TABLE 3

Symptom-limited maximal cycling constant work-rate exercise test (CWRET) at high altitude (2500 m) versus low altitude (470 m)

End-exercise low altitude (470 m)Change from rest to end-exercisep-valueEnd-exercise high altitude (2500 m)Change from rest to end-exercisep-valueDifference at end-exercise 2500 m versus 470 mp-value
CWRET cycling time, min23.9±8.917.4±11.3−6.4 (−9.5 to −3.3)<0.001
CWRET cycling time percentage of value at 470 m, %100.0±0.077.1±31.6−22.9 (−35.1 to −10.8)<0.001
Noninvasive blood and tissue oxygenation
 Pulse oximetry, %89±4−5 (−7 to −3)<0.00182±5−5 (−9 to −1)0.017−8 (−10 to −5)<0.001
 Cerebral tissue oxygen saturation, %59±12−3 (−5 to −1)0.01157±10−4 (−8 to −1)0.023−1 (−5 to 4)0.758
 Muscular tissue oxygen saturation, %66±11−1 (−5 to 2)0.46962±10−4 (−7 to −1)0.007−4 (−8 to 1)0.107
Arterial blood gases
 pH7.44±0.03−0.02 (−0.01 to −0.03)0.0097.45±0.04−0.04 (−0.01 to −0.04)<0.0010.01 (0.00 to 0.03)0.065
 Partial pressure of carbon dioxide, kPa4.3±0.7−0.3 (−0.1 to −0.4)0.0033.9±0.6−0.4 (−0.1 to −0.5)0.001−0.3 (−0.5 to −0.2)<0.001
 Partial pressure of oxygen, kPa8.3±1.2−2.0 (−0.4 to −1.8)<0.0016.2±1.2−1.0 (−1.5 to −0.5)#0.001−2.2 (−2.6 to −1.8)<0.001
 Hydrogen carbonate, mmol·L−123.2±2.4−2.3 (−0.3 to −1.3)<0.00122.3±2.6−3.9 (−0.5 to −2.0)<0.001−0.7 (−1.6 to 0.1)0.096
 Lactate, mmol·L−13.8±1.72.8 (−0.3 to −1.3)<0.0015.9±2.75.0 (3.9 to 6.1)#<0.0012.1 (1.3 to 2.8)<0.001
 Haemoglobin, g·dL−115.5±1.30.8 (−0.1 to −0.6)<0.00115.7±1.40.8 (0.6 to 0.9)<0.0010.2 (−0.1 to 0.5)0.260
 Arterial oxygen saturation, %91±4−3 (−5 to −2)<0.00181±7−8 (−11 to −4)<0.001−10 (−12 to −8)<0.001
 Arterial oxygen content, mL·dL−119±20 (−0 to 1)0.15617±2−1 (−1 to −0)#0.028−2 (−3 to −2)<0.001
Circulatory and respiratory parameters by PDX and Finapres
 Heart rate, beats·min−1116±2645 (34 to 55)<0.001130±2044 (36 to 52)<0.00115 (7 to 23)<0.001
 Breathing rate, breaths·min−132±612 (10 to 15)<0.00131±711 (6 to 15)<0.001−1 (−4 to 3)0.708
 Systolic arterial pressure, mmHg128±2814 (3 to 24)0.012134±3015 (3 to 28)0.0178 (−4 to 20)0.213
 Diastolic arterial pressure, mmHg81±1412 (3 to 21)0.01086±219 (0 to 18)0.0515 (−5 to 15)0.317
Echocardiography
 TRPG, mmHg65±2925 (16 to 35)<0.00184±3028 (20 to 36)<0.00118 (9 to 27)<0.001
 Systolic PAP, mmHg69±3026 (16 to 36)<0.00188±3128 (20 to 36)<0.00118 (9 to 28)<0.001
 Stroke volume, mL82±169 (6 to 12)<0.00181±216 (3 to 10)0.002−1 (−9 to 7)0.837
 CO, L·min−19.4±2.44.3 (3.4 to 5.2)<0.00110.5±2.54.0 (3.3 to 4.8)<0.0011.1 (0.1 to 2.1)0.036
 Oxygen delivery, mL·min−11958±360936 (762 to 1111)<0.0011825±493629 (401 to 857)#<0.001−98 (−310 to 114)0.365
 Pulmonary vascular resistance, WU4.3±3.10.3 (−0.6 to 1.2)0.4924.8±2.9−0.5 (−1.2 to 0.3)0.1950.7 (−0.2 to 1.6)0.120
 TRPG/CO, WU7.1±3.4−0.6 (−1.9 to 0.7)0.3488.4±3.9−0.9 (−2.1 to 0.3)0.1171.2 (0.0 to 2.5)0.050
 TRPG/CO slope during exercise, WU8.0±4.85.1±19.7−2.5 (−10.2 to 5.3)0.533
 Tricuspid annular plane systolic excursion, cm2.4±0.20.6 (0.4 to 0.8)<0.0012.4±0.50.6 (0.3 to 0.8)0.0010 (−0.3 to 0.2)0.749
Patient-reported outcomes under exercise
 Borg dyspnoea scale4.5±2.54.1 (3.2 to 5)<0.0015.0±2.74.3 (3.3 to 5.4)<0.0010.3 (−0.1 to 0.6)0.117
 Borg leg fatigue scale4±2.73.7 (2.7 to 4.7)<0.0014.4±2.83.9 (2.8 to 5)<0.0010.2 (−0.1 to 0.5)0.195

Data are presented as mean±sd or mean difference (95% CI), unless otherwise stated. TRPG: tricuspid regurgitation pressure gradient; PAP: pulmonary artery pressure; CO: cardiac output. #: significant difference of changes during exercise at 2500 m versus 470 m.