Relationship between Pack Year and Lung Function Parameters in Asymptomatic Smokers

Smoking has extensive effects on respiratory function. The rate of cigarette smoking among young people has continued to increase steadily. Exposure to cigarette smoking is usually measured in terms of 'Pack-Year'. The aim of the study was to observe the effect of pack years on pulmonary functions in apparently healthy asymptomatic smokers by measuring FVC, FEV₁, FEV₁/FVC ratio and PEFR value by digital spirometer. This cross-sectional observational study was conducted in the department of Physiology, Sylhet MAG Osmani Medical College in collaboration with department of Medicine, Sylhet MAG Osmani Medical College Hospital, Sylhet, Bangladesh from July 2016 to June 2017. A total number of 100 male smokers, age ranging from 18-60 years and BMI within normal limit (18.5-24.9kg/m²) were included in this study. Their pulmonary functions were studied by measuring FVC, FEV₁, FEV₁/FVC ratio and PEFR. Relationship between pack-year and pulmonary function test parameters was established by one way ANOVA test. In this study we found that lung function parameters shared an inverse relationship with pack year of smoking. The percentage of predicted values of FEV₁, FEV₁/FVC ratio and PEFR were significantly lower (p<0.001) in heavy smokers who smoked more than 30 pack years. Therefore, by this study we inferred that those who smoked more than 10 pack years are associated with accelerated decline in lung function.