Gastric gas dynamics in healthy humans.

Abstract

To cope with the daily increments of gastric gas, the stomach can propel gas to the small bowel or trigger the belching reflex. Our aim was to evaluate transit of free gastric gas in healthy humans, and its relationship with abdominal symptoms. In 24 healthy volunteers a gas mixture was infused into the stomach at 0mL/min (sham infusion), 25mL/min, 50mL/min, and 100mL/min (n=6 each) up to 1500mL. Belching, rectal gas evacuation, and abdominal perception were continuously recorded for 90min. Sham infusion was associated to low rectal gas evacuation (187±94mL after 90min), and belching (0±0). In contrast, gastric gas infusion increased rectal gas evacuation (1198±176mL; P=.025) and belching (4±1 belches; P=.0520) without differences between the infusion rates tested. Overall, there was a negative correlation between rectal gas evacuation and belching (r=-.72; P<.0001): 6 subjects had frequent belching (14±2 belches) and minor rectal gas evacuation (330±112mL), whereas 12 subjects had virtually no belches (1±1 belches) and greater rectal gas evacuation (1630±147mL; P<.001 vs belchers for both). Gas infusion induced lower abdominal symptoms in belchers (score increment 0.7±0.3) than in rectal gas evacuators (score increment 1.7±0.5; P=.033). An excellent balance between belching and distal gastric empting allows the stomach to adapt to great variations in gas intake. In general, most gastric gas is emptied to distal intestinal segments, but in some circumstances gastric gas induces belching, a mechanism that may improve gas tolerance.