Table 1.

Manual regression analysis of determinants of bronchial anatomy by CT

Predictor	β	Standard Error	R2	P Value
Univariate regression
Smoking status	0.148	0.016	0.241	<0.001
Anatomical location	0.064	0.011	0.124	<0.001
Male sex	0.025	0.019	0.007	0.184
Laterality	0.511	0.009	0	0.830
Multivariate backward regression
Smoking status	0.015	0.002	0.368	<0.001
Anatomical location	0.006	0.001	0.368	<0.001

In the univariate regression analysis of determinants of bronchial wall thickness (BWT), all variables, including smoke status, sex, anatomic location (apical vs. medial vs. caudal lung lobes), and laterality (left vs. right), were modeled for contribution in BWT. In the multivariate backward regression model for significant determinants of BWT in chronic obstructive pulmonary disease (COPD) ferrets, all variables, including smoke status, sex, and anatomic location and laterality, were considered in the original model. n = 252 ferrets, P < 0.0001, R² = 0.368.