FIGURE 1.

Comparison of residuals after applying two reference equations, segmented and linear, to the same population (830 men and women). The segmented model included height, sex, age and body mass index (BMI) as predictor variables, age being adjusted for two inflection points. The linear model only included height as a predictor variable. Resistance and reactance at 5 Hz (R₅ and X₅, respectively) and area of reactance (A_X) are plotted against height, age and BMI. Residuals indicate how much the observed impulse oscillometry system value departs from the value predicted by the respective equation.