Airflow limitation or static hyperinflation: which is more closely related to dyspnea with activities of daily living in patients with COPD?

Table 1 Demographic details and correlations with the BDI score (Spearman's rank correlation test) in 167 subjects with stable COPD.

variable	units	mean	SD	max	min	Correlations with BDI score
						Rs	p value
Age	years	71.6	8.7	90	40	-0.25	0.0014
BMI	kg/m²	21.1	3.2	32.2	13.3	0.17	0.0320
Cumulative Smoking	pack-years	71	42	268	4	-0.23	0.0033
VC	Liters	3.21	0.91	5.31	0.97	0.45	< 0.0001
VC	% pred	102.6	22.8	156.2	38.6	0.48	< 0.0001
FVC	Liters	3.05	0.89	5.25	0.99	0.47	< 0.0001
FVC	% pred	97.4	22.5	147.9	40.9	0.51	< 0.0001
FEV₁	Liters	1.52	0.72	3.46	0.39	0.60	< 0.0001
FEV₁	% pred	68.5	27.4	133.0	13.0	0.60	< 0.0001
FEV₁/FVC	%	48.2	13.9	69.9	22.1	0.56	< 0.0001
TLC	Liters	5.65	1.15	8.49	2.86	0.24	0.0022
TLC	% pred	111.3	17.5	160.6	57.3	0.24	0.0022
IC	Liters	2.09	0.68	3.57	0.69	0.45	< 0.0001
IC/TLC	%	36.8	8.6	60.3	11.8	0.47	< 0.0001
IC/predicted TLC	%	41.1	11.7	66.5	12.2	0.46	< 0.0001
DLco	mL/min/mmHg	10.26	5.45	24.66	0.22	0.55	< 0.0001
DLco	% pred	65.0	27.3	133.7	2.5	0.53	< 0.0001
DLco/V_A	mL/min/mmHg/L	2.35	1.16	6.52	0.03	0.52	< 0.0001
PaO₂	mmHg	80.1	11.5	104.8	50.3	0.48	< 0.0001
PaCO₂	mmHg	40.5	4.8	63.3	30.7	0.00	0.98
pH (arterial blood)		7.43	0.03	7.53	7.33	0.04	0.64
BNP	pg/mL	46.5	78.8	521.0	3.0	-0.23	0.0033
BDI score	(0-12)	8.5	2.8	12	0	-	-
Gender	147 Male/20 Female
Smoking Status	29 Current/138 Former

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