A 4-day-old infant, born at 27 weeks of gestational age, dev…

A 4-day-old infant, born at 27 weeks of gestational age, develops recurrent symptoms of RDS. The infant had been removed from mechanical ventilation and extubated at day 3 and was receiving NCPAP with an FIO2 of 0.4 when lung function acutely worsened. CXR shows a widespread, diffuse granular pattern, and analysis of arterial blood samples from the umbilical line demonstrates that oxygen saturation is refractory to increases in FIO2. The most likely cause for these recurrent symptoms of RDS is: