Infection with severe acute respiratory syndrome-CoV-2 (SARS-CoV-2) may be associated with diffuse alveolar damage and pulmonary vasculitis. Thus, it is likely that pulmonary function changes may be seen in COVID-19 survivors. The aim of the present study was to test that simultaneously-determined lung diffusing capacity for nitric oxide and carbon monoxide may be useful to detect post-viral diffusive gas exchange abnormalities early after mild-to-severe COVID-19-related pneumonias.

Infection with severe acute respiratory syndrome-CoV-2 (SARS-CoV-2) may be asymptomatic or associated with life-threatening interstitial pneumonia. Clinically, patients affected from severe coronavirus disease-19 (COVID-19) are described as exhibiting rapidly progressing acute respiratory failure with unusually low oxygen levels in arterial blood. On computed tomography scans, diffuse, peripheral "ground glass" opacities of the lung are seen while autopsy lung specimens showed diffuse alveolar damage and capillary endothelialitis.

The objective of the current study, conducted in patients who had recovered from mild-to-severe COVID-19 illness, was to test that simultaneously-determined lung diffusing capacity for nitric oxide (NO) and carbon monoxide (CO) may be of great use to early detect post-infective diffusive gas exchange abnormalities. More specifically, we hypothesized that measurement of membrane diffusive conductance for CO and pulmonary capillary volume may provide accurate information on residual changes of peripheral gas exchanging units of the lung related to previous SARS-CoV-2 infection.

Inclusion Criteria:

• subjects were selected after two nasopharyngeal swabs negative for SARS-CoV-2

Exclusion Criteria:

• severe comorbidities potentially affecting pulmonary gas exchange

We collected the data of 74 Caucasian consecutive subjects admitted to hospital who had recovered from mild-to-severe COVID-19 and attended our laboratory as outpatients for follow-up purposes