What Causes Clubbing Of Fingers After An Open Heart Surgery?

in Nov.12 2014 I had open heart surgery, then while in hospital my oxygen dropped, I came out of the hosp. on 4 l. oxygen 24-7 I saw my lung doc,the other day after he had a high contras. CT on me. he said it shows Rips & tears scaring. then looked @ my fingers & said they are clubbing a lots & we will have to deal with it soon, But did not say what that means or how we r going to take care of it or if I will ever get off the oxygen. Can u tell me what all that means ?Thank s