The situation last time was only a 2 hour flight so the trauma was more on me than it was for the dog I think. I'm sure it isn't a pleasant situation if your dog has a ton of freedom the way that mine does.
Service dogs can be seeing eye dogs, those dogs that can smell a seizure coming on or other disorders, and more recently they are comfort animals for people with PTSD or intense fear of flying but a lot of folks get their dog classified as this just so they can get the dog on the plane - I was contemplating this but thought it would be a disservice to those who genuinely have the problem.
There is a very small chance that the change in pressure can actually kill your dog but this is VERY small, even smaller than dying from Covid if you are under 20.