inclusion criteria: group 1 (covid-19 early pneumonia) * age \> 18 * positive sars-cov 2 nasal swab * interstitial pneumonia at either ct scan or chest x-ray * respiratory failure requiring cpap for less than 48 hours * fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) * age \> 18 * positive sars-cov 2 nasal swab * interstitial pneumonia at either ct scan or chest x-ray * respiratory failure requiring cpap * signs of severity with cpap 10 cmh2o and fio2 0.5: pulse oximetry (spo2) ≤ 93% associated to either: * dyspnea * two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 \< 35) group 3 (non covid-19 pneumonia) * age \> 18 * negative sars-cov 2 nasal swab * ct scan or chest x-ray non compatible with covid-19 associated pneumonia * respiratory failure requiring cpap

inclusion criteria: group 1 (covid-19 early pneumonia) * age \> 18 * positive sars-cov 2 nasal swab * interstitial pneumonia at either ct scan or chest x-ray * respiratory failure requiring cpap for less than 48 hours * fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) * age \> 18 * positive sars-cov 2 nasal swab * interstitial pneumonia at either ct scan or chest x-ray * respiratory failure requiring cpap * signs of severity with cpap 10 cmh2o and fio2 0.5: pulse oximetry (spo2) ≤ 93% associated to either: * dyspnea * two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 \< 35) group 3 (non covid-19 pneumonia) * age \> 18 * negative sars-cov 2 nasal swab * ct scan or chest x-ray non compatible with covid-19 associated pneumonia * respiratory failure requiring cpap

inclusion criteria: group 1 (covid-19 early pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or chest x-ray - respiratory failure requiring cpap for less than 48 hours - fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or chest x-ray - respiratory failure requiring cpap - signs of severity with cpap 10 cmh2o and fio2 0.5: pulse oximetry (spo2) ≤ 93% associated to either: - dyspnea - two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 < 35) group 3 (non covid-19 pneumonia) - age > 18 - negative sars-cov 2 nasal swab - ct scan or chest x-ray non compatible with covid-19 associated pneumonia - respiratory failure requiring cpap

inclusion criteria: group 1 (covid-19 early pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or chest x-ray - respiratory failure requiring cpap for less than 48 hours - fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or chest x-ray - respiratory failure requiring cpap - signs of severity with cpap 10 cmh2o and fio2 0.5: pulse oximetry (spo2) ≤ 93% associated to either: - dyspnea - two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 < 35) group 3 (non covid-19 pneumonia) - age > 18 - negative sars-cov 2 nasal swab - ct scan or chest x-ray non compatible with covid-19 associated pneumonia - respiratory failure requiring cpap

inclusion criteria: group 1 (covid-19 early pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or cxr - respiratory failure requiring cpap for less than 48 hours - fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or cxr - respiratory failure requiring cpap - signs of severity with cpap 10 cmh2o and fio2 0.5: spo2≤ 93% associated to either: - dyspnea - two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 < 35) group 3 (non covid-19 pneumonia) - age > 18 - negative sars-cov 2 nasal swab - ct scan or cxr non compatible with covid-19 associated pneumonia - respiratory failure requiring cpap

inclusion criteria: group 1 (covid-19 early pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or cxr - respiratory failure requiring cpap for less than 48 hours - fio2 ≤0.5 and cpap≤10 cmh2o group 2 (covid-19 severe pneumonia) - age > 18 - positive sars-cov 2 nasal swab - interstitial pneumonia at either ct scan or cxr - respiratory failure requiring cpap - signs of severity with cpap 10 cmh2o and fio2 0.5: spo2≤ 93% associated to either: - dyspnea - two or more signs of increased respiratory effort (respiratory rate ≥25 bpm, use of accessory inspiratory muscles , tirage, intercostal space depression, nasal flaring, expiratory abdominal efforts, paco2 < 35) group 3 (non covid-19 pneumonia) - age > 18 - negative sars-cov 2 nasal swab - ct scan or cxr non compatible with covid-19 associated pneumonia - respiratory failure requiring cpap