Lung function and exercise capacity after severe COVID-19

Rationale: COVID-19 can progress to severe disease requiring hospitalization and oxygen support in around 14% of the cases and 5% require admission in intensive care unit. The consequences of severe COVID-19 on lung function and exercise capacity remain to be determined. Methods: A multicenter prospective cohort study that aims to evaluate the early (Visit 1: 2-6 months after acute disease) and late (Visit 2: 9-15 months and Visit 3: 18- 24 months) effects of severe acute respiratory syndrome on lung function, exercise capacity, respiratory symptoms and health related quality of life in patients with confirmed diagnosis of SARS-CoV-2 infection by PCRRT from nasal swab (ClinicalTrials.gov: NCT04410107). Severe disease was defined by respiratory rate > 30breaths/min, peripheral oxygen saturation ≤93% on room air and/or by the presence of infiltrates > 50% on chest imaging in the first two days after laboratorial confirmation. This is a preliminary report of spirometry, lung volumes by body plethysmography, lung diffusion capacity for carbon monoxide (DLCO), and performance during 6-minute walk test (6MWT) after 2-6 months (early evaluation) of severe COVID-19. Results: 51 patients were included: 54% male, 55.4±12.9 yrs-old, 23 (45%) were current or former smokers. Around half (45%) were admitted to the ICU and 26 (50%) received ventilatory support (invasive or non-invasive). The most frequent comorbidities were systemic hypertension (41%), obesity (29%), and 9% reported history of previous respiratory disease. Mean lung function parameters were (% predicted): FEV1= 85±18;FVC= 82±16;total lung capacity (TLC)= 87±14;residual volume= 93±40;DLCO= 74±17;6-min walk distance= 85±20. Mean pulse oximetry values post-6MWT were= 93%. Although mean values were within the normal limits, 14 (27%) patients presented with restrictive ventilatory defect (↓TLC), 5 (9%) patients presented with obstructive ventilatory defect (↓FEV1/FVC), 21 (41%) with abnormal resting gas exchange (↓DLCO), and 12 with significant desaturation during 6MWT. 37 (69%) walked a distance below lower limit of normality. Of note, 22/31 (70%) of the patients presenting with any functional abnormality(ies) had no previous report of respiratory diseases. Conclusions: A substantial proportion of severe COVID-19 survivors (43%) presented with respiratory functional abnormalities indicative of restrictive ventilatory defect and/or with altered gas exchange at rest or during exercise after 2-6 months of acute infection, even without previous report of any lung disease. Further information regarding remission, stabilization or progression of these findings will be possible in the follow-up of this cohort.