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Development of a novel noninvasive system for measurement and imaging of the arterial phase oxygen density ratio in the retinal microcirculation
摘要： Purpose This study was conducted in order to develop a novel noninvasive system for measurement and imaging of the arterial oxygen density ratio (ODR) in the retinal microcirculation. Methods We developed a system composed of two digital cameras with two different filters, which were attached to a fundus camera capable of simultaneously obtaining two images. Actual measurements were performed on healthy volunteer eyes (n = 61). A new algorithm for ODR measurement and pixel-level imaging of erythrocytes was constructed from these data. The algorithm was based on the morphological closing operation and the line convergence index filter. For system calibration, we compared and verified the ODR values in arterioles and venules that were specified in advance for 56 eyes with reproducibility. In 10 additional volunteers, ODR measurements and imaging of the arterial phase in the retinal microcirculation corresponding to changes in oxygen saturation of the peripheral arteries at normal breathing and breath holding were performed. Results Estimation of incident light to erythrocytes and pixel-level ODR calculation were achieved using the algorithm. The mean ODR values of arterioles and venules were 0.77 ± 0.060 and 1.02 ± 0.067, respectively. It was possible to separate these regions, calibrate at the pixel level, and estimate the arterial phase. In each of the 10 volunteers, changes in the arterial phase ODR corresponding to changes in oxygen saturation of the peripheral arteries were observed before and after breath holding on ODR images. The mean ODR in 10 volunteers was increased by breath holding (p < 0.05). Conclusions We developed a basic system for arterial phase ODR measurement and imaging of the retinal microcirculation. With further validation and development, this may provide a useful tool for evaluating retinal oxygen metabolism in the retinal microcirculation.
关键词： Retinal microcirculation region,Arterial phase,Line convergence index filter,Oxygen density ratio,Morphological closing operation
更新于2025-09-23 15:23:52
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<p>Assessing Renal Microvascular Reactivity by Laser Speckle-Contrast Imaging in Angiotensin-II-Treated Mice</p>
摘要： The kidney is one of the main organs affected by microvascular damage wrought by hypertension. We developed an approach to investigate renal microcirculatory disturbance in live mice by measuring post-occlusive reactive hyperemia (PORH), a reactivity test exploring endothelial and neuro-microvascular functioning. Laser speckle-contrast analysis (LASCA) assesses microvascular blood flow; it provides real-time images of spatial and temporal blood flow dynamics. We compared basal blood flow and PORH test between control and angiotensin-II-treated mice (Ang-II) to validate the model.
关键词： hypertension,renal microcirculation,laser speckle-contrast analysis,microvascular reactivity
更新于2025-09-23 15:21:01
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Noninvasive Flap Monitoring using Sidestream Dark Field Microscan: A Method for Real-Time Observation of Submilimmetric Vessels
摘要： A timely diagnosis of vascular compromise improves free flap survival. The aim of this study was to determine the feasibility of monitoring flap vascular patency through noninvasive microcirculation monitoring using SDF. An experimental study was performed in five volunteers. A radial forearm flap was simulated in both upper extremities and cutaneous microcirculation assessment devices were used (SDF and NIRS), and compared with clinical and doppler evaluation. Conditions of venous occlusion (VO) and total vascular occlusion (TVO) were mimicked by using a cuff. The results of the Microscan SDF monitoring during VO and TVO showed a reduced microcirculatory flow at 16.5 (6-30) and 6 (2-11) seconds respectively. Both NIRS and clinical evaluation were slower than SDF at identifying vascular compromise. During VO the Doppler signal does not disappear; while in TVO the signal disappeared at 1.8 (1-5) seconds. This study shows that evaluation of microcirculation with Microscan SDF is a viable alternative that may allow detection of flap venous and total vascular occlusion earlier than Doppler, NIRS and clinical evaluation.
关键词： Evaluation,Microsurgery,Monitoring,Microcirculation
更新于2025-09-23 15:21:01
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Microcirculatory Response to Photobiomodulationa??Why Some Respond and Others Do Not: A Randomized Controlled Study
摘要： Photobiomodulation (PBM), a non‐ionizing, non‐thermal irradiation, used clinically to accelerate wound healing and inhibit pain, was previously shown to increase blood flow. However, some individuals respond to PBM, but others do not. The purpose of this study was to investigate factors affecting this patient‐specific response using advanced, noninvasive methods for monitoring microcirculatory activity. In this prospective, randomized controlled trial (NCT03357523), 20 healthy non‐smoking volunteers (10:10 males:females, 30 ± 8 years old) were randomized to receive either red‐ (633 nm and 70 W/cm2) or near‐infrared light (830 nm and 55 mW/cm2) over the wrist for 5 minutes. Photoplethysmography, laser Doppler flowmetry, and thermal imaging were used to monitor palm microcirculatory blood volume, blood flow, and skin temperature, respectively, before, during, and 20 minutes after irradiation. Participants with skin temperature change ≥0.5°C from baseline were considered “responders”. Near‐infrared PBM was found to induce a 27% increase in microcirculatory flow that increased to 54% during the 20‐minute follow‐up period (P = 0.049 and P = 0.004, respectively), but red light PBM did not increase the median flow. Only 10 of 20 participants were responders by thermal imaging (i.e., ≥0.5°C from baseline), and their initial skin temperature was between 33 and 37.5°C. The non‐responders had either “hot” hands (≥37.5°C) or “cold” hands (≤33°C). In responders, the meantime to 20% increase in microcirculatory blood volume and blood flow was less than 2.5 minutes after initiation of PBM irradiation. We demonstrated that PBM induces arteriolar vasodilatation that results in both immediate and long‐lasting increased capillary flow and tissue perfusion in healthy individuals. This response was wavelength‐dependent and modified by skin temperature. These findings regarding physiological parameters associated with sensitivity or resistance to PBM provide information of direct relevance for patient‐specific therapy.
关键词： body temperature regulation,laser‐Doppler flowmetry,microcirculation,low‐level laser therapy,vasodilation,thermal imaging,photoplethysmography
更新于2025-09-23 15:19:57
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The preliminary validation of laser Doppler flowmetry in systemic sclerosis in accordance with the OMERACT filter: A systematic review
摘要： Objectives: To investigate the validation status of laser Doppler flowmetry (LDF) in systemic sclerosis (SSc) according to the ‘Outcome Measures in Rheumatologic Clinical Trials’ (OMERACT) filter. Methods: The literature was systematically reviewed to identify all reports assessing the microcirculatory flow in SSc patients. The OMERACT filter (cid:1)including the domains of truth, discrimination and feasibility(cid:1) was applied and a quality assessment was done by the ‘Good Methods Checklist’. To ease the comparison between studies the results were grouped per dynamic test situation: basal, cold/heat challenge and occlusion. Results: The literature search resulted in 4332 hits. Based on title and abstract screening 243 hits were retained and of these, 52 full texts described an assessment by LDF in SSc patients. Finally, 18 studies passed the quality assessment and form the object of this review. The review reveals that expert consensus is lacking on the face and content validity of LDF in SSc. The construct validity of LDF, on the other hand is partially validated. Conflicting results exist on the discriminant capacity of LDF in distinguishing healthy from diseased patients, primary from secondary Raynaud’s phenomenon and in differentiating between disease subsets. Yet, complementing an LDF-measurement with a heat challenge, as well as the evaluation of the post-occlusive hyperaemic response, has the potential to elicit a difference between healthy and diseased patients. Lastly, data on the feasibility of LDF in SSc is lacking in the identified literature. Conclusion: This systematic review emphasizes the very preliminary validation status of LDF in the assessment of the microcirculatory flow in SSc.
关键词： OMERACT,Validity (epidemiology),Microcirculation,Outcome measure,Systemic scleroderma,Laser Doppler flowmetry
更新于2025-09-19 17:13:59
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Near-infrared spectroscopy for assessing microcirculation during laparoscopic gynaecological surgery under combined spinal-general anaesthesia or general anaesthesia alone: a randomised controlled trial
摘要： While pneumoperitoneum causes negative macrohaemodynamic effects, much less is known about microcirculatory effects of different anaesthetic techniques and laparoscopy. Therefore, we aimed to explore microcirculatory effects of combined spinal–general anaesthesia and laparoscopy, as measured by near-infrared spectroscopy over forearm and calf muscles utilising a 3-min ischemic challenge. Patients (n = 102) undergoing elective laparoscopic gynaecological surgery were randomised to receive general anaesthesia alone or in combination with high-dose or low-dose spinal analgesia (levobupivacaine 7.5 mg or 3.75 mg, respectively, plus sufentanil 2.5 μg). Primary outcomes were near-infrared spectroscopy derived parameters before general anaesthesia induction, 5 min after tracheal intubation, and 15 min after pneumoperitoneum commencement. General anaesthesia resulted in impaired post-ischaemic recovery rate in the forearm (p < 0.001, within all groups), which improved during laparoscopy. For the calf, before general anaesthesia induction, high and low dose spinal analgesia significantly slowed the post-ischaemic recovery compared to control (34 ± 16% min?1 and 36 ± 13% min?1 vs. 52 ± 27% min?1, respectively; p = 0.002 and p = 0.006). General anaesthesia abolished differences between the groups (24 ± 14% min?1 and 25 ± 12% min?1 vs. 27 ± 18% min?1), while during laparoscopy high-dose spinal analgesia further reduced the post-ischaemic recovery compared to low-dose spinal and control groups (p = 0.023 and p = 0.040, respectively). During gynaecological laparoscopy patients show impaired calf but maintain forearm microcirculatory function, regardless of the anaesthetic technique. Reduction in post-ischaemic recovery with high-dose spinal analgesia is explained by its sympatholytic effects: number of perfused capillaries is increased, leading to a haemodynamically more favourable state. Blood pressure is positively correlated with the post-ischaemic recovery rate in vascular beds not affected by spinal analgesia.
关键词： Haemodynamic,Microcirculation,Tissue oxygenation,Near-infrared spectroscopy,Laparoscopic surgery,Combined general spinal anaesthesia
更新于2025-09-19 17:13:59
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Use of Laser Speckle Contrast Imaging for Successful Fingertip Replantation
摘要： Fingertip replantation is a technical challenge for microsurgeons. For successful fingertip replantation, it is important to monitor the replanted fingertip vascularity for the early detection and revision of vascular compromise. Laser speckle contrast imaging (LSCI) is a camera-based technique that measures the perfusion by illuminating the tissue with a 785-nm-wavelength divergent laser beam. This creates a speckle pattern over the illuminated area. We present a case in which postoperative monitoring of the replanted fingertip microcirculation using LSCI allowed for successful Tamai zone I fingertip replantation. Postoperative monitoring using LSCI has 3 main advantages. First, this method is harmless to the patient and the replanted fingertip. A camera-based technique enables microcirculation monitoring without touching the patient or the replanted fingertip. Second, tissue perfusion is measured in real time and recorded continuously, allowing for the rapid response to the arterial or venous occlusion to be observed. Third, using LSCI, the skin perfusion can be measured quantitatively. Although further clinical investigations will be required to confirm its efficacy, LSCI has the potential to be a useful monitoring device.
关键词： fingertip replantation,microcirculation monitoring,Laser speckle contrast imaging
更新于2025-09-12 10:27:22
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The acute impact of local cooling versus local heating on human skin microcirculation using laser Doppler flowmetry and tissue spectrophotometry
摘要： Knowledge of thermally induced skin injury has increased, but its pathophysiology remains unclear. Although it is assumed that local cooling may protect tissue, little is known about the impact of local heating on human skin. This study aimed to evaluate acute skin perfusion dynamics following thermal stimuli in healthy human volunteers. In 54 subjects, a TSA-II-NeuroSensory Analyzer was used to induce local hypothermia (15°C and 5°C) and local hyperthermia (40°C and 45°C) at the palmar forearm of healthy volunteers. Changes in tissue microcirculation were assessed using an O2C device before and after each temperature change. Blood flow and velocity values showed a continuous decrease with decreasing skin temperature, whereas haemoglobin oxygen saturation (SO2) showed a continuous increase in superficial (2 mm) and deep layers (8 mm). With increasing skin temperature, flow, SO2 and velocity increased in the superficial and deep layers. The relative amount of haemoglobin (rHB) did not show a continuous alteration. Local cooling may protect damaged tissue due to increased SO2 (lower oxygen consumption). However, reduced blood flow and velocity in response to local cooling limit nutrient requirements and the transport of metabolites. Despite higher oxygen consumption of tissue at higher temperatures, both blood flow and SO2 increase. Thus, we hypothesize that not only hypothermia but also hyperthermia may provide tissue protection.
关键词： Hypothermia,Tissue protection,Microcirculation
更新于2025-09-12 10:27:22
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Quantitative Analysis of Heel Skin Microcirculation Using Laser Doppler Flowmetry and Tissue Spectrophotometry
摘要： OBJECTIVE: To examine perfusion changes in the heel skin of individuals with and without diabetes mellitus to understand how skin is pathologically affected by diabetes mellitus. METHODS: This case-control study was conducted at an academic hospital in Tuebingen, Germany. A total of 30 subjects were enrolled in the study: 15 with known type 2 diabetes mellitus and 15 without. Each subject was asked to lie in a supine position on a hard lateral transfer mat for 10 minutes. MAIN OUTCOME MEASURES: Heel perfusion was quantitatively assessed directly after relief of pressure and after 3 and 6 minutes after relief of pressure using laser Doppler flowmetry and tissue spectrophotometry. MAIN RESULTS: Directly after relief of pressure, blood flow increased in the superficial skin layers (2 mm below the surface of the skin) in both groups. However, in deep skin layers (8 mm below the surface of the skin), blood flow increased in patients with diabetes mellitus and decreased in healthy patients. Oxygen saturation (SO2) was higher in healthy subjects directly after pressure relief. CONCLUSIONS: The increase in blood flow in superficial skin layers indicates reactive hyperemia after exposure in both groups. The prolonged hyperemia in deep skin layers in patients with diabetes indicates increased tissue vulnerability. Despite the increase in blood flow in deep skin layers, the SO2 and thus supply of tissue in patients with diabetes were reduced.
关键词： diabetes mellitus,pressure injury,oxygen saturation,blood flow,perfusion,diabetic foot ulcers,laser Doppler flowmetry,pressure ulcer,microcirculation
更新于2025-09-12 10:27:22
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Preclinical vascular alterations in obese adolescents detected by Laser-Doppler Flowmetry technique
摘要： Background and aims: Childhood obesity promotes adverse changes in cardiovascular structure and function. This study evaluated whether alterations in skin microcirculation were already present in obese adolescents in a pre-clinical phase of cardiovascular disease. Methods and results: After an overnight fasting 22 obese adolescents and 24 normal-weight controls of similar age and gender distribution underwent clinical and blood examination and assessment of microvascular function by using two non-invasive techniques such as Peripheral Artery Tonometry (PAT) and Laser-Doppler Flowmetry (LDF). As compared to normal weight subjects, obese children had higher blood pressure, were significantly more hyper-insulinemic and insulin resistant, showing significantly higher plasma total cholesterol, LDL cholesterol, triglycerides and alanine aminotransferase (ALT). LDF showed lower pre- and post-occlusion forearm skin perfusion (perfusion units/second (PU/sec); median [IQR]) in obese than in normal weight subjects (pre-occlusion: 1633.8 [1023.5] vs. 2281.1 [1344.2]; p Z 0.015. Post-occlusion: 4811.3 [4068.9] vs. 7072.8 [7298.8]; p Z 0.021), while PAT revealed similar values of reactive hyperemia index (RHI). In entire population, fat mass % (FM%) was an independent determinant of both pre-and post-occlusion skin perfusion. Finally, being obese was associated with a higher risk to have a reduction of both pre- and post-occlusion skin perfusion (OR Z 5,82 and 9,27, respectively). Conclusion: LDF showed very early, pre-clinical, vascular involvement in obese adolescents, characterized by impaired skin microcirculation, possibly reflecting a more diffuse microvascular dysfunction to other body tissues. Whether changing life style and improving weight may reverse such pre-clinical alterations remains to be established.
关键词： Microcirculation,Obesity,Skin,Peripheral artery tonometry,Laser-Doppler flowmetry
更新于2025-09-11 14:15:04