title: Oxygen transport system before and after exposure to chronic hypoxia.
abstract: Maximal VO2 on the treadmill (VO2max) and on the bicycle ergometer (VO2peak), maximal cardiac output (Qmax), by a CO2 rebreathing method, maximal heart rate (HRmax), blood hemoglobin concentration (Hb), and hematocrit (Hct) were measured on six subjects before (B) and 3 weeks after (A) prolonged exposure to chronic hypoxia. It was observed that after high-altitude exposure VO2max, VO2peak, and Qmax were lower (P less than 005) than before [A: 4.13 +/- 0.67; 3.28 +/- 0.41 and 16.89 +/- 2.49 (l/min +/- SD); B: 4.39 +/- 0.39; 3.53 +/- 0.34 and 21.81 +/- 1.27, respectively], whereas Hb and Hct were larger (A: 162 +/- 8 g/l and 0.46 +/- 0.02; B: 142 +/- 7 and 0.41 +/- 0.02) and HRmax was unchanged (178 +/- 7 vs 175 +/- 9 bts/min). Thus, the calculated stroke volume of the heart and the Hb flow at VO2 peak were lower in A than in B (95 +/- 15 vs 124 +/- 7 ml and 2,723 +/- 307 vs 3,129 +/- 196 g/min) (P less than 0.05, respectively), whereas the arteriovenous O2 difference was greater in A than in B (195 +/- 16 vs 162 +/- 19 ml O2/l; P less than 0.05). At any given submaximal work load, VO2 and HR were the same in B and in A, whereas Q was lower in A by approximately 2-3 l/min. However, because of the increased Hb, leading to a higher arterial O2 content, at any work load the O2 flow remained unchanged.
authors.affiliation: Department of Physiology, University of Geneva Medical School, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Ferretti
authors.forename: U
authors.initials: U
authors.lastname: Boutellier
authors.forename: D R
authors.initials: DR
authors.lastname: Pendergast
authors.forename: C
authors.initials: C
authors.lastname: Moia
authors.forename: A E
authors.initials: AE
authors.lastname: Minetti
authors.forename: H
authors.initials: H
authors.lastname: Howald
authors.forename: P E
authors.initials: PE
authors.lastname: di Prampero
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D001835:Body Weight; D002302:Cardiac Output / Q000502:physiology*; D002908:Chronic Disease; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood / Q000502:physiology*; D010101:Oxygen Consumption; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D010100:Oxygen