A boy was born at 32 weeks gestation. 2 hours after birth he developed respiratory distress. The RD severity assessed by Silverman score was 5. The respiratory disorders progressed, respiratory failure couldn't be eliminated by Martin-Bouyer CPAP (continuous posi- tive airway pressure). Ro-gram of lungs shows reticular and nodular pattern, air bronhogram. What is the most likely cause of respiratory distress syndrome?