A premature baby born at 34 weeks of gestation presents with the following at 4 hours after birth: tachypnea, respiration with a seesaw motion, sternum depression, expiratory murmurs. Respiratory rate - 80/min. Auscultation detects weakened breathing with non-constant heterogeneous crackles over the lungs. X-ray of the lungs shows air bronchogram and a nodose-reticular lung pattern. What is the most likely diagnosis in this case?