A Study to Evaluate Pulmonary Function Test in Post Covid Patients

Abstract

Background: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily affects the respiratory system, and emerging evidence suggests that pulmonary impairment may persist well beyond the acute illness. Spirometric indices, particularly forced vital capacity (FVC), forced expiratory volume in 0.5 second (FEV0.5) and forced expiratory volume in one second (FEV1), provide an objective, reproducible means of quantifying such residual dysfunction. Aim: To evaluate and compare FVC, FEV0.5 and FEV1 in patients with a past history of moderate-to-severe COVID-19 infection against age and sex-comparable controls without such history. Materials and Methods: A retrospective case–control study was conducted on 70 subjects (35 cases with a past history of RT-PCR/rapid-antigen-test-confirmed COVID-19 infection and 35 controls), aged 18–55 years, recruited over one year. Smokers and individuals with pre-existing pulmonary, cardiac or malignant disease were excluded. Spirometry was performed using a computerised spirometer (RMS-HELIOS-702), and the best of three technically acceptable efforts was recorded. Continuous variables were expressed as mean values and compared using analysis of variance (ANOVA) with the least-significant-difference (LSD) post-hoc test; p<0.05 was taken as significant. Results: The mean FVC was significantly lower in cases (2.47 L) than controls (2.80 L; p=0.049). FEV0.5 was significantly reduced in cases (1.82 L) compared with controls (2.13 L; p=0.018), and FEV1 was significantly lower in cases (2.30 L) than controls (2.67 L; p=0.033). Other spirometric indices; FEV3, peak expiratory flow rate, FEF25–75%, FEF25%, FEF50%, FEF75%, the derived ratios (FEV0.5/FVC, FEV1/FVC, FEV3/FVC), maximum voluntary ventilation and its time, FVC time and extrapolated time did not differ significantly between groups. Conclusion: A past history of moderate-to-severe COVID-19 infection is associated with a significant, restrictive-pattern reduction in FVC, FEV0.5 and FEV1 that persists for months after recovery, while flow-dependent and ratio-based indices remain relatively preserved. These findings support structured post-COVID pulmonary follow-up and reinforce the value of simple, low-cost spirometric screening in survivors.

Keywords: COVID-19; spirometry; forced vital capacity; forced expiratory volume; pulmonary function tests; post-COVID sequelae.