1. Human Anatomy and Embryology Unit, Faculty of Medicine; University of Barcelona; Barcelona 08036 Spain
2. Antón de Borja Primary Care Center, Terrassa Health Consortium; Rubí 08191 Spain
3. Department of Anesthesiology; Madrid-Montepríncipe University Hospital, and School of Medicine, CEU San Pablo University; Madrid 28660 Spain
4. Department of Anesthesiology; Hospital Clínic, Universitat de Barcelona; Barcelona 08036 Spain