Hi My Father Had A Stroke Last Month And Is

Hi my father had a stroke last month and is now in rehab. My father is now on the peg tube and so he's learning how to swallow again. The issue we're having is that he has too much mucus in his throat that does not seem to clear or go away. We often used the suction machine to help with expelling the mucus out but it seems to not go away. Can you please let us know what we could do to help get the mucus out of my father's throat?