Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity

The goal of this trial is to investigate whether adding a small fraction of hydrogen gas to an oxygen-enriched breathing mixture can reduce pulmonary oxygen toxicity (POT) in healthy and active divers from the Swedish Armed Forces. The main questions it aims to answer are: * Does hydrogen gas reduce oxidative stress and changes in pulmonary function associated with prolonged hyperbaric oxygen exposure? * What are the underlying pathophysiological mechanisms of pulmonary oxygen toxicity? Researchers will compare oxygen-enriched breathing gas with 1-2% hydrogen to oxygen-enriched gas with 1-2% nitrogen (control) to see if hydrogen provides protective effects against POT during hyperbaric exposure. Participants will: * Complete two hyperbaric exposure sessions (hydrogen vs. nitrogen), each lasting 240 minutes at 1.75 ATA * Undergo pulmonary function tests and sampling of blod and urin before and after each session * Serve as their own controls in a double-blind, randomized, crossover study design

NCT Number	NCT07263399
Lead Sponsor	Blekinge Institute of Technology Collaborators: Karolinska Institutet, Göteborg University, Lund University, Swedish Armed Forces Diving and Naval Medicine Centre
Conditions	Oxygen Toxicity, Oxidative Stress, Hyperoxia, Hyperbaric Oxygen, Healthy Subjects (HS), Diving Medicine, Hydrogen-oxygen Gas
Enrollment	32 participants
Start Date	2026-01
Primary Completion	2029-12 (estimated)
Study Completion	2030-12 (estimated)
Updated on ClinicalTrials.gov	2025-12-04