Lung function indices in patients undergoing post-COVID assessment- An observational study

Abstract

Background: The study aims to describe various evaluations of lung function and determine the presence of pulmonary function test (PFT) abnormalities in patients undergoing post-COVID assessment.

Methods: Spirometry and diffusing capacity of lungs for carbon monoxide (DLCO) of 52 post-COVID patients were assessed. Lung function indices like FEV1 (forced expiratory volume at 1 second), FVC (forced vital capacity), FEV1/FVC ratio, DLCO, RV (residual volume), and RV/TLC ratio were assessed. Patients were categorized based on age, gender, BMI (WHO criteria), CTSS (CT-severity score), and cross-tabulations were done with lung function parameters. ANOVA was used for the comparison of continuous variables in sub-groups, and the chi-square test was used for categorical data.

Results: Mean (SD) FEV1, FVC, FEF and FEV1/FVC ratio in patients were 2.314 (0.62), 2.45 (0.76), 2.02 (6.22) and 87.88 (8.78) respectively. Abnormal spirometry parameters were present in 27 (51.9%) patients with restrictive pattern being the most common type of abnormality (n=23, 44.2%), more common in those from the age group of >55 years. Among those with restriction, 47.8% had mild, 43.5% had moderate and 8.7% had severe abnormality. Patients with higher CTSS scores had low % predicted FEV1. DLCO reduction was seen in 73.1% (n=38) patients with a mean (SD) % predicted DLCO of 63.68% (21.51) for all patients, suggestive of mild diffusion impairment. A high % predicted RV (171.53%) and RV/TLC ratio (145.75) were suggestive of air trapping in post-COVID patients, irrespective of pre-existing respiratory illness.

Conclusion: Spirometry abnormalities and impaired diffusing-capacity were present in patients undergoing post-COVID follow-up.