Independent relationships between functional indices and the major determinants of functional impairment on inspiratory and expiratory CT, generated using stepwise regression
| Extent of bronchiectasis (log) | Bronchial wall dilatation (log) | Bronchial wall thickness (log) | Decreased attenuation (exp) (log) | |
| FEV1
R 2= 0.39 | p = 0.04–50.4 (–99.9 to –0.8) | p<0.01 41.7 (10.6 to 72.7) | p<0.005 -34.6 (–57.8 to –11.5) | p<0.001–22.4 (–35.1 to –9.7) |
| FEV1/FVC (log) R 2 = 0.26 | p = 0.09–0.28 (–0.62 to 0.05) | p<0.01 0.29 (0.08 to 0.50) | p<0.005–0.23 (–0.38 to –0.07) | p = 0.02–0.10 (–0.19 to –0.02) |
| RV (log) R 2 = 0.37 | p = 0.02 1.17 (0.21 to 2.14) | p<0.01–0.80 (–1.40 to –0.21) | p<0.01 0.62 (0.15 to 1.09) | p<0.01 0.35 (0.09 to 0.60) |
| Tlco
R 2= 0.18 | p<0.01–26.1 (–44.5 to –7.8) | p = 0.15–7.8 (–18.3 to 2.80) | ||
| Kco
R 2 = 0.08 | p<0.01–59.6 (–102.6 to 16.5) | p = 0.03 26.6 (3.0 to 50.2) |
FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; RV = residual volume; Tlco = carbon monoxide transfer factor; Kco = carbon monoxide transfer coefficient.
Equation R 2 values, p values and regression coefficients (95% confidence intervals in parentheses) are shown: abnormally distributed CT scores and lung function indices were transformed logarithmically to correct skewness. For example, percentage predicted FEV1 was negatively related to the extent of bronchiectasis (p = 0.04), the severity of bronchial wall thickening (p<0.005), and the extent of decreased attenuation on expiratory CT scan (p<0.001) and was positively related to the severity of bronchial dilatation (p<0.01). EquationR 2 (explaining variation in FEV1 levels) = 0.39.