Paula Ramirez1, Antoni Torres2. 1. Critical Care Department, Hospital Universitario y Politécnico la Fe, Spain; Centro de Investigación Biomedica En Red-Enfermedades Respiratorias (CibeRes, CB06/06/0028), Instituto de Salud Carlos III, Villarroel 170, 08036 Barcelona, Spain. 2. Pneumology Department, Hospital Clinic, Universitat de Barcelona, IDIBAPS, Spain. Electronic address: atorres@ub.edu.