Role of hemoglobin P50 in 02 transport during normoxic and hypoxic exercise in the dog

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Bibliographic Details
Title translated into German:Die Rolle des Haemoglobins P50 beim Sauerstofftransport waehrend normoxischer und hypoxischer Belastungen beim Hund
Author:Schumacker, Paul T.; Suggett, Andrew J.; Wagner, Peter D.; West, John B.
Published in:Journal of applied physiology
Published:59 (1985), 3 , S. 749-757, Lit.
Format: Publications (Database SPOLIT)
Publication Type: Journal article
Media type: Print resource
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Identification number:PU198702027954


High hemoglobin affinity for 02 <low PO2 at 50 saturation of hemoglobin (P50)> could degrade exercise performance in normoxia by lowering mean tissue P02 but could enhance O2 transport in hypoxic exercise by increasing arterial 02 saturation. We measured 02 transport at rest and at graded levels of steady-state exercise in tracheostomized dogs with normal P50 (28.8 +/- 1.8 Torr) and again after P50 was lowered (19.5 +/- 0.7 Torr) by sodium cyanate infusions. Measurements were made during ventilation with room air (RA), 12 02 in N2, or 10 02 in N2. Cardiac output (QT) as a function of 02 consumption (V02) was not altered by low P50 at any inspired 02 fraction. With RA exercise, arterial content (CaO2) and O2 delivery (QT x CaO2) were unchanged at low P50, whereas mixed venous PO2 was reduced at each level of VO2. With exercise in hypoxia, CaO2 and 02 delivery were significantly improved at low P50. Mixed venous PO2 was lower than control during 12 02 but not different from control during 10 02 exercise at low P50. Despite a presumed decrease in tissue PO2 during RA and 12 O2 exercise, exercise performance and base excess decline were not significantly worse than control levels. We conclude that, in canine steady-state exercise, hemoglobin P50 is not an important determinant of tissue 02-extraction capacity during normoxia or moderate hypoxia. In extreme hypoxia, low P50 may help to maintain tissue PO2 by enhancing systemic 02 delivery at each level of QT. Verf.-Referat