Table 2.

Results of stepwise regression analysis for the number of respiratory drugs in patients with COPD

Model	Unstandardized coefficients		Standardized coefficients	t	Significance
	B	Standard error	Beta
(Constant)	6.015	0.777		7.742	0.000
SGRQ total	0.15	0.003	0.183	4.535	0.000
FEV1, % pred	−0.18	0.003	−0.233	−5.484	0.000
Exacerbations, no	0.095	0.020	0.170	4.663	0.000
6MWD, meters	−0.002	0.000	−0.139	−3.467	0.001
PaCO2, kPa	0.320	0.087	0.149	3.653	0.000
DLCO, % pred	0.009	0.003	0.124	3.166	0.002
PaO2, kPa	−0.100	0.041	−0.097	−2.428	0.015

Abbreviations: SGRQ, St George’s Respiratory Questionnaire; FEV₁, forced expiratory volume in one second; 6MWD, six-minute walk distance; P_aCO₂, arterial carbon dioxide tension; DL_CO, diffusing capacity for carbon monoxide; P_aO₂, arterial oxygen tension.