Non-invasive techniques to access in vivo the skin microcirculation in patients.

The microcirculation is composed of blood vessels with mean internal diameter smaller than 100 µm. This structure is responsible for survival of cells and in the last 50 years its study has become increasingly interesting because it often participates in the pathophysiology of several diseases or can determine better or worse prognosis for them. Due to the growing importance of knowing more about the microcirculation, several techniques have been developed and now it is possible to study its structure or function. In the last 25 years, the cutaneous microcirculation has emerged as an accessible and representative portion of generalized vascular bed allowing the examination of mechanisms of microcirculatory function and dysfunction. This mini review presents several techniques used for non-invasive access to skin microcirculation, such as Nailfold Videocapillaroscopy, Orthogonal Polarization Spectral Imaging, Sidestream Dark Field Imaging, Incident Dark field Illumination, Laser Doppler Flowmetry, and Laser Speckle Contrast Imaging applied. The techniques presented will describe which types of variables (structural or functional) can be evaluated, their limitations and potential uses.

Microvascular perfusion in cardiac arrest: a review of microcirculatory imaging studies.

Cardiac arrest represents a leading cause of mortality and morbidity in developed countries. Extracorporeal cardiopulmonary resuscitation (ECPR) increases the chances for a beneficial outcome in victims of refractory cardiac arrest. However, ECPR and post-cardiac arrest care are affected by high mortality rates due to multi-organ failure syndrome, which is closely related to microcirculatory disorders. Therefore, microcirculation represents a key target for therapeutic interventions in post-cardiac arrest patients. However, the evaluation of tissue microcirculatory perfusion is still demanding to perform. Novel videomicroscopic technologies (Orthogonal polarization spectral, Sidestream dark field and Incident dark field imaging) might offer a promising way to perform bedside microcirculatory assessment and therapy monitoring. This review aims to summarise the recent body of knowledge on videomicroscopic imaging in a cardiac arrest setting and to discuss the impact of extracorporeal reperfusion and other therapeutic modalities on microcirculation.

Lung structure and function in elastase-treated rats: A follow-up study.

Structural and functional longitudinal alterations of the lungs were followed in an emphysema model. Rats were treated with porcine pancreatic elastase (PPE, n=21) or saline (controls, C, n=19). Before the treatment and 3, 10, 21 and 105 days thereafter, absolute lung volumes (FRC, TLC and RV) and tissue mechanical parameters (elastance: H; damping: G) were determined. At 3, 21 and 105 days the lungs were fixed in subgroups of rats. From histological samples the equivalent diameter of airspaces (Dalv), elastin (Mec) and collagen densities were assessed. In the PPE group, FRC and RV were higher from 3 days after treatment compared to controls (p<0.001), while TLC exhibited a delayed increase. H and G decreased in the PPE group throughout the study (p<0.001). Higher Mec (p<0.001) and late-phase inflammation were observed at 105 days. We conclude that during the progression of emphysema, septal failures increase Dalv which decreases H; this reveals a strong structure-function relationship.

Non-invasive imaging of microcirculation: a technology review.

Microcirculation plays a crucial role in physiological processes of tissue oxygenation and nutritional exchange. Measurement of microcirculation can be applied on many organs in various pathologies. In this paper we aim to review the technique of non-invasive methods for imaging of the microcirculation. Methods covered are: videomicroscopy techniques, laser Doppler perfusion imaging, and laser speckle contrast imaging. Videomicroscopy techniques, such as orthogonal polarization spectral imaging and sidestream dark-field imaging, provide a plentitude of information and offer direct visualization of the microcirculation but have the major drawback that they may give pressure artifacts. Both laser Doppler perfusion imaging and laser speckle contrast imaging allow non-contact measurements but have the disadvantage of their sensitivity to motion artifacts and that they are confined to relative measurement comparisons. Ideal would be a non-contact videomicroscopy method with fully automatic analysis software.

A novel method for in vivo visualization of the microcirculation of the mandibular periosteum in rats.

OBJECTIVE: The periosteum plays an important role in bone physiology, but observation of its microcirculation is greatly limited by methodological constraints at certain anatomical locations. This study was conducted to develop a microsurgical procedure which provides access to the mandibular periosteum in rats. METHODS: Comparisons of the microcirculatory characteristics with those of the tibial periosteum were performed to confirm the functional integrity of the microvasculature. The mandibular periosteum was reached between the facial muscles and the anterior surface of the superficial masseter muscle at the external surface of the mandibular corpus; the tibial periosteum was prepared by dissecting the covering muscles at the anteromedial surface. Intravital fluorescence microscopy was used to assess the leukocyte-endothelial interactions and the RBCV in the tibial and mandibular periosteum. Both structures were also visualized through OPS and fluorescence CLSM. RESULTS: The microcirculatory variables in the mandibular periosteum proved similar to those in the tibia, indicating that no microcirculatory failure resulted from the exposure technique. CONCLUSION: This novel surgical approach provides simple access to the mandibular periosteum of the rat, offering an excellent opportunity for investigations of microcirculatory manifestations of dentoalveolar and maxillofacial diseases.

Multiple different laminar velocity profiles in separate veins in the microvascular network of brain cortex in rats.

The orthogonal polarisation spectral (OPS) imaging technique is a method that enables intravital microscopy of the tissue microvasculature particularly including the erythrocytes and leucocytes. As a new finding we here report multi flow, i.e, several different laminar velocity profiles in each and separate veins (diameters < 200 µm) of the microcirculation of the rat brain cortex. The phenomenon was present in all 20 preparations studied and these different laminar velocity profiles were regularly maintained in length beyond 20 times the diameter of parent vessel. In single veins up to 9 different laminar velocity profiles were discernible, each with a different red blood cell velocity. These multi flow profiles may theoretically be anticipated based on what is known in rheological physiology as the Fahreus - Lindqvist effect. It may also be predicted in tissues that have both high and heterogeneous blood flows in conjunction with large local variations in metabolic activity as are present in the cortex of the brain. The new information is that the extent and magnitude of this multi laminar flow phenomenon especially in the venular network of the brain exceeds what has previously been known. The physiological importance of these finding warrants further studies.

Estudo da microcirculação na hanseníase virchowiana com o uso da microscopia de luz ortogonal polarizada e com laser-doppler fluxometria / Study of microcirculation in lepromatous leprosy with the use of orthogonal polarized light microscopy and laser doppler flowmetry

A hanseníase é uma doneça infecciosa com características únicas, dentre elas o fato de atingir intensamente a inervação da pele e seus anexos. Entremeando estes anexos, está a microcirculação cutânea, que a principio também tem sua inervação comprometida. Vários artigos apontam para alterações de disautonomia microcirculatória, citando como exemplo as alterações no reflexo vasomotor. O presente estudo se propõe a avaliar a microcirculação cutânea na hanseníase virchowiana, tanto em sua morfologia quanto em sua reatividade vascular. Para isto, utilizamos a tecnologia de luz ortogonal polarizada através do equipamento Cytoscan, a análise de Fourier do sinal do laser Doppler para estudo da vasomotricidade e o laser Dopplerfluxometria associado à iontoforese de substâncias vasoativas (acetilcolina, nitroprussiato de sódio e noradrenalina) para avaliação da reatividade vascular. Dez pacientes portadores de hanseníase virchowiana sem outras comorbidades que pudessem alterar os parâmetros microcirculatórios, foram avaliados pelos métodos descritos e seus resultados foram comparados aos de dez controles sem hanseníase ou qualquer outra comorbidade. Em relação à vasomotricidade não foram observadas alterações estatisticamente significativas entre os grupos, o que fala a favor da teoria de origem miogênica para a vasomotricidade. Em relação à iontoforese de substâncias vasoativas constatou-se uma diminuição da resposta vasodilatadora à acetilcolina e ao nitroprussiato nos pacientes com hanseníase. Os exames com o Cytoscan mostraram aumento no tamanho dos capilares, bem como alterações em sua morfologia. Os resultados apresentados sugerem que, provavelmente devido ao longo período de alteração inervatória decorrente da hanseníase virchowiana, estes pacientes apresentam uma alteração significativa tanto morfológica quanto na reatividade vascular da microcirculação cutânea.

Leprosy is an infectious disease with unique characterístics. One of them is the fact that it compromises not only the cutaneous and adnexial innervation, but also the innervation of the cutaneous microcirculation. Several articles indicate the impact of disautonomy on the microcirculatory level, citing the example of changes in vasomotor level. The present study proposes to evaluate morphology and microvascular reactivity of the cutaneous microcirculation of the virchowian leprosy. Methods employed in the study were: the Cytoscan, which uses the orthogonal polarized light, the Fourier analysis of the laser Doppler signal to study vasomotion, and the laser Doppler flowmetry associated with iontophoresis of vasoactive substances (acetylcholine, sodium nitroprusside and norepinephrin). Ten patients with virchowian leprosy, without any other comorbidity that could modify the microvascular parameters were evaluated and their results were compared to ten controls without leprosy or any other comorbidity. Regarding the vasomotion, no statistical significant differences were noticed between the groups. Our data are in agreement with the vasomotion's miogenic origin theory. According to iontophoresis of vasoactive substances, it was found that there is a reduced endothelial-dependent and endothelial-independent vasodilation in patients with leprosy while tests by direct visualization we observed an increase in the size of capillaries, as well as changes in their morphology. The results suggest that the significant changes in morphology and vascular reactivity of skin microcirculation are probably due to the long period of innervatory changes arising from leprosy.