Resting assessments after >3 h at high altitude (2500 m) versus low altitude (470 m)
| Low altitude (470 m) | High altitude (2500 m) | 2500 m versus 470 m | p-value | |
| Noninvasive blood and tissue oxygenation | ||||
| Pulse oximetry, % | 94±2 | 87±8 | −7 (−10 to −4) | <0.001 |
| Cerebral tissue oxygen saturation, % | 61±12 | 61±9 | 1 (−4 to 5) | 0.707 |
| Muscular tissue oxygen saturation, % | 67±11 | 66±9 | −1 (−5 to 2) | 0.506 |
| Arterial blood gases | ||||
| pH | 7.45±0.03 | 7.50±0.04 | 0.04 (0.03 to 0.06) | <0.001 |
| Partial pressure of carbon dioxide, kPa | 4.6±0.6 | 4.3±0.6 | −0.3 (−0.4 to −0.1) | <0.001 |
| Partial pressure of oxygen, kPa | 10.4±1.5 | 7.3±0.8 | −3.2 (−3.6 to −2.8) | <0.001 |
| Hydrogen carbonate, mmol·L−1 | 25.0±2.8 | 26.0±1.8 | 1.2 (0.3 to 2.0) | 0.007 |
| Lactate, mmol·L−1 | 0.8±0.4 | 0.9±0.3 | 0.1 (−0.1 to 0.2) | 0.450 |
| Haemoglobin, g·dL−1 | 14.7±1.6 | 14.9±1.3 | 0.2 (−0.1 to 0.6) | 0.235 |
| Arterial oxygen saturation, % | 94±2 | 88±4 | −6 (−7 to −5) | <0.001 |
| Arterial oxygen content, mL·dL−1 | 19±2 | 18±2 | −1 (−2 to 0) | <0.001 |
| Circulatory and respiratory parameters by polygraphy (PDX) and finger-cuff manometry (Finapres) | ||||
| Heart rate, beats·min−1 | 71±16 | 86±18 | 15 (7 to 23) | <0.001 |
| Breathing rate, breaths·min−1 | 19±5 | 20±6 | 1 (−1 to 4) | 0.373 |
| Systolic arterial pressure, mmHg | 112±23 | 119±27 | 8 (−1 to 16) | 0.068 |
| Diastolic arterial pressure, mmHg | 69±18 | 76±16 | 7 (−2 to 17) | 0.136 |
| Echocardiography | ||||
| TRPG, mmHg | 40±15 | 56±25 | 17 (9 to 24) | <0.001 |
| Right atrial pressure, mmHg | 4±3 | 5±3 | 1 (−1 to 2) | 0.363 |
| Systolic pulmonary arterial pressure, mmHg | 44±17 | 60±25 | 17 (9 to 25) | <0.001 |
| Stroke volume, mL | 73±15 | 75±18 | 2 (−4 to 8) | 0.556 |
| CO, L·min−1 | 4.6±1.0 | 5.3±1.3 | 0.8 (0.4 to 1.2) | <0.001 |
| Oxygen delivery, mL·min−1 | 980±214 | 1148±410 | 174 (8 to 339) | 0.040 |
| Pulmonary vascular resistance, WU | 4.0±3.0 | 5.2±3.9 | 1.4 (0.2 to 2.7) | 0.025 |
| TRPG/CO, WU | 8.1±4.5 | 9.8±6.0 | 1.7 (0.1 to 3.3) | 0.040 |
| Tricuspid annular plane systolic excursion, cm | 2.0±0.4 | 2.1±0.3 | 0.0 (−0.1 to 0.2) | 0.650 |
| Fractional area change, % | 30±12 | 32±10 | 2 (−1 to 7) | 0.209 |
Data are presented as mean±sd or mean difference (95% CI), unless otherwise stated. CO: cardiac output; TRPG: tricuspid regurgitation pressure gradient.