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Results for “Laser-Doppler Flowmetry”

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At least 793 records · Page 44Linked to original sources
PubMed1994

Low frequency oscillations of skin blood flux in peripheral arterial occlusive disease.

Using the laser Doppler technique patterns of spontaneous oscillations of skin blood flux within the low frequency band (< 10 min-1; LF waves) were analysed in 12 healthy controls and 24 patients with different degrees of peripheral arterial occlusive disease (PAOD). Measurements were performed at 5 different sites at the dorsum of the foot in healthy controls and patients with severe claudication or rest pain and/or gangrene due to PAOD. Patterns were classified as "periodic", "aperiodic" or "no flux motion". The aperiodic pattern was characteristic for skin blood flux of controls. In severe claudication prevalence of periodic LF oscillations significantly increased (p < 0.05) whereas it decreased again in patients with severe ischemia. In the latter group, LF waves often were completely absent. Periodic LF waves mainly occurred between an ankle/arm pressure ratio of 0.4 to 0.8. We suggest that periodic LF waves most likely ar the result of a synchronized vasomotor activity of different arterioles within the sample volume, whereas the aperiodic pattern may resemble the net effect of simultaneous activities of different control mechanisms on skin blood flow. Based on animal experiments it is hypothesized that decreased postocclusive driving pressure and flow in patients with advanced PAOD may be the stimulus for synchronized arteriolar vasomotion.

Adult↗
PubMed1994

[Study of cutaneous microcirculation using the laser-Doppler method in syndrome X].

Aim of the study was to verify the relationship between syndrome X and generalized microangiopathy. Three groups of patients were selected: Group A, 11 patients with typical syndrome X; Group B, 8 patients with atypical chest pain; Group C, 12 control normal subjects. Microvascular circulation was investigated with a laser Doppler Periflux PF3 at rest (15 min); during ischemia (3 min); during post-ischemic hyperemia on the plantar side of the big toe (where arterovenous anastomoses are particularly abundant) and on the dorsum of the foot (where these anastomoses are very scanty). During each recording we calculated: the mean flux value (FV); the mean concentration of moving blood cells (CMBC); the FV/CMBC ratio (which is related to the flow velocity); the mean percent increase of the three parameters during hyperemia. Patients with syndrome X as compared to the other subjects showed: 1) a significantly higher FV/CMBC ratio at rest and during hyperemia both on the plantar side of the big toe (respectively p = 0.01 and 0.015) and on the dorsum of the foot (respectively p = 0.011 and 0.006). These findings suggest a higher flow velocity in microvascular circulation; significantly lower percent increase of FV and CMBC during hyperemia in the plantar side of the big toe (respectively p = 0.04 and 0.014) but not on the dorsum. The increase of flow velocity at rest and low vasodilatatory reserve after ischemia in an area which is rich of arterovenous anastomoses in patients with syndrome X might be explained by the presence of a basal arterovenous hyperstomia.

Adult↗
PubMed1994

Retinal blood flow changes during pregnancy in women with diabetes.

PURPOSE: To study retinal blood flow (RBF) during pregnancy in subjects with and without diabetes and to relate the changes to progression in diabetic retinopathy. METHODS: RBF in a major temporal retinal vein was measured, where possible, during all three trimesters (T1 to T3) and the postpartum period (PP) using laser Doppler velocimetry (measuring velocity [V]) and monochromatic fundus photographs (measuring diameter [D]). RESULTS: In the subjects without diabetes (n = 19), no significant change in RBF was demonstrated. V was significantly greater in T3 than in PP (P = 0.01). D was significantly smaller in T1 to T3 than in PP (P < or = 0.01). RBF in the subjects with diabetes was significantly higher in T2 and T3 than in PP (P < 0.05). V increased from T1 to T2 (P = 0.04) and decreased from T2 to PP (P = 0.001) and from T3 to PP (P = 0.002). The only significant change in D was a smaller value in T1 than in PP (P = 0.003). However, it was only those subjects whose DR progressed (n = 11) who had a significant increase in RBF during pregnancy (P = 0.0001). CONCLUSIONS: These data suggest that the hyperdynamic circulation present in pregnancy led to compensatory retinal vessel constriction (autoregulation) in the group without diabetes; this was largely absent in the patients with diabetes, with resultant increase in retinal blood flow associated with worsening retinopathy. This finding lends further support to the hypothesis that increased retinal blood flow is a pathogenic mechanism for diabetic retinopathy.

Adult↗
PubMed1994

[Comparison of different monitoring techniques for vascular access in chronic hemodialysis].

Aim of the study was to compare different techniques of monitoring for vascular accesses in our chronic hemodialysis patients. Twenty seven patients (14 men, 13 women) were investigated. The accesses studied consisted of 19 arteriovenous fistulas and 8 vascular protheses. Twenty-four were trouble free, venous pressure was high in two, one was difficult to puncture. Three measurements of recirculation percentage were made for each patient, as well as a color Doppler flow imaging, and a digital angiography of the access. Recirculation measurements were normal for all patients including those with functional abnormalities. A stenosis was found 9 times with the Doppler and 10 times by angiography, there being disagreement between the two techniques in one case. The location of the stenosis was the same in the 9 concordant cases. There was a very strong correlation between the degree of stenosis found using the two techniques (p < 0.0001). In conclusion, measurement of recirculation appears to us to be of no interest for verifying a vascular access. On the other hand, the color Doppler seems to be an excellent choice for detecting an abnormality. An arteriographic confirmation seems necessary before correction.

Adolescent↗
PubMed1993

[Evaluation of neonatal prognosis using Doppler velocimeter in cases of a high risk fetus].

The authors describe the main characteristics of the Doppler method in the early diagnosis of chronic fetal distress, and report their personal results in the study of 51 high risk pregnancies. In their study the fetal doppler ultrasound findings were correlated with birth weight related to gestational age, and neonatal morbidity. The parameters established from the doppler ultrasound assessment were the placenta resistance (calculated from the formula of Pourcelot: R = S-D/S applied to the umbilical artery) and the cerebro-placental index, Rp/Rc, Rc being the index of cerebral arterial resistance. The diagnosis performance of the method appeared very good: the Rp index was found to be highly specific for hypotrophy (85,7%) and for neonatal morbidity (90%), the RCP index adding its own good sensitivity (85% for hypotrophy and 83,3% for neonatal morbidity). The authors conclude upon the interest to study simultaneously the fetal umbilical and cerebral arterial circulations. The pathological significance of the two indexes appears different so that they are to be complementary in the evaluation of fetal distress.

Female↗
PubMed1994

The hyperperfusion of the psoriatic plaque correlates histologically with dilatation of vessels.

We examined psoriatic lesions on the upper legs in 20 patients, using a two-dimensional Laser-Doppler-Scanner (Laser Doppler Perfusion Imager LDI, Lisca Development, Linköping/Sweden). The plaques were evaluated weekly during therapy with dithranol. Five plaques were reconstructed three-dimensionally before and after therapy (reconstruction program ANAT 3D, SIS, Münster, Germany). The psoriatic plaque was represented in the Laser Doppler Perfusion image as a sharply demarcated, hyperperfused area. The perfusion of the plaques dropped during therapy with dithranol to just slightly increased values, compared with normal skin (2.04 arbitrary units AU, healthy skin 1.1 AU). Using three-dimensional reconstruction, we investigated the volume of dermal vessels and the density of papillae. When compared, the volume of papillary vessels was twice as large in psoriatic as in healthy skin. The number of the papillae per square millimetre, detected by three-dimensional reconstruction, was not reduced significantly during therapy. We think that the increased perfusion of the psoriatic plaque is due to the combination of morphological (dilatation of vessels), dynamic (increased blood flow) and optical effects (reduced scattering and increased sampling depth of the laser-beam in acanthotic tissue).

Anthralin↗
PubMedDate not supplied

Effects of nonsteroidal anti-inflammatory drugs upon intrarenal blood flow: selective medullary hypoperfusion.

Nonsteroidal anti-inflammatory drugs (NSAIDs) predispose to acute and chronic renal failure, possibly due to intrarenal hemodynamic effects. In anesthetized volume-expanded rats, total renal blood flow (RBF) was measured by an ultrasonic flowmeter placed around the left renal artery, superficial cortical blood flow (sCBF) by a flunt laser-Doppler probe placed over the kidney surface, mid-cortical (mCBF) and outer medullary blood flow (oMBF) by a needle laser-Doppler probe inserted into the renal parenchyma. Indomethacin (5 mg/kg i.v.) caused no significant change in RBF (n = 9) or mCBF (n = 6) and slightly increased sCBF (to 106 +/- 2% of baseline; n = 8, p < 0.05). By contrast, oMBF dropped significantly (to 55 +/- 4% of baseline; n = 8, p < 0.0001) within 30 min of indomethacin administration. Similarly, acetylsalicylate (50 mg/kg i.v.) slightly increased sCBF (to 110 +/- 3% of baseline; n = 5, p < 0.05) but caused a significant drop in oMBF (to 54 +/- 2% of baseline; n = 5, p < 0.0001). These results suggest that NSAIDs cause a profound and selective reduction in oMBF which may predispose to acute or chronic intrarenal damage by aggravating medullary hypoxia.

Animals↗
PubMed1994

Transcutaneous Po2 and Pco2 measurement in dermatology.

Although transcutaneous Po2 (tcPo2) and Pco2 (tcPco2) measurement was originally developed for the non-invasive Pao2 and Paco2 monitoring, its utilization in dermatology is discussed in this article. Our experimental and clinical studies have revealed that tcPo2 is easily influenced and reduced by various skin changes, such as hyperkeratosis, acanthosis, cellular infiltrate and fibrosis as well as the circulatory disturbance in the skin, and that tcPco2 is kept stable except in ischemic or bullous lesions. Although tcPo2 could be a marker reflecting the severity of some lesions, simultaneous measurement of tcPco2 and cutaneous blood flow would offer more precise information about the circulation and respiration in the skin.

Animals↗
PubMed1994

Bioengineering and the skin: from standard error to standard operating procedure.

Bioengineering techniques for examination of the skin, measuring principles and sources of error relative to technique, study design, measuring conditions and variability related to test subjects and preconditioning are reviewed. Principles of validation and standard operating procedures (SOP) are discussed, including guidelines for measurement of transepidermal water loss (TEWL) and laser Doppler cutaneous blood flow. Today typical errors are not related to a measuring device but to the way it is used.

Biomedical Engineering↗
PubMed1993

Laser Doppler flux and tissue oxygen tension as indicators of colonic perfusion in pigs.

OBJECTIVE: To evaluate laser Doppler flowmetry (LDF) and tissue oximetry (TpO2) for intraoperative assessment of colonic perfusion in pigs. MATERIAL: Eight pigs weighing from 19-22 kg. INTERVENTIONS: Relationships of laser Doppler flux and TpO2 to mean arterial pressure (MAP) were measured in porcine sigmoid colon. The influence of different fractional inspired oxygen concentrations (FiO2) and the variability of the laser Doppler flux were evaluated. RESULTS: Highly significant reproducible non-linear perfusion compared with pressure relations were found with both methods (r > or = 0.9, p < 0.0001). There was a rapid decrease when MAP fell below 90 mmHg. The dependency of TpO2 on FiO2 was omitted by using the ratio TpO2:PaO2. The coefficient of variation of repeated LDF recordings of 30 second duration with the hand held probe was 0.11 (0.07-0.16) (median and 95% confidence interval). Three recordings gave a reproducible mean flux with an estimated precision of 10% either way. Simultaneous recordings with sutured and hand-held probes correlated well (r > or = 0.9, p < or = 0.01). CONCLUSION: Both methods yielded quantitative and reproducible intraoperative assessments of colonic perfusion, and are applicable for clinical use.

Animals↗
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↗
PubMed1982

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↗
PubMed1988

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↗