Pulmonary gas exchange and acid-base state at 5,260 m in high-altitude Bolivians and acclimatized lowlanders.
Pulmonary gas exchange and acid-base state were compared in nine Danish lowlanders (L) acclimatized to 5,260 m for 9 wk and seven native Bolivian residents (N) of La Paz (altitude 3,600-4,100 m) brought acutely to this altitude. We evaluated normalcy of arterial pH and assessed pulmonary gas exchange and acid-base balance at rest and during peak exercise when breathing room air and 55% O2. Despite 9 wk at 5,260 m and considerable renal bicarbonate excretion (arterial plasma HCO3- concentration = 15.1 meq/l), resting arterial pH in L was 7.48 +/- 0.007 (significantly greater than 7.40). On the other hand, arterial pH in N was only 7.43 +/- 0.004 (despite arterial O2 saturation of 77%) after ascent from 3,600-4,100 to 5,260 m in 2 h. Maximal power output was similar in the two groups breathing air, whereas on 55% O2 only L showed a significant increase. During exercise in air, arterial PCO2 was 8 Torr lower in L than in N (P < 0.001), yet PO2 was the same such that, at maximal O2 uptake, alveolar-arterial PO2 difference was lower in N (5.3 +/- 1.3 Torr) than in L (10.5 +/- 0.8 Torr), P = 0.004. Calculated O2 diffusing capacity was 40% higher in N than in L and, if referenced to maximal hyperoxic work, capacity was 73% greater in N. Buffering of lactic acid was greater in N, with 20% less increase in base deficit per millimole per liter rise in lactate. These data show in L persistent alkalosis even after 9 wk at 5,260 m. In N, the data show 1) insignificant reduction in exercise capacity when breathing air at 5,260 m compared with breathing 55% O2; 2) very little ventilatory response to acute hypoxemia (judged by arterial pH and arterial PCO2 responses to hyperoxia); 3) during exercise, greater pulmonary diffusing capacity than in L, allowing maintenance of arterial PO2 despite lower ventilation; and 4) better buffering of lactic acid. These results support and extend similar observations concerning adaptation in lung function in these and other high-altitude native groups previously performed at much lower altitudes.
Wagner
Peter D
PD
Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA. pdwagner@ucsd.edu
Araoz
Mauricio
M
Boushel
Robert
R
Calbet
José A L
JA
Jessen
Birgitte
B
Rådegran
Göran
G
Spielvogel
Hilde
H
Søndegaard
Hans
H
Wagner
Harrieth
H
Saltin
Bengt
B
D000064:Acclimatization / Q000502:physiology*; D000136:Acid-Base Equilibrium / Q000502:physiology*; D000328:Adult; D000531:Altitude; D001838:Bolivia; D002245:Carbon Dioxide / Q000097:blood; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007773:Lactates / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology
D007773:Lactates; D002245:Carbon Dioxide