Table 3.
Univariate correlations between ∆X5 (EFL index) and predictor variables
| Rho | p value | |
|---|---|---|
| Age (years) |
0.087 |
0.4556 |
| Pack-years |
0.181 |
0.1217 |
| mMRC scale |
0.282 |
0.0161 |
| CAT score |
0.084 |
0.4712 |
| Emphysema score |
0.107 |
0.3609 |
| FEV1 (% predicted) |
-0.526 |
<0.0001 |
| FVC (% predicted) |
-0.365 |
0.0018 |
| FEV1/FVC (%) |
-0.518 |
<0.0001 |
| IC (% predicted) |
-0.212 |
0.0707 |
| FEF 25-75% (% predicted) |
-0.640 |
<0.0001 |
| FRC (% predicted) |
0.427 |
0.0003 |
| RV (% predicted) |
0.443 |
0.0002 |
| TLC (% predicted) |
0.245 |
0.0363 |
| RV/TLC (% predicted) |
0.448 |
0.0001 |
| Whole-breath R5 (cmH2O/L/s) |
0.669 |
<0.0001 |
| ∆R5 (cmH2O/L/s) |
-0.211 |
0.0709 |
| Whole-breath R20 (cmH2O/L/s) |
0.528 |
<0.0001 |
| ∆R20 (cmH2O/L/s) | -0.007 | 0.9539 |
Values are the Spearman rank correlation coefficient.
Abbreviations: CAT COPD assessment test, Δ difference between inspiratory and expiratory phases, R5 and R20 respiratory system resistance at 5 Hz and 20 Hz, EFL expiratory flow limitation, FEF 25-75% forced expiratory flow between 25% and 75% of FVC, FEV1 forced expiratory volume in 1 second, FRC functional residual capacity, FVC forced vital capacity, IC inspiratory capacity, mMRC modified Medical Research Council, NA not applicable, RV residual volume, TLC total lung capacity.