Table 5.
Correlation coefficients for plethysmography, HRCT, and the difference between plethysmography and HRCT
| Variables | Plethysmography | HRCT | Plethysmography–HRCT | |||
|---|---|---|---|---|---|---|
|
|
|
|
||||
| r | P | r | P | r | P | |
| FEV1/FVC | −0.39 | 0.00 | −0.35 | 0.01 | 0.02 | 0.88 |
| FVC (L) | 0.58 | 0.00 | 0.66 | 0.00 | 0.03 | 0.84 |
| FVC% | 0.06 | 0.65 | 0.02 | 0.87 | 0.11 | 0.40 |
| FEV1 (L) | 0.06 | 0.63 | 0.14 | 0.28 | 0.04 | 0.77 |
| FEV1% | −0.25 | 0.06 | −0.22 | 0.10 | 0.05 | 0.71 |
| FEF 25–75 (L) | 0.09 | 0.57 | 0.08 | 0.69 | 0.07 | 0.80 |
| FEF 25%–75% | −0.30 | 0.05 | −0.27 | 0.06 | 0.12 | 0.39 |
| RV (L) | 0.69 | 0.00 | 0.54 | 0.00 | 0.32 | 0.02 |
| RV% | 0.44 | 0.00 | 0.28 | 0.03 | 0.29 | 0.03 |
| TLC (L) | – | – | 0.90 | 0.00 | 0.31 | 0.02 |
| TLC% | 0.56 | 0.00 | 0.34 | 0.00 | 0.39 | 0.00 |
| RV/TLC | 0.07 | 0.60 | −0.06 | 0.67 | 0.16 | 0.21 |
| FRC (L) | 0.85 | 0.00 | 0.74 | 0.00 | 0.29 | 0.03 |
| FRC% | 0.48 | 0.00 | 0.33 | 0.01 | 0.27 | 0.04 |
| IC (L) | 0.38 | 0.00 | 0.43 | 0.00 | 0.04 | 0.78 |
| IC% | −0.02 | 0.87 | −0.06 | 0.67 | 0.07 | 0.60 |
| IC/TLC | −0.13 | 0.33 | −0.05 | 0.72 | −0.07 | 0.61 |
| DLCO/VA | −0.42 | 0.00 | −0.35 | 0.01 | −0.06 | 0.63 |
| DLCO/VA% | −0.42 | 0.00 | −0.35 | 0.01 | −0.05 | 0.71 |
| HRCT total (L) | 0.90 | 0.00 | – | – | −0.06 | 0.64 |
| HRCT tissue (L) | 0.39 | 0.00 | 0.52 | 0.00 | 0.10 | 0.43 |
| HRCT air (L) | 0.92 | 0.00 | 0.98 | 0.00 | −0.08 | 0.56 |
| HRCT density (HU) | −0.44 | 0.00 | −0.39 | 0.00 | 0.20 | 0.13 |
| % emphysema less than −950 | 0.43 | 0.00 | 0.41 | 0.00 | −0.18 | 0.18 |
| % emphysema less than −910 | 0.49 | 0.00 | 0.44 | 0.00 | −0.15 | 0.26 |
Abbreviations: DLCO/VA, carbon monoxide diffusing capacity corrected for alveolar volume; DLCO/VA%, carbon monoxide diffusing capacity corrected for alveolar volume, percent predicted; emphysema less than −950, percent of voxels with Hounsfield units less than −950; emphysema less than −910, percent of voxels with Hounsfield units less than −910; FEF 25–75(L), forced expiratory volume during midexpiratory flow; FEF 25%–75%, forced expiratory volume during midexpiratory flow, percent predicted; FEV1, forced expiratory volume in 1 second; FEV1%, forced expiratory volume in 1 second, percent predicted; FRC, functional residual capacity; FVC, forced vital capacity; FVC%, forced vital capacity, percent predicted; HRCT, high-resolution computed tomography; HU, Hounsfield units; IC, inspiratory capacity; RV, residual volume; RV%, residual volume, percent predicted; TLC, total lung capacity; TLC%, total lung capacity, percent predicted.