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Results for “Laser-Doppler Flowmetry”

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At least 1,387 records · Page 77Linked to original sources
PubMed1996

[Significance of middle cerebral artery doppler velocimetry based on behavioral states in intrauterine growth retarded fetuses--prediction of development of fetal distress].

Middle cerebral artery resistance indices (MCARI) based on fetal behavioral states were calculated in 60 normal and 20 intrauterine growth retarded (IUGR) fetuses between 33 and 40 weeks of gestational age. Fetal behavioral states were determined by recording fetal actocardiograms. The results obtained were as follows: 1. MCARI was significantly lower in the active phase than in the resting phase in normal fetuses. 2. Of the 20 IUGR fetuses, 9 subsequently developed fetal distress. Seven of 11 fetuses who did not develop fetal distress had abnormally low MCARI (less than M-2.0 SD) in the active phase. On the other hand, seven of the fetuses that subsequently developed fetal distress had abnormal MCARI not only in the active phase but also in the resting phase. The fetuses that did not develop fetal distress had different MCARIs in the two phase, but the fetuses that developed fetal distress exhibited no such difference. 3. The sensitivity and specificity in predicting the development of fetal distress in IUGR fetuses with abnormal MCARI in the resting phase were 77.8% and 81.8%, respectively. This study showed that in normal fetuses MCARI differs according to the behavioral state, and that resting phase MCARI is useful for predicting fetal distress in IUGR fetuses.

Adult↗
PubMed1996

Mechanisms of allodynia: interactions between sensitive mechanoreceptors and nociceptors.

We examined whether stimulation of sensitive mechanoreceptors from an area of allodynia evokes nociceptor activity expressed as axon reflexes. Experiments were conducted on human volunteers. Cutaneous blood flow was measured with a laser Doppler flowmeter. Allodynia was induced with mustard oil (25-100%) or by intradermal injections of capsaicin (25-50 micrograms) in the skin of the forearm or the hand. Tactile stimulation of normal skin or outside zones of allodynia did not evoke axon reflexes. The same stimulation in areas of allodynia evoked pain as well as axon reflexes. Cooling the area of primary hyperalgesia or blocking the A fibres in the nerve that innervated the allodynia area abolished the allodynia and the axon reflex. These results demonstrate central interactions between sensitive mechanoreceptors and nociceptors concomitant with the development of allodynia.

Adult↗
PubMed1996

A comparison of techniques to assess skin blanching following the topical application of glucocorticoids.

Glucocorticoid-induced dermal blanching provides a useful research tool to study steroid potency and sensitivity. Conventional measurement of the intensity of blanching relies on subjective assessment by a trained observer using a visual score. Several objective techniques have recently been reported to detect skin blanching, but their sensitivity has not been compared previously with subjective visual recordings. In this report we aimed to establish whether objective methods offer sufficient sensitivity to be employed in epidemiological studies of glucocorticoid responsiveness. In healthy subjects we applied beclomethasone dipropionate at three concentrations (1, 10 and 100 micrograms/ml) under an occluded dressing overnight. The following morning we measured blanching using a visual score, laser Doppler velocimetry with the MBF 3D monitor (Moor Instruments Ltd, U.K.) and a perfusion imager (Lisca, Sweden), and reflectance spectrophotometry with the Dia-Stron 'erythemameter'. Using the visual score, blanching was detected at all concentrations of steroid. Neither laser Doppler instrument detected vasoconstriction at any concentration. By contrast, the reflectance spectrophotometer successfully recorded blanching at 10 and 100 micrograms/ml, but not at 1 microgram/ml. We conclude that laser Doppler instruments, including the novel scanning perfusion imager, do not detect glucocorticoid-induced skin blanching, perhaps because it reflects venular rather than arteriolar vasoconstriction. By contrast, the Dia-Stron reflectance spectrophotometer has sufficient sensitivity to be used as an alternative to visual assessment in epidemiological studies of human glucocorticoid-induced dermal blanching.

Administration, Topical↗
PubMed1996

Postocclusive hyperaemia in skin measured in pigs by laser Doppler: influence of site of arterial stenosis in the limb.

OBJECTIVE: To investigate how site and severity of arterial stenosis, and distance between tourniquet and measuring probe influences the postocclusive hyperaemic response in limb skin recorded by laser Doppler. DESIGN: Open study. MATERIAL: Nine Norwegian Landrace pigs. INTERVENTION: Experimental stenoses in the abdominal aorta, the external iliac and femoral arteries. The hyperaemic responses were recorded with the probe at two different distances from the tourniquet. MAIN OUTCOME MEASURES: Curve pattern, relative reduction in flux between the two peaks in double humped curves, and time to peak hyperaemic flux. RESULTS: Double humped curves were produced at all sites, but the blood pressure gradient required at the stenosis was greater the more proximal the stenosis. In distal stenoses there was a greater relative reduction in flux between the two peaks (p < 0.05). The time to peak hyperaemic flux was related to the gradient of the stenosis (mmHg) (r = 0.62, p < 0.0001), but was independent of its site. Increased distance between the tourniquet and the probe gave lower laser Doppler amplitudes and prolonged the time to peak hyperaemia in experiments with femoral artery stenosis (p < 0.05). CONCLUSION: The hyperaemic response is governed by both the severity and the site of arterial stenosis. Stenoses distal to the tourniquet seem to impair the initial reperfusion more than comparable lesions proximal to the tourniquet. Time to reach peak hyperaemia is the single variable most closely related to the severity of the stenosis.

Animals↗
PubMed1996

Peripheral microcirculatory blood flow in haemodialysis patients treated with erythropoietin.

BACKGROUND: Haemodialysis patients have abnormal blood vessels, and increased morbidity from vascular causes, effects which may potentially be enhanced by erythropoietin (EPO) therapy. METHODS: Microcirculatory blood flow was assessed using a laser-Doppler flowmeter in a group of 19 haemodialysis patients before and during treatment with recombinant human (EPO). RESULTS: Haemodialysis patients had significantly impaired microcirculatory blood flow under both basal (25 degrees C) and hyperaemic (44 degrees C) conditions by comparison with 19 normal controls (baseline flow, median and range: patients 1.54 (0.28-2.54) volts, controls 3.39 (0.94-5.23) volts, p < 0.001 Mann Whitney U Test; hyperaemic flow, patients 2.69 (1.08-3.82) volts, controls 3.81 (1.32-8.00) volts, p < 0.001). There was no significant influence on microcirculatory blood flow of patient age, duration of haemodialysis, short-term EPO therapy (subcutaneous or intravenous), therapy with a calcium-channel blocker/vasodilator (nifedipine), or radiological evidence of vascular calcification. CONCLUSIONS: Haemodialysis patients have an abnormal peripheral microvasculature, which may be relevant to their increased risk of ischaemic tissue damage and poor wound healing.

Anemia↗
PubMed1996

Inhibited cold-induced vasodilatation in patients with vibration-induced white finger.

We investigated cold induced vasodilatation in 37 vibration-exposed men without vibration-induced white finger (VWF) and 20 men with VWF. The left third finger was dipped into a cooling box and was cooled with cold air of 5 degrees C for 15 min. Finger skin blood flow during the cold stimulus was measured using the laser-Doppler method. We observed that cold-induced vasodilatation was inhibited in patients with VWF and the cold air test was relatively useful for diagnosis VWF.

Aged↗
PubMed1995

[Observation of cristae of posterior ampullae with laser Doppler].

UNLABELLED: To set up the methodology of measuring vestibular blood flow was the key to the study of vestibular microcirculation. 10 guinea pigs' posterior ampullae cristae blood flow were measured with Laser Doppler Flowmetry. RESULTS: cochlear flow was 318.39 +/- 91.66mV. Cristae of posterior ampullae was 194.00 +/- 45.26mV. The arterial blood pressure was stable in 9.99 approximately 10.27kPa. The present results showed cochlear and vestibular blood flow were 62.14% and 37.86% in total inner ear blood circulation. The latter appeared to be about one half of cochlear blood flow. These suggested that the blood flow of posterior ampullae can reflect the blood flow of vestibular to some degree. Laser Doppler was technically simple, non-invasive, highly stable, reproducible and sensitive.

Animals↗
PubMed1995

The effect of wall roughness on velocity distribution in a model of the carotid sinus bifurcation--analysis of laser and ultrasound Doppler velocity data.

The purpose of this work was to find out whether a rough surface in the sinus of a carotid model affects the flow velocity distribution and the properties of the corresponding ultrasonic Doppler spectrum, in view of potential application to the evaluation of risk of cerebral embolism. True-to-scale elastic models of carotid artery were used in the experiments. Experiments were performed in three models with varying severity of roughness and a normal (physiological healthy) model. The different degrees of roughness in the three models were created by melting graded holes in the wax cast used to make the model. Velocity data were collected using 4 Mhz pulsed ultrasonic and single component laser Doppler velocimeters. The roughness resulted in modified velocity distribution, affecting to various extent ultrasonic Doppler spectral parameters, in particular the measure of symmetry of spectral distribution.

Blood Flow Velocity↗
PubMed1995

The dynamics of pulsatile flow in distensible model arteries.

Deposits and blockages are often found in the carotid, coronary, renal and femoral arteries. This paper deals with laser-Doppler velocity measurements in models of bifurcations of the human femoral arteries. Several models were prepared for the studies: a simplified 35 degrees glass model, two elastic-silicone-rubber models with a wall thickness of 1 mm and 2 mm, and true-to-scale rigid and elastic models. These measurements give a clearer picture of how hemodynamics influences the formation of atherosclerotic plaques where there is a hardening of the arterial walls and a loss of elasticity. In addition to the effects of elasticity, the influence of the flow's pulsatility were studied. The measurements were done in steady and pulsatile flow. From the velocity measurements the shear stresses were calculated.

Arteries↗
PubMed1995

[Adaptive procedures for measuring arterial blood flow velocity in retinal vessels using indicator technique].

There are highly significant differences in the measuring results of arterial blood velocity between the indicator and laser-Doppler techniques (up to 800%). A new measuring procedure for the analysis of indicator dilution curves was developed based on indicator model and experimental results. The use of this new measuring procedure results in reduced mean systematic error between the indicator and laser-Doppler techniques to values around 10%. With the introduction of adaptive measuring arrays for the creation of indicator dilution curves and the application of adaptive algorithms for centering and spectral normalizing of the dilution curves, improved reproducibility can be expected.

Blood Flow Velocity↗
PubMed1996

Microregional blood flow in murine and human tumours assessed using laser Doppler microprobes.

A multichannel laser Doppler system has been used to measure microregional fluctuations in perfusion in the HT29 human tumour xenograft and in patients with advanced malignant disease. A comparison is made with previously obtained data for the SaF, a transplantable murine tumour. The 300 microns diameter probes recorded fluctuations in erythrocyte flux in tumour microregions with an estimated volume of 10(-2) mm3. Of the 66 human tumour microregions sampled, 26% showed a change in erythrocyte flux by a factor of 2 or more over the 60 min measurement period, compared with 37% of HT29 and 48% of SaF microregions. In each of the studies more than 50% of changes were completed within 20 min, although slower changes were more common in the human tumours than in the experimental systems. Within the 1 h monitoring period at least 30% of the changes were reversed (human tumours 30%, HT29 45%, SaF 31%). These findings demonstrate that microregional changes in erythrocyte flux, consistent with transient, perfusion-driven changes in oxygenation, are a feature of human malignancies as well as experimental transplanted tumours.

Aged↗
PubMedDate not supplied

[Significance of the echo-Doppler method in the study of hemodynamic changes of the ophthalmic artery after ligation of the superficial temporal artery].

The authors report the utility of the Echo-doppler and Doppler CW exams before and after the surgical therapy of the chorioretinal and optic nerve's hypoperfusion conditions. They have studied 112 patients affected by these pathologies and evaluated the blood flow's modifications. This exam is even usefull for the patient's selection before surgery without any serious complications.

Adult↗
PubMedDate not supplied

Are the effects of local joint movement on blood flow limited to the vertebral and internal carotid arteries? Doppler studies of the ulnar artery.

OBJECTIVE: To determine what effect wrist extension has on ulnar artery blood flow. DESIGN AND SETTING: This is a descriptive study performed at a private chiropractic clinic. SUBJECT SELECTION: Sixty-three ulnar arteries were examined from thirty-two volunteers, 15 men and 17 women, whose ages ranged from 21-75 yr. Only wrists that were asymptomatic and freely mobile were candidates for ulnar artery examination. INTERVENTION: The arteries were insonated approximately 2 cm proximal to the pisiform bone using a continuous-wave Doppler flow meter in the neutral position and during passive wrist extension to the limit with the fingers straightened. MAIN OUTCOME MEASURES: The persistence or loss of Doppler signals. RESULTS: Doppler signals from 83% (0.99 confidence interval: 68% < p < 93%) of arteries stopped. In 4% of vessels, the signals were markedly reduced; in 13%, they remained apparently unchanged. CONCLUSION: Blood flow in ulnar arteries can be severely restricted during wrist extension. By using Doppler ultrasound, the ulnar artery may provide a good model of local joint movement effects on arterial blood flow.

Adult↗
PubMedDate not supplied

Ultrasound and duplex-Doppler in the diagnosis and follow-up of portal hypertension.

Ultrasound examination should be carried out as the first investigation in all patients with suspected hepatobiliary disease. It has a high accuracy in detecting signs of portal hypertension such as ascites, splenomegaly and collateral veins. The most common cause of portal hypertension in the Western world is cirrhosis. Although there is an overlap of ultrasound findings in normal liver, fatty liver, chronic liver disease with and without fibrosis, and cirrhosis, a correct diagnosis of cirrhosis by judgment of ultrasound findings is reported to be achieved in up to 80%. Diagnostic parameters used are size and outline of the liver, its reflectivity and attenuation of the echo-pattern. If used in combination with the Doppler duplex system, the information gained vastly increases. Areas where this technique is able to provide useful and reliable data have been defined in a consensus conference held in Bologna. Doppler flowmetry of hepatic vessels allows detection of presence, direction and characteristics of blood flow. The reliability of the quantitative measurements of blood flow in abdominal vessels is still questioned. When using the same equipment by skilled operators, however, duplex-Doppler data of the portal vein are of value in the assessment of the risk of variceal bleeding, in the evaluation of the progression of liver disease and in the evaluation of medical therapy for portal hypertension. Furthermore, the technique is of practical value in pre-and postoperative examinations for shunt surgery as well as in the pre-procedural work-up of transjugular intrahepatic portosystemic stent shunt (TIPS), during the TIPS procedure and in the post-TIPS followup.

Humans↗
PubMed1996

Perfusion of the juxtapapillary retina and the neuroretinal rim area in primary open angle glaucoma.

PURPOSE: The objective of this study is to evaluate capillary blood flow of the juxtapapillary retina and neuroretinal rim area in primary open angle glaucoma (POAG) by a new noninvasive method performing a high-definition topography of perfused vessels of the retina and the optic nerve head with simultaneous evaluation of blood flow. METHODS: Juxtapapillary retinal and neuroretinal rim area blood flow were measured by scanning laser Doppler flowmetry (SLDF). This new technique is a combination of a laser Doppler flowmeter with a scanning laser system by which the retinal perfusion is simultaneously quantified in 16,000 sites of a retinal area of 2.7 x 0.7 mm. In study I, retinal and optic nerve head blood flow were evaluated by SLDF in 43 patients with POAG and 43 healthy individuals. The mean age of the POAG group was 56 +/- 12 years and of the control group 42 +/- 15 years. In study II, age-matched normals (n = 21) were compared with glaucoma eyes with topical therapy (n = 30) and with glaucoma eyes without topical therapy (n = 16). RESULTS: In study I, the eyes with POAG had an average cup/disc ratio (C/D) of 0.75 +/- 0.20, with an average mean defect of the visual field of 5.3 +/- 5.4 dB. The actual intraocular pressure was 17.8 +/- 4.18 mm Hg in the POAG group and 15.45 +/- 1.82 mm Hg in the control group. For statistical analysis, two age-matched groups of 28 normal eyes of 28 persons with 27 glaucomatous eyes of 27 patients were compared. In normals the blood flow of the neuroretinal rim area was significantly higher than that of the juxtapapillary retinal area (+7.73%, p < 0.01). In POAG both juxtapapillary retinal blood flow and neuroretinal rim area blood flow were significantly decreased compared to an age-matched control group: neuroretinal rim area flow -71% and juxtapapillary retina flow -49%. The decrease of neuroretinal rim area blood flow did significantly correlate with C/D. We found no correlation between reduction of juxtapapillary retinal blood flow and C/D or mean defect. Both glaucoma eyes with and glaucoma eyes without topical therapy showed significant decreased juxtapapillary blood flow compared to normals. We found no significant difference in the juxtapapillary blood flow between glaucoma eyes with and without topical therapy. CONCLUSIONS: In POAG, optic nerve head blood flow and juxtapapillary blood flow were significantly decreased.

Adult↗
PubMed1996

Principle, validity, and reliability of scanning laser Doppler flowmetry.

PURPOSE: The objective of this study is to present the reliability and validity of scanning laser Doppler flowmetry (SLDF) performing a high-definition topography of perfused vessels of the retina and the optic nerve head with simultaneous evaluation of blood flow. METHODS: The examination of blood flow by SLDF is based on the optical Doppler effect. The data acquisition and evaluation system is a modified laser scanning device; the wavelength of the laser source is 670 mm, with a power of 100 microW (Heidelberg Engineering, HRF). The reliability of SLDF was estimated by performing five separate measurements in 10 eyes on 5 days. The validity of the method was tested by two experiments. First, in an experimental set-up, the capability of SLDF to measure the velocity of a moving plane in absolute units was estimated. Second, comparative measurements were performed of retinal blood flow in normal eyes and in 33 glaucomatous eyes with SLDF and a commercially available single-point laser Doppler flowmeter (Oculix). RESULTS: We found SLDF to produce a high reliability. The reliability coefficients r1 of flow, volume, and velocity were 0.82, 0.81, and 0.83, respectively. Comparative measurements of the retinal blood flow by SLDF and a single-point laser Doppler flowmeter of corresponding retinal points showed a linear and significant relationship between flow (r = 0.83, p < 0.0001), volume (r = 0.51, p < 0.0001), and velocity (r = 0.59, p < 0.0001). In the experimental set-up, SLDF was able to quantitatively measure velocity in absolute units. CONCLUSIONS: SLDF enables the visualization of perfused vessels of the juxtapapillary retina and the optic nerve head in high resolution by two-dimensional mapping of the optical Doppler shift and a reproducible evaluation of capillary blood flow.

Evaluation Studies as Topic↗
PubMed1996

Optic nerve head circulation after topical calcium channel blocker.

PURPOSE: Our purpose was to investigate the effects of the calcium channel blocker verapamil on intraocular pressure and blood circulation in the human optic nerve head. METHODS: The effects of three different concentrations of topical verapamil (0.063%, 0.125%, and 0.25%) on intraocular pressure and optic nerve head capillary blood speed were measured in 12 healthy normal subjects. In a randomized, double-masked design, each subject received one drop of either verapamil or placebo in one eye and the opposite treatment in the fellow eye. Anterior optic nerve circulation was assessed at baseline and 90 min after instillation of the drops using the laser Doppler technique. RESULTS: The intraocular pressure was significantly reduced compared with baseline in both verapamil- and placebo-treated eyes at each concentration. The reductions of intraocular pressure were greater in verapamil-treated eyes (12-17%) than in placebo-treated eyes (9-12%). No systemic effect on heart rate or blood pressure was detected after administration of topical verapamil. The capillary blood speed in the optic nerve head was increased in both verapamil- and placebo-treated eyes at each concentration, although the only statistically significant increases were with the 0.25% concentration. The mean +/- SEM increase compared with baseline at the 0.25% concentration was 10.4 +/- 3.6% in verapamil-treated eyes (p = 0.017), and 11.6 +/- 4.4% in placebo-treated eyes (p = 0.026). CONCLUSIONS: These results indicate that topical administration of verapamil lowers the intraocular pressure and increases the capillary blood speed in the optic nerve head in normal subjects. Changes measured in verapamil-treated eyes were also observed in placebo-treated eyes, indicating a crossover effect.

Administration, Topical↗