Why does the nurse give oxygen only as needed to an infant with a large ventricular septal defect?

1. 1Oxygen lowers pulmonary vascular resistance, which raises lung blood flow and congestion
2. 2Oxygen raises systemic vascular resistance and increases right-to-left shunting of blood
3. 3Oxygen causes the ductus arteriosus to reopen, which raises pressure in the right ventricle
4. 4Oxygen has no effect on defects that shunt blood from left to right, so it is wasted

Source: Nursing Health Promotion (Open RN, Chippewa Valley Technical College, 2025), Congenital Heart Defects: Nursing Interventions. Licensed under CC BY 4.0.