Longitudinal assessment of lung function in patients following COVID-19

Background: While effects of COVID-19 on lung function are commonly described in those with severe illness, less is known about those with less severe illness, and most studies do not extend beyond 6 months following initial presentation. Research question: What are the effects of COVID-19 on lung function in a cohort of participants that included those with more severe and less severe disease over a 1 year period from time of enrollment? Study design: We enrolled 52 participants who included those with more severe (had been hospitalized) and less severe (not hospitalized) illness and measured spirometry, lung volumes, diffusing capacity, oscillometry, maximal muscle pressures, inspiratory drive, exercise capacity, and symptom and quality of life surveys at presentation, and repeated the measurements 6 and 12 months later. Results: While participants who had been hospitalized had consistently lower lung function in all measures, all values were within normal reference ranges. The pattern of lung function change suggested a predominant restrictive physiologic defect with reduced exercise capacity. Over 1 year, there was no significant improvement in lung function. Similar findings were seen when participants were stratified by whether they had shortness of breath at presentation. Interpretation: In our cohort of participants with both more severe and less severe disease, there were only minor differences in lung function associated with severe illness or whether participants had shortness of breath. COVID-19 resulted in subtle changes related to physiologic restriction, but overall lung function remained in the normal range with little change over time, suggesting that other factors besides lung function contribute to shortness of breath in participants following COVID-19.