Respiratory distress is a common symptom of patients transported to hospitals by emergency medical services (EMS) personnel. The benefit of advanced life support for such patients has not been established. METHODS The Ontario Prehospital Advanced Life Support (OPALS) Study was a controlled clinical trial that was conducted in 15 cities before and after the implementation of a program to provide advanced life support for patients with out-of-hospital respiratory distress. Paramedics were trained in standard advanced life support, including endotracheal intubation and the administration of intravenous drugs
