Oxygen is a pulmonary vasodilator and plays an important role in mediating circulatory transition from fetal and postnatal period. Alveolar oxygen tension (PAO2) and pulmonary arterial PO2 are the main factors that influence hypoxic pulmonary vasoconstriction (HPV). Inability to achieve adequate pulmonary vasodilation at birth leads to persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen is the mainstay of PPHN management. However, optimal monitoring of oxygenation to achieve low pulmonary vascular resistance (PVR) and optimize oxygen delivery to vital organs is not known. Noninvasive pulse oximetry measures peripheral saturations (SpO2) and ranges 91-95% are recommended during acute PPHN management. However, for a given SpO2, there is wide variability in arterial oxygen tension, especially with variations in hemoglobin type (transfusions), pH and body temperature. This review evaluates the role of alveolar, preductal, postductal, and mixed venous oxygen tension and SpO2 in the management of PPHN. Translation and clinical studies suggest maintaining an arterial oxygen tension of 50-80 mmHg to help decrease PVR and optimize pulmonary vasodilator management. Nevertheless, there are no randomized clinical trials evaluating outcomes in PPHN based on targeting SpO2 or PO2. However, most critically ill patients have umbilical arterial catheters and postductal arterial oxygenation may not be an accurate assessment of oxygen delivery to vital organs or factors influencing HPV. The mixed venous oxygen tension from umbilical venous catheter blood gas may assess pulmonary arterial PO2 and potentially predict HPV. It is crucial to conduct randomized controlled studies with different PO2/SpO2 ranges and compare outcomes in PPHN.