Skin mechanical properties present adaptation to man's upright position. In vivo studies of young and aged individuals.

Normal microcirculation of the lower extremity is characterized by the venoarteriolar vasoconstriction reflex and the disappearance of vasomotion in the dependent position. Patients with sickle cell disease are prone to develop ischemic leg ulcers at an early age. Dysfunction of the microcirculation might promote the development of leg ulcers in patients with sickle cell disease. Using laser Doppler equipment we have studied the changes of blood flux in the skin overlying the medial malleolus after leg lowering. Contrary to the normal physiological situation seen in our control persons, the venoarteriolar reflex was abolished and vasomotion preserved in the dependent position of the leg in both patients. We conclude that this may represent an adaptation to the dependent position in sickle cell disease.