Successful transition at birth is dependent on establishment of lungs as the organ of gas exchange. Breathing at birth and an increase in alveolar oxygen tension (PAO2) leads to an 8-10 fold increase in pulmonary blood flow with a marked reduction in pulmonary vascular resistance (PVR). Failure to decrease PVR at birth results in hypoxemic respiratory failure (HRF) and persistent pulmonary hypertension of the newborn (PPHN). Hypoxemia exacerbates PPHN by increasing PVR. However, administration of excess oxygen in animal studies has been shown to increase free radical formation and reduce response to pulmonary vasodilators such as inhaled nitric oxide (iNO).
Thus, there is potential for benefit and also poor outcomes at both higher and lower oxygen saturations (SpO2), with the ideal range being unknown. The investigators will conduct a randomized unblinded, pilot trial to compare two ranges of target preductal SpO2 in late preterm and term infants with HRF or PPHN. During this trial the investigators will assess the reliability of a hypoxic respiratory failure/pulmonary hypertension (HRF/PH) score that could then be used in a larger clinical trial. The investigators will also assess trial feasibility and obtain preliminary estimates of outcomes. Our central hypothesis is that neonates with pulmonary hypertension (PH) and/or HRF, targeting preductal SpO2 of 95-99% (intervention) will result in lower PVR and lower need for non-oxygen based pulmonary vasodilators (iNO, milrinone and sildenafil) compared to a target of 91-95% (standard).
