Differences in pulmonary function based on height prediction obtained by using alternative measures.

Background: Standing height is an independent variable used to predict pulmonary function; however, some patients are not able to stand.

Objectives: The objectives of this study were to compare predicted pulmonary function values obtained by using various alternative measures to estimate height, analyse the values' reproducibility and evaluate their agreement.

Methods: Standing height, knee height, ulna length, demi-span and arm span were measured in 100 subjects who were able to stand. Five groups of values were generated for predicted FVC and FEV(1) based on measured standing height and the height estimated using each alternative measure.

Results: The differences found between the height estimated using the different measures and measured standing height were statistically significant. The reproducibility was excellent; however, agreement was poor and all the measures tended to overestimate the predicted values based on standing height although this tendency was less marked in the case of knee height.

Conclusions: The use of alternative measures to predict height introduces a certain degree of error in predicted pulmonary function and this error should be quantified. Knee height is the measure that shows the greatest agreement and, thus, could be used in patients who are unable to stand.