Pulmonary gas exchange at maximal exercise in Danish lowlanders during 8 wk of acclimatization to 4,100 m and in high-altitude Aymara natives

Abstract

-We aimed to test 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 wk of acclimatization to 4,100 m (2W and 8W) and compared with Aymara high-altitude natives residing at this altitude. As expected, alveolar PO2 was reduced during AH but increased gradually during acclimatization (61 Ϯ 0.7, 69 Ϯ 0.9, and 72 Ϯ 1.4 mmHg in AH, 2W, and 8W, respectively), reaching values significantly higher than in Aymaras (67 Ϯ 0.6 mmHg). Arterial PO 2 (PaO 2 ) also decreased during exercise in AH but increased significantly with acclimatization (51 Ϯ 1.1, 58 Ϯ 1.7, and 62 Ϯ 1.6 mmHg in AH, 2W, and 8W, respectively). Pa O 2 in lowlanders reached levels that were not different from those in high-altitude natives (66 Ϯ 1.2 mmHg). Arterial O 2 saturation (SaO 2 ) decreased during maximum exercise compared with rest in AH and after 2W and 8W: 73.3 Ϯ 1.4, 76.9 Ϯ 1.7, and 79.3 Ϯ 1.6%, respectively. After 8W, Sa O 2 in lowlanders was not significantly different from that in Aymaras (82.7 Ϯ 1%). An improved pulmonary gas exchange with acclimatization was evidenced by a decreased ventilatory equivalent of O2 after 8W: 59 Ϯ 4, 58 Ϯ 4, and 52 Ϯ 4 l⅐ min ⅐ l O2 Ϫ1 , respectively. The ventilatory equivalent of O2 reached levels not different from that of Aymaras (51 Ϯ 3 l⅐ min ⅐ l O2 Ϫ1 ). However, increases in exercise alveolar PO2 and PaO 2 with acclimatization had no net effect on alveolar-arterial PO2 difference in lowlanders (10 Ϯ 1.3, 11 Ϯ 1.5, and 10 Ϯ 2.1 mmHg in AH, 2W, and 8W, respectively), which remained significantly higher than in Aymaras (1 Ϯ 1.4 mmHg). In conclusion, lowlanders substantially improve pulmonary gas exchange with acclimatization, but even acclimatization for 8 wk is insufficient to achieve levels reached by high-altitude natives. chronic hypoxia; acute normoxia; ventilation HIGH-ALTITUDE NATIVES from North America (8), Tibet (27), and South America (19, 25) have unique pulmonary gas transport abilities, maintaining low alveolar-arterial PO 2 difference (A-aPO 2 ) at maximum exercise, thus preserving arterial PO 2 (Pa O 2 ) and saturation (Sa O 2 ). This confers a clear advantage to high-altitude natives compared with the lowlanders during exercise at altitude. Although pulmonary gas exchange in high-altitude natives has been the focus of several studies, only a few reports exist on pulmonary gas exchange during exercise in lowlanders acclimatized to high altitude. The classic study by Dempsey et al. (8) investigated lowlanders acclimatized to 3,100 m for 4, 21, and 45 days and compared these with firstto third-generation high-altitude residents. Despite the limited number of subjects analyzed (4 lowlanders), a comparatively low exercise A-aPO 2 was observed in the natives, whereas the lowlanders seemed to reduce their exercise A-aPO 2 as the altitude exposure was prolonged (8). More recently, Calbet et al. (5, 6) also found reduced exercise A-aPO 2 in seven lowlanders after chronic (9 wk) compared ...

Air to Muscle O2Delivery during Exercise at Altitude

“…However, peak exercise V E in altitude-acclimatized lowlanders may be similar (Calbet et al, 2003b), higher (Marconi et al, 2004), or slightly lower than observed in normoxia (Lundby et al, 2004a).…”

“…Compared to acute hypoxia, submaximal exercise V E remains at the same level with altitude acclimatization, while peak exercise V E is increased at moderate to high altitudes (Calbet et al, 2003b;Marconi et al, 2004) and reduced at 4000 m (Lundby et al, 2004a). However, peak exercise V E in altitude-acclimatized lowlanders may be similar (Calbet et al, 2003b), higher (Marconi et al, 2004), or slightly lower than observed in normoxia (Lundby et al, 2004a).…”

“…This is also true when acclimatized lowlanders are compared with Andean altitude natives, both measured at altitude Lundby et al, 2004a). Unlike Caucasians, secondgeneration Tibetans living at 1300 m do not increase V Emax in response to acclimatization to 5050 m above sea level (Marconi et al, 2004).…”

Acclimatization to 4100 m does not change capillary density or mRNA expression of potential angiogenesis regulatory factors in human skeletal muscle

“…Blood sampling from the highaltitude natives was done at 4100·m. For further details see Lundby et al (2004).…”

Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: a systematic review

“…With sojourns at altitude over several days, the resting cardiac output normalizes through a decrease in stroke volume, which is attributed to a hypoxia-induced reduction in plasma volume and thus lower left ventricular end-diastolic volume (55). Ventilation and heart rate, however, remain increased even after acclimatization mediated by a sustained sympathetic response driven by peripheral chemoreceptors sensitized by the persistent hypoxemia (25,26,33). Under exercise, these adaptive mechanisms are additionally stressed, and performance is, therefore, limited in the hypoxic environment at altitude.…”