Characteristics of the participants
| Controls | COPD patients | |
| Subjects | 6 | 5 |
| Demographics | ||
| Age years | 44.2±18.4 | 59±7.5 |
| Sex | ||
| Male | 2 | 1 |
| Female | 4 | 4 |
| Weight kg | 70.3±15.4 | 81.3±11.0 |
| Height cm | 164.8±12.4 | 167.6±6.8 |
| BMI kg·m−2 | 25.3±6.0 | 28.3±3.2 |
| Lung function | ||
| FEV1/FVC % | 83.5±14.9 | 55.0±6.3 |
| FEV1 % pred | 86.8±15.4 | 53.8±10.4 |
| Baseline values | ||
| Pulse beats·min−1 | 69.3±11.1 | 76.4±16.0 |
| SpO2 % | 95.2±2.3 | 97±0.7 |
| ETCO2 mmHg | 40.9±2.1 | 42.7±5.1 |
Data are presented as n or mean±sd. COPD: chronic obstructive pulmonary disease; BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; SpO2: arterial oxygen saturation measured by pulse oximetry; ETCO2: end-tidal carbon dioxide. We enrolled six controls and five COPD patients. Our sample consisted of more females in both groups. Patients with COPD were older, but with similar BMI. FEV1 % pred was lower for COPD patients, as determined by enrolment, but there were no differences in SpO2 and ETCO2 during baseline measurements at the beginning of the protocol.