difference between radiation pneumonitis and COPD/emphysema?

Good Morning,
My father was diagnosed with Limited Stage SCLC. He has undergone 7 weeks of radiation concurrent with chemo and has been finished for 2 1/2 weeks.He wasn't diagnosed with COPD/emphysema until he was diagnosed w/ SCLC. He has been coughing terribly, says he feels he make pass out sometimes. Went to pulmonologist who wants to wait for CT scan results to see if he is cancer free before really agressively treating COPD, he is on Prednisone for 10 days, Combivet inhaler, DuoNeb for the nebulizer and Nasacort nose drops for an annoying "something feels like it is stuck in my throat". Radiation pneumonitis (sp) was never mentioned. What is done for it, and how is it detected? Can't walk very far without becoming very short of breath... Anyone else have similar problems?
Thank you for listening,
Annie