 Continuous positive airway pressure ventilation CPAP has been shown to be effective in avoiding endotracheal intubation ETI for patients with acute respiratory failure in hospital but despite several case series, the effectiveness of the prehospital application of CPAP by paramedics has not been studied in a randomized fashion. We performed a prospective, randomized, non blinded trial to determine whether patients in acute respiratory failure treated with CPAP in the prehospital setting had lower overall ETI rates than those treated with standard care. 