Suggest Treatment For Excessive Belching

My 77 yr old mother has been to 2 or 3 local gastrologist that told her she was swallowing air. They prescribed previcid or nexium and there was no improvement. She belches from the time she gets up until she goes to sleep regardless of what she eats, when she eats, or IF she eats. Is there any help for her? She even belches water.