Measurement Of Blood Flow Volume Research Articles

Fetal volume blood flow and umbilical artery flow velocity waveform analysis: a comparison

The estimation of fetal umbilical vein and aortic volume blood flow was compared with umbilical artery flow velocity-time waveform analysis in 42 pregnancies. The volume blood flow measurements were made with a combined linear array B-mode and pulsed Doppler ultrasound system. The umbilical artery flow velocity-time waveform analysis was made with either pulsed or continuous wave 2 MHz Doppler ultrasound and the systolic/diastolic (A/B) ratio was used as an index of flow resistance. There was no difference when continuous wave was compared to pulsed Doppler ultrasound as a method of recording flow velocity waveforms. Analysis of the umbilical artery flow velocity-time waveform was more sensitive (100%-50%) than the measurement of umbilical vein volume blood flow (ml/kg/min) in the detection of the small-for-gestational age (SGA) fetus. The predictive value of a positive test was higher (71%-45%) while specificity was similar (88%-81%). Descending aortic volume flow was reduced in only one SGA fetus. The increase in umbilical placental downstream resistance (high systolic/diastolic ratio) was associated with a reduction in the percentage of fetal aortic blood flow directed to the umbilical placental circulation.

Hemodynamic study of internal carotid artery stenosis and occlusion: value of combined isotopic measurements of regional cerebral blood flow and blood volume

The assessment of the intracranial hemodynamic consequences of obstructive lesions of the carotid artery by measuring resting rCBF is inadequate because cerebral blood flow may remain constant in spite of significant drops in the intraluminal pressure due to autoregulation. Moreover, flow may be permanently decreased following cerebral infarction, even if the arterial anatomical conditions have resumed their normal state because of the decreased metabolic demand of an infarcted area. Measurement of the regional cerebral blood volume (rCBV) helps with the hemodynamic assessment of these conditions, since there is a linear and inverse relationship between intraarterial pressure and intracranial blood volume. In 24 patients exhibiting various carotid and ischemic brain lesions we studied both rCBF and rCBV. The latter is a comparative measure between hemispheres obtained by single photon emission tomography after autotransfusion of 99m Technetium labeled erythrocytes. There was no correlation between rCBF and clinical status, CT scan or arterial lesions. There was no correlation between rCBV and clinical status or CT scan. There was, however, an interesting correlation between rCBV and the severity of the arterial lesion. The rCBV was symmetrical in all patients with normal or moderately stenotic carotid arteries before and after operation. In some patients with severe unilateral stenosis or occlusion, there was a significant relative increase of rCBV in the hemisphere downstream from the lesion, which disappeared after surgery (endarterectomy or extra-intracranial bypass). In some patients with severe and bilateral carotid lesions, we noted an asymmetry in rCBV that disappeared after a unilateral operation. Other patients with similar lesions develop asymmetry only after an operation that resulted in a relative increase in rCBV in the hemisphere supplied by the non-operated artery. In conclusion analysis of these results suggests that in this series of patients, rCBV modifications were the consequence of cerebral autoregulation distal to the arterial lesions and provided satisfactory assessment of hemodynamic improvement after surgical repair.

Estudio hemodinamico de la estenosis y oclusion de la arteria carotida interna: valor de la combinación de la medida de flujo regionam cerebral y volumen sanguíneo mediante isótopos

Estudio hemodinamico de la estenosis y oclusion de la arteria carotida interna: valor de la combinación de la medida de flujo regionam cerebral y volumen sanguíneo mediante isótopos

Fetal volume blood flow and umbilical artery flow velocity waveform analysis: a comparison

Summary. The estimation of fetal umbilical vein and aortic volume blood flow was compared with umbilical artery flow velocity‐time waveform analysis in 42 pregnancies. The volume blood flow measurements were made with a combined linear array B‐mode and pulsed Doppler ultrasound system. The umbilical artery flow velocity‐time waveform analysis was made with either pulsed or continuous wave 2 MHzDoppler ultrasound and the systolic/diastolic (A/B) ratio was used as an index of flow resistance. There was no difference when continuous wave was compared to pulsed Doppler ultrasound as a method of recording flow velocity waveforms. Analysis of the umbilical artery flow velocity‐time waveform was more sensitive (100%‐50%) than the measurement of umbilical vein volume blood flow (ml/kg/min) in the detection of the small‐for‐gestational age (SGA) fetus. The predictive value of a positive test was higher (71%‐45%) while specificity was similar (88%‐81%). Descending aortic volume flow was reduced in only one SGA fetus. The increase in umbilical placental downstream resistance (high systolic/ diastolic ratio) was associated with a reduction in the percentage of fetal aortic blood flow directed to the umbilical placental circulation.

Positron emission tomography in neuropsychology

By positron emission tomography (PET) of 18F-2-fluoro-2-deoxy- D-glucose (FDG) local cerebral metabolic rate for glucose (LCMRGl) can be measured in man. Normal values in cerebral cortex and basal ganglia range from 35 to 50 μmol/100 g/min, the values in gray matter structures of the posterior fossa were 25–30 μmol/100 g/min, the lowest LCMRGl was found in the white matter (15–20 μmol/100 g/min). During sensory stimulation by various modalities functional activation increases LCMRGl in the respective special areas, while sleep decreases metabolic rate in all cortical and basal gray matter structures. In many neurological disorders CMRGl is altered in a disease-specific pattern. In dementia of the Alzheimer type CMRGl is impaired even in early stages with accentuation in the parieto-temporal cortex, while in multi-infarct dementia glucose uptake is mainly reduced in the multifocal small infarcts. In Huntington's chorea the most conspicuous changes are found in the caudate nucleus and putamen. In cases of focal lesions (e.g. ischemic infarcts) metabolic disturbances extend far beyond the site of the primary lesion and inactivation of metabolism is found in intact brain structures far away from the anatomical lesion. Additional applications of PET include determination of the metabolism of various substrates, of protein synthesis, of function and distribution of receptors, of tumor growth and of the distribution of drugs as well as the measurement of oxygen consumption, blood flow and blood volume.

Doppler developments in the last quinquennium

The major advances which have taken place during the last five years in the development of ultrasonic Doppler devices and methods of Doppler signal analysis are reviewed. The following aspects of instrumentation are considered: crossed beam Doppler systems, range measuring Doppler systems, duplex systems, flow mapping systems, transducers and measurements of system performance. Analytical methods are discussed in the following categories: waveform analysis, including the extraction of single-value waveforms and their applications to the diagnosis of vascular disease; spectral analysis, including the derivation of frequency spectra and their application in the study of blood flow; and volume flow estimation. It is concluded that it is likely to be in the study of the information in Doppler frequency spectra, two-dimensional real-time Doppler images and in the measurement of blood flow volume that most progress will be made.

EVALUATION OF CEREBRAL PERFUSION RESERVE IN PATIENTS WITH CAROTID-ARTERY OCCLUSION

Regional cerebral blood flow, oxygen utilisation, fractional oxygen extraction, and cerebral blood volume were measured by positron emission tomography in thirty-two patients with internal-carotidartery occlusion. In most cases, any reduction in cerebral blood flow in the territory distal to an occluded carotid artery was matched to diminished cerebral metabolic demands. Cerebral blood flow was inappropriately low in only six patients, in whom regional oxygen utilisation was maintained by a compensatory rise in oxygen extraction ratio. The frequent finding of high cerebral blood volume distal to occluded vessels was consistent with a state of focal vasodilatation in response to diminished cerebral perfusion pressure. Analysis of the relation between cerebral blood flow, blood volume, and oxygen extraction ratio suggested that the reduction in cerebral perfusion pressure, and hence circulatory reserve; could be most reliably predicted by the ratio of cerebral blood flow to blood volume. By identifying those patients with carotid occlusion who are most compromised on haemodynamic grounds, combined measurement of cerebral blood flow and blood volume should be valuable in selection of candidates for extracranial-intracranial bypass surgery.

EVALUATION OF CEREBRAL PERFUSION RESERVE IN PATIENTS WITH CAROTID-ARTERY OCCLUSION

Regional cerebral blood flow, oxygen utilisation, fractional oxygen extraction, and cerebral blood volume were measured by positron emission tomography in thirty-two patients with internal-carotidartery occlusion. In most cases, any reduction in cerebral blood flow in the territory distal to an occluded carotid artery was matched to diminished cerebral metabolic demands. Cerebral blood flow was inappropriately low in only six patients, in whom regional oxygen utilisation was maintained by a compensatory rise in oxygen extraction ratio. The frequent finding of high cerebral blood volume distal to occluded vessels was consistent with a state of focal vasodilatation in response to diminished cerebral perfusion pressure. Analysis of the relation between cerebral blood flow, blood volume, and oxygen extraction ratio suggested that the reduction in cerebral perfusion pressure, and hence circulatory reserve, could be most reliably predicted by the ratio of cerebral blood flow to blood volume. By identifying those patients with carotid occlusion who are most compromised on haemodynamic grounds, combined measurement of cerebral blood flow and blood volume should be valuable in selection of candidates for extracranial-intracranial bypass surgery.

In vivo measurements of regional cerebral blood flow and blood volume in patients with brain tumours using positron emission tomography.

In 21 patients with cerebral tumours regional cerebral blood flow (rCBF) and blood volume (rCBV) were measured. In the tumours, blood flow and volume were variable and unrelated even in tumours of the same type and grade. In the contralateral grey and white matter a (linear) relationship was found between rCBF and rCBV. Following operation, rCBF and rCBV in the contralateral hemisphere may increase due to lowering of intracranial pressure. Preliminary data shows that both factors decrease following whole brain irradiation.

Cardiac output measurement using N2O uptake: a method to subtract cardiogenic oscillations.

Plethysmographic (box) methods using N2O uptake to measure pulmonary capillary blood flow, right ventricular stroke volume, and pulmonary arterial flow pulse conduction time have been complicated by the presence of so-called "cardiogenic oscillations" in the box flow records on air and N2O breathing. The exact cause of these oscillations is unknown but believed to be secondary to instantaneous changes in net blood flow into and out of the thorax during the cardiac cycle. We examined these oscillations and pulmonary capillary blood flow in normal human subjects in a flow plethysmograph using a pressure compensation circuit to extend the frequency response. The cardiogenic oscillations in flow recorded at the mouth (with glottis open) are much greater in amplitude and 90 degrees out of phase from those recorded from the plethysmograph. We derived a theoretical analysis of this and designed an analogue electrical circuit to enable us to eliminate these oscillations by electrical subtraction from the box flow record generated by N2O uptake in the pulmonary capillary bed. Measurements of pulmonary capillary blood flow and ventricular stroke volume using our method correlate with measurements made with acetylene-rebreathing blood flow measurements performed sequentially at the same sitting.

Measurement of local blood flow and distribution volume with short-lived isotopes: a general input technique.

A new technique for measuring local blood flow and distribution volume is proposed. The technique uses short-lived isotopes but is different from the equilibrium method in that no constant input is necessary, and no assumption about distribution volume is needed. The theoretical basis of the technique is developed, and the results of a computer-simulation study are presented to show the potential of the technique. The technique is expected to be easier to perform and to give more accurate flow values than the equilibrium method.

Determination of volume of arterial blood flow by an ultrasonic device.

This paper describes the results of a reevaluation of the reliability of a newly developed ultrasonic volume flow meter which was developed by Yoshimura and his co-workers (1978). Measurements of volume blood flow (cc/sec) by this new technique were compared with measurement by the electromagnet flow meter. Experiments were performed with an in vitro model as well as with physiological pulsatile flow in an animal model. Results of the study indicated a high degree of correlation between values measured by both techniques with a correlation coefficient of 0.99 I believe that this is an important technical development in the field of noninvasive quantitative determination of blood flow.

Pulmonary blood flow and tissue volume. Assessment of a non-invasive technique of measurement.

Pulmonary blood flow and tissue have been measured by a rebreathing technique in which the disappearance of soluble and insoluble gases from an inhaled mixture is followed continuously using a respiratory mass spectrometer. Although measurements made with diethyl ether are more reproducible than those made with freon-22, they are inaccurate because ether (the more soluble gas) is taken up by the tissues surrounding the respiratory dead space. Experiments carried out on four normal subjects demonstrate that measurements of both pulmonary blood flow and tissue volume are influenced by the volume of gas in the lungs during the manoeuvre. Possible reasons for this are discussed and an exponential relationship between the two variables and lung volume is suggested.

Blood Flow Measurement Using the Attenuation-Compensated Volume Flowmeter

Measurement of blood volume flow using Doppler ultrasound has traditionally required determination of the Doppler angle, vessel size, and shape of the velocity profile. In transcutaneous measurements of blood flow, this problem has been a serious drawback in clinical usage. Volume flow is formally defined as the area integral of fluid flux normal to an arbitrary sample plane. Based on this definition, a pulsed Doppler volume flowmeter has been developed which measures flow normal to a thin uniformly illuminated sample volume. Calibration of the flowmeter is described, and implications for clinical use are discussed.

Blood flow measurement using the attenuation-compensated volume flowmeter

Measurement of blood volume flow using Doppler ultrasound has traditionally required determination of the Doppler angle, vessel size, and shape of the velocity profile. In transcutaneous measurements of blood flow, this problem has been a serious drawback in clinical usage. Volume flow is formally defined as the area integral of fluid flux normal to an arbitrary sample plane. Based on this definition, a pulsed Doppler volume flowmeter has been developed which measures flow normal to a thin uniformly illuminated sample volume. Calibration of the flowmeter is described, and implications for clinical use are discussed.

An ultrasound system for combined cardiac imaging and Doppler blood flow measurement in man.

An ultrasound instrument has been developed that combines a real-time cross-sectional imaging system and a spectrum analyzer-based Doppler velocimeter. This combination allows the Doppler sample volume to be superimposed on the cross-sectional image of the heart so that the sample volume can be located accurately. The same 2.2 MHz transducer utilized for cross-sectional imaging is stopped mechanically and quickly switched to transmit and receive the Doppler ultrasound signal. Preliminary experience in 20 young and adult normal subjects indicates that it is possible to place the Doppler sample volume in the proximal main pulmonary artery at a point where the sound beam and blood flow stream are parallel. Measurement of the distance from transducer to the sample volume and the peak blood flow velocities in the main pulmonary artery of normal subjects indicates that these quantities are within the measurement capabilities of the system. The ultimate goal of this device is to make measurements of volume blood flow in man noninvasively.

Improved method for noninvasive measurement of regional cerebral blood flow by 133Xenon inhalation. Part I: description of method and normal values obtained in healthy volunteers.

A clinical method for noninvasive measurement of regional cerebral blood flow (rCBF) and blood volume (rCBV) is described, based on Obrist's 10 minute, desaturation method after 1 minute inhalation of 133Xe. Sixteen collimated probes are placed over both hemispheres and brain stem-cerebellar regions. End-tidal 133Xe curves are used for correction of recirculation. KEV discriminators are set to record gamma and x-ray activity separately. Values are printed out automatically by a computer on a brain map. Extracerebral contamination is reduced by 1) computing curves from gamma activity, 2) applying pressure on the scalp beneath the probes, 3) 1 minute inhalation of 133Xe and recording desaturation curves for 10 minutes, thereby minimizing slow clearance from extracranial tissues. Normal values for both fast and slow compartments are reproducible and are in good agreement with the carotid injection method. The speech dominant hemishpere has higher flow than the right under conditions described. Posterior portions of the cranium over the cerebellum and brain stem appear to have higher flow gray values than the cerebral cortex. Gray matter flow decreases with advancing age.

Abnormal cerebrospinal fluid-blood flow dynamics. Implications in diagnosis, treatment, and prognosis in normal pressure hydrocephalus.

Increased cerebral blood flow (CBF) has been proposed as responsible for the clinical improvement after cerebrospinal fluid (CSF) shunting in patients with normal pressure hydrocephalus (NPH). In order to determine any abnormal CSF-CBF pressure-flow relationships in NPH, measurements of regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) were made before and after lowering CSF pressure (CSFP) in 15 patients with NPH, and in ten patients with presumed hydrocephalus ex vacuo. Maximal reduction of rCBF and rCBV occurred in the territory of the anterior cerebral artery in NPH but no in dementia due to brain atrophy. Both CBF and rCBV increased after lowering the CSFP by lumbar puncture in patients with NPH. Patients with higher preoperative rCBF and maximal increases in rCBR and rCBV after lowering CSFP showed the most consistent clinical improvement after CSF shunting. Evidence is offered that CBF autoregulation is impaired in NPH. The CBF test assists in both diagnosis and selection of patients for CSF shunting.

Measurements of umbilical blood flow and vascular volume by dye dilution

The dye dilution principle was applied to the measurement of blood flow in the fetal placental circulation of goats under barbiturate or halothane anesthesia and with the fetus in utero. Dye dilution curves obtained from the umbilical vein after dye injection into the umbilical artery showed no evidence of major arteriovenous anastomoses to account for the known finding that a significant portion of umbilical arterial blood flow does not participate in placental gaseous exchange. Values for umbilical blood flow and fetal oxygen consumption were obtained which are similar to those determined by other methods. The dye dilution method allows evaluation of short-term changes in blood flow at short time intervals and also permits calculation of the volume of dye distribution. The values for blood volume in the placenta obtained from our data average 40 ml. per kilogram of fetus, representing nearly one third of the total volume of fetal blood.

Pathogenesis of pulmonary edema by alloxan.

Alloxan causes pulmonary edema in anesthetized dogs by a local action in the lungs. Measurements of blood pressures, flow, vascular resistance and blood volume of intact and perfused lungs suggest that the initiation of edema is due to capillary congestion brought about by constriction of Pulmonary veins.