Oral delivery of other PDE5 inhibitor tadalafil in a hypoxia-induced piglet model of neonatal PPHN decreased a pulmonary arterial pressure on average by 54%, increased a cardiac output by 88%, and increased a PaO2 as a result of reduction in the alveolar-arterial oxygen gradient expressing reduced lung shunt fraction [167]. This evidence concerns the gene PDE5A and persistent fetal circulation syndrome.