The investigators hypothesise that CPAP + pharmaceutical treatment, compared to pharmaceutical treatment alone, improves the respiratory and hemodynamic status of the patients before H2 after the inclusion time and decreases the rate of death and tracheal intubation during the first 48 hours.

Patients are included at home after informed consent by the emergency medical team and transported during the following 2 hours to a cardiac intensive care unit were the treatment is purchased as well. Randomization process has been done previously with envelopes ; group A : pharmaceutical treatment alone , B pharmaceutical plus CPAP. Medical treatment includes furosemide and nitroglycerin (continuous perfusion and bolus), inotropes if needed, and all other specific treatment required (ex : anti antiarrhythmic drugs). Doses are free, adapted to the clinical response for respiratory and hemodynamic distress. CPAP is a passive high flow venturi system device alimented by a hyperbaric oxygen. FiO2 can be controlled and adapted to the pulsed oxygen saturation. PEP must be initially celled at least at 7.5 cmH2O and increased to 10 if well tolerated.

Inclusion Criteria:

• age > 18
• acute respiratory insufficiency with hypoxia in air
• KILLIP score from 2 to 4
• absence of known ST elevation acute coronary syndrome
• accepted inform consent.

Exclusion Criteria:

• age < 18
• immediate intubation criteria (bradypnea, coma status)
• refractory shock