Mucosal reactivity of the intestinal allograft during acute rejection.
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Acute Disease↗
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Results for “Laser-Doppler Flowmetry”
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Comparative effects of exposure to different light sources (He-Ne laser, InGaAl diode laser, a specific type of noncoherent LED) on skin blood flow for the head.
BACKGROUND AND OBJECTIVE: This study assessed the effects of optic stimuli emitted by three different light sources on head skin blood flow. MATERIALS AND METHODS: The irradiation effects of the He-Ne laser (632.8 nm, 10 mW, total energy appr. 9.4 J), the InGaAl diode laser (670 nm, 60 mW, appr. 108 J) and monochromatic light (635 nm, 112.5 mW, appr. 202.5 J) were measured using laser Doppler technology. The corresponding fluences (energy densities) varied from 0.01 J/cm2 (He-Ne) to a range of 0.12-0.72 J/cm2 (InGaAl) and 0.22-1.36 J/cm2 (LED). The investigation was completed under single-blind, placebo-controlled conditions where the subjects (10 male healthy volunteers) were exposed on two occasions to the placebo (LED)-device against the laser (He-Ne or InGaAl). RESULTS: A short lasting vasodilation, a 54 per cent increase (p < 0.05) in skin blood flow was seen after the InGaAl irradiation (fluences between 0.12-0.36 J/cm2) whereas the non-coherent monochromatic irradiation (0.68-1.36 J/cm2) used in this particular study decreased blood flow by 36 per cent (p < 0.05). The He-Ne irradiation (0.01 J/cm2) had no effect. Skin temperature changes were insignificant. CONCLUSIONS: Skin blood flow changes seemed to be related more on radiant exposures then coherency.
Adult↗
The effect of aminophylline on pharmacological stress with intravenous adenosine.
Myocardial perfusion imaging with adenosine pharmacological stress may be useful in patients with obstructive lung disease who are unable to exercise. However, these patients are often treated with medications containing theophylline, which is an adenosine antagonist. This study assessed the effect of aminophylline on coronary vasodilation produced by intravenous adenosine as commonly used during cardiac imaging. Changes in coronary flow velocity (measured by intracoronary Doppler catheter) heart rate, arterial pressure and changes in coronary resistance were measured during intravenous infusion of adenosine at 140 micrograms/kg/min before and after aminophylline, 6 mg/kg intravenously in 12 patients. After aminophylline infusion, the theophylline level averaged 14 +/- 1 microgram/mL. The coronary hemodynamic effects of adenosine were markedly attenuated by aminophylline. Adenosine increased coronary blood flow velocity by 192 +/- 39% at control and 78 +/- 16% after aminophylline (P < .05 v control). Adenosine produced a 63 +/- 5% decrease in coronary vascular resistance at control and 40 +/- 6% (P < .05) after aminophylline. The utility of myocardial imaging techniques using coronary vasodilation with intravenous adenosine may be reduced in patients treated with theophylline-containing preparations.
Adenosine↗
Left ventricular cavitary geometry and dynamic intracavitary left ventricular obstruction during dobutamine stress echocardiography.
To investigate the relationship between left ventricular cavity geometry and dynamic intracavitary left ventricular obstruction occurring during dobutamine stress echocardiography, we evaluated 44 patients who underwent dobutamine stress echocardiography. Dynamic intracavitary left ventricular obstruction appeared in 10 (23%) patients (Group 1), and was absent in the remaining 34 patients (Group 2), during dobutamine stress echocardiography. The ratio of the apicalto-narrowest mid-left ventricular minor-axis dimension (D1/D2), as an index of the left ventricular cavitary geometry, was measured in the baseline two dimensional apical long-axis view. The left ventricular out-flow blood Doppler velocity was measured in the apical long-axis or five-chamber view at each stage during dobutamine infusion. Left ventricular end-systolic dimension was smaller (21 +/- 4 mm v 29 +/- 6 mm; p< .01), percent fractional shortening of the left ventricle was greater (51 +/- 4% v 39 +/- 8%, P>.01), and D1/D2 was greater (1.13 +/- 0.08 v.0.96 +/- 0.09; p < .0001) in Group 1 than in Group 2 in the baseline echocardiogram. Maximal out flow blood Doppler velocity during dobutamine infusion correlated moderately with percent fractional shortening of the left ventricle (r = .53; P < .01) and D1/D2 (r = .60; P < .0001). Dynamic intracavitary left ventricular obstruction, defined as an elevated intracavitary Doppler flow velocity with late-systolic peaking, was not related to the presence of left ventricular hypertrophy or the development of hypotension during dobutamine infusion. We conclude that dynamic left ventricular intracavitary obstruction during dobutamine infusion is associated with a characteristic (narrower-waisted) left ventricular cavitary geometry and increased contractility.
Adult↗
Laser Doppler vibrometer (LDV)--a new clinical tool for the otologist.
We describe a laser Doppler system (LDS) that can be used clinically for the measurement of tympanic membrane (TM), malleus and prosthesis head displacement in response to sound inputs of 80-to 100-dB sound-pressure level (SPL). It also has the potential for use in the operating room to perform measurements of prosthesis and stapes displacement. The information provided by such testing gives the otologist knowledge of TM and ossicular function that is unique in evaluating middle ear function; it should help select the best type of reconstruction in a given case and direct us toward new and better methods of TM and ossicular reconstruction. The results of umbo displacement measurements in 95 human ears are reported. Examples are provided of LDS measurements in representative ears and how they can be of help to the clinician. The potential of multisite TM-displacement testing is demonstrated in two temporal bones, including before and after partial ossicular replacement prosthesis (PORP) insertion.
Audiometry, Pure-Tone↗
[Effects of beta-adrenergic blockers on retinal circulation].
We evaluated the effects of 0.5% betaxolol hydrochloride and 0.5% timolol maleate on retinal blood flow. We measured the diameter of the retinal artery (Da) and vein (Dv), and retinal venous blood flow rate (V) in 8 healthy young volunteers by laser speckle velocimetry before and after the application of betaxolol or timolol topically to both eyes daily for one week. There were no any significant changes. Da before and after the application of betaxolol was 114.2 +/- 6.3 (mean +/- standard deviation) microns and 115.6 +/- 6.7 microns and before and after the application of timolol, 117.5 +/- 12.7 microns and 101.3 +/- 9.5 microns. Dv before and after the application of betaxolol was 149.5 +/- 11.1 microns and 148.4 +/- 13.3 microns, and before and after the application of timolol 148.5 +/- 9.2 microns and 146.2 +/- 10.3 microns. V before and after the application of timolol was 12.3 +/- 2.6 mm/s and 12.6 +/- 2.4 mm/s, and before and after the application of betaxolol, 11.6 +/- 1.5 mm/s and 11.4 +/- 2.1 mm/s. Thus one-week application of the beta-blockers, betaxolol and timolol did not change the retinal arterial or venous blood flow.
Adolescent↗
Age-related changes in gastric blood flow in rats.
The present study was designed to examine the influence of aging on the gastric blood flow, a major mucosal protective mechanism against experimental gastric mucosal injury, basally and after treatment with acid, a known stimulant of gastric blood flow. Our data demonstrated that aging was associated with a significant decline in basal gastric blood flow (both mucosal and serosal). However, there were no significant differences in acid-induced increases in gastric blood flow between the young and aged animals. These findings suggest that aging is associated with selective and specific reductions in mucosal protective mechanisms that may predispose aged animals to gastric mucosal injury.
Aging↗
The accuracy of magnetic resonance phase velocity measurements in stenotic flow.
Nuclear magnetic resonance (MR) can be used to measure velocities in fluid flow using the technique of phase velocity mapping. Advantages of MR velocimetry include the simultaneous mapping of the entire flow field through a non-contacting, magnetic window. The phase velocity mapping technique assumes that velocity is constant over the measurement time (typically around 10 ms). For many fluid flows, this assumption is not valid. The current study showed that MR phase velocity measurements of velocity through stenotic flow can be in error by over 100% immediately upstream and downstream of the stenosis throat and by 20% far downstream of the throat in comparison with laser Doppler anemometer measurements taken at the same location. Highly turbulent flow also led to significant errors in velocity measurement. These errors can be attributed to several sources including low signal-to-noise ratio, additional phase shifts due to non-constant velocities, and non-stationary transit-time effects. Velocity measurement errors could be reduced to under 30% at all measurement locations through the use of MR sequences with high signal-to-noise ratios, low echo times, and thick slices.
Arterial Occlusive Diseases↗
Lasers in dentistry: a review. Part 2: Diagnosis, treatment and research.
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Dental Caries↗
A microstructural flow analysis within a bileaflet mechanical heart valve hinge.
BACKGROUND AND AIMS OF THE STUDY: During recent clinical trials, the Medtronic Parallel bileaflet heart valve was found to have an unacceptable thrombosis complication rate. As patient- and material-related factors proved negative causes for this outcome, it was hypothesized that the flow fields within the valve's hinge pocket contributed to the thrombus formation. METHODS: A microstructural flow analysis within the hinge pocket is presented which uses the techniques of flow visualization, computational fluid dynamics (CFD), and laser Doppler velocimetry (LDV). The application of these techniques towards solving this problem has become possible through (i) the ability to manufacture dimensionally correct 1-X transparent heart valve housings, (ii) advances in CFD technology, and (iii) advances in LDV measurement techniques. RESULTS: This analysis showed that a vortex was present at the hinge pocket's inflow channel during forward flow and degenerated to a disturbed three-dimensional structure during reverse flow with zones of turbulent shear stress large enough to cause blood cell damage. In addition, multiple zones of flow stagnation and disturbed flow existed along the leaflet's pivot throughout the entire cardiac cycle. It was felt that these complex fluid structures created conditions which resulted in the formation of thrombus within the hinges of the Medtronic Parallel valve. These findings were supported by limited clinical explant data which illustrated early thrombus formation within the Parallel valve's hinge pocket at sites predicted by the analysis. CONCLUSIONS: This study provides, for the first time, an understanding of the detailed flow structures within the hinges of a mechanical heart valve and demonstrates an analysis technique by which future mechanical heart valve designs may be assessed for the potential of thrombus formation within the valve's hinge regions.
Computer Simulation↗
Influence of healing on the disturbed blood flow regulation in venous ulcers.
Cutaneous blood flow regulation is disturbed in severe chronic venous insufficiency (CVI). The feedback system between the transmural pressure in the postcapillary venules and the precapillary resistance regulating arterioles has gone awry. The upregulated control system causes "luxus"-hyperperfusion. In this study laser Doppler fluxmetry was performed in 6 patients' florid venous ulcers (U) and later in the former ulcer area after healing (H) and in the inner ankle area of 12 healthy volunteers (C). Laser Doppler flux (LDF) changes were measured with the leg elevated and lowered as well as after arterial and during venous occlusion. The results proved a diminished (p < 0.01) flux increase with the leg elevated (U: LDF = -9%, H: LDF = 3.1%, C: LDF = 80%) and after arterial occlusion (U: LDF = 1.3%, H: LDF = 0%; C: 189.6%) in severe CVI both in florid ulcers and after healing. The ability to reduce flux when transmural pressures were increased remained. Leg lowering reduced flux by 46.4% in ulcers and by 36.8% after healing. This postural response to high transmural pressures, however, seemed weakened compared to controls, where LDF decreased by 65.8%. Our findings suggest that the postural feedback system remains disturbed and upregulated even after a venous ulcer has healed.
Adult↗
[Influence of hemodialysis on changes in cerebral artery blood flow velocity in patients with chronic renal failure].
The effect of hemodialysis on the cerebral circulation have been inadequately studied. Because of repeatability, safety and non-invasiveness transcranial Doppler sonography is well suited for evaluation of cerebral circulation and for estimation of cerebral blood flow during hemodialysis as well. The aim of our study was to find out whether hemodialysis affects the velocity of blood flow in extra- and intracranial arteries and in what way. 41 patients aged 18-71 (mean 43.9 +/- 13) years suffering from chronic renal failure made up the investigation group. We investigated 17 men and 24 women. Doppler examination was done to each dialized patient immediately before and then 120 and 240 minutes after the onset of hemodialysis. We used pulsed wave Doppler (TC2-64B, EME). Mean blood flow velocities were obtained from extracranial (CCA, ICA, ECA) and intracranial vessels (MCA, ACA, PCA). Simultaneously the series of biochemical blood parameters and arterial blood pressure were monitored. On the basis of investigation results the following conclusion have been drawn: Hemodialysis significantly affects on changes of blood flow velocities in extra-an intracranial arteries. Above mentioned changes consist in decrease of blood flow velocity in both CCA, left ICA, both MCA and PCA and right ACA.
Adolescent↗
Multimodal monitoring and assessment of cerebral haemodynamic reserve after severe head injury.
This article contains an overview of selected clinical techniques employed for neurointensive care monitoring and testing of cerebral autoregulation of patients following severe head injury. Multiple modalities are used for monitoring of cerebral haemodynamic reserve, including intracranial pressure, cerebral perfusion pressure (CPP), blood flow velocity (FV) in the middle cerebral artery (MCA), jugular bulb oxygen saturation, laser-Doppler cortical flowmetry, near infrared spectroscopy of cerebral cortex, tissue oxygenation, and microdialysis. Large volumes of information demand specialised computer support for sensible interpretation and filtration of artifacts. Methods of testing of cerebral autoregulatory reserve based on transcranial Doppler ultrasonography are reviewed. Repetitive or continuous assessment is important in practice as autoregulatory reserve may fluctuate in time. Static and dynamic rates of autoregulation show sensitivity to carbon dioxide-induced vasodilatation, but fail to correlate with outcome following head injury. The carotid artery compression test, useful for assessment of patients after subarachnoid haemorrhage, has yet to prove its usefulness in head injury. Continuous waveform analysis of MCA FV and CPP correlates with coma score after resuscitation and outcome and hence may be considered as a robust method for the assessment of autoregulation in ventilated head trauma patients.
Cerebrovascular Circulation↗
[Microcirculatory changes in mitral prolapse as an expression of a systemic change in the connective tissue].
Many authors hypothesize that mitral valve prolapse (MVP) can be, in most cases, only a clinical sign of a primitive and systemic disorder of the connective tissue, like in Marfan Syndrome (MS). In our previous works we supported the presence of morphological and functional alterations of the microcirculation in patients affected by MS. In order to characterize a possible common denominator between these pathologies we have studied the cutaneous microcirculation in a group of patients affected by MVP, divided into 2 groups: anatomic MVP (MVP) and MVP syndrome (MVPS). The morphologic parameters have been investigated by nailfold capillaroscopy while digital laser-Doppler was used to study skin flowmetry. The results have been compared with a control group. Capillaroscopic remarkers showed an architecturally disorganized microvasculature with aspects related to a reduced compactness of the microvasculature unit with a significatively higher score compared with controls (7.3 +/- 2.9 vs 3.6 +/- 1 p less than 0.0005). Laser-Doppler flowmetry showed a significatively reduced rest flow; ischemic test showed: spike time 48.9 +/- 36.9 vs 15.3 +/- 7.7 s (p less than 0.0005), hyperemic acme 6.6 +/- 2.7 vs 12.5 +/- 8.4 UP (p less than 0.002); % increase 32.1 +/- 20.2 vs 51.5 +/- 15.4 (p less than 0.002). Thermic test showed a significatively higher thermic acme 8.7 +/- 4.2 vs 12.6 +/- 9.11 UP (p less than 0.05). These results appeared to be correlated with stage pathology as it was observed a severe microvasculature disorders in MVPS. Therefore we suppose that a phenotypic continuum may exist between MS and MVP.
Adult↗
Effects of neural blockade and general anesthesia on the laser-Doppler skin blood flow waves recorded from the finger or toe.
Effects of neural blockade and general anesthesia on the basic wave (BW) and the reflex wave (RW) among the laser-Doppler (L-D) skin blood flow waves recorded on the finger or toe were studied in 2 volunteers and 42 patients. The BW was continuous, rhythmic and independent of respiratory movements. The RW, which was induced by a deep inspiration or a snapping sound, was a transient marked reduction in blood flow. The BW was almost flattened and the RW was no longer induced at the finger under complete wrist block (n = 2), or under cervical or upper thoracic epidural anesthesia extended caudally over T7 (n = 2). On the other hand, the BW was still detected with reducing frequency and the RW could be provoked with one exception at the finger on the side with a sympathetic ganglion block at the C6 vertebral level (n = 14). The BW and RW at the toe were retained under lumbar subdural anesthesia (n = 6) as well. However, under the combination of lumbar subdural anesthesia and lower thoracic epidural anesthesia extending rostrally over T4 (n = 6), both the BW and the RW disappeared at the toe. In the course of deepening nitrous oxide/enflurane anesthesia (n = 10), the BW gradually reduced in frequency until it was almost flattened, and it became difficult to provoke the RW. L-D flowmetry of the finger or toe could be a useful clinical measure for detecting the presence or absence of sympathetic function controlling cutaneous vasomotion.
Adult↗
Current status of noninvasive tests in the diagnosis of peripheral arterial disease.
In this review of the current status of the vascular laboratory, the major emphasis has been upon those tests that have become well-established and documented, including resting pressure, pulse volume measurements, velocity studies, and three stress measurements--exercise ankle pressure, postocclusive reactive hyperemia, and the toe pulse reappearance time. Additional technology that may have application to peripheral arterial disease includes photoplethysmography, transcutaneous oxygen tension, laser-Doppler velocimetry, fluorescein angiography, infrared thermography, and transcutaneous electromagnetic flowmetry. These techniques, which are currently in development and experimental trial, were not discussed but are likely to provide significant additional information. The future role of the vascular diagnostic laboratory in the area of peripheral arterial occlusive disease appears clear. It has already become a standard resource of the community hospital and tertiary referral center. Its functions will become more and more generally accepted with time as newly graduating physicians who have been exposed to this technology enter the practice of medicine. It should permit obtaining an evaluation of all patients at the expert level, aid in the education of all physicians concerned with peripheral arterial disease, and play an important part in guaranteeing a higher level of patient care than has heretofore been available.
Arterial Occlusive Diseases↗
Partitional measurement of capillary and arteriovenous anastomotic blood flow in the human finger by laser-Doppler-flowmeter.
This study was made to see whether changes in blood flow through the capillaries and arteriovenous anastomoses (AVA's) of the human finger can be measured by noninvasive flowmetry. Total finger blood flow (FBF) was measured by venous occlusion plethysmography; blood flow was measured by a laser-Doppler flowmeter (ADVANCE, ALF-2100, Tokyo, Japan) using probes with optic fiber separations of 0.3 mm (LDF-0.3) and 0.7 mm (LDF-0.7). The maximum sensitivities for LDF-0.3 and LDF-0.7 were at depths of 0.8 and 1.2 mm from the tissue surface respectively. Two series of experiments were performed on separate days. In the first series the test hand was immersed in a water bath whose temperature (Tw) was 25 degrees C at an ambient temperature (Ta) of 25 degrees C. Tw was raised to 35 degrees C (local hand warming), which was then followed by an increase in Ta to 35 degrees C (whole body warming). FBF, LDF-0.3, and LDF-0.7 increased during these thermal stimulations. However, the relationship of FBF to LDF-0.3 showed two different regression lines. In contrast, the relationship of FBF to LDF-0.7 showed a single regression line. In the second series, with Ta at 35 degrees C, the test hand was immersed in a water bath at Tw 35 degrees C. Tw was then raised every 10 min by 2 degrees C steps from 35 to 41 degrees C. At Tw 39-41 degrees C, FBF and LDF-0.7 in the test hand were significantly decreased compared with those at Tw 35 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Selective vasodilators redistribute intestinal blood flow and depress oxygen uptake.
In this paper we report the effects of adenosine and isoproterenol on intestinal oxygen consumption. Using the recently developed technique of laser-Doppler velocimetry (LDV), we also studied the effects of these two agents on regional blood flow in the canine intestinal mucosa and muscularis. In isolated gut loops perfused at constant blood flow, both vasodilators depressed O2 uptake, but isoproterenol increased rubidium extraction while adenosine depressed rubidium extraction. Under constant pressure perfusion both dilators depressed O2 uptake but increased total flow. Isoproterenol increased the capillary filtration coefficient (Kf), but adenosine depressed Kf. LDV flowmetry showed adenosine increased muscularis flow and depressed mucosal flow. Both LDV flowmetry and radioactive microspheres showed isoproterenol increased mucosal but depressed muscularis flow. Our data indicate that the deleterious effects of isoproterenol and adenosine in depressing intestinal oxygen uptake can be explained by the ability of these agents to selectively vasodilate one of the regional circulations within the gut wall and by a "vascular steal" mechanism to reduce blood flow in the other vascular bed not as sensitive to the agent in question. The reduction in the regional blood flow thus depresses the O2 consumption of the gut as a whole. By comparing our regional laser-Doppler blood flow data with a simple analog model, we show that the seemingly paradoxical effect of vasodilators in depressing a regional blood flow while increasing total perfusion is explicable by a "vascular steal" mechanism.
Adenosine↗