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1 Rigshospitalet, The Copenhagen Muscle Research Centre, Copenhagen, Denmark
2 Rigshospitalet, The Copenhagen Muscle Research Centre, Copenhagen, Denmark; University of Las Palmas de Gran Canaria, Department of Physical Education, Las Palmas, Spain
* To whom correspondence should be addressed. E-mail: carsten{at}cmrc.dk.
We aimed to test the effects of altitude acclimatization on pulmonary gas exchange at maximal exercise. Six lowlanders were studied at sea level, in acute hypoxia (AH), and after 2 and 8 weeks acclimatization to 4100m (2W and 8W), and compared to Aymara high altitude natives (Nat) residing at this altitude. Alveolar oxygen tension (PAO2) as expected was reduced during AH, but increased gradually during acclimatization (AH, 61?0.7; 2W, 69?0.9; 8W, 72?1.4 mmHg) reaching values significantly higher than in Aymaras (Nat, 67?0.6 mmHg). Arterial oxygen tension PaO2) also decreased during exercise in AH, but increased significantly with acclimatization (AH, 51?1.1; 2W, 58?1.7; 8W, 62?1.6 mmHg). PaO2 in lowlanders reached levels that were not different from the high altitude natives (Nat, 66?1.2 mmHg). Arterial oxygen saturation (SaO2) decreased during maximum exercise compared to rest in AH, 2W and 8W (AH, 73.3?1.4; 2W, 76.9?1.7; 8W, 79.3?1.6%). After 8W SaO2 was not significantly different from Aymaras (Nat, 82.7?1%). An improved pulmonary gas exchange with acclimatization was evidenced by a decreased ventilatory equivalent of oxygen (VE/VO2) after 8W (AH, 59?4; 2W, 58?4; 8W, 52?4 l.min.lO2-1). VE/VO2 reached levels not different from the Aymaras (Nat, 51?3 l.min.lO2-1). However, the increases in exercise PAO2 and PaO2 with acclimatization had no net effect on the alveolar-arterial oxygen tension difference (A-aPO2) in the lowlanders (AH, 10?1.3; 2W, 11?1.5; 8W, 10?2.1mmHg), which remained significantly higher than in Aymaras (Nat, 1?1.4 mmHg). In conclusion, lowlanders substantially improve pulmonary gas exchange with acclimatization, but even 8 weeks is insufficient to achieve high altitude native levels.
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