Forced expiratory indices in normal black southern African children aged 6-19 years.

Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory ratio (FEV1/FVC x 100), forced mid expiratory flow (FMF), and peak expiratory flow (PEF) were measured in 2000 non-smoking black African schoolchildren aged 6-19 years from Umtata in the Republic of Transkei in Southern Africa. FVC, FEV1, FMF, and PEF were highly correlated with each other and all were highly correlated with age and standing height in both sexes. There was a significant negative correlation between FEV1/FVC and both age and standing height. An increase in the slope of the increase in FVC for both age and height occurred at 11 years and 143 cm in girls and at 13 years and 150 cm in boys. This continued for about two years and 10 cm in both groups before it declined. The mean values of FEV1, FEV1/FVC, and PEF in the present study were 14% lower than those obtained in black American schoolchildren. The present study is the largest study of urban black African schoolchildren and provides useful reference values.