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
Military divers actively serving, aged 20-64 years
Meeting the Swedish Armed Forces physical standards for diving
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
Blekinge Institute of Technology
Lead sponsor
Karolinska Institutet
Collaborator
Göteborg University
Collaborator
Lund University
Collaborator
Swedish Armed Forces Diving and Naval Medicine Centre
Collaborator