Barium swallow

Has anyone had this done for their baby? We go in morning and was just wondering what to expect. Luckily I have to be there at 730 am since he has to go 6 hours without eating. I'm hoping he stays asleep when put him in carseat and on way since it's about an hour away. If not that will be a very long ride with a screaming hungry baby. I feel so bad when I have to make him go without eating for test. But I hope they figure out something because I'm tired of seeing him in pain and tired of him having to take medicine every 4 hours.and has been on medicine since 2 weeks old. I'm ready to get my baby well so I'll do whatever it takes, including driving 2-4 hours to see a specialist. Any advice and knowledge on this would be greatly appreciated!