Preductal Oxygen Saturation Target in Term and Late Preterm Neonates With Hypoxemic Respiratory Failure or Pulmonary Hypertension

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).

Inclusion criteria

• Corrected gestational age (postmenstrual age) > 34 6/7 weeks
• postnatal age ≤ 28 d
• on respiratory support with invasive mechanical ventilation, non-invasive ventilation, CPAP or high flow nasal cannula (defined as flow rates ≥ 2 LPM with a humidifier), inspired oxygen concentration, FiO2 ≥ 0.3
• and echocardiography shows any finding suggestive of PH (or score > 0 for PH in table 2).
• Infants with congenital diaphragmatic hernia (CDH), Down syndrome, hypoxic ischemic encephalopathy (HIE) on therapeutic hypothermia and patent ductus arteriosus (PDA), patent foramen ovale/atrial septal defect (PFO/ASD) and ventricular septal defect (VSD) (single or multiple) < 2 mm can be included in the study.

Exclusion criteria

• < 32 weeks gestation at birth (31 6/7 or lower)
• Weight < 2000 g at the time of enrollment
• Severe HRF with OI > 35 or SpO2 < 75% on FiO2 = 1.0 on mechanical ventilation for > 60 minutes in spite of correction of reversible factors such as pneumothorax
• A condition or congenital anomaly known to be lethal (high likelihood of death during infancy) - e.g., trisomy 18 or trisomy 13
• Congenital heart disease other than ASD/PFO, PDA or VSD (single or multiple defects) < 2 mm.