Gonzalo Hernandez1, Oriol Roca2. 1. Department of Critical Care Medicine, University Hospital Virgen de la Salud, Toledo, Spain. Electronic address: ghernandezm@telefonica.net. 2. Department of Critical Care Medicine, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain; Ciber Enfermedades Respiratorias (Ciberes), Instituto de Salud Carlos III, Madrid, Spain.