Bit confused, CLKD. Reminders for what? As far as I can tell from talking to him, he did everything he could. I doubt I could have done better, though I would have probably smelt the contents of the commode!

What he does need is nursing help with Mum and a means of lifting her, when she has an attack, but she doesn't need or want care the rest of the time. I shall do some ringing around on Monday, but suspect it will be difficult to arrange help just here and there when she gets an attack. At least they could afford private help if available.
He was up several times in the night, assisting her in and out of bed to use the commode. She is now able to call him. Earlier, she was screaming and calling out incoherently. He says it was frightening. In the past, she has been admitted to hospital, but they don't or can't do anything medically for her and discharge her as soon as possible. Hospital stays are traumatic for both of them.
I did Google the effects of sudden low blood pressure. Other than collapsing as she does, she is in danger of having a stroke. She had one years ago and takes appropriate medication, which is left off during an attack. She is 88 and I agree with Dad she is better at home if possible. I think they would rather be at home if she died. They've lived there since 1958.
Dad has a chronic back problem and hurt it trying to lift her. I can talk to him about leaving her on the floor, just making sure she is breathing and warm, until she can help him move her. She becomes incontinent during these attacks. Dad wondered where all of it comes from when she's not eating! He has been able to give her rehydrating drinks at least.
It's so distressing when this happens. It helps to think more clearly when you write it down. Thanks for your support.