Assessment of pulmonary functions in COVID-19 survivors and their clinical correlation at 6-month follow-up: A prospective observational study

Abstract

Background: Long term impact of COVID-19 on pulmonary functions is still an area of active research. Objective: To assess pulmonary functions and their relationship with clinical severity of disease among COVID-19 survivors at six-month follow-up after being discharged from the hospital. Methods: It was a hospital based prospective observational six-month follow-up study. After fulfillment of all inclusion and exclusion criteria, subjects underwent spirometry and diffusion capacity of lung for carbon monoxide (DLco). Ninety-six subjects had completed the tests and were enrolled for the study. Categorization of subjects was made based on their clinical disease severity profile according to Government of India guidelines. Test results were correlated with clinical severity of disease. Results: Of 96 subjects, 46 were mild, 28 were moderate, 18 were severe and 4 were critical cases. Majority of subjects had normal spirometry (65.6 %) and DLco (66.6 %). Among abnormal lung functions, the commonest was reduced DLco (33.3%) followed by restrictive (18.7%), small airway disease (10.4 %), obstructive (3.1 %) and mixed (2%) spirometry patterns. With the advancement of clinical disease severity, the frequency of restrictive pattern (P<0.01) and reduced DLco increases significantly (P<0.05). Conclusion: After six months, few COVID-19 survivors had residual lung function impairment in terms of reduced DLco and restrictive spirometry pattern. Hence, we recommend regular lung function assessment with various methods such as spirometry and DLco in COVID-19 survivors and advocate more large scale - long term follow-up studies to investigate the further progression or resolution in these abnormalities over the time.