Use of laser Doppler flowmetry for estimation of the depth of burns

The trend for treatment of deep second degree burns and third degree burns is toward early excision and skin grafting. The ability to predict burn depth accurately as early as possible is important for early excision and skin grafting. This study, prospectively evaluated the ability of laser Doppler flow measurements, obtained within 72 hours after burn injury, to predict the depth of burn wounds. A Periflux system 4001 laser Doppler flowmeter was used to measure the cutaneous microflow circulation of 100 selected points of burn wounds on 44 inpatients and of 1680 selected points on 120 volunteers from March of 1993 to February of 1994. The mean value of superficial second degree burns checked by laser Doppler was 194.6 perfusion units (PU). The value of deep second degree burns was 59.7 PU, and the value of third degree burns was 5.1 PU. The mean normal cutaneous blood flow of 120 volunteers (control group) was between 4 and 9 PU, except on the head, neck, hand, and foot. Blood flow of more than 100 PU correctly predicted (90.2 percent of cases) a superficial second degree burn. Blood flow between 100 and 10 PU correctly predicted (96.2 percent of cases) a deep second degree dermal burn. That of less than 10 PU correctly predicted (100 percent of cases) a third degree burn. There was also a significant correlation between initial flow measurements and the depth of burn wounds. We conclude that laser Doppler flow measurements performed early after burn injury are useful in predicting the depth of burn wounds. Laser Doppler flowmetry has the advantage of being easy to use and noninvasive and of providing immediate results for early determination of burn depth. Laser Doppler flowmetry is useful in selecting patients for early excision and grafting of burn wounds.     

Possible involvement of neuropeptidergic sensory nerves in alopecia areata

Alopecia areata (AA) is a dermatosis involving the sudden occurrence of bald patches on the scalp. Although the aetiology is unknown, experimental data indicate that cutaneous microcirculation plays an important role. The skin is richly innervated by neuropeptidergic sensory nerves that help regulate microvascular circulation. This study shows a reduction of cutaneous levels of substance P and calcitonin gene-related peptide (CGRP) but not of vasoactive intestinal polypeptide in scalp biopsies from patients with AA. Laser-Doppler flowmetry was used to study microcirculation of the scalp. Results indicate that patients with AA have lower basal blood flow and greater vasodilatation following intradermal CGRP injection than control subjects. A vascular hyper-reactivity to vasodilatatory substances such as neuropeptides, probably because of the lack of these substances, is hypothesized.     

Modern aspects of surgical treatment of myopia

The Doppler laser flowmetry was used in order to study the microcirculation in the skin, muscles and bone marrow at different stages of obliterating atherosclerosis of the lower extremity arteries. Progress of the disease is characterized by a decrease of the absolute indices of blood flow in combination with disturbed regulation of vascular tension. The lumbar sympathectomy causes intensification of microcirculation not only in the skin, but also in the muscular and bone marrow tissues.     

Oxidation of low carbon steel in multicomponent gases: Part II. Reaction mechanisms during reheating

Oxidation behavior of low carbon steel during reheating in an industrial walking-beam steel reheat furnace was investigated. It was observed that scaling (oxidation) rates were reduced by reducing the input air/fuel ratio to the furnace, thereby lowering concentrations of free oxygen in the combustion products from about 3 to 1.5 pct. Laboratory experiments involving isothermal and nonisothermal oxidation were carried out in atmospheres consisting of oxygen, carbon dioxide, water vapor, and nitrogen. A general equation for the prediction of weight gains due to oxidation during reheating, using isothermal oxidation rate constants, was developed. The prediction of weight gains from nonisothermal oxidation conducted in the laboratory was poor, owing to a separation of the scale from the metal substrate which took place at about 900 °C. The predicted weight gains during reheating in the industrial reheat furnace indicated that oxidation rates during reheating were intermediate between linear and parabolic, especially during reheating with high air/fuel ratio. However, the linear mechanism predominated. Laboratory isothermal experiments for oxidation in atmospheres containing free oxygen showed that the magnitude of the linear oxidation rates was determined by the oxygen concentration in the atmosphere. It was concluded that the observed reduction in scaling rates during reheating of low carbon steel in the industrial reheat furnace was a result of the lower free oxygen level in the furnace atmosphere.     

Microcirculation in systemic hypertension

In 40 patients with idiopathic systemic hypertension, skin blood flow was evaluated with laser-Doppler flowmetry, transcutaneous measurements of partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2), and determination of capillary permeability before and after treatment with nifedipine (10 mg tid for four weeks). Also 35 normal subjects matched for age and sex distribution were studied. Before treatment, microcirculatory studies showed a significant decrease in skin flow and venoarteriolar response in hypertensive patients in comparison with normal subjects. Moreover, PO2, PCO2, and capillary permeability were significantly lower in hypertensives. All these microcirculatory parameters significantly increased after nifedipine treatment while both systolic and diastolic pressures decreased. In conclusion, laser-Doppler flowmetry used with other microcirculatory techniques was able to discriminate between normal subjects and hypertensive patients, and it was able to show the improvement in the microcirculation after nifedipine treatment.     

Mechanisms of anticarcinogenic properties of curcumin: the effect of curcumin on glutathione linked detoxification enzymes in rat liver

Clinicians lack a practical method for measuring CBF rapidly, repeatedly, and noninvasively at the bedside. A new noninvasive technique for estimation of cerebral hemodynamics by use of near-infrared spectroscopy (NIRS) and an intravenously infused tracer dye is proposed. Kinetics of the infrared tracer indocyanine green were monitored on the intact skull in pigs. According to an algorithm derived from fluorescein flowmetry, a relative blood flow index (BFI) was calculated. Data obtained were compared with cerebral and galeal blood flow values assessed by radioactive microspheres under baseline conditions and during hemorrhagic shock and resuscitation. Blood flow index correlated significantly (rs = 0.814, P < 0.001) with cortical blood flow but not with galeal blood flow (rs = 0.258). However, limits of agreement between BFI and CBF are rather wide (+/- 38.2 +/- 6.4 mL 100 g-1 min-1) and require further studies. Data presented demonstrate that detection of tracer kinetics in the cerebrovasculature by NIRS may serve as valuable tool for the noninvasive estimation of regional CBF. Indocyanine green dilution curves monitored noninvasively on the intact skull by NIRS reflect dye passage through the cerebral, not extracerebral, circulation.     

Transcranial Doppler and cortical microcirculation at increased intracranial pressure and during the Cushing response: an experimental study on rabbits

The effect of increased intracranial pressure on the flow velocity of the basilar artery was measured with transcranial ultrasonic Doppler in New Zealand White rabbits under alpha-chloralose anesthesia and artificial respiration. Laser Doppler flowmetry served to study changes of the cortical microcirculation. The results confirm a high inverse correlation of the diastolic flow velocity, the pulsatility index, and the resistance index with the cerebral perfusion pressure (CPP). During acute intracranial hypertension, however, these parameters do not show a good correlation with the local cortical blood flow. The absence of a correlation was evident over a wide CPP range down to values of 35 mm Hg. Only at CPP values below this critical threshold is the microcirculation impaired. The threshold is reached at pulsatility index values of more than 2.0 and at resistance index values of more than 0.8. Therefore, transcranial Doppler indices permit the detection of critical reductions of microcirculatory blood flow. The Cushing reaction occurred with a constant time lag of 5.5 +/- 0.7 seconds after the loss of CPP. The Cushing reaction did not establish systolic blood flow, which remained below the functional threshold, as concluded from the temporary loss of somatosensory evoked potentials.     

Use of ultrasound methods in vascular and circulatory diseases (author's transl)

The paper summarizes the principles, techniques and efficiency of ultrasound methods as indicator systems in the assessment of the peripheral and cerebral arteries; our studies predominantly refer to the use of these simple, non-invasive procedures in combination with sphygmo-oscillography and dynamographic circulation analysis, respectively. Ultrasound Doppler flowmetry (Pulse Doppler method), which permits relative measurements of the flow velocity in the peripheral haemodynamic regions, is of great importance in the rapid ascertainment of the patency of the major arterial trunks and the non-palpable vessels and also in the diagnosis, localization and follow-up control of stenoses and occlusions. Changes in the flow velocity due to organic or functional factors can be recorded by this method acoustically, oscilloscopically and graphically; measurements of the systolic blood pressure in the limb arteries by the Doppler technique provide semi-quantitative information in regard to the condition of the circulation. The registration of Doppler signals over the supra-orbital artery before and after compression of the superficial temporal artery and the common carotid artery has become established as a screening procedure for stenoses of the internal carotid artery. Ultrasound echography, which enables pulse registration and determination of vessel diameters, especially of the carotid siphon, can also be used for the detection of obstructions in the region of the internal carotid artery, as well as the vertebral artery.     

Nonintrusive Uncertainty Quantification in the Simulation of Steel Reheating Using Polynomial Chaos Expansion

Uncertainty quantification (UQ) is deemed critical in steel reheating simulations due to the significant input uncertainties arising when defining steel surface properties and atmospheric furnace conditions. In order to conduct UQ, the study utilizes polynomial chaos expansion, which has been found to significantly curtail the computational effort needed to obtain reliable convergent statistics for the model of interest. Results from a comprehensive UQ analysis of a walking-beam reheat furnace simulated using Tata Steel's reheat furnace control model, online slab temperature calculation, are presented. Slab temperature evolution and oxide scale growth are chosen as the study's QoIs. The analysis reveals that at the earlier stages of reheating, the majority of the output variance in slab temperature can be traced back exclusively to the emissivity of the slab surface, and the majority of the output variance in oxide scale growth is traced back to the combination of slab's surface emissivity and the initial scale thickness found on steel products prior to reheating. However, as the steel product advances toward the furnace's discharge end, inputs related to oxide scale growth become increasingly important, ultimately becoming the most influential input parameters, although the dynamics of this transition differ between the QoIs.     

Comparative study of artificial circulation for the liver after cardiogenic shock: pulsatile or nonpulsatile?

Because of multiple organ failure (MOF), the survival rate of patients with mechanical circulatory support has not been satisfactory, The purpose of this study is to estimate the effects of pulsatile and nonpulsatile artificial circulation on hepatic microcirculation and function. Cardiogenic shock was induced experimentally by ligating of left anterior descending branch in pigs. For the right ventricular assist device, a nonpulsatile pump (Nikkiso HPM-15) was employed. The left ventricular function was supported by either a nonpulsatile pump (Nikkiso HPM-15: NP group) or a pulsatile pump (Zeon Medical: P group). NP group was further divided into 80% support (NP-1 group) and 100% support (NP-2 group) of the control cardiac output. All groups were maintained at an equivalent mean aortic pressure of 3 hours. We measured the hepatic artery blood flow, portal vein flow and hepatic regional blood flow. For the metabolic and hepatic oxygen metabolic data, GOT, GPT, arterial blood ketone body ratio (AKBR), lactate/pirubic acid (L/P), and hyaluronic acid were evaluated. The mean aortic pressure was higher in the NP-2 group than in the other groups. The hepatic arterial blood flow was significantly higher in the P group than in the others. The AKBR and hepatic oxygen metabolism showed significant improvement in the P group in comparison with others. The regional blood flow in the liver showed improvements in the P and NP-2 groups. These findings suggested that pulsatile circulation may be beneficial for microcirculation of the liver; and the augmented nonpulsatile flow had effects similar to those of pulsatile flow in hepatic circulation.     

高效蓄热式烧嘴在二段式轧钢加热炉上应用的可行性研究

介绍了高效蓄热室技术的特点及技术关键。通过对大型厂现有二段式加热炉的分析,论述了高效蓄热式烧嘴在二段式加热炉上应用的可行性,并分析了其经济效益和社会效益。     

Local response of the primate retinal microcirculation to increased metabolic demand induced by flicker

PURPOSE: To study the response of the macular circulation to a local increase in metabolic demand created by a flickering source of illumination. METHODS: Laser-targeted angiography (release of a fluorescent dye from heat-sensitive liposomes using a laser pulse) was used to study, in subhuman primates, changes in hemodynamic parameters of the retinal circulation that were induced by a flickering source of illumination. Changes in the macular macrocirculation were compared with those in the macular microcirculation and were evaluated at various distances from the foveola. RESULTS: In response to monochromatic light flicker, the blood flow in retinal arteries increased by 30%. The response of the microcirculation was not homogeneous. It showed a maximum increase in the mid-perifoveal region where there is an increase in ganglion cells and nerve fibers. Interestingly, the maximum change in the index representing capillary blood flow exceeded the blood flow change in the artery (P < 0.08). CONCLUSIONS: A stimulus expected to cause increased metabolic demand results in a regulatory response by the retinal microcirculation. This response shows spatial variations that correspond with known variations in retinal anatomy. The authors propose that a redistribution of blood can occur between the capillary layers to fulfill high metabolic demands by neuronal tissue remote from the choroid.     

Early hemodynamic changes at the microcirculatory level and effects of mannitol following focal cryogenic injury

Changes in cerebral blood flow due to infusion of hyperosmolar solutions are of considerable importance in states of raised intracranial pressure. The present study was aimed to evaluate the effects of mannitol on the cerebral microcirculation, in a model of vasogenic brain edema. A right fronto-parietal craniotomy was performed in 30 adult Sprague-Dawley rats. Vasogenic edema was produced by placing dry-ice over the dura for 1 min. The cortical blood flow was monitored for 120 min using a laser-Doppler flowmeter (Perimed, Stockholm, Sweden), and graphics were recorded using a personal computer. Animals were randomly divided into three groups: group 1 (control group) received no mannitol; group 2 was treated with a bolus injection of 20% mannitol (1 mg kg-1); group 3 received the same dose over a 30 min infusion. Mean blood pressure, temperature, and respiratory rate were continuously monitored. At the end of the procedure, an intravenous injection of Evan's blue 2% was given. Results were compared by using repeated measures of analysis of variance and a two-sample t-test at each time. After the production of a cryogenic injury, we found a marked decrease in the cerebral blood flow, whereas mannitol partially reversed that effect. There was not significant difference between groups 2 and 3; however, there was a significant difference between mannitol and control groups after 15 min. During the early phase of vasogenic edema, early use of mannitol did not increase the blood flow, but stabilized it, preventing further decrease. Laser-Doppler flowmetry is a valuable method for continuous estimation of hemodynamic changes in the cerebral microcirculation.     

Genetic and behavioral determinants of waist-hip ratio and waist circumference in women twins

1. The microcirculation of the kidney is arranged in a manner that facilitates separation of blood flow to the cortex, outer medulla and inner medulla. 2. Resistance vessels in the renal vascular circuit include arcuate and interlobular arteries, glomerular afferent and efferent arterioles and descending vasa recta. 3. Vasoactive hormones that regulate smooth muscle cells of the renal circulation can originate outside the kidney (e.g. vasopressin), can be generated from nearby regions within the kidney (e.g. kinins, endothelins, adenosine) or they can be synthesized by adjacent endothelial cells (e.g. nitric oxide, prostacyclin, endothelins). 4. Vasoactive hormones released into the renal inner medullary microcirculation may be trapped by countercurrent exchange to act upon descending vasa recta within outer medullary vascular bundles. 5. Countercurrent blood flow within the renal medulla creates a hypoxic environment. Relative control of inner versus outer medullary blood flow may play a role to abrogate the hypoxia that arises from O2 consumption by the thick ascending limb of Henle. 6. Cortical blood flow is autoregulated. In contrast, the extent of autoregulation of medullary blood flow appears to be influenced by the volume status of the animal. Lack of medullary autoregulation during volume expansion may be part of fundamental processes that regulate salt and water excretion.     

Effects of electrical stimulation of cervical sympathetic trunks on microcirculation in the facial nerve

This study evaluates the circulatory effects of electrical stimulation of the cervical sympathetic trunks on blood flow in the common carotid artery and facial nerve tissue in dogs. Marked increases in arterial pressure and heart rate were observed due to electrical stimulation of the cervical sympathetic trunks, while blood flow volume in the common carotid artery and in the facial nerve tissue decreased markedly. It was assumed that microcirculation of the facial nerve is definitely impaired by electrical stimulation of the cervical sympathetic trunks, and the tonicity of the sympathetic nervous system appears to be a major factor in changes in the microcirculation of the facial nerve. It is well known that impaired circulation in the nutrient vessels of the facial nerve has an important effect on the pathogenesis of facial palsy. The hypertonicity of the sympathetic nervous system is closely involved in the onset of facial palsy.     

Hand blood flow at rest and during submaximal exercise in acute and chronic heat stress (author's transl)

Three groups of subjects, Europeans without any heat acclimation (called EE), Europeans after 3 weeks of acclimatization in India (EI), and Indians in their natural environment (II) were studied during exposure to an ambient temperature of 33 degrees C. Hand blood flow (Q), rectal temperature (Tre), mean cutaneous temperature (Tsk) were simultaneously recorded at rest and during 2 periods of muscular exercise (0.44 and 0.7 Vo2 max) of 35 mn duration. The results showed (1) at rest, Q was very high in EE, quite low in both EI and II; (2) at the onset of exercise, a hand vasoconstriction was observed in all cases; (3) during exercise, there was a progressive increase of Q until 200% maximum above rest values; (4) at the end of exercise, Q was proportional to the intensity of the exercise for each group and inversely proportional to the duration of heat exposure, the highest Q was observed in EE, the lowest in II and an intermediate value for EI close to the latter). These differences in hand blood flow could not be explained by differences in deep and/or superficial temperatures between subjects. Thus, during chronic heat exposure, there is, especially for an exercising man, a progressive modification of heat transport in the body: that is, a reduction of skin perfusion and a greater Tre-Tsk difference which are both adaptative responses. The value of hand blood flow as an estimation of whole superficial circulation is discussed.     

Herpes gestationis. A clinicopathologic study

Herpes gestationis is a pruritic, blistering eruption of pregnancy and the puerperium. In three patients with immunologically verified disease, the clinical presentation consisted of widespread erythematous, edematous papules and plaques, grouped vesicles on erythematous bases, and tense bullae. Histologically, these lesions showed a moderately dense, mixed-inflammatory cell infiltrate around superficial and deep dermal blood vessels, and focal necrosis of epidermal basal cells. Papillary dermal edema, subepidermal bullae, and spongiosis were prominent. Eosinophils were frequently present in the subepidermal and intrepidermal vesicles. Differentiation of herpes gestationis from other blistering diseases and other dermatitides of pregnancy may be difficult.     

Influence of Hydrodynamics on the Performance of a Biofilm Airlift Suspension Reactor

Five biofilm airlift suspension (BAS) reactors filled with ceramic materials as biocarriers were used to investigate the hydrodynamics, liquid mixing, and biofilm detachment kinetics in the BAS reactor. A mathematical model was developed to describe the internal liquid circulation within the BAS reactor. The Froude number was introduced to correlate the relationship between the Froude number and superficial gas velocity at different biocarrier concentrations. The validity of the empirical model was verified over a wide range of experimental conditions and the result shows that the internal liquid circulation velocity was proportional to the square root of the reactor height and the superficial gas velocity. Because the internal liquid circulation flow rate was much larger than influent flow rate, the BAS reactor had a strong capacity to resist shock loading caused by the change in influent organic matter concentration. Shock loading resistance increased with the height of a BAS reactor. Although biofilm detachment was a very complicated process which involved many mechanisms, dimensional analysis was employed to successfully analyze the biofilm detachment kinetics. It was found that the biofilm detachment rate was proportional to the first power of the superficial gas velocity and biofilm thickness, and to the 2/3 power of the number of biocarriers in the reactor, respectively. Use of the Froude number and dimensional analysis provide an effective and accurate method to study the characteristics of the BAS reactor.     

Superior mesenteric artery blood flow in celiac disease

Measurements of the hemodynamic parameters of the superior mesenteric artery were performed in 18 patients with celiac disease. Ten were studied at the time of diagnosis, when a small bowel biopsy showed a flat mucosa. The remaining eight patients were studied after complete clinical and histological recovery induced by a gluten-free diet. Doppler ultrasound flowmetry was used to measure blood flow in physiological and fasting conditions and after a mixed liquid test meal (Ensure-Plus). The results were compared with those of healthy subjects (N = 7). Mean basal flow was 50% higher in untreated celiac disease patients than in healthy controls and patients with chronic pancreatitis (P = NS). Postprandial mesenteric blood flow was significantly increased (P < 0.002) and delayed in time (P < 0.005) in celiac disease as compared to controls. Successful treatment reduced the mesenteric blood flow in celiac disease to normal values. Our study demonstrates that pathophysiological changes in the small bowel mucosa during the active clinical phase of celiac disease induce an abnormal splanchnic circulation.     

大方坯轴承钢的加热工艺探讨和优化

针对轴承钢坯料在加热炉加热中存在的问题,通过“黑匣子”（即在钢坯中植入热电偶装置,温度记录仪包在水冷装置内,随钢坯加热后炉外再提取数据）对钢坯实际加热工艺进行了测试,分析测试数据,讨论加热曲线变化趋势,结合现场加热炉实际炉长,对轴承钢的加热工艺进行了优化,改善了带状组织,使碳化物带状级别达到1.0级。