Participating centers: 41 prehospital emergency services employing mobile intensive care units and located in urban areas in France participated in this study. In France, the management of out-of-hospital medical emergencies is under the responsibility of the Service d'Aide Medicale Urgente (SAMU). Mobile intensive care units are staffed by an attending emergency physician or anesthesiologist, a nurse, and an ambulance driver. The study is coordinated by the prehospital emergency service of Lariboisiere Hospital, University Paris 7 (Paris, France)