Table 3. Correlations between airway luminal areas and physiological function tests in patients with COPD.

	3rd-generation bronchi		4th-generation bronchi		5th-generation bronchi		6th-generation bronchi
	r	p-value	r	p-value	r	p-value	r	p-value
Spirometry
FVC, %predicted	0.349	<0.001	0.291	0.005	0.385	<0.001	0.418	<0.001
FEV1, %predicted	0.375	<0.001	0.392	<0.001	0.474	<0.001	0.548	<0.001
FEV1/FVC ratio	0.235	0.024	0.322	0.002	0.339	<0.001	0.415	<0.001
MMF, %predicted	0.321	0.002	0.368	<0.001	0.423	<0.001	0.497	<0.001
Respiratory impedance, whole-breath
R5	−0.508	<0.001	−0.492	<0.001	−0.435	<0.001	−0.435	<0.001
R20	−0.460	<0.001	−0.486	<0.001	−0.422	<0.001	−0.421	<0.001
R5-R20	−0.400	<0.001	−0.330	0.001	−0.324	0.002	−0.318	0.002
X5	0.394	<0.001	0.317	0.002	0.304	0.003	0.364	<0.001
Fres	−0.472	<0.001	−0.392	<0.001	−0.361	<0.001	−0.384	<0.001
ALX	−0.431	<0.001	−0.362	<0.001	−0.335	0.001	−0.372	<0.001

Data are expressed as Spearman rank correlation coefficient and p-value. R5, respiratory resistance at 5 Hz; R 20, respiratory resistance at 20 Hz: X5, respiratory reactance at 5 Hz; Fres, resonant frequency; ALX, low-frequency reactance area. The other abbreviations are as described in Table 1.