A single-center, prospective observational cohort study evaluating potential biochemical, clinical, and/or genetic biomarkers in neonates admitted with a diagnosis of PPHN that may predict iNO response. Thus, it is important to collect data prior to the initiation of iNO to be able to identify biomarkers that can predict response. For patients who meet the screening criteria and when consent is not attainable prior to initiation of the potential life-saving iNO therapy, then samples will be obtained with deferred written informed parental consent obtained within the first 4 hours after enrollment. These patients will have one sample of blood, urine, and tracheal aspirate (if available) collected. If the patient meets the inclusion and exclusion criteria, the patient will be recruited for study participation. To ensure no delay in care or in the initiation of the only FDA-approved vasodilator for this population, iNO, a deferred written informed parental consent is requested to allow for the collection of blood, urine, tracheal aspirate specimens (if available) prior to the initiation of iNO. Only one sample of blood and tracheal aspirate specimens will be collected prior to the deferred consent. Samples are often collected during the routine collections that are obtain from patients who are critically ill such as in our study participants, therefore, no additional discomfort will be expected from this study. Urine collection will be from cotton ball collection that would normally be discarded and is noninvasive. All data and biospecimens obtained from eligible infants whose parent(s) decline consent or do not qualify for the study will be discarded.
