Small Airway Disease as long-term Sequela of COVID-19: Use of Expiratory CT despite Improvement in Pulmonary Function test

Garg, A.; Nagpal, P.; Goyal, S.; Comellas, A. P.

Background- It is important to understand the spectrum of pulmonary diseases that patients are presenting after recovery from initial SARS-CoV-2 infection. We aim to study small airway disease and changes in Computed Tomography (CT) and pulmonary function tests (PFTs) with time. Methods: This is retrospective observation study including adult patients with confirmed SARS-CoV-2 infection with at-least two CT scans either during acute (defined as < 1 month) or subacute (1-3 months) or chronic (>3months) phase after positive test. Radiological features and follow up PFTs were obtained. Results: 22 patients met the inclusion criteria with mean age 57.6 years (range 36-83). Out of these,18 (81.81%) were hospitalized. Mean duration of diagnosis to CT and PFT was 192.68 (112-385) days and 161.54 (31-259) days respectively. On PFTs, restrictive pulmonary physiology was predominant finding during subacute 56.25% (9/16) and chronic phases 47% (7/15). PFTs improved significantly with time {FEV1((p=0.0361), FVC (p=0.0341), FEF 25%-75% (p=0.0259) and DLCO (p=0.0019)}, but there was persistent air trapping in the expiratory chronic phase CT. There was resolution of ground glass opacity, consolidation, and bronchiectasis however air trapping increased with time in 41.61% (10/21) of subacute CTs compared to 81.25% (13/16) in chronic CTs. Conclusion - Our study shows evidence of airway as well as parenchymal disease as relatively long-term sequel of SARS-CoV-2 infection. It also highlights the natural course and spontaneous recovery of some radiological and pulmonary function test abnormalities over time with evidence of persistent small airway disease (air trapping) on expiratory CT imaging months after infection.