A 2-year-old boy was brought to the emergency with the complaints of sudden onset of respiratory distress with irritability. On examination, the child is disoriented and he has both peripheral and central cyanosis. He has deep sighing respiration with SpO2 < 65% at room air. On oxygen therapy, his SpO2 is increased to 80%. He has no organomegaly or neurological deficit. Write the complete diagnosis of this boy?