Redistribution of cardiac output and oxygen delivery in the hypoxemic fetal lamb |
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Authors: | R E Sheldon L L Peeters M D Jones E L Makowski G Meschia |
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Affiliation: | 1. Division of Perinatal Medicine, Department of Physiology, University of Colorado Medical Center, Denver, Colorado, USA;2. Department of Pediatric, University of Colorado Medical Center, Denver, Colorado, USA;3. Department of Obstetrics-Gynecology, University of Colorado Medical Center, Denver, Colorado, USA |
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Abstract: | In hypoxia, fetal cardiac output and the product arterial O2 content x blood flow to the fetal heart and central nervous system (CNS) tend to remain constant. As a consequence the percentage of cardiac output directed to the heart and CNS increases hyperbolically in inverse relation to the oxygen content of the fetal ascending aorta, [O2]as. The fetal lamb maintains [O2]as approximately 0.45 mM (0.45 +/- 0.02 SEM) higher than the O2 content in the abdominal aorta, [O2]ab, over a wide range of oxygenation. When [O2]as decreases below the 2 mM level, the [O2]as--[O2]ab difference (delta O2) decreases also. A mathematical model of the fetal circulation shows that delta O2 is a function of the ratio oxygen consumption of fetal upper body/abdominal aorta blood flow (VU/FA). The behavior of delta O2 in hypoxia can be explained by assuming that the VU/FA ratio is maintained in moderate hypoxia and decreases in sever hypoxia. |
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Keywords: | Reprint requests: Dr. Giacomo Meschia Department of Physiology University of Colorado Medical Center Denver Colorado 80262 |
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