It seems very difficult differential diagnosis of premature baby's clinical status.I think it will be done right first ECHO. We also think that the baby is low ventilator settings.if you are using drug I suggest you use paracetamol rather than ibuprofen for the clinical situation is not good.
http://www.clinicaltrials.gov/ct2/show/NCT01291654
http://summaries.cochrane.org/CD010061/paracetamol-acetaminophen-for-patent-ductus-arteriosus-in-preterm-andor-low-birth-weight-infants