Fig. 1 Examples of microcirculatory blood flow measurements in the skin area in 2 patients in response to Ach iontophoresis before (blue curve,H0) and after (red curve, H1). Left, RBC transfusion impaired microvascular reactivity to acetylcholine; right, RBC transfusion improvedmicrovascular reactivity to acetylcholine. PU for perfusion units