Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity

Condition(s) studied

Investigational drug(s) / intervention(s)

Inhaled Hydrogen-Enriched Oxygen Gas: Participants will inhale a gas mixture consisting of 98-99% oxygen and 1-2% hydrogen via a breathing circuit during a single hyperbaric exposure. The exposure will be conducted at a partial pressure of 1.75 ATA for 240 minutes. The intervention aims to evaluate the protective effect of hydrogen gas against pulmonary oxygen toxicity.

Inhaled Nitrogen-Enriched Oxygen Gas: Participants will inhale a gas mixture consisting of 98-99% oxygen and 1-2% nitrogen via a breathing circuit during a single hyperbaric exposure. The exposure will be conducted at a partial pressure of 1.75 ATA for 240 minutes. The intervention aims to evaluate the protective effect of hydrogen gas against pulmonary oxygen toxicity.

Study 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

Eligibility

Primary outcome measure(s)

• Change in Vital Capacity (ΔVC) — Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
  Absolute change in vital capacity (VC), calculated as the difference in liters (L) between pre-exposure and post-exposure spirometry values, measured after each hyperbaric oxygen exposure session.

Trial sites (2)

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