New techniques for clinical assessment of the peripheral microcirculation.

Current methods for clinical investigation of the cutaneous microcirculation in patients are based mainly on laser Doppler and capillary microscopy. The use of laser Doppler gives a semi-quantitative index of superficial tissue perfusion. The most recent devices are capable of analysing both the volumetric and velocimetric components. New instruments use two different frequencies to compare tissue perfusion at different depths beneath the skin surface. The combination of a laser probe and a small automate produces a 2-dimensional image, allowing the evaluation of spatial heterogeneity in tissue perfusion, an important pathophysiological concept in vascular diseases. Capillaroscopy has recently been improved by the emergence of the flexible videomicroscope, allowing easy exploration of not only the classical site of the nail-fold but also of the body skin surface. The use of this method was therefore extended--from peripheral vascular disease and connective tissue diseases to the whole spectrum of trophic changes in the skin of the extremities. Systems for digital image analysis allow quantification of the structure of the microvascular bed (quantitative appraisal of microangiopathies) and function (capillary haemodynamics and exchange). Laser Doppler and capillaroscopy can also be combined for the measurement of red blood cell velocity in single capillaries.