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ClinicalTrials.gov ID

NCT07263399

Lead Sponsor

Blekinge Institute of TechnologyOTHER

Overall Status

Not yet recruiting

Study Type

Interventional

Phase

Not Applicable

Enrollment

32Estimated

Last Update Posted

Dec 4, 2025Actual

Start Date

Jan 2026Estimated

Primary Completion Date

Dec 2029Estimated

Completion Date

Dec 2030Estimated

Official Title

Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity - A Randomized Controlled Cross-Over Trial

Brief Summary

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

• Oxygen Toxicity
• Oxidative Stress
• Hyperoxia
• Hyperbaric Oxygen
• Healthy Subjects (HS)
• Diving Medicine
• Hydrogen-oxygen Gas

• Inhaled Hydrogen-Enriched Oxygen Gas
• Inhaled Nitrogen-Enriched Oxygen Gas

Ages Eligible for Study

Adult (18-64)

Sexes Eligible for Study

All

Accepts Healthy Volunteers

Yes

Eligibility Criteria

Inclusion Criteria:

• Military divers actively serving, aged 20-64 years
• Meeting the Swedish Armed Forces physical standards for diving

Exclusion Criteria:

• Ongoing infection or illness that may impact pulmonary function
• Use of alcohol or smoking cigarettes within 48 hours
• Diving with any breathing gas within 48 hours
• Diving with oxygen-enriched gas (100% O₂) within 2 weeks
• Use of medications that could affect oxidative stress, lung function, or neurological status
• Medical history of serious diving-related injuries or long-term complications

Primary Purpose

Basic Science

Allocation

Randomized

Interventional Model

Crossover Assignment

Masking

Triple

Lead Sponsor

Blekinge Institute of TechnologyOTHER

Collaborators

Karolinska InstitutetOTHER

Göteborg UniversityOTHER

Lund UniversityOTHER

Swedish Armed Forces Diving and Naval Medicine CentreOTHER

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