Flowmeter System Research Articles

Development of Pulse Ultrasonic Doppler Method for Flow Rate Measurement in Power Plant Multilines Flow Rate Measurement on Metal Pipe

Ultrasonic Doppler method for a flow metering system has been developed. The method has the capability to obtain instantaneous velocity profiles along the ultrasonic beam. Our purpose is to apply the ultrasonic Doppler method to a flow rate measurement of feed- or recirculation- water in power plants. The principle of the flow measurement method is based on the integration of an instantaneous velocity profile over a pipe diameter. Hence, it is expected to eliminate installation problems such as entry length, also to follow transient flow rate precisely by increasing ultrasonic transducers. In this paper, we report that the errors are less than 1% just below a bend and sudden expansion pipe employing three measuring lines. And then, for constructing a basic system of a flow rate measurement in power plants, a transmission of ultrasound through a metallic wall is investigated, at first. Afterward, since there is no ultrasonic reflectors in the feedwater in power plants, cavitation bubbles are induced as ultrasonic reflectors and the results are appeared that cavitation bubbles are effective when the pipe material is metallic.

Development of Pulse Ultrasonic Doppler Method for Flow Rate Measurement in Power Plant Multilines Flow Rate Measurement on Metal Pipe

Ultrasonic Doppler method for a flow metering system has been developed. The method has the capability to obtain instantaneous velocity profiles along the ultrasonic beam. Our purpose is to apply the ultrasonic Doppler method to a flow rate measurement of feed- or recirculation- water in power plants. The principle of the flow measurement method is based on the integration of an instantaneous velocity profile over a pipe diameter. Hence, it is expected to eliminate installation problems such as entry length, also to follow transient flow rate precisely by increasing ultrasonic transducers. In this paper, we report that the errors are less than 1% just below a bend and sudden expansion pipe employing three measuring lines. And then, for constructing a basic system of a flow rate measurement in power plants, a transmission of ultrasound through a metallic wall is investigated, at first. Afterward, since there is no ultrasonic reflectors in the feedwater in power plants, cavitation bubbles are induced as ultrasonic reflectors and the results are appeared that cavitation bubbles are effective when the pipe material is metallic.

Apparent slip flows in hydrophilic and hydrophobic microchannels

The slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth are examined experimentally. High-precision microchannels were treated chemically to enhance their hydrophilic and hydrophobic properties. The flow rates of pure water at various applied pressure differences for each surface condition were measured using a high-precision flow metering system and compared to a theoretical model that allows for a slip velocity at the solid surface. The slip length was found to vary approximately linearly with the shear rate with values of approximately 30 nm for the flow of water over hydrophobic surfaces at a shear rate of 105 s−1. The existence of slip over the hydrophilic surface remains uncertain, due to the sensitivity of the current analysis to nanometer uncertainties in the channel height.

304 超音波ドップラー流速分布測定法を用いた複測定線流量計測法

Ultrasonic Doppler method for flow metering system has been developed. The principle is based on the integration of instantaneous velocity profile over a pipe diameter so that it is expected to be able to eliminate installation problems such as entry length as well as to follow transient flow rate precisely. Therefore, in the present study, we reported the results of multiline flow rate measurement employing this method Flow metering principle by ultrasonic Doppler method in a circular pipe depends on the alignment of measuring lines. And in most cases, metallic pipes are used both in industrial factories and power plants. In this paper, the influence of the number of measuring lines and the comparison among several kinds of metallic pipes on the flow rate measurements have been investigated for nondeveloped flows in a vertical pipe.

ICONE11-36615 DEVELOPMENT OF PULSE ULTRASONIC DOPPLER METHOD FOR FLOW RATE MEASUREMENTS OF POWER PLANT : Multiline flow rate measurement on metal wall pipe flow

Pulse Ultrasonic Doppler method for flow metering system has being developed. The principle is an integration of instantaneous velocity profile over a pipe diameter so that it is expected to be able to eliminate installation problems such as entry length as well as to follow transient flow rate precisely. Flow metering principle by pulse ultrasonic Doppler method in a circular pipe depends on the alignment of measuring lines. In most cases metallic pipes are used at power plant and other plants. This system has been developed to be applied for conventional piping system of metallic wall [1] [2]. Laboratory experiments have shown a very good agreement with the flow rate measurement using conventional orifice flow meter. Additionally, it shows a good tractability for transient behavior. In order to establish the technique and investigate its absolute accuracy, the comparison among experimental results has been performed at the NIST calibration stand [3]. On the other hand, reflectors are needed for flow rate measurement using Pulse Ultrasonic Doppler method, and it's not easy to seed the water with some particles at power plants. In this paper, influence of number of measuring lines and the difference of some metallic pipes on the flow rate measurements have been investigated for non-developed flows in a vertical pipe. And for reflectors ultrasonic cavitations bubbles have been applied. [1] Kikura, H., et al., Proc. of 3^<rd> ASME/JSME Joint Fluid Engin. Conf. (1999), FEDSM99-7141. [2] Mori, Metallic., 7th Int. Conf. on Ncl. Engin. (ICONE7), Tokyo (1999), ICONE-7429. [3] Takeda, Y., et al., ASME 2000 Fluids Engn. Divi. Summer Meet., (2000), FEDSM2000-11102

Development of a novel flow metering system using ultrasonic velocity profile measurement

A new flow metering system using an ultrasonic Doppler method has been developed. By this method, an instantaneous velocity profile is measured and its integral is evaluated to give flow rate. Instead of making multidimensional flow mapping to evaluate its performance, the method was assessed in laboratory experiments where single line measurements were used over the whole pipe diameter or radius to determine the flow rate. The system shows a good capability of tracking transient flows. Its accuracy was investigated using the National Institute of Standards and Technology (NIST) flow standards in Gaithersburg, MD, USA; averaged results show its deviation from NIST results to be 0.18% for Re=400 K and 0.58% for Re=2.6 M. Good repeatability and reproducibility were also confirmed.

Detection of hydraulic pathways in fractured rock masses and estimation of conductivity by a newly developed TV equipped flowmeter

We developed a flowmeter well logging system that can detect hydraulic pathways in fractured rock mass and applied it to a site where granitic rock is widely distributed. Hydraulic pathways were detected by flow velocity measurement using the Doppler effect of ultrasonic waves, and fractures which acted as hydraulic pathways were specified by a borehole TV camera attached to the system. Fractures with hydraulic conductivity more than 10−7m/s were detected by the logging system, and the accuracy of the measured conductivities was within one order of magnitude. The newly developed flowmeter system can provide information on the location and conductivity of hydraulic pathways at the borehole for field employment in the earliest stages of site characterization surveys.

Determination of parotid urea secretion in sheep by means of ultrasonic flow probes and a multifactorial regression analysis.

For determination of the dynamics of parotid urea secretion in conscious sheep, a previously standardized transit time ultrasonic flow metering system was used to measure bilateral parotid flow. Six ewes fed for ad libitum consumption were prepared under halothane anesthesia with ultrasonic probes around both parotid ducts; these ducts were also cannulated orally. After probe encapsulation (8 d), parotid flows were recorded during 24 h, and samples of saliva and blood for urea determination were obtained hourly. Jaw movements were recorded by means of a submandibular balloon to monitor feeding behavior. Urea concentration in parotid saliva was 60 to 74% of that in plasma (a positive linear correlation existed) and was poorly influenced by the parotid flow. The amount of urea secreted with parotid saliva was directly related to the salivation rate. To calculate the urea secretion in parotid saliva, a multiple linear regression model was developed from computer-calculated parotid flows over 1-min periods and plasma urea concentration. The model was accurate because the plot of calculated vs measured values was not significantly different from the line of identity. The daily parotid urea N varied from .35 to 1.02 g among ewes. The higher urea secretion rate found during rumination and eating (1.32+/-.42 and .98 +/-.33 mg/min, respectively) vs. during rest (.60+/-.39 mg/ min, P<.05) was due to higher salivation rates (5.17 +/-1.46, 3.56+/-.90, and 2.04+/-.52 mL/min, respectively, P<.05) rather than to changes in saliva urea concentrations (saliva:plasma urea ratio = .65+/-.04, .67+/-.04, and .68+/-.03, respectively). Of the daily parotid urea output, 40.8% was secreted during rest. The contribution of parotid urea N to the ruminal N pool was relatively small (1.2 to 3.7% of the N intake, which was 23.0 to 33.6 g/d). These techniques allowed direct and precise measurements of parotid urea secretion without disturbing the animal or altering the physiological regulation of salivary secretion.

Numerically based design of an orifice plate flowmetering system for human respiratory flow monitoring.

During certain medical procedures, it is important to continuously measure the respiratory flow of a patient, as lack of proper ventilation can cause brain damage and ultimately death. The monitoring of the ventilatory condition of a patient is usually performed with the aid of flowmeters. However, water and other secretions present in the expired air can build up and ultimately block a traditional, restriction-based flowmeter; by using an orifice plate flowmeter, such blockages are minimized. This paper describes the design of an orifice plate flowmetering system including, especially, a description of the numerical and computational techniques adopted in order to simulate human respiratory and sinusoidal air flow across various possible designs for the orifice plate flowmeter device. Parallel computation and multigrid techniques were employed in order to reduce execution time. The simulated orifice plate was later built and tested under unsteady sinusoidal flows. Experimental tests show reasonable agreement with the numerical simulation, thereby reinforcing the general hypothesis that computational exploration of the design space is sufficiently accurate to allow designers of such systems to use this in preference to the more traditional, mechanical prototyping techniques.

Changes in tissue oxygenation of the porcine liver measured by near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) is a novel method for the measurement of tissue oxygenation and may have a role in monitoring liver oxygenation and viability. The aim of this study is to validate the application of NIRS for monitoring hepatic tissue oxygenation. Large Landrace pigs (n = 12) underwent laparotomy and liver exposure. Total hepatic blood flow (THBF) was measured by the Transonic Medical Flowmeter system. NIRS probes were placed on the liver surface to continuously record changes in hepatic tissue oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and the reduction-oxidation state of cytochrome oxidase (Cyt Ox). Reduction of hepatic tissue oxygenation was achieved by hepatic vascular inflow occlusion (n = 6) or reduction of inspired oxygen (FIO2; n = 6). The THBF changes correlated significantly with hepatic HbO2 (r = 0.84; P <.001) and Cyt Ox (r = 0.88; P <.001). With reduction of FIO2, a significant correlation was found between arterial oxygen saturation and hepatic HbO2 and Hb (r = 0.99 and r = -0.99, respectively; P <.0001). NIRS measurement of liver parenchymal oxygenation correlates well with changes in liver blood flow and arterial oxygenation.

Heterogeneous distribution of microcirculatory flow in the gastrointestinal tract during haemorrhage in anaesthetized pigs

O-9 Introduction: Hypoperfusion of splanchnic organs during haemorrhagic shock may lead to sepsis and multiple organ failure. Little is known about dynamic flow distribution within the splanchnic region in circulatory shock. Recently a multichannel laser Doppler flowmeter system (LDF) has become available that can measure microcirculatory flow (MBF) in multiple organs simultaneously and continuously. Objectives: The aim of this study was to compare systemic (cardiac index; CI), regional (superior mesenteric artery flow; SMA flow), and local flow (MBF) in multiple abdominal organs during haemorrhagic shock in anaesthetized pigs. Methods: Seven pigs (25 kg), anaesthetized with 0.6% halothane, N2O:O2(2:1), fentanyl and pancuronium, were bled to a MAP of 40 mmHg. After 180 min the shed blood was retransfused. MBF was measured in the intestinal mucosa (stomach, jejunum, colon), pancreas, liver and kidney by LDF, and SMA flow by ultrasonic transit time flowmetry. Data are presented as mean percentages of baseline. Results: During shock, MBF decreased by 15-30% in the stomach and colon mucosa, similar to the SMA flow, while the jejunal flow remained virtually unchanged. Flow in the liver and kidney decreased somewhat more (30-40%), but flow in the pancreas was most severely affected and decreased by 60%. After retransfusion of shed blood, SMA flow increased to 30% above baseline. Although microcirculatory flow in the pancreas increased slightly after retransfusion it remained 20% below baseline. Conclusion: 1. MBF in the intestinal mucosa of the stomach and colon decreased similarly to the SMA flow during shock and recovered promptly after retransfusion of shed blood. 2. In contrast, MBF in the jejunal mucosa did not decrease during shock, suggesting an intact autoregulation. 3. The pancreas appears to be particularly vulnerable to haemorrhage, since MBF decreased significantly more than CI and SMA flow.

Hemodynamic Monitoring of the Contralateral Testis during Unilateral Testicular Torsion Describes the Mechanism of Damage

Contralateral testicular perfusion during unilateral testicular torsion was evaluated using simultaneous blood flow and O₂ content determinations. Two groups, each consisting of 7 rats, were studied. Sham operation or 720° clockwise twisting was performed on the left testes, and blood flow, O₂ content and temperatures were monitored in the right testes for 180 min. An ultrasonic perivascular Doppler flowmeter system, an electronic thermometer and an O₂ electrode were used for the monitoring. The contralateral testicular blood flow and relative O₂ contents were stable in the control group. However, the initial and 180 min blood flow values decreased from 0.21 ± 0.04 to 0.11 ± 0.02 ml/min (p < 0.001), and the O₂ contents from 0.857 ± 0.123 to 0.319 ± 0.037 (1.0 corresponds to 19.6 mm Hg pO₂, p < 0.05) in the experimental group. Unilateral testicular torsion decreases the blood flow and O₂ content of the contralateral testis. The contralateral testicular injury encountered following unilateral testicular torsion might result from hypoxia following the decrease in blood flow.

Validation of transonic small animal flowmeter for measurement of cardiac output and regional blood flow in the rat.

The objective of the present study was to validate a transonic flowmeter system with two probes (model 3SS for cardiac output (CO) and 1RB for organ flows) in Sprague-Dawley (SD) rats first by measuring blood flow through pump-infused isolated renal artery and ascending aorta, and then through measurements of CO and renal, mesenteric, and hindquarter blood flow (RBF, MBF, HBF) in vivo. We measured in vivo baseline flow and changes in flow induced by dopamine and propranolol for CO, prostaglandin E2 (PGE2), and angiotensin II (AII) for RBF and pentobarbital sodium for MBF and HBF. Correlations between meter and pump flow were linear (r = 0.999, p < 0.001) with close agreement both in ascending aorta and renal artery flow measurements. The baseline values were 15 +/- 0.7 ml/100 g/min for CO, 4 +/- 0.1 ml/100 g/min for RBF, 7 +/- 0.3 ml/100 g/min for MBF, and 6 +/- 0.3 ml/100 g/min for HBF, respectively. The system reliably detected increase and/or decrease in CO and regional blood flows. The transonic flowmeter system is accurate, highly reproducible, and compatible with other established techniques for measuring CO and regional blood flows in the rat.

Operating Experience With ESP's and Permanent Downhole Flowmeters in Wytch Farm Extended-Reach Wells

Summary One-third of the recoverable reserves in British Petroleum CO.'s U.K. onshore oil field, Wytch Farm, lie in an offshore extension of the field. These reserves, which have been undeveloped until recently, are now being exploited with electric submersible pumps (ESP's) in extended-reach wells drilled from onshore wellsites. The relatively high productivities achieved as a result of successful horizontal completions have pushed ESP technology to the limits in terms of capacity and power requirements. This paper presents a case history of the unique set of problems encountered during and subsequent to startup of the ESP's in the first three wells. The problems, in particular pump-suction-blockage problems, were directly attributable to the position of the ESP's in the near-horizontal section (82 to 85°) of the wells. The paper also describes the innovative permanent downhole flowmeter system incorporated in the completion. The system measures and logs flow-rate data, pump-suction and -discharge pressures, and temperature. Examples are presented that clearly demonstrate how these data have been invaluable in understanding the problems encountered in the initial extended-reach wells and the role the system has played in extending ESP run lives. Finally, completion-equipment modifications and operating-procedure changes, successfully introduced to resolve the problems encountered in the first two wells and to avoid them in subsequent wells, are described. Introduction Wytch Farm, on the southern coast of England ˜100 miles southwest of London (Fig. 1), is the largest onshore oil field in western Europe. The main reservoir lies under Poole Harbor and extends offshore under Poole Bay. Poole Harbor has been designated as an area of outstanding natural beauty, with sites of special scientific interest and special protection areas, and is noted for its landscape, ecology, and amenity value.

Respiratory and cardiovascular adjustments during exercise of increasing intensity and during recovery in thoroughbred racehorses.

A new design of flowmeter is described and used in a comprehensive study of the respiratory and cardiovascular adjustments that occur during a standardised exercise test in Thoroughbred horses. The flowmeter system and associated lightweight, fibreglass mask (total mass, 0.7 kg) have a maximum dead space of 500 ml and negligible resistance to airflow. They have no systematic effect on blood gases and, together with a rapidly responding mass spectrometer, enable an accurate computation of gas exchange to be performed together with breath-by-breath determination of other respiratory variables. At the highest level of exercise (12 ms-1 on a 3 degrees incline), the rate of oxygen uptake (VO2) and carbon dioxide production (VCO2) increased to 29.4 times and 36.8 times their resting values, respectively. Respiratory minute volume (VE) increased to 27.0 times its resting value, with respiratory frequency (fR) making the major contribution at the walk and trot. However, with increasing cantering speeds, fR changed little as it was locked in a 1:1 fashion to stride frequency, and tidal volume (VT) then made the major contribution to the increase in VE. The ratio of ventilatory dead space (VD) to VT in resting horses was lower than that previously reported in the literature and this could be the result of the different respiratory recording systems that were used. There was a close relationship between VT and stride length at increasing cantering speeds. Despite the fact that alveolar ventilation (VA) was well matched to VO2, there was a significant reduction in arterial PO2 (PaO2) when the horses cantered at 8 ms-1 and this eventually fell to 34% below the resting value. The present data tend to support the idea that VA/Vb (where Vb is cardiac output) inequalities are important in causing this hypoxaemia. However, the reduction in PaO2 was more than compensated for by an increase in haemoglobin concentration, [Hb], so the concentration of oxygen in the arterial blood (CaO2) was significantly above the resting value at all levels of exercise. Both lactate concentration and PaCO2 increased during exercise, causing substantial reductions in pH of both arterial and mixed venous blood. This would have inevitably shifted the oxygen equilibrium curve of the Hb to the right, desaturating the arterial blood and thus exacerbating the effect of the hypoxaemia, as would the almost 4 degrees C rise in blood temperature. The tight respiratory/locomotor linkage might prevent the acidosis and hyperthermia having the stimulatory effects on VE that they have in humans at high work loads.(ABSTRACT TRUNCATED AT 400 WORDS)

Subsea Processing and Control System in the GASP Project: Testing of the Prototype System

Summary The subsea production and processing system developed under the Goodfellow Assocs. Subsea Production (GASP) project involved two stages of separation thatled to the production of exportable-quality crude oil production ofexportable-quality crude oil by pipeline. The produced gas is transported alonga separate line. This paper describes key elements of the subsea processsystem. A prototype system was developed during the second phase of theproject. The system was tested under dry and submerged conditions in a drydock. Key features of the proto type system and the tests carried out aredescribed. Prototype testing proved the viability of the GASP system and helpedidentify areas requiring particular attention and improvement for futureapplications. Introduction The main objective of the GASP project was to develop a subsea productionsystem suitable for the development of satellite marginal fields. This was ajoint industry project supported by the European Community project supported bythe European Community and eight major oil companies. An overview of the systemand the economics are addressed in a separate paper. This paper highlights somekey features of the process and control system and the extensive testing of theprototype system. The base case was a satellite field 30 km from the motherplatform. The field consists of four production wells and four water-injectionwells. A general view of the field scenario is shown in Ref. 1. Design Parameters. Table 1 summarizes the main parameters for the design ofthe system. The sensitivity case shows the range of values of interest to theparticipating oil companies and does not reflect the limits for future fieldapplications. The quality requirements for the processed crude oil were notnecessarily the processed crude oil were not necessarily the minimum or optimumfor the system but were set to a relatively more demanding level to allowexport of produced oil directly through an existing trunkline. The high exportpressure specified for the crude oil was to meet the operating pressurespecified for the trunkline. Options for simplifying the process system arediscussed later. process system are discussed later. Process Flow Diagram. Fig.1 shows the Process Flow Diagram. Fig. 1 shows the simplified process flowdiagram (PFD). Two identical production trains were adopted. Each train servestwo wells with an option to divert flow from one train to another through thetest-meter loop. Production testing of individual wells is achieved through abypass valve leading to the test header. The multiphase test meter enablessubsea measurement of individual wells without the need for a test line or aseparate test separator. The separator comprises two stages of gas/liquidseparation to meet the specified true vapor pressure (TVP) requirements. Thisleads to production of gas at different pressures (first- and second-stageseparators). pressures (first- and second-stage separators). An ejector is usedto commingle the gas products from the two sources for export products from thetwo sources for export through a single line. Oil and water are transportedalong separate lines for the base case. Separate booster pumps are used foreach train. This helps to keep the pump duty requirements within the range ofexisting pump designs and improves the availability pump designs and improvesthe availability of the system. A fiscal flowmetering system shown in the PFD, measures the crude oil rate for fiscal PFD, measures the crude oil rate forfiscal metering purposes as the product enter a common subsea trunkline. If theproduced oil is transported directly to the mother platform, this meter is notnecessary. The platform, this meter is not necessary. The first phase of thestudy established that designing a reliable subsea meter that met the desiredaccuracy, proving, and availability targets needed for fiscal metering wouldnot be easy and would require a novel approach. Adapting the existinggeneration of fiscal meters was feasible but would result in a cumbersome andtedious system requiring a costly maintenance and proving program. Process System Design. At the outset of Process System Design. At the outsetof work, the aim was to simplify the system as much as possible. Separation ofgas, oil, and water is a well-developed technology. For subsea application, however, the following points affect the design of the separator and may changeits features from those of topside units.Modularization to reduce size andweight if the unit is to be retrieved for maintenance purposes.Capacity tocope with the expected slug and plug flow conditions.Minimum use ofinternals to minimize maintenance requirements.Generous capacity to copewith flow functions, any slowness in control-valve responses, and possiblefoaming.Generous capacity to cope with slackness in the level monitoringand control and to avoid unnecessary system shutdown for minor equipmentmalfunctions.Capability to withstand pressures well above the operatingpressure, although it is feasible to include a pressure-relief system on theseparator to minimize the rating.

Characteristics of laser Doppler flowmeters with differing optical arrangements.

Recently, various laser Doppler flowmeter (LDF) systems have been used for evaluation of tissue microcirculation. However, indifference has often been shown by doctors and researchers regarding their sampling volume, stability and accuracy, which differ with various optical arrangements. In this study we evaluated the characteristics of three LDF systems with different optical arrangements. The sampling depths in both blood and tissue were found to differ with the different optical arrangements, although the laser power emitted from the probes is nearly equivalent. Each depth significantly changed at haematocrits between 5.0 and 36.5%. The stability and the accuracy of the measurements also differed. In the practical case of tissue microcirculation it is important to measure blood flow with an understanding of the material differences in the characteristics of the LDF systems.

Effect of postural change on common femoral artery volume flow, measured by duplex ultrasound, in normal subjects and patients with peripheral vascular disease

Regulatory peripheral vasoconstriction occurs in response to adoption of the erect posture. Mildly ischaemic limbs are thought to exhibit near normal responses, but patients with rest pain show increases in blood flow on limb dependency. Previous methods of limb blood flow quantification (xenon clearance and venous occlusion plethysmography) have inherent difficulties when applied in these situations. We studied orthostatic responses in 12 normal subjects (aged 22–74 years (median 52)) and 16 patients (aged 21–83 (median 48)) with mild and severe peripheral vascular disease, using a duplex flowmeter system. In the normal subjects changes in the 60s mean, common femoral artery volume flow values were as follows (mlmin −1 (1 SD)): 77 (83), − 78 (116) and − 190 (136), for elevation, dependency, and standing respectively. For claudicants ( n = 7) the values were 18 (37), − 112 (123) and − 216 (103) respectively. In rest pain patients ( n = 9) the responses were reversed, being − 252 (124), 131 (89) and 184 (85) respectively. Significant differences were apparent between elevation, dependency and standing flows in each of the three groups ( P < 0.0001). Normal subject and claudicant responses on elevation and dependency differed significantly ( P < 0.0001 and 0.03 respectively). On standing, the responses were similarly significantly different. The rest pain group displayed characteristically different responses compared with both normal subjects and claudicants for each postural change ( P < 0.0001 in all cases). Duplex ultrasound volume flowmetry is non-invasive and offers an excellent method of quantifying physiological changes.

Selective Electrical Stimulation of Postganglionic Cerebrovascular Parasympathetic Nerve Fibers Originating from the Sphenopalatine Ganglion Enhances Cortical Blood Flow in the Rat

Recently, the origins and pathways of cerebrovascular acetylcholine- and vasoactive intestinal polypeptide-containing nerves have been elucidated in detail in the rat: The sphenopalatine ganglion is the major source for postganglionic parasympathetic fibers to the vascular beds of the cerebral hemispheres. To clarify the functional role of the nerves on cerebral blood vessels in vivo, brain cortical microvascular blood flow was measured in rats during electrical stimulation of these particular postganglionic fibers. Animals were subjected to transection of the right nasociliary nerve 2 weeks before the flow measurements to eliminate activation of peptidergic sensory fibers. Relative change in microvascular blood flow was continuously recorded by a laser-Doppler flowmeter system under alpha-chloralose anesthesia. The postganglionic fibers were electrically stimulated just proximal to the ethmoidal foramen by a bipolar platinum electrode (5 V; 0.5 ms; 3, 10, 30, 60 Hz; as a continuous stimulation for 90 s). Stimulation at 10 Hz induced a marked increase of the cortical blood flow (CoBF) on the ipsilateral side, whereas no change was observed on the contralateral side. It reached a maximum mean value of 42.5% at 46 s, and then slightly declined during the remaining stimulation period. No significant changes were observed in the mean arterial blood pressure or blood gases during or after stimulation. Both atropine and scopolamine failed to alter this flow increase. Electrical stimulation of the postganglionic fibers at different frequencies revealed a maximal increase in the CoBF at 30 Hz in the control situation (47.2%), but at 10 Hz after scopolamine administration (51.6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect on cortical blood flow of electrical stimulation of trigeminal cerebrovascular nerve fibres in the rat

It has recently been demonstrated in the rat that the majority of cerebrovascular pain fibres containing immunoreactive substance P and calcitonin gene-related peptide reach the vessels via the nasociliary nerve, a branch of the ophthalmic trigeminal division. In order to elucidate the effect of these nerves on blood flow in vivo, the relative changes in cortical microvascular flow were continuously monitored by a laser-Doppler flowmeter system during electrical nerve stimulation, with the central nerve connection cut and after removal of neighbouring dilatory parasympathetic nerves. The nasociliary nerve on one side was stimulated proximal to the ethmoidal foramen by a bipolar platinum electrode. Activation at different frequencies, continuously or as bursts with a constant voltage, impulse duration and total stimulus length, revealed that a maximum increase in blood flow amounting to 16.7% after 36 s was obtained with continuous stimulation at 10 Hz. Flow markedly declined during the following 1-min stimulation period. No changes in contralateral cortical blood flow, mean arterial blood pressure or blood gases were observed during or after stimulation. The present study demonstrates for the first time that direct and selective electrical activation of trigeminal cerebrovascular nerves induces an increase, albeit small and transient, in blood flow within the brain.