Microgravity Simulated by the 6° Head-Down Tilt Bed Rest Test Increases Intestinal Motility but Fails to Induce Gastrointestinal Symptoms of Space Motion Sickness.

Abstract

BACKGROUND:

Space motion sickness (SMS) is the most relevant medical problem during the first days in microgravity. Studies addressing pathophysiology in space face severe technical challenges and microgravity is frequently simulated using the 6° head-down tilt bed rest test (HDT).

AIM:

We were aiming to test whether SMS could be simulated by HDT, identify related changes in gastrointestinal physiology and test for beneficial effects of exercise interventions.

METHODS:

HDT was performed in ten healthy individuals. Each individual was tested in three study campaigns varying by a 30-min daily exercise intervention of either standing, an upright exercise regimen, or no intervention. Gastrointestinal symptoms, stool characteristics, gastric emptying time, and small intestinal transit were assessed using standardized questionnaires, (13)C octanoate breath test, and H2 lactulose breath test, respectively, before and at day 2 and 5 of HDT.

RESULTS:

Individuals described no or minimal gastrointestinal symptoms during HDT. Gastric emptying remained unchanged relative to baseline data collection (BDC). At day 2 of HDT the H₂ peak of the lactulose test appeared earlier (mean ± standard error for BDC-1, HDT2, HDT5: 198 ± 7, 139 ± 18, 183 ± 10 min; p: 0.040), indicating accelerated small intestinal transit. Furthermore, during HDT, stool was softer and stool mass increased (BDC: 47 ± 6, HDT: 91 ± 12, recovery: 53 ± 8 g/day; p: 0.014), indicating accelerated colonic transit. Exercise interventions had no effect.

CONCLUSION:

HDT did not induce symptoms of SMS. During HDT, gastric emptying remained unchanged, but small and large intestinal transit was accelerated.

• Authors: Meher Prakash, Ron Fried, Oliver Götze, Francisca May, Petra Frings-Meuthen, Edwin Mulder, Judit Valentini, Mark Fox, Michael Fried, Werner Schwizer, Benjamin Misselwitz
• Journal: Digestive diseases and sciences (Dig Dis Sci) Vol. 60 Issue 10 Pg. 3053-61 (Oct 2015) ISSN: 1573-2568 [Electronic] United States
• PMID: 26055239 (Publication Type: Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)

Topics

• Adult
• Bed Rest
• Cross-Over Studies
• Female
• Gastric Emptying (physiology)
• Gastrointestinal Transit (physiology)
• Head-Down Tilt
• Healthy Volunteers
• Humans
• Male
• Middle Aged
• Posture
• Space Motion Sickness (physiopathology)
• Weightlessness Simulation (methods)
• Young Adult