An infant is born at 32 weeks gestation weighing 1.4 kg. He has difficulty in breathing immediately after bih and his condition worsens thereafter. After 5 hours of delivery, the child's respiratory rate is 60/min. On examination grunting, chest retraction and marked cyanosis is present and poor air movement in chest on auscultation. Which of the following is the most probable cause for respiratory distress of this neonate?

Based on prematurity and clinical picture provideda probable diagnosis is hyaline membrane disease (infant respiratory distress syndrome). HMD is caused by surfactant deficiency, and the incidence is increased with decreasing gestational age and bih weight. In this disease, lung compliance is reduced; lung volume is also reduced, and a significant right-to-left shunt of blood can occur. The combination of hypercapnia, hypoxia and acidosis produces pulmonary aery vasoconstriction, with increased right to left shunt through ductus aeriosus or foramen ovale, and within the lung itself.