G Hedenstierna1, L Edmark2, G Perchiazzi3. 1. Department of Medical Sciences, Clinical Physiology, Uppsala University, S-75185 Uppsala, Sweden goran.hedenstierna@medsci.uu.se. 2. Department of Anesthesia and Intensive Care, Västerås Hospital, Västerås, Sweden. 3. Department of Anesthesiology and Intensive Care, University Hospital, Bari, Italy.