| Characteristic | COPD patients (n = 2) | Healthy controls (n = 40) | p Value |
| Age (y) | 73.0 (8.0) | 70.9 (9.3) | 0.32 |
| Sex (male:female) | 77:5 | 19:21 | <0.01 |
| Smoking status (current:former:never) | 10:72:0 | 1:17:22 | <0.01 |
| No of cigarette packs*year | 65.3 (37.8) | 11.2 (15.9) | <0.01 |
| BMI (kg/m2) | 21.5 (3.0) | 24.1 (3.5) | <0.01 |
| FEV1 (l) | 1.5 (0.6) | 2.2 (0.7) | <0.01 |
| %FEV1 (% pred) | 56.9 (20.4) | 101.3 (15.9) | <0.01 |
| RV/TLC (%) | 43.6 (7.7) | ND | |
| Dlco/Va (ml/min/mmHg/l) | 2.7 (1.0) | ND | |
| Pao2 (kPa) | 8.3 (0.9) | ND | |
| Paco2 (kPa) | 4.6 (0.5) | ND |
Gender and smoking status were evaluated by the χ2 test. The number of cigarette packs*year was evaluated by the Mann–Whitney U test. All other indices were evaluated by the unpaired t test.
BMI, body mass index; COPD, chronic obstructive pulmonary disease; Dlco, diffusing capacity of the lung for carbon monoxide; FEV1, forced expiratory volume in 1 s; ND, not done; Paco2, partial pressure of arterial carbon dioxide; Pao2, partial pressure of oxygen in arterial blood; RV, residual volume; TLC, total lung capacity; Va, alveolar volume.