Abstract
Predicted normal spirometric values have been shown to have significant geographical and ethnic variation. These variations are of epidemiological significance in determining the prevalence of disease and of clinical importance in measuring the effects on pulmonary function of various diseases. A total of 599 men were chosen from employees of a package manufacturer, a general hospital in Lahore, and a village in northern Pakistan; 94 students and staff of a women's college in Lahore were also studied. The forced vital capacity (FVC) was recorded from three satisfactory efforts, and the FVC, one second forced expiratory volume (FEV1), and maximal midexpiratory flow (MMF, or FEF25-75%) were calculated from the best FVC effort. The FVC and FEV1 in men were found to be similar to those of a group of emigrant Pakistanis and a north-western Indian population (Delhi) but higher than populations in south and eastern India. Pakistani women had values similar to those of women in northern India. None of the women smoked and, among Pakistani men, the smokers (285) averaged 6.7 pack years. While the FVC and FEV1 values did not differ between smokers and non-smokers, there was a significant difference in MMF (FEF25-75%) in the two groups. This latter finding corroborates studies on North American populations in which smokers generally have had a higher lifelong cigarette consumption. This confirms the MMF (FEF25-75%) to be a more sensitive test of subtle, asymptomatic changes in pulmonary function than the more widely used FVC and FEV1.