Risk factors associated with mortality among elderly patients with COVID-19: Data from 55 intensive care units in Spain C. Cilloniz; A. Motos; J.M. Pericàs; T.G. Castañeda; A. Gabarrús; R. Ferrer; D. García-Gasulla; O. Peñuelas; D. de Gonzalo-Calvo; L. Fernandez-Barat; F. Barbé; A. Torres;