1. Development of pulmonary vascular response to oxygen
- Author
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F. C. Morin rd, Edmund A. Egan, C. E. Lundgren, and William H. Ferguson
- Subjects
Pulmonary Circulation ,medicine.medical_specialty ,Physiology ,Partial Pressure ,chemistry.chemical_element ,Oxygen ,Fetus ,Pregnancy ,Physiology (medical) ,Internal medicine ,medicine ,Animals ,Respiratory system ,Lung ,Hyperbaric Oxygenation ,Sheep ,Chemistry ,business.industry ,Oxygen tension ,Blood pressure ,medicine.anatomical_structure ,Blood Circulation ,Circulatory system ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,Nuclear medicine ,business ,Blood vessel - Abstract
The ability of the pulmonary circulation of the fetal lamb to respond to a rise in oxygen tension was studied from 94 to 146 days of gestation. The unanesthetized ewe breathed room air at normal atmospheric pressure, followed by 100% oxygen at three atmospheres absolute pressure in a hyperbaric chamber. In eleven near-term lambs (132 to 146 days of gestation), fetal arterial oxygen tension (PaO2) increased from 25 +/- 1 to 55 +/- 6 Torr (mean +/- SE), which increased the proportion of right ventricular output distributed to the fetal lungs from 8 +/- 1 to 59 +/- 5%. In five very immature lambs (94 to 101 days of gestation), fetal PaO2 increased from 27 +/- 1 to 174 +/- 70 Torr, but the proportion of right ventricular output distributed to the lung did not change, 8 +/- 1 to 9 +/- 1%. In five of the near-term lambs, pulmonary blood flow was measured. It increased from 34 +/- 3 to 298 +/- 35 ml.kg fetal wt-1.min-1, an 8.8-fold increase. We conclude that the pulmonary circulation of the fetal lamb does not respond to an increase in oxygen tension before 101 days of gestation; however, near term an increase in oxygen tension alone can induce the entire increase in pulmonary blood flow that normally occurs after the onset of breathing at birth.
- Published
- 1988