For how long can one use c-pap after surgery

Hi
A week ago my father had quadriple bypass heart surgery. Since then we could not see him because he is still in the care intensive room. The problem is that he can not easily breath without the c-pap (which is being used and removed several times since a week ago). It seems that his lungs are not properly responding. My question is: for how long the c-pap can be used and in the case of lung failure does it mean that no chance for my father to survive.
Thank you for explaning to me this situation.

[CCFCardio MD1]

During the post-operative period, patients are often very weak and need aggressive rehab to regain their strength.  There can be several causes that require a person to use CPAP, including complications of lung function following surgery (infection, lung collapse, fluid in the lungs, etc).  Lung failure in these cases are typically temporary and resolve with treatment of the underlying cause.  This process may take a while (days to weeks) during which time intermittent use of CPAP may be used.

[Nizo]

Thank you a lot for the answer. The CPAP is been used now for 17 days. Doctors said that they will apply the Tracheotomy (temporarily) if my father's respiratory function is not fully improved.
Thank you again