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Results for “Laser-Doppler Flowmetry”

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At least 1,081 records · Page 60Linked to original sources
PubMed1993

Postocclusive reactive hyperemia and postural vasoconstriction in different kinds of leg ulcers--investigations with laser Doppler.

Laser-Doppler fluxmetry was performed in 42 patients with leg ulcers (18 venous, 8 arterial, 12 diabetic-arteriolar and 4 mixed arterio-venous) and in 9 healthy controls. Using a bipolar probe measurement was carried out at the ulcer border and on the dorsum of the foot in the supine and in the sitting position. Reactive hyperemia after three minute arterial occlusion was produced in both body-positions. In every ulcer-group resting and peak fluxes showed a statistically significant increase in the ulcer region as compared to normal skin of the lower leg in the control group, the quotient between peak and resting flux ("reactive hyperemia index" RHI) being significantly lower. The RHI values for four ulcer-patients with a dramatic deterioration worsening eight months later were close to one, while the unchanged and improved cases showed median values above 1,2. Sitting up was followed by a decrease of flux in all ulcer-groups as well as in the control group. On the dorsum of the foot there was an increase of the laser Doppler flux in patients with arterial occlusive disease, i.e. in the group with arterial and mixed ulcers. This study shows that the kind of microcirculatory flow damage is not different in various causes of ulcerations. The reduced reactive hyperemic response compared to the increased resting fluxes (amount of RHI-decrease) might be a useful predictor for healing or non-healing of the ulcer.

Adult↗
PubMed1993

[Experimental research on choroidal circulation. 1. Effect of sectioning or stimulation of the cervical sympathetic nerve upon choroidal blood flow].

Choroidal blood flow (CBF) was continuously measured with a laser doppler flowmeter (LDF) in 32 pentobarbital-anesthetized cats. A rise in intraocular pressure (IOP) caused a decrease in CBF, but when the IOP increase was slight, it induced a CBF increase. A sustained increase of CBF occurred following sectioning of the cervical sympathetic nerve (CSN) in 7 out of 18 eyes, but no noticeable blood flow change was observed in the remaining 11 eyes. Two different vasomotor responses in CBF were observed in response to electrical stimulation of the peripheral cut end of the CSN; one was a decrease and the other an increase. From the present experiments, decrease of CBF elicited by CSN stimulation is considered to be due to an increase in the activity in vasoconstrictor fibers of choroidal capillary blood vessels, but the exact mechanism of the CBF increase is unknown. Slight changes in position of the LDF probe sometimes alter the vasoresponses, suggesting that the site at which CBF was measured is crucial for investigating the effects of dissection or electrical stimulation of the CSN on CBF.

Animals↗
PubMed1993

[An apparatus using laser speckle phenomenon for noninvasive 2-dimensional analysis of microcirculation in the optic nerve head].

A new instrument using the laser speckle phenomenon for noninvasive 2-dimensional analysis of the microcirculation in the optic nerve head (ONH) was developed. The ONH was illuminated with a diode laser spot and its image speckle was detected by an area array sensor. The difference between a pair of output data for successive scannings of the image speckles at the sensor plane was calculated and integrated for each pixel to obtain the average difference (AD), which is a quantitative index of blood speed. The results were displayed in color graphics showing the 2-dimensional variation of the AD level in the area of interest. The AD had good correlation with the speed of ground glass in a range between 0 and 8 mm/sec. Using this instrument, the effect of intraocular pressure (IOP) on the circulation in the area of the rabbit ONH free from surface vessels was studied. The coefficient of reproducibility was 4.7% when measured in this area twice at 5-minute intervals. A stepwise reduction in the ocular perfusion pressure (OPP) was introduced by elevating the IOP manometrically. The AD was little affected by OPP change when OPP was above 40 mmHg, but with the OPP below 40 mmHg, a linear correlation was found between the AD and OPP.

Animals↗
PubMed1993

[An apparatus using laser speckle phenomenon for noninvasive 2-dimensional analysis of choroidal microcirculation].

A new instrument using the laser speckle phenomenon for noninvasive 2-dimensional analysis of the choroidal microcirculation was developed. The fundus was illuminated with a diode laser spot and its image speckle was detected with an area sensor. The difference between the average of the output data (I-mean) and the output data from successive scannings of the image speckles at the sensor plane was calculated and integrated to give as D-mean, and I-mean/D-mean was defined as normalized blur (NB), which is a quantitative index of blood flow velocity. The results were displayed in color graphics showing the 2-dimensional variation of the NB level in the area of interest. The NB had good correlation with the speed measured on ground glass in the range between 2 and 130mm/sec. Using this instrument, the effect of intraocular pressure on the chroidal circulation of the rabbit was studied. The coefficient of reproducibility was 6.9% when measured in the same area twice at 5-minute intervals. A stepwise reduction in the ocular perfusion pressure was introduced by elevating the intraocular pressure manometrically. A linear correlation was found between the NB and the ocular perfusion pressure.

Animals↗
PubMed1993

Effects of topical isoproterenol on bile acid-induced gastric mucosal injury.

Topical isoproterenol protects the gastric mucosa from the severe necrosis induced by 100 per cent ethanol. Its effect on gastric mucosal blood flow is unknown. The purpose of this study was to determine the effect of topical isoproterenol on gastric mucosal blood flow and on the less severe gastric mucosal injury caused by dilute bile acid. Prior to injury with topical 5 mM acidified taurocholate (pH 1.2), stomachs were pretreated with either saline or isoproterenol (low dose = 50 micrograms/kg; high dose = 500 micrograms/kg). Mucosal injury was assessed by measuring net transmucosal ion fluxes (H, K) and the appearance of DNA into the gastric lumen (DNAE). Gastric mucosal blood flow was determined by using laser doppler. Pretreatment with isoproterenol significantly decreased bile acid-induced net transmucosal ion fluxes and luminal accumulation of DNA, suggesting mucosal protection. Furthermore, this effect was dose-dependent on H and DNAE but not K. Pretreatment with topical high dose isoproterenol had no significant effect on gastric mucosal blood flow. Thus, topical pretreatment with isoproterenol dose dependently protects the gastric mucosa from the superficial injury caused by the application of dilute bile acid. This protective effect appears to be mediated by a mechanism other than augmentation of gastric mucosal blood flow.

Administration, Topical↗
PubMed1993

Soft tissue reconstruction. Monitoring.

Despite recent advances in technology, no safe and completely reliable monitoring device is available for clinical use. As a result, direct clinical evaluation remains the mainstay of post-operative monitoring efforts. Although we have found this technique to be reliable, we tend to supplement it with Doppler ultrasonography, particularly in those patients in whom the flap remains buried beneath the skin. In patients with replants, we use pulse oximetry as an adjunct to clinical findings. This has proved to be reliable in our experience. However, should any question arise concerning altered tissue perfusion, we remain liberal in our indications for reexploration. The old adage of "better safe than sorry" certainly applies, for it is much easier to reexplore a flap than to lose a potentially salvageable reconstruction. The future remains promising for techniques such as laser Doppler study and various methods of measuring transcutaneous oxygen. However, further experimental and clinical trials are necessary to determine the efficacy of these methods.

Blood Gas Monitoring, Transcutaneous↗
PubMedDate not supplied

[Measurement of cutaneous blood flow by laser Doppler velocimetry. Importance of probe effect and solvent effect after topical application].

A comparative methodological study of the probe and/or vehicle effects was performed in Human volunteers with two laser Doppler velocimeters (L.D.V.): Laserflo BPM 403, T.S.I., U.S.A. and Periflux PF2B, Perimed, Sweden. Individual variations of skin blood flow are great (up to 1,400%); this could be related to spontaneous variations and/or to the occlusive effect of the probe. Skin blood flow was significantly increased in 35% of the subjects after the application of the probe alone, and in 70 to 90% of the cases after topical application of water or ethanol (20 to 50 microliters). Lag times before vasodilatation measured only when the probe was applied on the skin were between 7.4 and 27 minutes, they were reduced between 5.2 and 8.3 minutes when the vehicles were applied. These data suggest that in any protocol for L.D.V. determination an absolute control and a vehicle control should be included to evaluate objectively topical vasoactive drugs.

Administration, Topical↗
PubMed1993

Effects of oxygen and carbon dioxide on human retinal circulation.

PURPOSE: Carbogen, a gas mixture of 95% O2 and 5% CO2, is given to patients with retinal artery obstruction in an attempt to improve retinal oxygenation. The purpose of this study was to compare the effects of carbogen and 100% O2 breathing on retinal blood flow. METHODS: On two separate occasions, 12 normal, healthy volunteers breathed air and then either 100% O2 or carbogen while laser Doppler velocimetry measurements and monochromatic fundus photographs were taken. Retinal vessel diameter, maximum velocity of red blood cells, and volumetric blood flow rate were determined in a main temporal vein. RESULTS: Both 100% O2 and carbogen caused significant average reductions in vessel diameter (14.1% and 10.6%, respectively), maximum red blood cell velocity (42.1% and 27.3%, respectively), and blood flow (56.4% and 42.2%, respectively). The average vasoconstriction of the large retinal veins caused by carbogen was not significantly smaller than that caused by 100% O2. The average reductions in maximum red blood cell velocity and blood flow caused by carbogen were significantly smaller than those caused by 100% O2 (P < .001 and P < .01, respectively). CONCLUSIONS: In normal subjects, inhalation of carbogen leads to less reduction in blood flow than inhalation of 100% O2, presumably by reducing the vasoconstriction of small arterioles induced by elevated oxygen levels.

Adult↗
PubMedDate not supplied

[Instrumental research of the functional character of the skin adnexa and microcirculation during chronic venous insufficiency].

We have led a microcirculatory and functional research of skin adnexa over 3 groups of 20 people each, who were affected with IVC at different grades and we have compared them to another group of 20 normal people. The microcirculatory researches (laser-Doppler, skin oximetry and thermometry) and functional ones of skin adnexa (sebometry and skin hydration) allowed us to get a nonunivocal behaviour between normal subjects and phlebopathies of I degree. For this reason, it is possible to consider these exams as screenings tests to determine the starting phases of phlebopathy, failing any skin marks. The reduced fluximetrical response taken by laser Doppler after postural variation and the reduction of hydration degree have been considered particularly significant.

Blood Gas Monitoring, Transcutaneous↗
PubMed1993

Sequential measurements of cerebral blood flow in the acute phase of subarachnoid hemorrhage.

Cerebral blood flow (CBF) measurements were made at predetermined intervals over the first 20 days after a subarachnoid hemorrhage (SAH) by the method of 133Xe inhalation clearance in 39 patients, Hunt and Hess degrees I, II or III. Mean hemispheral and regional blood flow showed a similar pattern of behavior over time: namely an initial hypoperfusion, being more marked in patients with consistent or thick blood deposition at CT scanning, followed by transient improvement and subsequent deterioration in the second week, this being especially conspicuous in patients who developed vasospasm; deterioration, at any rate, was distributed widely regardless of the initial CBF readings or magnitude of bleeding. Patients developing later neurological deficit (23% of the total) were those who showed a statistically significant increase of hemispheric asymmetries and regional hypoperfusion at the time when deterioration occurred. Accordingly, the Author calls attention to the practical value of CBF measurements in SAH patients, in view of the relationships that obtain between certain CBF patterns and the emergence of late neurologic deficits.

Acute Disease↗
PubMed1993

[Effect of hydralazine on the blood flow of normal and tumor tissues in hyperthermia].

We examined changes in blood flow in normal muscle and SCC-VII tumors of C 3 H/He mice following hyperthermia (HT) combined with the vasodilator hydralazine (Hyd) and compared them with similar changes after Hyd treatment or HT alone. Blood flow was measured by the Laser Doppler method, and oxygen tension was evaluated by polarography. The mean blood flow for the tumors in the Hyd group decreased. After HT treatment, it decreased to a low level. The largest decrease in tumor blood flow was observed after HT combined with Hyd administration. In normal muscle, no decrease in blood flow was induced by HT, Hyd or their combination. The magnitude of action of Hyd on the heat-induced changes in tumor blood flow and on damage to tumor vessels is considered to depend on the initial perfusion level. Therefore, we tried to clarify how this parameter was correlated with Hyd and/or HT-induced changes. In the HT and combined groups, the higher the temperature, the more significant the decrease in blood flow. In conclusion, these results suggest that the decrease in blood flow inside the tumor caused by Hyd plays an important role in enhancement of the hyperthermic anti-tumor effect.

Animals↗
PubMed1993

Nasal blood flow.

Although the assessment of allergic reactions was subjective for many years, it is now possible to evaluate nasal blockage objectively by measuring nasal airway resistance. To explore the pathophysiology of nasal blockage, however, it is necessary to analyze the separate components of obstruction, including secretions, cellular infiltrates, and microcirculatory parameters. The preferred techniques for measuring nasal mucosal blood flow are laser-Doppler velocimetry and radioactive xenon washout. Laser-Doppler velocimetry allows the measurement not only of blood flow but also of blood volume, red blood cell speed, and pulsatility of flow. It also permits continuous measurement of microcirculatory parameters over time. This technique has been used to assess the nasal microvascular response to neurohormones, antigenic challenge, and histamine challenge with and without antihistamine pretreatment.

Humans↗
PubMed1993

Variability of different patterns of skin oscillatory flux in healthy controls and patients with peripheral arterial occlusive disease.

Variability of patterns of laser Doppler flux motion was analysed at 5 different sites at the foot of 12 healthy controls and 24 patients with different degrees of ischemia due to peripheral arterial occlusive disease. Patterns were evaluated by means of the frequency histogram method. Three main flux motion components were detected at mean frequencies of 3.5 +/- 1.1 min-1 (low frequency waves, LF), 17.2 +/- 2.7 min-1 (high frequency waves, HF) and at 62.6 +/- 8.5 min-1 (pulsatile waves, PF). The characteristic pattern in normals consisted of LF and PF waves. In severe ischemia oscillatory flux was predominantly characterized by the combination of LF and HF waves and loss of pulsatile flux, or by the absence of any flux motion. Claudicants covered the entire spectrum of the flux motion patterns. In controls spatial variations were mainly due to the occasional presence of HF waves at one of the 5 sites. With increasing ischemia spatial variability of HF waves decreased due to more homogeneous presence. Loss of pulsatile flux was inhomogeneous in claudicants but almost complete in severe ischemia. Whereas LF waves were almost always observed at all sites of controls and claudicants there was considerable spatial variability in severe ischemia due to inhomogeneous loss of LF waves. Prevalence of the distinct flux motion patterns was well reproducible in controls and patients. Patterns showed a marked day to day variability when sites of measurement were compared.

Adult↗
PubMed1993

Betahistine-induced vascular effects in the rat cochlea.

Betahistine (BH) has been used widely to treat cochlear disorders, such as tinnitus and Meniere's disease. The mechanism of action of BH in the cochlea is assumed to be based on its histamine-like effect on H1 receptors in the cochlear vasculature, leading to an increased cochlear blood flow (CBF). Recently it has been shown that BH can strongly affect H3 heteroreceptors (a novel histamine receptor subclass) in the periphery, via an autonomic ligand. This mechanism may also contribute to the BH effects on CBF. This study was to validate BH effects in the cochlear vasculature and to investigate the possible mechanisms of action of this drug in the inner ear vasculature. We assessed the effects of BH on CBF with the laser Doppler flowmeter in 23 rats and concluded that BH affects vascular conductivity in the cochlea in a dose-dependent fashion; betahistine diffuses through the round window, but does not have access to vascular receptors or ligands once in the labyrinthine fluids; and the H1 receptors mediate the systemic and peripheral vascular effects of BH, whereas the cochlear effect involves cholinergic receptors.

Animals↗
PubMed1993

Retinal hemodynamics in proliferative diabetic retinopathy. A laser Doppler velocimetry study.

PURPOSE: This study investigated retinal hemodynamic changes associated with different pathologic features observed on fundus color and fluorescein angiography in patients with proliferative diabetic retinopathy. METHODS: Retinal circulatory characteristics were investigated in 25 eyes of 23 diabetic patients with proliferative retinopathy using a combination of bidirectional laser Doppler velocimetry and monochromatic fundus photography. RESULTS: Eyes with severe capillary nonperfusion had 32% less average volumetric blood flow rate (Q) than eyes with less severe nonperfusion (P = 0.0005). In addition, eyes with severe vessel staining with fluorescein had 20% less average Q than eyes without staining (P = 0.0508). Eyes with severe fluorescein leakage in the macula had a 17% larger total venous cross-section than eyes with milder leakage (P = 0.027). Eyes with clinically significant macular edema had 11% larger average venous diameter than eyes without this feature (P = 0.0085). CONCLUSIONS: Severe capillary nonperfusion and vessel staining with fluorescein are associated with decreased retinal blood flow rates. Vasodilatation may be an important factor for increased vascular permeability and macular edema in proliferative diabetic retinopathy.

Adult↗
PubMed1992

[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↗
PubMed1994

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↗