Functional study of the dermal microcirculation in systemic sclerosis.

To measure the effect of cooling on digital blood pressure we used a strain-gauge and photoplethysmograph, with an automatic cooling device. Eighteen patients were compared with 18 matched controls. Laser-doppler technique was used to measure the perfusion changes after heating a small area of the skin in 5 locations on the body, readings were given in perfusion units. Eighteen patients with systemic sclerosis were compared with 25 individuals with primary Raynaud's phenomenon and 30 healthy controls. Cooling to 10 degrees C caused a significant digital blood pressure drop of 58 mmHg in patients with systemic sclerosis and 61 mmHg in Raynaud's phenomenon, as compared with controls. The microcirculation in patients with systemic sclerosis responded in the same way to local heating as in the normal population, increasing the perfusion to the same extent. In conclusion, an unselected group of patients with systemic sclerosis have normal dermal microcirculatory response to heating in spite of severe cold intolerance.