Aim: The purpose of this study is to evaluate the use feasibility of FreeO2 so as to deliver automatically oxygen in the emergency department in a patient population admitted for acute respiratory failure.

Hypothesis: The principal hypothesis is that FreeO2 is possible and well-accepted by nurses and medical personnel and there are advantages to use this system. In comparison with the common oxygen delivery (the rotameter), the hypothesis is that FreeO2 system will make for a better control of the oxygen saturation in function of designed target, reducing the desaturation time and hyperoxia. We think that oxygen weaning will be faster than classical way if it is automated. In addition, FreeO2 could reduce the number of intervention by nurse personnel.

Inclusion Criteria:

• Admission to the emergency for respiratory disease (or cardiac - acute pulmonary edema)justifying an oxygen administration to over 3 L / min to maintain a SpO2 ≥ 92%.
• Inclusion within a time less than two hours after the start of the oxygen at the emergency.
• Patient consent,or a close.

Exclusion Criteria:

• Necessity of an oxygen flow exceeds 15 L / min to maintain a SpO2 higher than 92%.
• Criteria of gravity justifying immediately a different technique of ventilatory support:
• Disturbance of consciousness with a Glasgow Coma Score ≤ 12
• Serious ventricular rhythm disorders
• Hemodynamic instability (SBP <80mmHg or recourse to vasopressors)
• Cardiac or respiratory arrest
• pH < 7.35 and PaCO2 > 55 mm Hg
• Necessity of a urgent surgery, or coronary revascularization
• Age <18 years
• Pregnant women, lactating
• Patient not relevant
• Unavailability of the prototype FreeO2