Influence of body posture on intestinal transit of gas

Patients with irritable bowel syndrome and functional bloating frequently report that abdominal symptoms, such as bloating and distension that they attribute to intestinal gas, develop progressively during the day and tend to resolve with bed rest. ¹ However, the effect of body posture on intestinal gas transit and evacuation has not been investigated.

As gas within the abdominal cavity tends to float and rise to the top, theoretically caudal gas progression would be facilitated in the supine position. Hence we hypothesised that intestinal gas transit and evacuation are enhanced in the supine compared with the upright position. Using a new technique developed in our laboratory, ² we compared the effect of body posture, upright versus supine, on gas transit.

MATERIAL AND METHODS

Participants

Eight healthy individuals (three women and five men; age range 21-28 years) participated in the study after giving written informed consent. Subjects completed a pre-entry questionnaire to determine the absence of gastrointestinal symptoms, particularly symptoms of constipation, ¹ difficult gas evacuation, feeling of excessive abdominal gas, or excessive gas evacuation. The protocol for the study had been previously approved by the Institutional Review Board of the University Hospital Vall d'Hebron.

Gas transit test

Jejunal gas infusion

We used a polyvinyl tube assembly (4.1 mm OD) that incorporated a gas infusion channel (2.0 mm ID) with multiple side holes scattered over the distal 2 cm segment. Gas was continuously infused into the proximal jejunum at 12 ml/min, using a modified volumetric pump (Asid Bonz PP 50-300; Lubratronics, Unterschleissheim, Germany). We infused a gas mixture containing 88% nitrogen, 6.5% carbon dioxide, and 5.5% oxygen, bubbled into water for saturation, that mimicked the partial pressures of venous blood gases to minimise diffusion across the intestinal-blood barrier. ^{3, 4} A non-absorbable stable gaseous marker, 6 ml sulphurhexafluoride (SF₆ ), was added to the gas mixture infused during the first 10 minutes. ⁵

Rectal gas collection

To prevent potential effects of the anal sphincters on gas evacuation, gas was collected via an intrarectal catheter (Foley 20 F; Bard, Barcelona, Spain) with the balloon inflated with 5 ml of water. The rectal catheter was connected via a leak proof low resistance collection line to a barostat, ^{6, 7} and the volume of gas evacuated was continuously...