Baseline characteristics
| Lowlanders n=22 | Highlanders n=52 | p-value | |
| Male/female n | 14/8 | 26/26 | |
| Age years | 42.3±8.0 | 47.9±10.7 | 0.033 |
| Height cm | 168.5±10.4 | 162.2±9.4 | 0.014 |
| Weight kg | 75.9±10.4 | 70.2±13.4 | 0.078 |
| BMI kg·m−2 | 26.9±4.1 | 26.7±4.6 | 0.845 |
| Body surface area m2 | 1.89±0.16 | 1.75±0.19 | 0.017 |
| Heart rate beats·min−1 | 68±7 | 75±11 | 0.010 |
| Blood pressure systolic mmHg | 121±15 | 127±23 | 0.274 |
| Blood pressure diastolic mmHg | 82±10 | 85±12 | 0.348 |
| New York Heart Association functional class I/II/III | 18/3/1 | 30/18/4 | 0.379 |
| Workload achieved Watts | 48±11 | 45±14 | 0.344 |
| SpO2 % | 96±1 | 91±5 | <0.001 |
| Haemoglobin concentration g·dL−1 | 14.4±1.7 | 16.0±2.3 | 0.008 |
| Haematocrit % | 39.1±5.0 | 46.8±7.6 | <0.001 |
| PaO2 mmHg | 79.3±10.9 | 56.2±6.2 | <0.001 |
| PaCO2 mmHg | 38.9±2.9 | 32.5±2.8 | <0.001 |
| Oxygen content mL O2·dL−1 | 18.3±2.4 | 18.9±2.8 | 0.447 |
| Pack-years | 1.9±5.2 | 3.7±6.2 | 0.227 |
Data are presented as mean±sd, unless otherwise stated. BMI: Body mass index; SpO2: oxygen saturation by pulse oximetry; PaO2: partial pressure of arterial oxygen; PaCO2: partial pressure of arterial carbon dioxide.