1 Department of Intensive Care and Intermediate Care, University Hospital RWTH, Aachen, Germany; William Harvey Research Institute, Queen Mary University London, London, England. Electronic address: lmartin@ukaachen.de.
2 Department of Intensive Care and Intermediate Care, University Hospital RWTH, Aachen, Germany.
3 William Harvey Research Institute, Queen Mary University London, London, England.
4 Department of Anesthesia and Intensive Care, University Hospital Rostock, Rostock, Germany.