When a horse is getting ready to founder, they have alot of heat in their feet. Maybe that's when you should put them in the cold water. Perhaps when it's a full blown founder is when you use the nitro. I'm just guessing on all this, I need to look it up to be sure. If you can get a copy of Adam's Lameness In Horses by Ted Stashak, I highly recommend it. I got a vet dictionary when I bought it because it's really technical but it's the definitive book on horse lameness. I bought mine used from Amazon and saved a little money.
By the way, the nitro patch can only stay on for so many hours, I think it was 12 but I'm not sure. I know I accidently left George's on longer with no ill effects.
Yeah - without my vet telling me step by step what to do, I'd be at a loss. I think I'll read through my vet books on the subject so I know more too.