Abstract
A decrease in oxygen affinity of hemoglobin could contribute to the adaptation to chronic hypoxemia in a right-to-left shunt. We studied P50, systemic oxygen delivery (SOD) and oxygen uptake (VO2) in the 6th week of life in 11 chronically hypoxemic and in 14 nonroxemic lambs. Hypoxemia had been experimentally induced in the 2nd week of life by means of an atrial septal defect and a pulmonary stenosis. Hypoxemic lambs had a decreased arterial oxygen saturation (66±7 vs 93±2 %, mean ± SD, p<0.001) and an increased hemoglobin concentration (145±14 vs 104±14 g.l−1,p<0.001). Heart rate was increased (171±28 vs 143±32 beats. min−1, p<0.05) but systemic blood flow (SBF) was not different Also SOD (23±10 vs 23±5 ml.min−1.kg−1) and the P50 were not different (5.03±0.43 vs 5.10±0.45 kPa). VO2 was maintained in hypoxemic lambs (9±3 vs 9±1 ml.min−1.kg−1) but mixed venous oxygen saturation (SmvO2) (41±9 vs 58±2 %, p<0.001) and oxygen tension (6.0±1.0 vs 7.2±0.5 kPa,p<0.001) were decreased. We conclude that P50 does not change in chronically hypoxemic lambs. These results suggest that the minimally attainable SmvO2 will be equal in hypoxemic and control lambs so the amount of oxygen that can be unloaded will be decreased in hypoxemia. We speculate that the ability to increase oxygen-extraction and SBF is limited in hypoxemia. This will impair the ability to meet increased demands for oxygen.
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Dalinghaus, M., Kuipers, J., Gratama, J. et al. 126: THE ROLE OF OXYGEN AFFINIY IN THE ADAPTATION TO CHRONIC HYPOXEMIA IN 5-WEEK-OLD LAMBS. Pediatr Res 24, 281 (1988). https://doi.org/10.1203/00006450-198808000-00151
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DOI: https://doi.org/10.1203/00006450-198808000-00151