Hypoxia and Inflammatory Bowel Disease

IBD

Bincy P. Abraham, MD, MS reviewing Vavricka SR, et al. Am J Gastroenterol 2025 Dec 16.

Environmental factors may contribute to worsening disease activity in inflammatory bowel disease (IBD). One such factor, hypoxia, may impact patients with ulcerative colitis (UC) or Crohn’s disease (CD), but few studies have examined this.

In this small, prospective, nonrandomized interventional study comparing 10 healthy controls with 11 patients with CD and 9 with UC, researchers simulated hypoxia by exposing patients to a hypobaric low-pressure chamber for 3 hours, mimicking an altitude of 4000 meters. After this intervention, the researchers assessed clinical, biomarker, endoscopic, and microbiome outcomes at days 1, 7, and 30 from baseline.

Key findings include:

Primary outcome: There was no significant overall increase in postintervention clinical or endoscopic activity in those with preexisting disease activity.
Clinical flares: After exposure, 33.3% of patients with UC experienced a flare compared with none of the patients with CD.
Biological activity: Fecal calprotectin-based activity levels increased significantly across all groups after intervention (26.7% vs 63.3%; P = .013). No significant changes were observed in C-reactive protein levels.
Microbiota changes:
- Controls experienced a reduction in beneficial Firmicutes phylum (Oscillospiraceae/Lachnospiraceae).
- Patients with UC had increased levels of Proteobacteria taxa (Caulobacteraceae, Haemophilus, Campylobacter).
- Patients with CD showed no major changes.
Oxygen saturation: During exposure, oxygen saturation dropped from 97.5% to 80.9% but returned to normal afterward.

Comment:

In this small study, short-term hypoxia did not broadly increase endoscopic clinical disease activity, but it did trigger UC flares and transient microbiota changes. The rise in fecal calprotectin indicates biological inflammation can occur with hypoxia, suggesting it may be a potential environmental trigger for UC activity, but not for CD. Given the study limitations, especially the small sample size and brief exposure duration, larger studies are necessary to confirm these findings. Nevertheless, patients with UC should be aware of the potential for hypoxia to trigger flares, especially those who travel frequently or hike in mountainous areas at high elevation.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Bincy P. Abraham, MD, MS

Bio and Disclosures

Citation(s):

Vavricka SR, Zeitz J, Madanchi M, et al. A prospective interventional study to evaluate the effect of hypoxia on healthy volunteers and patients with inflammatory bowel disease: the Altitude IBD Study. Am J Gastroenterol 2025 Dec 16. (Epub ahead of print) (https://doi.org/10.14309/ajg.0000000000003888)