I would talk to your doctor. This behavior may cause choking.

My father is 80 and was diagnosed with Parkinson's maybe 6 years ago. His mouth often hangs open with his tongue lolling out unless he is trying to concentrate on something. When he is trying to focus his tongue darts all over the place and he gets extremely tongue-tied when trying to speak while upset. I guess this is from the excessive tongue-wag. His voice is often so weak he can't force words out. He has stated that his tongue shakes just like his left arm so I know this is all related to the disease. He is on carpidopa levidopa and requip. I've noticed that he struggles more now than he did a year ago. Water chokes him so he only drinks soda, lemonade or Gatorade. When he manages to fall asleep his mouth gapes wide with his tongue hanging out. He does not shake while sleeping but he does have terrible, violent nightmares. He is able to move while dreaming and has managed to punch me or grab me when I've come too close trying to check on him. Please, please keep an eye on your husband if he is having similar struggles. I know my father has said that he feels like he is choking and sometimes begins to cough in his sleep after breathing in excessive drool from his tongue issues.

@ Ruth - at least he sleeps!