Excessive swallowing of environmental air is called aerophagia, and has been shown in a few case reports to be responsible for increased flatus volume.
Another tube releases the air which builds up in her stomach as a result of aerophagia, which causes her to continually gulp air, resulting in a bloated, distended stomach.
The word "bloat" is often used as a general term to cover gas distension without twisting and is often a normal change after eating or with aerophagia.