1. Department of Medicine and Care, Clinical Physiology and Department of Biomedical Engineering, Linko¨ping University, SE-581 85 Linko¨ping, Sweden
2. Department of Medicine, University of California, San Francisco, CA
3. Department of Medicine and Care, Clinical Physiology, Linko¨ping University, SE-581 85 Linko¨ping, Sweden
4. Department of Biomedical Engineering, Linko¨ping University, SE-581 85 Linko¨ping, Sweden