In December 2019 the first case of human infection by a new coronavirus was identified, currently called SARS-COV-2 (Severe Acute Respiratory Syndrome - Coronavirus - 2), characterized by high contagiousness and the possibility of causing a severe acute respiratory distress syndrome from which its acronym derives and which caused the state of a global pandemic in a few months. The most frequent clinical manifestation of COVID-19 is pneumonia, which in about 20% of cases results in acute respiratory failure. Very few studies have so far addressed the problem of clinical and functional recovery in these patients, most of them just before or after discharge and none specifically focused on patients admitted for ARF. Indeed most of these investigations were limited to a specific field such as symptoms, pulmonary function and radiological changes. There are no guidelines for the follow-up of COVID-19 patients, despite the British Thoracic Society (BTS) has published a guidance for scheduling post-hospitalization assessments.

Aim of this study is to describe the long term (6 to 12 months) evolution of lung involvement in patients discharged after an episode of ARF due to COVID-19, identifying possible factor associated to lasting clinical, functional or radiological abnormalities collecting data from hospital stay, 1-month after hospital discharge, 3-months after hospital discharge and 6-to-12-months after hospital discharge.

Coronaviruses are a family of viruses with marked tropism for the respiratory system, being able to cause heterogeneous pathological states in humans ranging from the common cold to more serious diseases such as Respiratory Syndrome severe acute respiratory syndrome (SARS). In December 2019 in Wuhan in China, the first case of human infection by a new coronavirus was identified, currently called SARS-COV-2 (Severe Acute Respiratory Syndrome - Coronavirus - 2), characterized by high contagiousness and the possibility of causing a severe acute respiratory distress syndrome from which its acronym derives and which caused the state of a global pandemic in a few months. The disease caused by the SARS-COV-2 virus is called COVID 19.

The most frequent clinical manifestation of COVID-19 is pneumonia, which in about 20% of cases results in acute respiratory failure requiring oxygen therapy or ventilatory support. sometimes resulting in a picture similar to that caused by acute respiratory distress syndrome (ARDS), found in 60-70% of patients admitted to intensive care. The pathogenesis of classical ARDS involves three phases of the disease: an exudative, a proliferative and a fibrotic phase, which occurs when the removal of alveolar collagen fails and leads to progressive pulmonary fibrosis. It is not known whether the long-term evolution of the COVID 19 disease could result in the establishment of a fibrotic phase similar to that predicted by the pathogenesis of classical ARDS, which would lead to a chronic ventilatory deficit similar to that of pulmonary interstitial diseases, with serious impact on quality of life and mortality.

However, it is not well-known whether SARS-COV-2 pneumonia causes restitutio ad integrum or whether it can induce persistent parenchymal alterations and lung function abnormalities.

Very few studies have so far addressed the problem of clinical and functional recovery in these patients, most of them just before or after discharge and none specifically focused on patients admitted for ARF. Indeed most of these investigations were limited to a specific field such as symptoms, pulmonary function and radiological changes.There are no guidelines for the follow-up of COVID-19 patients, despite the British Thoracic Society (BTS) has published a guidance for scheduling post-hospitalization assessments.

Aim of this study, spontaneous,observational, both prospectic and retrospective, is to describe the long term (6 to 12 months) evolution of lung involvement in patients discharged after an episode of ARF due to COVID-19, identifying possible factor associated to lasting clinical, functional or radiological abnormalities.

Investigators will collect clinical, functional and radiological parameters during:

• the hospital stay due to COVID-19 (H);
• the 1-month after hospital discharge followup visit (V1);
• the 3-months after hospital discharge followup visit (V2);
• the 6-to-12-months after hospital discharge followup visit, performed for study subjects that at V2 show clinical and/or functional and/or radiological abnormalities due to sequelae of COVID-19 (V3).

For data analysis, all variables will be analyzed using descriptive method. Continuous variables will be presented as means, standard deviation, median and respective minimum and maximum values; the discrete or nominal variables will be expressed as frequencies and relative percentages. Subgroup analysis will be performed using X- 2 test or Fischer test when appropriate; parametric variables not normally distributed will be analyzed by Kruskal-wallis non-parametric test. Association between two or more parameters will be calculate with Spearman Correlation. p <0.05 values will be considered statistically significant.

This study was approved by the Local Ethic Committee.

Inclusion Criteria:

• acute respiratory failure due to SARS-COV-2 pneumonia
• sign of informed consent

Exclusion Criteria:

• none

all patients with SARS-COV-2 pneumonia discharged from our Insitution (Respiratory and Critical Care Unit - S.Orsola-Malpighi University Hospital, Bologna, IT) or patients referred to our Clinic for the followup of SARS-COV-2 pneumonia after hospital stay.