Non-invasive Laser Doppler Flowmetry Research Articles

Caspase-1 As a Therapeutic Target in Intravascular Hemolysis-Induced Microvascular Inflammation and Occlusive Processes

Hemolytic anemias, such as sickle cell disease (SCD), are a group of acute and acquired conditions characterized by the accelerated destruction of red blood cells (RBC). Intravascular hemolysis (IVH), or RBC lysis within the bloodstream, incurs the release of damage-associated molecular patterns (DAMPs), trigging cell activation and immune responses. Caspase-1 (Casp-1), a protease enzyme, plays a critical role during inflammatory processes by initiating programed cell death and promoting the cleavage of pro-interleukin (IL)-1β into its active form, IL-1β, through inflammasome assembly. Here, we aimed to elucidate the complex mechanisms involved in IVH-induced inflammation, leukocyte-endothelium interactions, and microvascular dynamics. Acute IVH was induced in C57BL/6 mice (HEM) by the injection of sterile water (i.v., 150 µl), and control mice received i.v. saline (CON) (n=3-8 per group). Intravital microscopy was performed at 15 min post IVH induction on the cremaster muscle of mice to quantify venular leukocyte (WBC) rolling and adhesion, and non-invasive laser Doppler flowmetry (LDF) measured blood perfusion in the murine pelvis microvasculature. Blood samples were collected at 1-hour post-IVH for ELISA and flow cytometry analyses. Immortalized human endothelial cells (HUVEC; n=7 per group) were stimulated with heme or S100A8 for 3 hours. HEM mice demonstrated significantly increased plasma heme (P<0.0001) and cell-free hemoglobin (P<0.001), in association with significantly decreased plasma haptoglobin (P<0.05), compared to CON mice, thereby confirming the occurrence of IVH. Furthermore, HEM mice exhibited significantly increased plasma concentrations of the S100A8 alarmin (P<0.001) and IL1-β (P<0.001), as well as augmentations (P<0.001) in plasma TNF-ɑ and IL-6 levels. Flow cytometry was used to measure active Casp-1 in neutrophils and monocytes of mice using the FAM-FLICA probe. FLICA staining was significantly higher in the neutrophils (P<0.05) and monocytes (P<0.05) of HEM mice, compared to CON mice, implying Casp-1 activation in these cell subsets. WBC-endothelium interactions are a hallmark of vaso-occlusion in SCD. HEM mice exhibited elevated venular WBC rolling and adhesion to the endothelium, compared to CON mice (P<0.001), as previously shown (Almeida et al., 2015; PMID: 26019278). In addition, IVH significantly reduced the velocity of microvascular blood flow in mice (P<0.001), and impaired perfusion (P<0.001). To address the role of IVH-induced Casp-1 activation in microvascular dynamics, mice received i.p. administrations of the Casp-1 inhibitor, YVAD, at 1 hour prior to induction of IVH, or not, and were subjected to intravital microscopy or LDF. Interestingly, the inhibition of Casp-1 significantly abrogated IVH-induced WBC rolling (P<0.01) and adhesion to vessel walls (P<0.05) in HEM mice and significantly improved microvascular blood perfusion and flow velocity (P<0.05), suggesting a role for Casp-1 activation in the WBC-endothelium and occlusive interactions observed (See Figure). We then evaluated how heme and S100A8 may induce endothelial cell activation, as these DAMPs were found elevated in the plasma of HEM mice. As expected, compared to unstimulated HUVEC, heme induced endothelial cell activation in vitro, as shown by higher expressions of ICAM-1 (P<0.05), VCAM-1 (P<0.01) and E-selectin (P<0.01), and increased Casp-1 activity (P<0.01). In turn, S100A8 alone significantly elevated ICAM-1 (P<0.05) and E-selectin (P<0.01) expressions on HUVEC, as well as IL-1β release (P<0.001), however no significant increase in Casp-1 activity was observed. HUVEC, when pre-treated with YVAD, displayed a significant reduction in S100A8-induced E-selectin expression (P<0.05), but neither ICAM-1 nor VCAM-1 expression were significantly decreased. In contrast, no changes in the expressions of these adhesion molecules were observed in heme-stimulated cells after YVAD treatment. Taken together, these findings suggest that targeting caspase-1 activation and its associated pathways may represent a potential therapeutic intervention to mitigate the adverse inflammatory and microvascular effects of IVH, a disease mechanism that occurs in severe hemolytic anemias such as SCD.

Investigation of changes in the skin blood microcirculation when performing the hatha yoga breathing technique

Introduction. Yoga breathing exercises improve the ability to significantly reduce the respiratory rate. A decrease of the minute respiration volume results in compensatory reactions of the microcirculatory bed caused by changes in the gas composition. The reaction of the regulatory mechanisms of the microvascular bed can be evaluated by the optical non-invasive laser Doppler flowmetry method. The aim of the study was to assess the tissue microcirculation parameter changes in people performing yoga breathing exercises. Materials and methods. 25 volunteers performed yoga breathing exercises at a frequency of 3 times per minute, 2 times per minute, 1.5 times per minute, 1 time per minute for 5 minutes, and free breathing for 6 minutes before and after breathing exercises. Parameters aimed to defin the reaction of skin microcirculation in different body areas were simultaneously recorded in six sites by laser Doppler flowmetry using a distributed system of wearable analyzers. The parameters of tissue microcirculation recorded by the method of laser Doppler flowmetry were: the index of microcirculation (Im), nutritive blood flow (Imn), the amplitude of myogenic (Am), neurogenic (An), endothelial (Ae), respiratory (Ar) and cardiac (Ac) regulation circuits. Results. Yoga breathing exercises led to increase of microcirculation index at all breathing frequencies. Breathing at a frequency of 1.5 and 1/minute leads to a significant increase in nutritional blood flow. Low-frequency breathing exercises lead to an increase in blood pressure at the lowest breathing rates – 1.5/minute and 1/minute. The most significant changes were achieved at the lowest respiration rates (1 and 1.5/minute), that could be associated with hypoxic-hypercapnic mechanisms. Conclusion. The absence of significant changes in microcirculation parameters after low-frequency respiration during measurements in the supraorbital arteries in both groups characterizes the work of homeostatic mechanisms for maintaining brain perfusion in stressful situations for the body (low-frequency types of respiration, hypercapnia and hypoxia). When measured in the extremities, a change in the effect of the circulatory system regulatory mechanisms was observed; along with an increase in skin perfusion and the nutritional component, it can characterize the compensatory reaction of the microcirculation to respiration change.

Evaluation of Shoulder Microcirculation Abnormality Using Laser Doppler Flowmetry

Severe neck-shoulder pain induces functional limitations in both life and work. The purpose of this study was to determine the characteristics of shoulder microcirculation abnormality in workers. This study recruited 32 workers and patients, both n = 16. Questionnaires were administered, and Laser Doppler Flowmetry (LDF) was used to measure microcirculatory blood flow (MBF) at the myofascial trigger points (MTrPs) on the shoulders. The absolute-deviationMMBF represented the mean MBF (MMBF) variability among subjects. The differences in the life characteristics, shoulder pain level, and microcirculatory characteristics at MTrPs between the two groups were compared. It was found that shoulder pain level was significantly higher in the patient than in the control group (p < 0.001). Deviation of the MMBF value beyond the postulated “normal range” of 60–80 was significantly higher in the patient than in the control group (p < 0.001). The MMBF deviation was significantly correlated with shoulder pain level, pain duration, and the symptom effect (p < 0.01, n = 32). A normal range for the MMBF of 60–80 on the shoulder near MTrPs is hypothesized for the first time based on this study. Noninvasive LDF can be used to assess abnormality in the MBF on shoulder MTrPs at an early stage.

Myofascial Treatment for Microcirculation in Patients with Postural Neck and Shoulder Pain.

Vascular impairment is a crucial factor associated with chronic muscle pain, but relevant research from the microcirculatory aspect is lacking. Here, we investigated the differences in neck muscle microcirculation detected through laser-doppler flowmetry (LDF) and cervical biomechanics by a videofluoroscopic image in asymptomatic participants and patients with postural neck and shoulder pain. To understand the mechanism behind the effect of myofascial treatment, transverse friction massage (TFM) was applied and the immediate effects of muscular intervention on microcirculation were monitored. In total, 16 asymptomatic participants and 22 patients (mean age = 26.3 ± 2.4 and 25.4 ± 3.2 years, respectively) were recruited. Their neck muscle microcirculation and spinal image sequence were assessed. The differences in the baseline blood flow between the asymptomatic and patient groups were nonsignificant. However, the standard deviations in the measurements of the upper trapezius muscle in the patients were significantly larger (p < 0.05). Regarding the TFM-induced responses of skin microcirculation, the blood flow ratio was significantly higher in the patients than in the asymptomatic participants (p < 0.05). In conclusion, postintervention hyperemia determined through noninvasive LDF may be an indicator for the understanding of the mechanism underlying massage therapies and the design of interventions for postural pain.

Laser Doppler flowmetry to assess myocardial microcirculation.

Several different methods enable the study peripheral microcirculation. Among them, non-invasive laser Doppler flowmetry (LDF) is routinely used to assess microvascular function by quantifying rapid changes in skin blood flow in response to a given pharmacological or mechanical stimulus [1]. Owing to its accessibility, peripheral microvascular function has been proposed as a diagnostic and prognostic marker in cardiovascular disease. Importantly, it has been shown that peripheral microvascular endothelial dysfunction correlates with endothelial function in coronary microvessels suggesting that endothelial dysfunction is a globalized pathological condition [2]. However, there is still a strong need in clinical practice to develop a tool which enables heart microcirculation in vivo assessment. Although, a direct assessment of the target microvascular bed such as coronary microcirculation is technically challenging. Cardiac surgery, especially coronary artery bypass grafting (CABG), may be associated with several cardiovascular complications, including ischemia or acute myocardial infarction, arrhythmias and hemodynamic instability. Therefore, the possibility of intra- and postoperative myocardial microvascular perfusion assessment is of major clinical importance. Various studies have indicated that LDF is able to detect the real-time oscillations in myocardial perfusion in different experimental setups [3]. Of note, there is relatively little data concerning myocardial microvascular measurements in humans.

Performance of noninvasive laser Doppler flowmetry and laser speckle contrast imaging methods in diagnosis of Buerger disease

Buerger disease (BD) is a nonatherosclerotic, inflammatory, segmental vascular occlusive disease, which affects small and medium-sized arteries and veins and is triggered by substantial tobacco exposure. Angiographic findings consistent with BD are required for diagnosis. Laser Doppler flowmetry (LDF) and laser speckle contrast imaging (LSCI) could represent potential noninvasive alternative techniques to angiography. We report the case of a 49-year-old smoker who developed an ischemic ulcer in the distal segment of the second finger of the left hand. He had no medical history. In our vascular center, LDF and LSCI are conducted routinely for digital artery disease diagnosis. LDF was indicative of digital obstructive artery disease (DOAD). Postocclusive reactive hyperemia, assessed by LCSI, demonstrated no skin blood flow (SBF) perfusion in the distal phalanx of the thumb, index, middle, and auricular fingers. Angiography confirmed BD, showing distally located multisegmental vessel occlusion and corkscrew collaterals in this patient's hands. Ilomedine treatment was initiated and smoking cessation was definitive. Recently, the patient had an improvement in clinical condition despite the persistence of a small zone of necrosis of the left index finger 28 days post-treatment. Our observation suggests that where suspicion of BD is based on clinical criteria, combining LDF and LSCI could represent a noninvasive, safe means of reaching BD diagnosis. Further clinical trials are necessary to confirm this novel observation.

Patterns of microcirculation changes in acute systemic cold injury

The aim of the work is to reveal patterns of changes in blood flow fluctuations due to autonomic tone in patients with acute systemic cold injury (ASCI) in hypothermic period. Materials and methods. 45 patients aged 18 to 45 years (3 groups of 15 patients with mild, moderate and severe cold trauma) were examined in the hypothermic period. The control group included 15 healthy volunteers. The subjects studied in the groups did not differ in gender, age and body weight. Microcirculation was assessed in all patients on admission using non-invasive laser doppler flowmetry (LDF). Results. In the study of perfusion and blood flow oscillations, it was established that the PM and σ values were increased in patients with mild degrees of ASCI relative to the control group, decreased in severe ASCI, and were not different from controls in moderate degree of ASCI. The parameters of Kv, A max (H), and A max (M) in patients with mild and moderate degree of ASCI did not significantly differ from the control group; however, in patients with acute intravascular coagulation, there was a marked increase in these parameters in comparison with the control group and with mild and moderate intensity ASCI. The A max (C) index did not show any difference in ASCI of mild and moderate degree relative to the control group, however, its decrease was noted in patients with a severe degree of ASCI compared with the control group and with mild and moderate degree of ASIDC. When studying the vibrational component of sympathetic regulation of blood vessels, it was established that the parameters of the normalized maximum amplitude A max (H)/σ and A max (M)/σ were decreased in patients with mild degree of hypothermia relative to the control group, increased with severe hypothermia and did not have a statistical difference with controls in moderate degree of ASCI. Conclusion. The hypothermic period of ASCI of mild degree is accompanied by a decrease in the vibrational component of sympathetic regulation of the vessels. In the hypothermic period of the moderate degree of ASCI, there is no pronounced change in the amplitude of the neurogenic regulation of the vessels. Severe degree of ASCI in this period is accompanied by a significant increase in blood flow fluctuations due to sympathetic regulation.

MICROCIRCULATORY DISORDERS IN NEWBORNS WITH HYPOXIC-ISCHEMIC LESIONS OF THE CENTRAL NERVOUS SYSTEM

The article explored microcirculatory disorders in newborns with hypoxic-ischemic lesions of the central nervous system. The obtained results made it possible to use a non-invasive laser Doppler flowmetry method for diagnosing microcirculation disorders and studying the regulatory factors controlling microhemodynamics in this category of patients. The ischemic type of microcirculatory disorders involving predominant ergotropic central regulation of the blood flow was observed in newborns with hypoxic-ischemic lesions of the central nervous system.

Optogenetic induction of cortical spreading depression in anesthetized and freely behaving mice

Cortical spreading depression, which plays an important role in multiple neurological disorders, has been studied primarily with experimental models that use highly invasive methods. We developed a relatively non-invasive optogenetic model to induce cortical spreading depression by transcranial stimulation of channelrhodopsin-2 ion channels expressed in cortical layer 5 neurons. Light-evoked cortical spreading depression in anesthetized and freely behaving mice was studied with intracortical DC-potentials, multi-unit activity and/or non-invasive laser Doppler flowmetry, and optical intrinsic signal imaging. In anesthetized mice, cortical spreading depression induction thresholds and propagation rates were similar for invasive (DC-potential) and non-invasive (laser Doppler flowmetry) recording paradigms. Cortical spreading depression-related vascular and parenchymal optical intrinsic signal changes were similar to those evoked with KCl. In freely behaving mice, DC-potential and multi-unit activity recordings combined with laser Doppler flowmetry revealed cortical spreading depression characteristics comparable to those under anesthesia, except for a shorter cortical spreading depression duration. Cortical spreading depression resulted in a short increase followed by prolonged reduction of spontaneous active behavior. Motor function, as assessed by wire grip tests, was transiently and unilaterally suppressed following a cortical spreading depression. Optogenetic cortical spreading depression induction has significant advantages over current models in that multiple cortical spreading depression events can be elicited in a non-invasive and cell type-selective fashion.

Combined Laser-Doppler Flowmetry and Spectrophotometry: Feasibility Study of a Novel Device for Monitoring Local Cortical Microcirculation during Aneurysm Surgery

Background Monitoring of cortical cerebral perfusion is essential, especially in neurovascular surgery. Study Aims To test a novel noninvasive laser-Doppler flowmetry and spectrophotometry device for feasibility during elective cerebral aneurysm surgery. Material and Methods In this prospective single-institution nonrandomized trial, we studied local cerebral microcirculation using the noninvasive laser-Doppler spectrophotometer "Oxygen-to-see" (O2C) in 20 consecutive patients (15 female, 5 male; median age: 60.5 ± 11.7 years) who were operated on for incidental cerebral aneurysms. Capillary-venous oxygenation (oxygen saturation ["SO2"]), postcapillary venous filling pressures (relative hemoglobin content ["rHb"]), blood cell velocity ("velo"), and blood flow ("flow") were measured in 7-mm tissue depth using a subdural fiberoptic probe. Results Representative recordings were acquired immediately after dural opening over a median time span of 88 ± 21.8 seconds (range: 60-128 seconds) before surgical manipulation. Baseline values (median ± 2 standard deviations) of brain perfusion as measured with the O2C device were SO2, 39 ± 16.6%; rHb, 53 ± 18.6 arbitrary units (AU); velo, 60 ± 20.4 AU; and flow, 311 ± 72.8 AU. Placement of the self-retaining retractor led to a decrease in SO2 of 17% ± 29% (p < .05) and flow of 10% ± 11% (p < .01); rHb increased by 18% ± 20% (p < .01), and velo remained unchanged. Retractor removal caused the opposite with an increased flow of 10% ± 7% (p < 0.001) and velo (3% ± 6%, p = 0.11), but a decrease in SO2 of 24% ± 33% (p = 0.09) and rHb of 12% ± 20% (p =0.18). No neurologic or surgical complications occurred. Conclusion Using this novel noninvasive system, we were able to measure local cerebral microcirculation during aneurysm surgery. Our data indicate that this device is able to detect changes during routine neurosurgical maneuvers. Thus it may be useful for early detection of cerebral microcirculatory disturbances.

A Novel Assessment of Flexibility by Microcirculatory Signals

Flexibility testing is one of the most important fitness assessments. It is generally evaluated by measuring the range of motion (RoM) of body segments around a joint center. This study presents a novel assessment of flexibility in the microcirculatory aspect. Eighteen college students were recruited for the flexibility assessment. The flexibility of the leg was defined according to the angle of active ankle dorsiflexion measured by goniometry. Six legs were excluded, and the remaining thirty legs were categorized into two groups, group H (n = 15 with higher flexibility) and group L (n = 15 with lower flexibility), according to their RoM. The microcirculatory signals of the gastrocnemius muscle on the belly were monitored by using Laser-Doppler Flowmetry (LDF) with a noninvasive skin probe. Three indices of nonpulsatile component (DC), pulsatile component (AC) and perfusion pulsatility (PP) were defined from the LDF signals after signal processing. The results revealed that both the DC and AC values of the group H that demonstrated higher stability underwent muscle stretching. In contrast, these indices of group L had interferences and became unstable during muscle stretching. The PP value of group H was a little higher than that of group L. These primary findings help us to understand the microcirculatory physiology of flexibility, and warrant further investigations for use of non-invasive LDF techniques in the assessment of flexibility.

Assessment of Retinal and Choroidal Blood Flow Changes Using Laser Doppler Flowmetry in Rats

Purpose: A new noninvasive laser Doppler flowmetry (LDF) probe (one emitting fiber surrounded by a ring of eight collecting fibers, 1-mm interaxis distance) was tested for its sensitivity to assess the retinal/choroidal blood flow variations in response to hypercapnia, hyperoxia, diverse vasoactive agents and following retinal arteries photocoagulation in the rat.Materials and Methods: After pupil dilation, a LDF probe was placed in contact to the cornea of anesthetized rats in the optic axis. Hypercapnia and hyperoxia were induced by inhalation of CO2 (8% in medical air) and O2 (100%) while pharmacological agents were injected intravitreously. The relative contribution of the choroidal circulation to the LDF signal was estimated after retinal artery occlusion by photocoagulation.Results: Blood flow was significantly increased by hypercapnia (18%), adenosine (14%) and sodium nitroprusside (16%) as compared to baseline values while it was decreased by hyperoxia (-8%) and endothelin-1 (-11%). Photocoagulation of retinal arteries significantly decreased blood flow level (-45%).Conclusions: Although choroidal circulation most likely contributes to the LDF signal in this setting, the results demonstrate that LDF represents a suitable in vivo noninvasive technique to monitor online relative reactivity of retinal perfusion to metabolic or pharmacological challenge. This technique could be used for repeatedly assessing blood flow reactivity in rodent models of ocular diseases.

Laser Doppler flowmetry detection of endothelial dysfunction in end-stage renal disease patients: Correlation with cardiovascular risk

Prediction of cardiovascular (CV) complications represents the Achilles' heel of end-stage renal disease. Surrogate markers of endothelial dysfunction have been advocated as predictors of CV risk in this cohort of patients. We have recently adapted a noninvasive laser Doppler flowmetry (LDF) functional testing of endothelium-dependent microvascular reactivity and demonstrated that end-stage renal disease patients are characterized by profound alterations in thermal hyperemic responsiveness. We hypothesized that such functional assessment of the cutaneous microcirculation may offer a valid, noninvasive test of the severity of endothelial dysfunction and CV risk. To test this hypothesis, we performed a cross-sectional study, in which we compared LDF measurements to conventional risk factors, and performed a pilot longitudinal study. LDF studies were performed in 70 patients and 33 controls. Framingham and Cardiorisk scores were near equivalent for low-risk patients, but more divergent as risk increased. C reactive protein (CRP) levels and LDF parameters (amplitude of thermal hyperemia (TH), area under the curve of TH) showed significant abnormality in high-risk vs low-risk patients calculated using either Framingham or Cardiorisk scores. Patients who had abnormal LDF parameters showed increased CV mortality, however, had similar risk assessments (Framingham, Cardiorisk, CRP, and homocysteine) to those with unimpaired LDF tracings. In conclusion, LDF parameters of microvascular reactivity offer a sensitive characterization of endothelial dysfunction, which may improve CV risk assessment through incorporation into the Framingham or Cardiorisk algorithm.

Free flap monitoring using simultaneous non-invasive laser Doppler flowmetry and tissue spectrophotometry

Early identification of flap failure is an indispensable prerequisite for flap salvage. Although many methods of free flap monitoring are available, there is still no single reliable non-invasive technique for early recognition of flap failure and for differentiation between arterial occlusion and venous congestion. The aim of this study was to investigate the benefits of the tissue oxygen analysis system O(2)C for monitoring patients undergoing maxillofacial reconstruction with fasciocutaneous radial forearm flaps. In a prospective clinical study the microcirculatory parameters of blood flow, flow velocity, haemoglobin concentration (AU, Arbitrary Units) and oxygen saturation (%) were assessed by clinical means, by laser Doppler flowmetry and tissue spectrophotometry in 61 patients intraoperatively. Measurements were carried out before flap harvest, in the separated radial forearm flap, immediately after anastomoses and up to 14 days after reconstruction. Following anastomosis, blood flow and flow velocity exceeded the level before flap elevation and reached significant differences by the third postoperative day (p<0.05). Oxygen saturation decreased significantly by the third postoperative day and haemoglobin oxygenation showed stable values after performing anastomosis. Simultaneous, non-invasive laser-Doppler flowmetry and tissue spectrophotometry detected vascular complications in all cases with no false positive or false negative results and prior to clinical assessment. For the first time this new device allows reliable prediction of venous congestion by an increase of haemoglobin-concentration, and of arterial occlusion by a decrease in blood flow parameters and oxygen saturation. It can thus differentiate the mechanisms of flap failure before clinical assessment.

2 Regional variations in skin blood flow under hot and humid conditions

Forearm skin blood flow has often been adopted in environmental studies to represent skin blood flow (SKBF) distribution to the whole body. In part, this can be attributed to the use of venous occlusion plethysmography which is commonly performed on the arm. However, more recently the use of non-invasive laser Doppler flowmetry has been employed to measure SKBF. Pre-pubertal children (5 female, 6 male; mean age 9.5 yr, range 7-12 yr) undertook a 45 min lower body intermittent exercise protocol under hot and humid conditions (32.5 ± 0.1 C, 70.6 ± 0.8% r.h.). The protocol included 10 min seated rest followed by three bouts of cycling separated by 5 min rest. Each exercise bout consisted of 5 min continuous cycling at 60% HRMAX followed by three 20 s sprints. Laser Doppler SKBF assessments were taken after each workload at four sites including forehead, back, forearm and medial calf. SKBF significantly increased after each of the workloads when compared to resting levels (p<0.01). Skin blood flow of the forearm (59.79 ± 5.85 mV) and calf (51.11 ± 6.94 mV) were significantly less than the forehead (119.83 ± 11.01 mV) and back (101.23 ± 8.24 mV; p<0.01). Additionally, calf SKBF was lower than head SKBF after workloads 2 and 3 while forearm and calf SKBF were lower than back SKBF after the final workload (p<0.05). These results suggest that employing forearm SKBF may not provide an accurate portrayal of SKBF to other body sites in children exercising under hot and humid conditions.

Efficacy of ice packs in the management of epistaxis.

There are no uniformly accepted criteria for the management of epistaxis. The usefulness of ice application in the treatment of epistaxis as a first aid method is not generally accepted, but is widespread. In order to evaluate the effect of cold application on the blood vessels of the nasal mucosa, their blood flow and blood content were investigated on 56 healthy volunteers before and after exposure to cold in the neck area. Nasal mucosal microcirculatory blood flow was measured directly by non-invasive laser Doppler flowmetry in Kiesselbach's area. Changes in the nasal mucosal blood content were estimated using a conventional computer-aided rhinomanometer by measuring alterations in nasal airflow. After ice application in the neck area, no statistically significant effects on the blood vessels of the nasal mucosa were seen. These results do not support the usefulness of this manoeuvre in the treatment of epistaxis.

Acute Effects of Vascular Modifying Agents in Solid Tumors Assessed by Noninvasive Laser Doppler Flowmetry and Near Infrared Spectroscopy

The potential of noninvasive laser Doppler flowmetry (LDF) and near infrared spectroscopy (NIRS) to detect acute effects of different vascular-modifying agents on perfusion and blood volume in tumors was evaluated. C3H mouse mammary carcinomas (∼200 mm3) in the rear foot of CDF1 mice were treated with flavone acetic acid (FAA, 150 mg/kg), 5,6-dimethylxanthenone-4acetic acid (DMXAA, 20 mg/kg), combretastatin A-4 disodium phosphate (CAMP, 250 mg/kg), hydralazine (HDZ, 5 mg/kg), or nicotinamide (NTA, 500 mg/kg). Tumor perfusion before and after treatment was evaluated by noninvasive LDF, using a 41°C heated custombuilt LDF probe with four integrated laser/receiver units, and tumor blood volume was estimated by MRS, using light guide coupled reflectance measurements at 800±10 nm. FAA, DMXAA, CAMP, and HDZ significantly decreased tumor perfusion by 50%, 47%, 73%, and 78%, respectively. In addition, FAA, DMXAA, and HDZ significantly reduced the blood volume within the tumor, indicating that these compounds to some degree shunted blood from the tumor to adjacent tissue, HDZ being most potent. CAMP caused no change in the tumor blood volume, indicating that the mechanism of action of CAMP was vascular shut down with the blood pool trapped in the tumor. NTA caused no change in either tumor perfusion or tumor blood volume. We conclude that noninvasive LDF and MRS can determine acute effects of vascular modifying agents on tumor perfusion and blood volume.

Influence of restorative manipulations on the blood perfusion of human marginal gingiva as measured by laser Doppler flowmetry.

Plaque accumulation caused by deficient fixed prosthodontics may evoke unequal degrees of gingival inflammation. Clinical investigation was performed to study the reaction of marginal gingiva during the course of routine prosthetic rehabilitation, e.g. replacement of two two-unit fixed partial dentures for aesthetic and functional reasons in a female patient. To characterize the actual state of gingival margin we recorded conventional gingivitis indices in conjunction with the employment of non-invasive laser Doppler flowmetry (LDF) for gingival perfusion measurements. Prior to the treatment procedures (control phase) the gingival indices were scored to 1 at all the five measuring points. At the end of the rehabilitation those values decreased to zero. A significant correlation was found between gingival indices and LDF readings (r=0.37, n=49, P < 0.01). Thus, our data suggest that monitoring of gingival blood perfusion by LDF may provide valuable information on the healing process of inflamed marginal gingiva.

Effect of the sensory neuropeptide antagonists h-CGRP (8–37) and SR 140.33 on pulpal and gingival blood flow in ferrets

In a previous study, it was concluded that the neuropeptides calcitonin gene-related peptide (CGRP) and substance P are released during resting conditions in the (exposed) ferret dental pulp, contributing to a basal vasodilator tone in the pulpal vessels. In order to exclude the possibility that the method used elicited axon reflexes, which might be responsible for neuropeptide release, the present study was designed without pulp exposure. Non-invasive laser–Doppler flowmetry was used to measure the effects of intra-arterial infusions of the antagonists h-CGRP (8–37) and SR 140.33 (neurokinin 1-receptor antagonist) on pulpal and gingival blood flow before, during and after electrical tooth stimulation. Infusions of h-CGRP (8–37) reduced the basal blood flow in the pulp by 31.4±5.2% ( p<0.001) and in the gingiva by 22.6±4.8% ( p<0.05). A further significant decrease in basal blood flow was measured in both pulp and gingiva following SR 140.33 administration. The reduction in blood flow was 16.9±1.9% ( p<0.005) in the pulp and 19.3±5.6% ( p<0.05) in the gingiva. The systemic arterial pressure remained unchanged both during and after the periods of infusion. Tooth stimulation before the antagonist infusion significantly increased the pulpal blood flow by 71.9±15.3% ( p<0.005). Infusion of h-CGRP (8–37) greatly reduced this electrically induced vasodilatation, indicating that CGRP is the principal factor responsible for the vasodilatation observed after tooth stimulation. This study confirms the previous finding that a resting vasodilator tone due to the release of CGRP and SP exists in the ferret dental pulp. It is concluded that spontaneous, basal release of the neuropeptides CGRP and substance P exists both in dental pulp and gingiva in the ferret.

Reproducibility of Laser Doppler Flowmetry in the Human Optic Nerve Head

We sought to demonstrate reproducibility of the noninvasive laser Doppler flowmetry technique for measuring microvascular hemodynamics of the optic nerve head in human subjects. Laser Doppler flowmetry was performed by four examiners on four human optic nerve heads during multiple sessions. Intersubject, interexaminer, intersession, and intrasession variabilities were calculated for velocity, blood volume, and blood flow (flux). Initial variability of measurements improved after 3 months' experience. The standard deviation of the intrasession variation for single readings was 18% of the velocity mean value and 24% of the flow (flux) mean value. Based on this, a sample size of 17 (power beta = 0.8, alpha = 0.05, paired t test) will demonstrate a 10% physiologic change in flux within a session if the average of five readings is used before and after the experimental perturbation. The intersession variation was 12% and 32% for velocity and flux, respectively. Because of this, a larger sample size or additional measurement sessions are required for detection of an experimental influence between two sessions. The coefficient of variation among subjects for single readings was 7% and 10% for velocity and flux, respectively. Reproducibility of velocity measurements is better than reproducibility of flux measurements. After experience with the method, laser Doppler flowmetry is sufficiently precise to permit feasible studies of human optic nerve head microvascular hemodynamics when physiologic perturbations are applied.