inclusion criteria: * age\> 18 years old * patients with acute respiratory failure related to suspected community acquired pneumonia (viral and non viral) requiring oxygen therapy \< 6 l/min (or fio2\< 0.50) (to maintain spo2 between 90 and 94% spo2) without criteria for immediate intubation or icu transfer. * patients hospital admission \< 72 hours

inclusion criteria: * age\> 18 years old * patients with acute respiratory failure related to suspected community acquired pneumonia (viral and non viral) requiring oxygen therapy \< 6 l/min (or fio2\< 0.50) (to maintain spo2 between 90 and 94% spo2) without criteria for immediate intubation or icu transfer. * patients hospital admission \< 72 hours

inclusion criteria: - age> 18 years old - patients with acute respiratory failure related to suspected community acquired pneumonia (viral and non viral) requiring oxygen therapy < 6 l/min (or fio2< 0.50) (to maintain spo2 between 90 and 94% spo2) without criteria for immediate intubation or icu transfer. - patients hospital admission < 72 hours

inclusion criteria: - age> 18 years old - patients with acute respiratory failure related to suspected community acquired pneumonia (viral and non viral) requiring oxygen therapy < 6 l/min (or fio2< 0.50) (to maintain spo2 between 90 and 94% spo2) without criteria for immediate intubation or icu transfer. - patients hospital admission < 72 hours