,1.8%,7.3%and 3.6%,(all P＜0.05).Conclusion Ultrasonic umbilical artery flow analysis in pregnancy with GDM is a good method to forecast the placenta function and perinatal outcomes.The poor perinatal outcome is associated with the S/D≥2.5 in GDM. Key words: Pregnancy; Gestational diabetes mellitus; Umbilical arteries; Perinatal

BLOOD FLOW IN RAT CAROTID ARTERY AFTER MECHANICAL INJURY

Introduction. Reactive neointimal proliferation following mechanical injury in rat carotid artery is a commonly used animal model for postangioplasty restenosis. The majority of studies dealing with prevention of restenosis use the anatomical index of neointimal area as the only indicator for success of intervention. The goal of our study is to characterize blood flow in injured carotid arteries. Such information will provide an essential data to be used in studies of the effects of vasoactive anesthetic drugs given to patients with carotid artery stenosis. Methods. The left common carotid artery of 24 Sprague-Dawley rats weighting 350-450 g was injured by three passages of inflated 2F Fogarty catheter under general anesthesia. Blood flow was assessed in the common carotid artery before injury and 30 min after injury. The rats were recovered and a second operation was performed at different time points to study flow in the injured artery. Measurements were performed at 4, 7, 14 and 21 days after injury. For flow measurements an Ultrasonic Blood Flowmeter (Transonic Systems Inc., USA) with microcirculation probe 1RB was used. We also measured flow in other 8 rats at 14 days after injury and compared the flow in the injured artery to the right, uninjured, common carotid artery. Degree of anatomical narrowing was determined by ratio of neointima area to media area (I/M), measured by morfometric computerized planimetry. Results. (Table 1)Table 1Reduction in flow was found immediately after injury and was followed by slow rise in flow to up to 80% of baseline. In the 8 rats studied at 14 days flow in the left common carotid artery was 62% of the flow value in the right uninjured common carotid artery. Neointimal proliferation was not found at the 4th day and only in two rats at 7th day. Significant proliferation was observed at the 14th and 21st day, I/M ratio was 1,28 +/- 0.6 and 1,17 +/- 0.1 accordingly. Discussion. Blood flow in rat carotid artery continued to rise progressively up to 21st day after mechanical injury despite progressive neointimal proliferation and lumen narrowing. Characterization of blood flow in the narrowed rat carotid arteries may serve as a potent research tool for the study of vasoactive anesthetics.

The effect of endovascular aortic stents placed across the renal arteries

To investigate renal artery patency and renal function after deployment of aortic stents covering the orifices of renal arteries. Prospective open animal study. Department of Experimental Surgery at a university hospital. Twenty-three pigs were used. Ten pigs were observed for 1 h after graft-anchoring aortic stents, Gianturco (5) and Palmaz (5), were placed so that the stents covered the renal arterial orifices. In 13 pigs, Gianturco (6) and Palmaz (7) stents without grafts were placed over the renal arteries and left in situ for 7 days. Renal function and blood flow were measured by renograms, iohexol clearance and ultrasonic blood flow meter and patency was verified by angiograms. The kidneys were microscopically examined for signs of ischaemia and microemboli. One renal artery covered by a graft-anchoring Gianturco stent occluded. The remaining renal arteries remained patent without any significant decrease in renal blood flow after stent deployment. Normal renal function and histology was maintained. Aortic stents placed at the level of the renal arteries do not affect renal blood flow within 1 week in this experimental model. This may prove valuable in endovascular treatment of aortic aneurysms and in other procedures involving stents.

Radio telemetry directional ultrasonic blood flowmeter for use with unrestrained animals.

Radio telemetry directional ultrasonic blood flowmeter for use with unrestrained animals.

A hemodynamic study of the biventricular bypass total artificial heart with special reference to intrarenal flow distribution

The present study was undertaken to determine whether a biventricular bypass total artificial heart driven in an independent variable rate mode can maintain circulation in vital organs such as the brain and kidney. Special emphasis was placed on investigating flow distribution. Two pusher-plate pumps were used to bypass the right and left ventricles in 11 goats and 12 sheep with fibrillating hearts. The carotid artery and renal artery flows were then measured using an ultrasonic blood flow meter and the regional renal blood flow calculated using the hydrogen gas clearance method. Thirteen animals were kept alive for 24 hours in physiological hemodynamics but 10 animals died of shock within 24 hours. In the latter group, a decrease in the fractional distribution of flow to the kidney and renal cortex were observed. At a peak aortic pressure of less than 100 mmHg, the renal flow ratio was significantly correlated with the peak aortic pressure. It was thus concluded that the biventricular bypass total artificial heart operated in an independent variable rate mode maintains physiological circulation and is therefore able to substitute for native heart function in any situation.

Integrated circuits for a bidirectional implantable pulsed Doppler ultrasonic blood flowmeter

The application of integrated circuits in medical implants and the complexity of these implants have increased at a rapid pace in the past few years. The need, however, still exists for a highly accurate and stable telemetry system for the measurement of blood flow. Two custom-designed ICs have been realized to resolve this problem. These ICs form the heart of a totally implantable pulsed Doppler ultrasonic bidirectional blood flowmeter; one circuit performs the basic timing functions, and the second implements low-level linear signal processing. For a small implanted package (3.8/spl times/2.8/spl times/0.8 cm/SUP 3/), these ICs must meet the stringent requirements of low-voltage operation (2.2-2.8 V), low power (<40 mW), high stability (short-term timing jitter <50 ppm), and the minimum of external components. Using a quadrature direction detecting technique, the circuits sense both positive and negative flow and produce a multiplexed telemetry signal. The approach used minimizes parts count and power drain and maximizes channel-to-channel matching in the multiplexed signal.

Direct calibration of a totally implantable pulsed Doppler ultrasonic blood flowmeter

Page H537: H. V. Allen, M. F. Anderson, and J. D. Meindl. “Direct calibration of a totally implantable pulsed Doppler ultrasonic blood flowmeter.” Page H542: Table 1, footnote--the equation for the correlation coefficient should read (See PDF) Similarly, the equation for flow should read (See PDF)

Direct calibration of a totally implantable pulsed Doppler ultrasonic blood flowmeter.

A totally implantable pulsed Doppler ultrasonic blood flowmeter has recently been developed to provide information on the velocity-flow profile in a vessel as well as its diameter. Volume flow can be indirectly obtained according to the formula: Q = (phi/4)(diam)2-v. In order to determine the accuracy of this estimate, in vivo direct bleedout measurements were performed on the abdominal aorta of six dogs with an overall accuracy in 77 trials of +2.0 +/- 8.7% (mean +/- 1 SD). The best-fit mean linear regression line was found to be: flowmeter output = 1.013-true flow + 5.1 ml/min. The scatter in the flowmeter's accuracy is thought to be due to small variations in the angle of the transducer. The source of the 2% overestimation in the mean accuracy could not be directly attributed to any one condition; the error is sufficiently small that in many cases it can be neglected.

Low power integrated circuits for an implantable pulsed Doppler ultrasonic blood flowmeter

Describes two custom integrated circuits which were developed for an implantable pulsed Doppler ultrasonic blood flowmeter. Prime design goals were a minimum circuit volume, minimum power consumption, and operation at low supply voltages. The first of the two IC's performs system timing functions and produces the ultrasonic transmit burst. It can deliver up to 40 mW of peak output power at 50 percent efficiency and requires 3.7 mW standby power. The second IC, containing an RF amplifier, mixer and output amplifier, provides 54 dB conversion voltage gain for an 0.8 MHz bandwidth centered at 5.8 MHz, <3 dB noise figure, a dynamic range of 40 dB, and 1 /spl mu/s recovery time from a 1 V overload. This chip requires 2.7 mW power input.

Ultrasonic blood flowmeter yielding instantaneous velocity profile by real-time phase detection

A new method of measuring the spatial velocity profile in blood vessels is presented. It is based on the detection of the phase difference between successive echoes arising from bursts of ultrasound. The echoes are preconditioned by a circuit that cancels the stationary components without affecting the range information.

Pitfalls using Doppler ultrasound to transduce blood flow.

General testing procedures which will ascertain whether a Doppler ultrasonic blood flowmeter is correctly designed and operating properly are presented. A commercial Doppler ultrasonic blood flowmeter using the procedure is evaluated. Two pitfalls were encountered which prevented its proper operation. High-frequency response was inadequate, which introduced a nonlinearity into the input-output calibration curve. Low-frequency gain was too high, resulting in wall-motion artifacts. These problem areas are described in detail, and a remedy for each is suggested.