My husband has end-stage emphysema and is on continuous (4L/m) home O2. He wants to know, why he has to urinate, or is practically incontinent of urine, when he desats, when he gets into the low 80's or high 70's he has to pee. Is it because it causes a bladder spasm or something? Does it take oxygen for his bladder to keep it's tone, so is it because his bladder doesn't have enough, that it relaxes, and that is when he urinates?