Pediatrics C.V.S. 99fde1c6 Ductus arteriosus closes in response to: A Decrease in peripheral oxygen saturation B Indomethacin therapy C Prostaglandin E1 D Increase in pulmonary vascular resistance High-Yield Explanation b. Indomethacin therapy(Ref: Nelson's 20/e p 2197, Ghai 8/e p 417)Indomethacin, a Prostaglandin inhibitor is used in medical closure of Ductus arteriosus.