Hi thanks for asking question. If mild interstitial pneumonia is the cause it is treated with antibiotic. But here in your case it seems to be severe and inflammatory scarring might be occured. To reduce inflammation steroid can be taken like that of predniselone. If inflammation is still severe then immunosuppresive drug has the role like azathioprine used. We can t revert the scar and fibrosis that has already occured.But with use of these drug furhter damage can be delayed. Oxygen therapy needed as your case is worsening to maintain oxygen level. Today pulmonary rehabilitation programme also gaining popularity in which breathing technique,energy saving technique, exercise conditiomning , pshycological support etc.being teach. The final ultimate treatment is lung transplantation but it is costly. I hope my suggestion will help you.