Prehospital oxygen-therapy and mortality in patients treated by emergency medical services: a prospective, observational multicenter study - Vegas, Carlos del Pozo; Sanz-Garcia, Ancor; Duenas-Ruiz, Antonio; Castro, Pedro de Santos; Contreras, Ana Gil; Gonzalez, Maria Blanco; Galan, Alberto Correas; Soriano, Joan B; Lopez-Izquierdo, Raul; Martin-Rodriguez, Francisco (WORLD JOURNAL OF EMERGENCY MEDICINE, 2025)