Table 1.
Baseline characteristics of the study population.
| Total (n = 294) | Dyspnea group (n = 215) | Leg fatigue group (n = 58) | p-value | |
|---|---|---|---|---|
| Age, years | 70.7 (7.4) | 70.1 (7.3) | 71.7 (7.2) | 0.127 |
| BMI, kg·m−2 | 20.6 (3.2) | 20.5 (3.1) | 20.4 (3.5) | 0.850 |
| GOLD, I/II/III/IV | 14/81/135/64 | 7/49/108/51 | 3/19/24/12 | 0.250 |
| PULMONARY FUNCTION TEST | ||||
| FEV1, L | 1.16 (0.52) | 1.10 (0.50) | 1.23 (0.54) | 0.077 |
| %FEV1, % predicted | 44.6 (17.7) | 42.3 (16.7) | 46.8 (17.8) | 0.073 |
| FEV1/FVC, % | 44.4 (11.9) | 43.1 (11.6) | 45.6 (11.5) | 0.151 |
| VC, L | 2.89 (0.76) | 2.87 (0.77) | 2.90 (0.76) | 0.832 |
| CARDIOPULMONARY EXERCISE TESTING | ||||
| At Rest | ||||
| PaO2, mmHg | 81.0 (11.4) | 80.2 (11.2) | 84.0 (11.8) | 0.024 |
| PaCO2, mmHg | 37.6 (4.7) | 37.6 (4.8) | 37.7 (4.1) | 0.792 |
| pH | 7.423 (0.026) | 7.423 (0.025) | 7.424 (0.004) | 0.617 |
| At Peak Exercise | ||||
| Dyspnea, Borg scale | 7.0 (2.5) | 7.4 (2.3) | 5.8 (0.3) | < 0.0001 |
| Dyspnea index, % | 102.3 (24.9) | 105.6 (24.9) | 96.0 (24.0) | 0.009 |
| Breathing reserve, L·min−1 | 1.5 (10.7) | 0.0 (10.2) | 4.3 (10.6) | 0.005 |
| %HR reserve, % | 83.9 (13.5) | 83.0 (13.8) | 83.3 (9.4) | 0.856 |
| , mL·min−1·kg−1 | 16.9 (5.4) | 16.9 (5.5) | 16.5 (4.9) | 0.626 |
| , L·min−1 | 39.0 (14.2) | 38.5 (14.1) | 38.9 (13.9) | 0.855 |
| VT, mL | 1206 (391) | 1173 (390) | 1251 (401) | 0.178 |
| Breathing frequency, breaths·min−1 | 33.5 (8.2) | 34.0 (7.0) | 32.0 (6.1) | 0.032 |
| VD/VT | 0.31 (0.08) | 0.31 (0.08) | 0.31 (0.07) | 0.758 |
| PaO2, mmHg | 62.2 (12.5) | 60.1 (11.7) | 68.0 (13.7) | < 0.0001 |
| PaCO2, mmHg | 41.3 (6.7) | 42.0 (6.8) | 40.3 (6.2) | 0.086 |
| ΔPaCO2, mmHg | 3.9 (4.3) | 4.4 (4.3) | 2.6 (3.7) | 0.003 |
| Plasma lactate, mg·dL−1 | 27.7 (13.4) | 26.8 (12.8) | 30.6 (15.4) | 0.100 |
| Plasma norepinephrine, ng·mL−1 | 2.48 (1.46) | 2.45 (1.40) | 2.35 (1.48) | 0.648 |
| pH | 7.365 (0.041) | 7.363 (0.039) | 7.369 (0.047) | 0.324 |
Values are presented as mean (SD) and were analyzed using the Student's t-test. BMI, body mass index; ΔPaCO2, peak PaCO2 – resting PaCO2; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; GOLD I, FEV1% predicted ≥ 80%; II, 80% > FEV1% predicted ≥ 50%; III, 50% > FEV1% predicted ≥ 30%; IV, FEV1% predicted < 30%; HR, heart rate; PaO2, arterial oxygen tension; PaCO2, arterial carbon dioxide tension; VC, vital capacity; VD/VT, physiologic dead space/tidal volume ratio; , minute ventilation; , oxygen uptake; VT, tidal volume.