Relationship between sRaw0.5 and forced expiratory flow rates as assessed by Spearman's signed rank test.

*Spearman correlation coefficient, data adjusted for age and height.**FEF25–75%/FVC ratio is a crude index of airway size relative to lung size [18].Correlation coefficients are calculated for expiratory flow rates expressed in terms of both absolute and of % predicted values (left column), as well as in terms of values adjusted for age and height (right column) showing that for the latter we obtained very similar results to those obtained for values expressed in % predicted.