Severe Acute Respiratory Syndrome (SARS) SARS-CoV-2, name of the Coronavirus Group of international Committee on taxonomy of viruses, is an emerging virus from the family of coronaviridae, responsible for the COVID-19 pandemic. This infection can progress to viral pneumonia, and in 3% of cases up to acute respiratory distress syndrome (ARDS) which conditions the prognosis of the disease.

Due to its unusual clinical presentation with a risk of sudden deterioration on the 8th day as a result of possible hyperinflammatory response, the respiratory impairment of COVID is unique and many questions remain unanswered concerning its evolution once the acute phase has passed. Knowledge of the evolution of pulmonary involvement, particularly in patients requiring hospitalization, can help reduce the morbidity linked to the persistent abnormalities identified by establishing early therapeutic management. It can also provide a better understanding of the mechanisms of pulmonary involvement in the acute phase. Current data regarding the acute phase of COVID-19 suggest that persistent abnormalities remain distant from this infection at all levels of the respiratory system: gas exchange, perfusion, ventilatory mechanics, and interstitial lung disease.

The main objective is to characterize persistent gas exchange anomalies 4 months after documented COVID-19 pneumonia, resulting in oxygen desaturation and requiring hospitalization.

Inclusion Criteria:

• Patient with COVID-19 pneumonia
• Positive PCR for COVID-19 on respiratory sample (saliva, nasopharyngeal, bronchial, tracheal aspiration or LBA)
• Having required hospitalization in the pulmonology service, intensive care in pneumology or resuscitation service at the Toulouse University Hospital
• Saturation <94% in ambient air at diagnosis
• Patient having a chest CT-scan proving pneumonia during his hospitalization
• Patient ≥ 18 years old
• Patient who has given written consent to participate in the study

Exclusion Criteria:

• Patient hospitalized for pneumonia not documented by a chest CT-scan
• Patient with negative COVID PCR
• Patient known before the episode of COVID-19 pneumonia for a respiratory or cardiac pathology which can lead in itself to an alteration of gas exchanges
• Patient under curators / guardianship
• Pregnant patient
• Minor patient
• Absence of consent for participation in the study
• Medical condition that does not allow for pulmonary function test