A model for standardization of lung function parameters by height

Lung function parameters are closely associated with the height of the individual and this is the reason why this genetically determined characteristic is present obligatorily in the equations giving their reference values. The present work studies a large group of models by analysing two groups of healthy individuals - 20 healthy boys aged 7 to 14 years (10.6 +/- 2.2; mean +/- SD) with a height of 121 to 170 cm (145.0 +/- 14.2) and 98 healthy men aged 30 to 60 years (44.7 +/- 6.7) with a height of 159 to 192 cm (171.0 +/- 9.1), all of them non-smokers. Statistical analysis shows that standardization of lung function parameters by height of healthy individuals is achieved by using a power function of the height - FEV1/2.7 and VC/H2.6 for boys aged 7 to 14 years and FEV1/H2.5 and VC/H2.4 for men aged 30 to 60 years. The model proposed for children practically neutralizes age completely and can be used as a reference equation. The graphic and correlation analysis of the residuals obtained as a difference between the actual and predicted values of the respective models indicated clearly presence of age peculiarities. In men the correlation coefficients between the residuals and the height were close to zero, and the residuals themselves were relatively evenly distributed around the zero line (a homoscedastic distribution). In children the differences scattering increased with the height, i.e. there is a heteroscedastic distribution.