Hello, My Husband Is Recovering From A CABG He Just

Hello, my husband is recovering from a CABG he just had done June 27 and he is now coughing so hard that he passes out. Sometimes phlegm comes out and it was grayish-beige and is now turning more green. He had a smoking history counting back 30+ years up until the night before the surgery and because of that he had to stay with the breathing tube an extra day to help keep in his oxygen. His oxygen intake now is satisfactory and the hospital discharged him but he is afraid of the passing out. Is there a problem or is it slightly common among smokers?