Spirometric studies on normal Turkish subjects aged 8 to 20 years.

Total lung capacity and its subdivisions, maximal breathing capacity and forced expiratory volume in one second expressed as a percentage of the forced vital capacity, were measured in 130 male and 130 female normal Turkish subjects 8 to 20 years old to establish normal values. The subjects were from different socio-economic communities. Statistical analysis was performed to determine the relationship of the measurements to age and the physical characteristics of the body, and the best regression equations were found for predicting lung volumes and maximal breathing capacity. It was found that all physical characteristics were highly correlated with spirometric measurements. Best prediction formulae were found to be based on body surface area and height. All volumes and maximal breathing capacity were found, in general, to be higher in males. This sex difference in measurements became significant after 16-17 years of age. The difference in height between the two sexes also became significant after 16 years of age. In the same age group and in both sexes, taller subjects had higher lung volumes and maximal breathing capacity. These findings suggest that height and respiratory muscle power are the main factors of sex difference in the measurements. Vital capacity and maximal breathing capacity related to age in both sexes were compared with those of some previous studies and it was found that all data, except a few, fell within the 95% confidence limits of the present study. Similar observations were, in general, made when height was taken into consideration for comparison. The value of FEV/FVC% was altered little for the age group studied and its mean value was about 86·6 ± 4·2% for males and 87 ± 4·2% for females. There was no significant relationship between age or sex and RV/TLC% and the mean value of this parameter was 23·6 ± 1·9 for males and 25·5 ± 1·6 for females. There was a slight but clinically unimportant difference between the values of these two measurements and the value from the literature.