I think its difficult to train a service dog for POTS, which make them a much more expensive service animal to own. However I think they are great to offer stability and emotional support. You can teach Peggy to get help, if you feel faint or if you do faint. I've read they can be taught to even recognize symptoms before they occur. I have no idea how you would train. You can probably reach out to usserviceanimals.org to get some details.