Is there anything that helps clear the mucus/ropiness post treatment?

I'm hoping to find something to help with the mucus/ropiness that my husband has post tonsil cancer treatment (2009). It's getting worse every year. He is 78 and has a really good grasp on his food intake and diet etc., but he feels like his throat is closing and he just can't clear it and breathe easily. Has anyone found anything to help the mucus/ropiness in the throat?

Thank you!