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Latest revision as of 02:44, 25 September 2026
When does pulmonary vascular resistance (PVR) in an infant reach adult values?
A. 24 hours
B. 2 weeks
C. 2 months
D. 6 months
E. 2 years
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Answer
The answer is C. This is a tricky one. At delivery, there are mechanical and biochemical factors lead to the abrupt fall in PVR. The lungs expand which decrease the collapse of the intrapulmonary vessels. The rise in oxygen also causes release of potent vasodilators including nitric oxide and prostacyclin. This initial decrease is followed by remodeling that occurs over the next several months. The PVR has decreased to adult levels by 2 months of age and is at its nadir at 6 months of age.
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