My dear child your son has a condition called bronchopulmonary dysplasia following a severe attack of pneumonia ,that has caused one lobe of lung to be damaged .There are 3 parts in the lung ,the tubes called airways that allow air to pass through ,there are the air sacs or alveoli that exchange the oxygen and carbon dioxide and then the part of the lung inbetween .basically lining is destroyed and the elasticity is lost .This causes a lot of bbreathing problems -----and also he cannot exchange gases and his oxygen level will be low unless extra oxygen is given.These are the things one can help the repair process in the lung-----1.Give him very good nutrition ,high energy formulas will help and vitamin supplentation especially vitamin A .Ca,Phosdphorous and Vit D for integration of Chest wall bone cage. 2.Gentle chest physiotherapy 3.Protect from recurrent viral infections --good hand hygiene,avoid too many visitors ,do not take him to malls or crowded areas ,4.avoid smoking,pets ,perfumes,carpets near him.5.Medications like inhaled bronchodilators to keep airways open ,courses of corticosteroids 6.Protectors like monteleucast 7.regular vaccinations 8.There will be gradual recovery ,may take a year or more ----follow up with a pulmonologist is a must,who will rule out some inherited disorders like cystic fibrosis and also with general pediatrician .I am sure with regular dedicated care your son should improve.