Laser Doppler Flowmetry Analysis Research Articles

Functional State of the Mesenteric Arteries and Vessels of the Skin Microcirculation Bed in Rats with Experimental Kidney Dysfunction

Chronic kidney disease is accompanied by cardiovascular complications, including endothelial dysfunction, arterial hypertension, and atherosclerosis. The aim of this work is to compare the reactivity of the vessels of the microcirculatory bed (MCR) of the skin, assessed by laser Doppler flowmetry (LDF) and mesenteric arteries in rats with resection of 5/6 of the mass of the kidneys, and to evaluate the possibility of using LDF analysis as a method that reflects the functional state of large resistive vessels. Wistar rats were divided into two groups: animals of the NE-group (n = 15) had 5/6 of the mass of kidney tissue removed, control animals of the SO-group (n = 15) underwent a sham operation. After 8 weeks, the reactivity of rat skin microvessels to acetylcholine (ACh) and sodium nitroprusside (NP) iontophoresis was assessed. A week later, in rats, the effect of NE on the reactivity of mesenteric arteries preconstricted with phenylephrine was evaluated in vivo using microphotographic and video recording of the diameter. It has been shown that NE does not affect the average value of perfusion in the skin of rats at rest, however, it changes the structure of the frequency range of the spectrum of fluctuations in the MCR index, increasing the value of endothelial, neurogenic, and myogenic tone. NE led to the development of endothelial dysfunction of the mesenteric arteries and MCR vessels of the skin, which was expressed in a decrease in vascular reactivity to the action of endothelium-dependent (ACh) and endothelium-independent (NP) vasodilators. Thus, the development of experimental kidney dysfunction led to changes in the spectral components of fluctuations in the MCR index in the skin, indicating an increase in tonic effects of various genesis on the vessels. NE was accompanied by a decrease in the reactivity of microvessels of the skin and mesenteric arteries, however, there was no correlation between an increase in the MCR index and dilatation of the mesenteric arteries under the action of vasodilator agonists.

Beat-to-beat and spectral analyses of the noninvasive radial pulse and laser-Doppler signals in patients with hypertension.

This study performed beat-to-beat and spectral analyses of 20-minute skin-surface laser-Doppler-flowmetry (LDF) and radial blood-pressure-waveform (BPW) signals in order to compare the blood-flow perfusion condition and regulatory mechanisms between essential-hypertension (EHT) patients and aged-matched control subjects. Beat-to-beat LDF analyses yielded the pulse width (PW), AC-to-DC ratio (AD), and their corresponding variability indices (coefficients of variation [CVs]). The relative energy contributions (RECs) of five characteristic frequency peaks (defined as FR1-FR5) were also calculated. Spectral BPW analysis obtained the amplitude proportion (Cn) and phase angle (Pn) of each harmonic component n. PW, AD, AD_CV, and REC of FR2 were significantly smaller in the EHT group than in the control group. Regarding BPW indices, C1, C2, C4, and C5 were significantly larger and P2-P8 were significantly smaller in EHT patients than in controls. The present results indicate that BPW and LDF indices can be used to evaluate the blood-flow perfusion efficiency and microcirculatory regulatory activities in EHT. Sex differences were found, with the effects being more prominent in female patients. These findings may be partly attributable to impairment of endothelial and neural regulatory functions. The present findings might aid the development of new noninvasive methods for reducing the risk of EHT-induced damage.

Clinical Outcomes and Gingival Blood Flowmetry of Two Types of Subepithelial Connective Tissue Graft for Root Coverage in Multiple Gingival Recessions: A Preliminary Study.

This randomized split-mouth preliminary clinical trial aimed to evaluate periodontal parameters and gingival blood flowmetry, comparing sites that received subepithelial connective tissue graft from the palate after deepithelialization (DE) or obtained with parallel incision (PI). Periodontal parameters were evaluated at baseline and 6 months postoperative. Gingival blood flows were analyzed by laser Doppler flowmetry (LDF) at baseline and 2, 7, and 14 days postoperative. Statistical and LDF analyses were performed with R version 3.5.1 and MATLAB software, and clinical parameters through ANOVA and Wilcoxon signed-rank tests. LDF showed superior decrease in power spectral density (PSD) for DE after 2 days. After 7 days, PSD returned to initial values only for PI, and DE had not returned to the initial values by day 14. Despite major initial revascularization challenges for DE sites, both grafts promoted satisfactory root coverage in the treatment of multiple gingival recessions.

Clinical Outcomes and Gingival Blood Flowmetry of Two Types of Subepithelial Connective Tissue Graft for Root Coverage in Multiple Gingival Recessions: A Preliminary Study

This randomized split-mouth preliminary clinical trial aimed to evaluate periodontal parameters and gingival blood flowmetry, comparing sites that received subepithelial connective tissue graft from the palate after deepithelialization (DE) or obtained with parallel incision (PI). Periodontal parameters were evaluated at baseline and 6 months postoperative. Gingival blood flows were analyzed by laser Doppler flowmetry (LDF) at baseline and 2, 7, and 14 days postoperative. Statistical and LDF analyses were performed with R version 3.5.1 and MATLAB software, and clinical parameters through ANOVA and Wilcoxon signed-rank tests. LDF showed superior decrease in power spectral density (PSD) for DE after 2 days. After 7 days, PSD returned to initial values only for PI, and DE had not returned to the initial values by day 14. Despite major initial revascularization challenges for DE sites, both grafts promoted satisfactory root coverage in the treatment of multiple gingival recessions.

Microcirculation as a goal of correction in macroangiopathy (atherogenesis)

Background. The microcirculatory system (MCS) is a network of blood vessels that includes arterioles, capillaries, venules, and terminal lymphatic vessels. Microcirculation is characterized by the constant variability. Factors of atherogenesis development due to MCS dysfunction include shear stress, hyperglycemia, dyslipidemia, systemic and local inflammation, hypoxia and endothelial dysfunction mediated by oxidative stress. Laser Doppler flowmetry (LDF) is used to study microcirculation in the clinical settings. The advantages of LDF include simplicity, accessibility and non-invasiveness.
 Objective. To describe the features of microcirculation disorders and their elimination.
 Materials and methods. Analysis of literature data on this topic; own study. The study involved 98 patients (59 females; 39 males) with a mean age of 52.0 years. The first group consisted of patients with coronary heart disease (CHD) and chronic heart failure of I-IIA grades, the second – of relatively healthy individuals. All patients underwent LDF, ultrasound examination of the carotid arteries, and determination of anthropometric parameters.
 Results and discussion. MCS dysfunction is not only a risk factor for atherogenesis, but also a trigger for its acute complications (myocardial infarction, stroke, sudden death). Nitric oxide (NO) deficiency plays an important role in this. A potential target of therapeutic influence in the treatment of coronary heart disease is not only macrovascular system, but also vasa vasorum. The condition of the latter determines the course of atherosclerosis. According to the results of our own study, patients with CHD demonstrated a muscle mass decrease, an increase in waist and hip circumference, and in body mass index. In addition, the groups differed in thickness of the intima-media complex of both common carotid arteries (right common carotid artery: CHD group – 0.79±0.18 mm; group of relatively healthy individuals – 0.69±0.13 mm, p<0,05; left common carotid artery: CHD group – 0.81±0.19 mm, group of relatively healthy individuals – 0.70±0.14 mm, p<0,05). When assessing the indicators of wavelet analysis of LDF, a significant decrease in the rate of microcirculation and capillary blood flow reserve is revealed in the CHD group, as well as an increase in peripheral vascular resistance. According to previous own studies, sorbitol (Reosorbilact, “Yuria-Pharm”) and pentoxifylline (Latren, “Yuria-Pharm”) can be used to correct microcirculation disorders. The use of these drugs leads to vasodilation of precapillary sphincters and improvement of regional microperfusion.
 Conclusions. 1. Disorders of MCS are the pathogenetic factors of the atherogenesis. 2. Laser Doppler flowmetry is used to study microcirculation in the clinical settings. 3. In patients with CHD there is an increase in neuro- and myotonus of the MCS, which is associated with the impaired release of nitric oxide. 4. Changes in microcirculation contribute to the development of atherosclerosis, which should be taken into account when choosing treatment for such patients. 5. Sorbitol (Reosorbilact) and pentoxifylline (Latren) can be used to correct microcirculation disorders.

Functional rehabilitation of patients after endovitreal surgery of rhegmatogenous retinal detachment with complete retinal attachment

To increase the functional effectiveness of endovitreal surgery in patients with RRD by including Cytoflavin in the system of postoperative rehabilitation. The study involved 68 patients with RRD aged 37 to 65 years. Patients underwent vitrectomy using the 25 Gauge technology with endolaser coagulation of rupture zones and silicone oil tamponade in the vitreous cavity. Three months after the surgery, silicone oil was removed from the vitreous cavity. Patients were divided into 2 groups: the main - 34 people who received Cytoflavin in addition to standard therapy, and the control - 34 people receiving only standard postoperative treatment. The time course of the treatment's functional effectiveness was analyzed using best corrected visual acuity (BCVA) and macular photosensitivity. Laser Doppler flowmetry (LDF) was used to register the microcirculation and microcirculation efficiency indices. Morphological signs of macular ischemia were registered by optical coherence tomography angiography (OCT-A). Patients of the main group showed higher level of restoration of macular function compared with the control group. The increase in functional activity of the macular area correlated with postoperative dynamics of restoration of central retinal thickness. Analysis of LDF and OCT-A indices showed that improvement of visual functions in patients treated with Cytoflavin is directly related to restoration of chorioretinal blood flow. The use of Cytoflavin in patients after endovitreal surgery of RRD led to improvement of BCVA by an average of 2.6 times and photosensitivity of the macula by 2 times. The visual functions of patients improved after using Cytoflavin due to its positive effect on chorioretinal microcirculation and the density of macular capillary plexuses.

Wavelet Analysis of the Temporal Dynamics of the Laser Speckle Contrast in Human Skin.

Spectral analysis of laser Doppler flowmetry (LDF) signals has been widely used in studies of physiological vascular function regulation. An alternative to LDF is the laser speckle contrast imaging method (LSCI), which is based on the same physical principle. In contrast to LDF, LSCI provides non-scanning full-field imaging of a relatively wide skin area and offers high spatial and temporal resolutions, which allows visualization of microvascular structure. This circumstance, together with a large number of works which had shown the effectiveness of temporal LSCI analysis, gave impetus to experimental studies of the relation between LDF and LSCI used to monitor the temporal dynamics of blood flow. Continuous wavelet transform was applied to construct a time-frequency representation of a signal. Analysis of 10 minute LDF and LSCI output signals recorded simultaneously revealed rather high correlation between oscillating components. It was demonstrated for the first time that the spectral energy of oscillations in the 0.01-2Hz frequency range of temporal LSCI recordings carries the same information as the conventional LDF recordings and hence it reflects the same physiological vascular tone regulation mechanisms. The approach proposed can be used to investigate speckle pattern dynamics by LSCI in both normal and pathological conditions. The results of research on the influence of spatial binning and averaging on the spectral characteristics of perfusion monitored by LSCI are of considerable interest for the development of LSCI systems optimized to evaluate temporal dynamics.

Comparing the effects of human hind limb massage by analysis of Laser Doppler Flowmetry and Photoplethysmography signal components using the wavelet transform

Comparing the effects of human hind limb massage by analysis of Laser Doppler Flowmetry and Photoplethysmography signal components using the wavelet transform

Kidney dysfunction in the low-birth weight murine adult: implications of oxidative stress

Maternal undernutrition (MUN) during pregnancy leads to low-birth weight (LBW) neonates that have a reduced kidney nephron endowment and higher morbidity as adults. Using a severe combined caloric and protein-restricted mouse model of MUN to generate LBW mice, we examined the progression of renal insufficiency in LBW adults. Through 6 mo of age, LBW males experienced greater albuminuria (ELISA analysis), a more rapid onset of glomerular hypertrophy, and a worse survival rate than LBW females. In contrast, both sexes experienced a comparable progressive decline in renal vascular density (immunofluorescence analysis), renal blood flow (Laser-Doppler flowmetry analysis), glomerular filtration rate (FITC-sinistrin clearance analysis), and a progressive increase in systemic blood pressure (measured via tail-cuff method). Isolated aortas from both LBW sexes demonstrated reduced vasodilation in response to ACh, indicative of reduced nitric oxide bioavailability and endothelial dysfunction. ELISA and immunofluorescence analysis revealed a significant increase of circulating reactive oxygen species and NADPH oxidase type 4 (NOX4) expression in both LBW sexes, although these increases were more pronounced in males. Although more effective in males, chronic tempol treatment did improve all observed pathologies in both sexes of LBW mice. Chronic NOX4 inhibition with GKT137831 was more effective than tempol in preventing pathologies in LBW males. In conclusion, despite some minor differences, LBW female and male adults have a reduced nephron endowment comparable with progressive renal and vascular dysfunction, which is associated with increased oxidative stress and subsequent endothelial dysfunction. Tempol treatment and/or NOX4 inhibition attenuates renal and vascular dysfunction in LBW adults.

Characteristic of the cerebral cortex microcirculation after ischemia

Introduction. The outcome of ischemia is depending on a condition of microcirculatory bed. The important factor in development of cerebral ischemia is regulation of microvascular function, influencing both perfusion and oxygenation of cerebral tissue. The aim of the current study was to examine the time course of micirculatory changes in rat cerebral cortex, as well as to assess the changes in oscillatory components of myogenic, neurogenic and endothelial levels of cortical microvessel tone within 21 days after ischemia. Methods. Transient global cerebral ischemia was induced in anesthetized Wistar rats by clamping of both common carotid arteries for 12 min with simultaneous controlled hypotension to 45±3 mm Hg, followed by blood reinfusion and recovering from anesthesia. Five different groups of rats were re-anesthetized at 1 hour and 2, 7, 14 or 21 days after ischemia and subjected to studies using continuous wavelet transform analysis of laser Doppler flowmetry. Results. In the first 7 days of the post-ischemic period, peripheral resistance was reduced in the cerebral cortex, which was associated with domination of nutritive blood flow. By 14th day after ischemia it resulted in the blood stagnation connected with development of endothelial dysfunction. From 14th to 21st day post-ischemia, the increase of shunt blood flow was noted. It was possibly a consequence of blood shunting processes happening in a cerebral cortex bypassing a nutritive level that prevents microcirculation from congestion. Conclusions. It is established that transient global cerebral ischemia results in significant changes of microcirculation in cerebral cortex lasting at least 3 weeks after ischemia. Initial dominant nutritive blood flow is probably due to blood congestion because of endothelial dysfunction. Three weeks post-ischemia, it is followed by increase in shunt blood flow that can prevent blood congestion in microcirculatory vascular bed.

Bifurcation in Blood Oscillatory Rhythms for Patients with Ischemic Stroke: A Small Scale Clinical Trial using Laser Doppler Flowmetry and Computational Modeling of Vasomotion.

We describe application of spectral analysis of laser Doppler flowmetry (LDF) signals to investigation of cerebrovascular haemodynamics in patients with post-acute ischemic stroke (AIS) and cerebrovascular insufficiency. LDF was performed from 3 to 7 days after the onset of AIS on forehead in the right and left supraorbital regions in patients. Analysis of LDF signals showed that perfusion in the microvasculature in AIS patients was lower than that in patients with cerebrovascular insufficiency. As a result of wavelet analysis of the LDF signals we obtained activation of the vasomotion in the frequency range of myogenic oscillation of 0.1 Hz and predominantly nutritive regime microcirculation after systemic thrombolytic therapy of the AIS patients. In case of significant stroke size, myogenic activity, and nutritive pattern microhaemodynamics were reduced, in some cases non-nutritive pattern and/or venular stasis was revealed. Wavelet analysis of the LDF signals also showed asymmetry in wavelet spectra of the LDF signals obtained in stroke-affected and unaffected hemispheres in the AIS patients. A mechanism underlying the observed asymmetry was analyzed by computational modeling of vasomotion developed in Arciero and Secomb (2012). We applied this model to describe relaxation oscillation of arteriole diameter which is forced by myogenic oscillation induced by synchronous calcium oscillation in vascular smooth muscle cells. Calculation showed that vasomotion frequency spectrum at the low-frequency range (0.01 Hz) is reciprocally modulated by myogenic oscillation (0.1 Hz) that correlates with experimental observation of inter-hemispheric variation in the LDF spectrum.

Relationship of oscillating and average components of laser Doppler flowmetry signal.

Signals from laser Doppler flowmeters widely used in intravital studies of skin blood flow include, along with a slowly varying average component, an oscillating part. However, in most clinical studies, pulsations are usually smoothed by data preprocessing and only the mean blood flow is analyzed. To reveal the relationship between average and oscillating perfusion components measured by a laser Doppler flowmeter, we examined the microvascular response to the contralateral cold pressor test recorded at two different sites of the hand: dorsal part of the arm and finger pad. Such a protocol makes it possible to provide a wide range of perfusion. The average perfusion always decreases during cooling, while the oscillating component demonstrates a differently directed response. The wavelet analysis of laser Doppler flowmetry (LDF) signals shows that the pulsatile component is nonlinearly related to the average perfusion. Under low perfusion, the amplitude of pulsations is proportional to its mean value, but, as perfusion increases, the amplitude of pulsations becomes lower. The type of response is defined by the basal perfusion and the degree of vasoconstriction caused by cooling. Interpretation of the results is complicated by the nonlinear transfer function of the LDF device, the contribution of which is studied using artificial examples.

Multifractal analysis of heart rate variability and laser Doppler flowmetry fluctuations:comparison of results from different numerical methods

To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.

Recovery of 0.1 Hz microvascular skin blood flow in dysautonomic diabetic (type 2) neuropathy by using Frequency Rhythmic Electrical Modulation System (FREMS)

Synchronized oscillation of smooth muscle cells tension in arterioles is the main control system of microvascular skin blood flow. An important autogenic vasomotion activity is recognized in 0.1 Hz oscillations through power spectrum analysis of laser Doppler flowmetry. Severe dysautonomia in diabetic neuropathy is correlated with loss of 0.1 Hz vasomotor activity, hence with impaired blood microcirculation. FREMS is a novel transcutaneous electrotherapy characterized by sequences of electrical stimuli of high voltage and low pulse duration which vary both in frequency and duration. We have evaluated the changes in laser Doppler flow in the volar part of the forearm before, during and after FREMS. Normal controls ( n = 10 , 6 females, age range 21–39 years) demonstrated significant 0.1 Hz vasomotion power spectra at baseline conditions associated with large oscillations of adrenergic cutaneous sweat activity sampled from the hand; people with diabetes type 2 and severe dysautonomia ( n = 10 , 5 females, age range 63–75 years) displayed a significant decrease of 0.1 Hz vasomotion power spectra. During FREMS application we observed an increase ( p < 0.05 ) of 0.1 Hz vasomotion power spectra only in the diabetic group, despite persistence of adrenergic cutaneous sweat activity suppression in this group. However, after the application of the stimuli, the relative energy values around the 0.1 Hz peak remained significantly higher than preapplication values in the diabetic group ( p < 0.05 ). From these findings, we suggest that FREMS is able to synchronize smooth cell activity, inducing and increasing 0.1 Hz vasomotion, independently from the autonomic nervous system.

Sympathetic mediated vasomotion and skin capillary permeability in diabetic patients with peripheral neuropathy.

A loss of sympathetic function could lead to changes in capillary fluid filtration in diabetic patients. We investigated whether a decreased sympathetically mediated vasomotion in the skin in diabetic patients with peripheral neuropathy is associated with an abnormal capillary leakage. Three matched groups were studied: 18 diabetic patients with documented peripheral neuropathy (DN), 18 diabetic patients without peripheral neuropathy (D), and 18 healthy control subjects (C). Sensory and motor nerve function of the distal extremities were assessed by standard neurography, and expressed in a sensory-motor nerve function score. Sympathetic vasomotion of the skin microcirculation was assessed by determining the power of blood flow variability in the low-frequency (0.02-0.14 Hz) band by spectral analysis of laser Doppler flowmetry at the median ankle. Skin capillary leakage was evaluated by sodium fluorescein videodensitometry at the same site of the foot. Sympathetically mediated vasomotion of the foot skin microcirculation was lower in diabetic patients with documented peripheral neuropathy compared with diabetic patients without peripheral neuropathy and control subjects (p<0.001). Capillary sodium fluorescein leakage was larger in 18 diabetic patients with documented peripheral neuropathy than in diabetic patients without peripheral neuropathy (p<0.02) and C (p<0.005). Multiple regression analysis disclosed that a reduced sympathetically mediated vasomotion, together with a lower sensory-motor nerve function score, independently contributed to the variance in sodium fluorescein leakage, for 30% (p<0.001) and 17% (p<0.01), respectively. A loss of sympathetic tone, apart from sensory-motor nerve dysfunction, seems to be a major determinant of an increased capillary permeability in diabetic patients with neuropathy.

Evaluation of autonomic disorders in familial amyloidotic polyneuropathy (FAP)

Most serious complaint of familial amyloid0tic polyneuropathy (FAP) patients, beside polyneurolmthy, is disorder of the autonomic nervous system such as alternating diarrhea and constipation, orthostatic hypotension, urinary incontinence, dry mouth and dry eyes. To evaluate various autonomic dysfunctions found in FAP patients systematically, we performed various upto-date autonomic function examinations, such as reflex blood flow in the palm by laser Doppler flowmetry (LDF), power spectrum of cardiographic R-R interval, day profile and oral glucose tolerance test, modified gam test, tear secretion test, pupillary function test by iris corder, and detection of abnormal vessels in the conjunctiva. Especially, analysis of LDF and R-R interval revealed that the autonomic nervous system was first affected in asymptomatic carriers of FAP and FAP patients at the very early stage of FAP. Abnormalities of day profile of glucose, oral glucose tolerance test and modified gain test were seen even at the early stages of FAP. However, ophthalmological autonomic examinations revealed that severity of autonomic dysfunction did not correlate with the progressive course of FAP. Since FAP patients with severe autonomic disorders show the undesirable prognosis, precise examinations and therapy for the autonomic dysfunctions may be indispensable for controlling the clinical symptoms of FAP patients.

Clinical use of laser Doppler flowmetry in a burns unit.

Laser Doppler Flowmetry (LDF) is a new noninvasive technique by which microcirculation changes in tissue can be studied. This has been done in a Burns Unit on burned as well as non-burned patients (volunteers). There were no infection problems with this device in a Burns Unit. Four kHz was the upper wave length limit analysing the doppler signal from burns. A topical temperature load test was defined and used in different situations. Homogeneous flows in reference points from a control group were demonstrated in unheated and heated skin, in this way standardizing the LDF analyses of skin microflow. Ability of LDF to define different degrees of burns was demonstrated.