[Current techniques for the clinical evaluation of the microcirculation].

Three main types of approaches are currently used for the exploration of the microcirculation in man: Clinimetric measurements of the cutaneous temperature (thermometry), skin color (chromametry) and tissue volume (leg or foot volumetry) allow a quantification of clinical indexes of skin blood flow, blood volume and edema that are useful in therapeutic trials. Global parameters evaluating the hemodynamic or nutritional efficacy of the microcirculation in a tissue sample (laser Doppler and TcPO(2)) are easy to perform in clinical routine. TcPO(2) measurements through Clarke electrodes or fluorescence lifetime imaging technology evaluate the nutritional efficacy of the microcirculation. Laser Doppler devices are producing a semi-quantitative index of superficial tissue perfusion, that can be split into a volumic and a velocimetric components; its high sensitivity makes it a valuable tool for clinical research, mainly for dynamic measurements of reactivity of the superficial microcirculation to various stimuli. New instruments are able to use two different frequencies in order to compare tissue perfusion at different depths beneath the skin surface. The combination of a laser probe and a small automate can produce a two-dimensional image allowing the evaluation of spatial heterogeneity in tissue perfusion. Visualization of the skin capillary bed, i.e. capillaroscopy, was recently improved by the emergence of flexible videomicroscopes easily allowing the exploration of the whole body skin surface and not only the classical site of the nailfold. The use of the method was therefore broadened from vascular acrosyndromes and connective tissue diseases to the whole spectrum of skin trophic changes of the extremities. Combination with digital image analysis systems allows the quantification of the microvascular and microlymphatic structure (quantitative appraisal of microangiopathies) and function (capillary hemodynamics and exchange). Laser-doppler and capillaroscopy can also be combined for the measurement of red blood cell velocity in single capillaries.