Table 3.

Unadjusted Correlations Between Quantitative Small Airway Measures and Spirometry

Small Airway Measures	FEV1	P Value	pp FEV1	P Value	FEV1/FVC	P Value
2011 (n = 404)
Exp−856	0.011	.831	–0.112	.024	–0.446	< .001
E/I MLA	–0.210	< .001	–0.232	< .001	–0.354	< .001
RVC−856 to −950	–0.292	< .001	–0.240	< .001	–0.232	< .001
Residual−856	–0.149	.003	–0.189	< .001	–0.410	< .001
2016 (n = 404)
Exp−856	–0.072	.149	–0.126	.011	–0.486	< .001
E/I MLA	–0.292	< .001	–0.233	< .001	–0.385	< .001
RVC−856 to −950	–0.324	< .001	–0.220	< .001	–0.223	< .001
Residual−856	–0.216	< .001	–0.181	< .001	–0.413	< .001

Data are presetned as Pearson correlation coefficients unless otherwise indicated. P < .05 was considered significantly different from zero. E/I MLA = expiratory-to-inspiratory ratio of mean lung attenuation; Exp₋₈₅₆ = percentage of voxels with attenuation less than -856 HU on expiratory CT scans; HU = Hounsfield unit; pp FEV₁ = percent predicted FEV₁; Residual_–856 = residuals from the linear regression of Exp₋₈₅₆ on the percentage of voxels with attenuation less than –950 HU; RVC_{−856 to −950} = relative volume change in voxels with attenuation between –856 HU and –950 HU.