Determinants of oxygen delivery and hemoglobin saturation during incremental exercise in horses

Clara K. Fenger, Kenneth H. McKeever, Kenneth W. Hinchcliff, Catherine W. Kohn

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Objective - To determine components of the increase in oxygen consumption (Vo2) and evaluate determinants of hemoglobin saturation (So2) during incremental treadmill exercise in unfit horses. Animals - 7 unfit adult mares. Procedures - Horses performed 1 preliminary exercise test (EXT) and 2 experimental EXT. Arterial and mixed venous blood samples and hemodynamic measurements were taken during the last 30 seconds of each step of the GXT to measure Po2, hemoglobin concentration ([Hb]), So2, and determinants of acid-base state (protein, electrolytes, and Pco2). Results - Increased Vo2 during exercise was facilitated by significant increases in cardiac output (CO), [Hb], and widening of the arteriovenous difference in O2. Arterial and venous pH, Pao2, and Pvo2 decreased during exercise. Arterial Pco2, bicarbonate ([HCO3-]a, and [HCO3]v decreased significantly, whereas Pvco2 and increased. Arterial and venous sodium concentration, potassium concentration, strong ion difference, and venous lactate concentration all increased significantly during exercise. Conclusions and Clinical Relevance - Increases in CO, [Hb], and O2 extraction contributed equally to increased Vo2 during exercise. Higher Pco2 did not provide an independent contribution to shift in the oxyhemoglobin dissociation curve (OCD) in venous blood. However, lower Paco2 shifted the curve leftward, facilitating O2 loading. The shift of ODC resulted in minimal effect on O2 extraction because of convergence of the ODC at lower values of Po2. Decreased pH appeared responsible for the rightward shift of the ODC, which may be necessary to allow maximal O2 extraction at high blood flows achieved during exercise.

Original languageEnglish (US)
Pages (from-to)1325-1332
Number of pages8
JournalAmerican journal of veterinary research
Volume61
Issue number10
DOIs
StatePublished - Oct 2000

All Science Journal Classification (ASJC) codes

  • veterinary(all)

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