Hi @jmill, I would like to add my welcome to Connect along with @jeff79922 and others. I would also like to say congratulations on your father's successful bypass. Here's some information I found on the his symptoms after bypass surgery and some possible helpful breathing and coughing exercises. @danab may be able to offer some suggestions.

"Is it normal to have shortness of breath after bypass surgery?
Postoperative dyspnea is common after cardiac surgery, even in low-risk patients."
-- Causes of Dyspnea after Cardiac Surgery: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6196911/

Deep Breathing and Coughing Exercises: https://share.upmc.com/2015/04/breathing-and-coughing-exercises-after-heart-surgery/

Have you had a chance to discuss the shortness of breath and coughing with your father's surgeon or care team?