Husband is in the adv stage dementia.sometime he seems to forget or hold his breathe and then breathes faster and harder to catch up, sats 98%im scare

Apnea: Question arises here of some brainstem or even diffuse respiratory problem, and one might also consider sleep apnea, or even paroxysmal issues, such as seizure problems (9% of dementia pts). Might seek out answers with an eeg and perhaps an overnight sleep study) pulmonary function studies will not reveal these kinds of issues. A neurologist can help immensely.