1. Faculty of Medicine, Valladolid University, Valladolid, Spain
2. Advanced Life Support, Emergency Medical Services, Valladolid, Spain
3. Emergency Department, Hospital Universitario Rio Hortega, Valladolid, Spain
4. Emergency Department, Hospital Clínico Universitario, Valladolid, Spain
5. Data Analysis Unit, Health Research Institute, Hospital de la Princesa, Madrid, Spain
6. Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina