I've been noticing the past few days that every time my dad coughs loudly, it is because there is a problem - he is sitting/lying in the same position for too long, sweating from being covered too long with a blanket, and/or because he is sitting/lying in urine. He is not able to speak, so I think this is his way of communicating. As soon as I change him and have him sit or lie in a different position, he stops coughing.