Pre- and Post-bronchodilator Spirometry in Asthmatic Smokers Versus Non-smokers: A Hospital-Based Cross-Sectional Study

Abstract

Background Cigarette smoking is a major risk factor for impaired lung function and the development of chronic respiratory diseases. Early detection of pulmonary changes using spirometry can help in timely intervention and prevention of long-term complications. Objective To compare spirometry parameters between smokers and non-smokers, and to evaluate the effect of bronchodilator administration on pulmonary function in both groups. Methods A cross-sectional study was conducted involving 60 participants (30 smokers and 30 non-smokers). Spirometry was performed before and after bronchodilator administration to measure vital capacity (VC%), forced vital capacity (FVC%), forced expiratory volume in the first second (FEV₁%), FEV₁/FVC ratio, forced expiratory flow over the middle one half of the FVC (FEF25-75%), maximal voluntary ventilation (MVV%), and expiratory time. Paired t-tests were used for within-group comparisons, and independent t-tests for between-group comparisons. A p-value < 0.05 was considered statistically significant. Results Smokers had significantly lower baseline spirometry values compared to non-smokers across all parameters (p < 0.001). Both groups showed statistically significant improvements post-bronchodilator (p < 0.001), with smokers exhibiting a smaller magnitude of improvement. Notably, FEV₁% increased from 47.2 ± 6.8 to 60.3 ± 11.5 in smokers and from 56.3 ± 7.1 to 73.3 ± 7.4 in non-smokers. The FEV₁/FVC ratio and other flow rates showed similar patterns. Expiratory time also increased post-bronchodilator in both groups. Conclusion Smoking is associated with marked reductions in lung function and diminished bronchodilator responsiveness. Early spirometric screening in smokers is essential to identify functional decline and guide smoking cessation and treatment strategies to prevent progression of pulmonary disease.