Comparative Study of Lung function in Healthy Adults and Chronic Smokers Applying Different Techniques of Smoking

Abstract

In man breathing in and breathing out are independent skills determined by separate factors and affected differently by various diseases so the three components of the lung function ventilation, perfusion and diffusion are in a balance during normal health. Any imbalance will result in a reduction in effective transfer of gases. Due to the developments of past quarter century, different techniques have been invented for measuring the main subdivisions of lung functions. To obtain high rate of precision, the test must not only be safe but also relatively free of discomfort for subjects. Test results should not be influenced by subjects cooperation or observer’s bias. Spirometry meets these criteria quite well and has found wide use in studying lung diseases (Bohlecke and Merchant, 1981). In 1846 Hutchinson devised the spirometer and measured the vital capacity. Spirometric tests of ventilator capacity have been extensively used to give knowledge of overall ventillatory capacity in subjects of different heights, all age groups and both sexes. These tests can provide comparison of established physiological data obtained from healthy subjects with patients suffering from respiratory insufficiency. Before puberty the lung function of the two sexes are identical but after puberty the pulmonary functions diverge, as anatomical and physiological changes are taking place. The vital capacity in males is greater as compared to females due to more muscular strength. Since the lungs of adult men contain less collagen tissue than the woman, the airways being less supported, forced expiratory volume in one second is lesser in former than the latter (Cotes, 1978). Predicted normal spirometric values have been shown to have significant ethnic variation (Williams, et al., 1978). Gould (1869) observed that vital capacity in blacks was lesser as compared to white Americans of the same height and age. No satisfactory explanation has been offered for racial variation of lung volumes. Elebure and Pearse (1971) postulated the possibility of racial difference in thoracic cage size or shape. However the magnitude of different appears to vary with the respective levels of habitual activity (Lawther et al., 1978). In adult life functions of the lungs deteriorate with increasing age (Khudson et al., 1983). The crosssectional studies provide an accurate estimate of the mean rate of change in FEV1 and FEV1 with age; whearas in longitudinal studies the results are not reproducible. All the indices show a constant decline as a result of reduction in strength of respiratory muscles, increase in stiffness of the thoracic cage or may be augmented by the effect of smoking or recurrent episodes of bronchitis (Cotes, 1978). The standing height is believed to be a good guide to the size of the lung. However it is not a reproducible measurement. Body weight provides an alternate index of the lung capacities. Similar considerations apply for the body surface area (Hall et al., 1979 Leech et al., 1983).