Fig. 1

Mean R_5–20, A_x and X₅ values based on the COPD assessment test (CAT) score. Mean oscillometry values are reported for R_5–20, A_x and X₅ based on the CAT Score. R_5–20 is a measure of small airway resistance. A_x is a measure of the area under the reactance curve. X₅ is a measure of airway elastance. CAT score is classified as low (< 10), medium (10–20), high (21–30) and very high (> 30). p Values were generated using the ANOVA test. p Values for R_5–20, A_x and X₅ based on CAT score were 0.009, 0.007, and 0.05, respectively. Sample size based on CAT score group were as follows, low n = 10, medium n = 29, high n = 15, and very high n = 5