Abstract
Background: Smoking is known as the major cause of chronic obstructive pulmonary disease (COPD). In COPD, most of pulmonary function tests (PFTs) those indicating the diameter of airways are reduced. There are reports that bronchodilator drugs have no or a very little effect on PFT of COPD patients.

Aims & Objective: PFTs of smokers were compared with those of non-smokers and the effect of bronchodilator inhaler
(salbutamol) on PFTs of smokers was also examined.

Materials and Methods: Pulmonary function tests were measured in 100 male smokers (height 171.71 ± 6.68 cm, age
36.49 ± 13.06 years old) and compared with 100 male nonsmokers (height 171.79 ± 8.81 cm, age 35.56 ± 12.83 years
old). The subjects underwent measurement of spirometric flow and volume. The following variables were measured: forced vital capacity (FVC), forced expiratory volume in one second (FEV1), maximal mid-expiratory flow (MMEF), peak expiratory flow (PEF), maximal expiratory flow at 75%, 50%, and 25% of the FVC (MEF75, MEF50, and MEF25 respectively). In addition, pulmonary function tests of 33 male smokers (height 172.79 ±11.94 cm, age 38.30 ± 6.65 years old) before and 10 minutes after administration of 200 μg salbutamol inhaler were measured.

Results: Most values of PFTs in smokers were significantly lower than those of non-smokers (p<0.001 for FVC, FEV1, PEF, MEF75, p<0.01 for MMEF, and p<0.02 for MEF50). However, there were not significant differences in MEF25 of smokers and non-smokers. There were significant correlations between the smoking duration and FEV1, PEF, MEF75, and MEF50 (p<0.05 to p<0.01), but correlations between smoking quantity and values of PFTs were not significant. The results also showed that all values of PFTs were significantly increased after salbutamol administration (p<0.05 to p<0.01). The enhancement in PEF, MEF75, and MEF50 was around 12% and that of MEF25 was 17%.

Conclusion: The effect of smoking on PFT showed that smoking leads to constriction of large and medium sized airways which is mostly due to duration not to quantity of smoking. The airway constriction in smokers was reversible which, was mostly seen for medium sized airways.

Key words: Pulmonary function test, Reversibility, Smoking.