Oxygen ToxicityNCT07263399
Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity
A study testing Inhaled Hydrogen-Enriched Oxygen Gas and Inhaled Nitrogen-Enriched Oxygen Gas in people with Oxygen Toxicity and Oxidative Stress, run by Blekinge Institute of Technology at 2 sites in Sweden.
Trial 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. Read more about this study
- Who is it for?
- Ages 20 to 64 yearsHealthy volunteers can take part
- Conditions the study is for
- Oxygen Toxicity, Oxidative Stress, Hyperoxia
- What is being tested?
- Inhaled Hydrogen-Enriched Oxygen Gas and Inhaled Nitrogen-Enriched Oxygen Gas
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 32 participants
- Where
- 2 sitesSweden
- Study dates
- Jan 2026to Dec 2030
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 20 to 64 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Military divers actively serving, aged 20-64 years
- Meeting the Swedish Armed Forces physical standards for diving
Who cannot join
- 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
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Sweden2 sites
Blekinge Institute of Technology
Karlskrona, Blekinge County, 37179
Swedish Armed Forces Diving and Naval Medicine Centre (DNC)
Karlskrona
Johan Douglas, MD, +46, johan.a.douglas@mil.se
Oscar Plogmark, MD, +46768899938, oscar.plogmark@mil.se
About this study
Official title: Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity - A Randomized Controlled Cross-Over Trial
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?
Read more
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
- Conditions
- Oxygen Toxicity, Oxidative Stress, Hyperoxia, Hyperbaric Oxygen, Healthy Subjects (HS), Diving Medicine
- Being tested
- Inhaled Hydrogen-Enriched Oxygen Gas, Inhaled Nitrogen-Enriched Oxygen Gas
- Keywords
- Pulmonary Oxygen Toxicity, Hydrogen Gas, Diving Physiology, Lung Function, Hyperbaric Oxygen, Human Study, Military Divers
- Medical subject headings
- Hyperoxia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Inhaled Hydrogen-Enriched Oxygen GasOther
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 GasOther
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 group | Role | What they receive |
|---|---|---|
| Hydrogen Gas Intervention | Experimental | In this arm, participants will undergo a single hyperbaric exposure breathing a gas mixture composed of 98-99% oxygen and 1-2% hydrogen (H₂) at a partial pressure of 1.75 ATA for 240 minutes. The intervention aims to evaluate whether hydrogen gas has protective effects against pulmonary oxygen toxicity. Pulmonary function tests and blood and urin sampling for oxidative stress biomarkers will be performed both before and after the exposure session. The order of intervention and control exposures is randomized and the study is conducted in a double-blind fashion.
A washout period of at least two weeks will follow before the control Receives: Other: Inhaled Hydrogen-Enriched Oxygen Gas; Other: Inhaled Nitrogen-Enriched Oxygen Gas |
| Nitrogen Gas Control | Active comparator | In this arm, participants will undergo a single hyperbaric exposure breathing a gas mixture composed of 98-99% oxygen and 1-2% nitrogen (N₂) at a partial pressure of 1.75 ATA for 240 minutes. This exposure serves as the control condition and represents the standard oxygen-enriched breathing gas currently in use. Pulmonary function tests and blood and urin sampling for oxidative stress biomarkers will be performed both before and after the exposure session. Participants will be randomized to the order of exposures, and both participants and investigators will be blinded to the gas composition. A washout period of at least two weeks will follow before the intervention. Receives: Other: Inhaled Hydrogen-Enriched Oxygen Gas; Other: Inhaled Nitrogen-Enriched Oxygen Gas |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in Vital Capacity (ΔVC)
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.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Secondary outcomes (15)
Forced Expiratory Volume in One Second (FEV₁)
As part of the spirometric and plethysmographic measurements, Forced Expiratory Volume in 1 second (FEV₁) will be analyzed. This represents the change (ΔFEV₁) in liters (L) between pre- and post-exposure spirometry, indicating expiratory flow capacity. Measurements follow ATS/ERS 2019 standards.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure
Change in FEV₁/FVC ratio
As part of the spirometric and plethysmographic measurements, the ratio between Forced Expiratory Volume in 1 second and Forced Vital Capacity (FEV₁/FVC) will be calculated. The change (ΔFEV₁/FVC) is expressed as a percentage (%) to assess airflow limitation or restriction following hyperbaric oxygen exposure.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure
Change in Forced Expiratory Flow 25-75% (FEF25-75%)
As part of the spirometric and plethysmographic measurements, the mid-expiratory flow (FEF25-75%) will be assessed. This parameter reflects the mean expiratory flow between 25% and 75% of FVC and serves as an indicator of small airway function. Values are expressed in liters per second (L/s).
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Peak Expiratory Flow (PEF)
As part of the spirometric and plethysmographic measurements, Peak Expiratory Flow (PEF) will be analyzed. The change (ΔPEF) represents the maximum flow achieved during forced exhalation, measured in liters per second (L/s). This outcome evaluates large airway performance.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Inspiratory Capacity (IC)
As part of the spirometric and plethysmographic measurements, Inspiratory Capacity (IC) will be determined. The change (ΔIC) in liters (L) reflects the maximal volume of air that can be inspired after a normal exhalation, providing insight into potential restrictive changes following exposure.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Total Lung Capacity (TLC)
As part of the spirometric and plethysmographic measurements, Total Lung Capacity (TLC) will be assessed. The change (Δ TLC) in liters (L) represents the total volume of air contained in the lungs after maximal inspiration, used to detect restrictive or hyperinflation patterns following hyperbaric oxygen exposure.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Residual Volume (Δ RV)
As part of the spirometric and plethysmographic measurements, Residual Volume (RV) will be assessed. The change (Δ RV) in liters (L) represents the volume of air remaining in the lungs after maximal exhalation, used to detect gas-trapping or hyperinflation patterns associated with pulmonary oxygen toxicity
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Functional Residual Capacity (Δ FRC)
As part of the spirometric and plethysmographic measurements, Functional Residual Capacity (FRC) will be assessed. The change (Δ FRC) in liters (L) represents the volume of air remaining in the lungs at the end of a normal tidal exhalation, used to detect early alterations in lung compliance or airway closure during hyperbaric oxygen exposure.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Diffusing Capacity for Carbon Monoxide (ΔDLCO)
Absolute change in lung diffusing capacity for carbon monoxide (DLCO) , measured (mmol/min/lkPa) with single-breath DLCO test before and after each exposure, to evaluate alveolar-capillary gas exchange efficiency. DLCO values are adjusted for hemoglobin levels to improve measurement accuracy.
Measured: Pre-exposure, 30-120 minutes post-exposure and 24-36 hours post-exposure.
Airway Resistance (Impulse Oscillometry, Tremoflo™)
Assessment of central and peripheral airway resistance (R5, R20, X5) using impulse oscillometry (Tremoflo™) before and after exposure. Evaluates small airway mechanics related to hyperbaric oxygen exposure with or without hydrogen supplementation. Unit of Measurement: cmH₂O·s/L
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Index of Oxygen Stress (ΔiOS)
Composite index derived from impulse oscillometry (Tremoflo™) representing the mean relative change from baseline in airway impedance parameters (R5, R20, X5). The Index of Oxygen Stress (iOS) quantifies oxidative stress-related changes in small airway mechanics following hyperbaric oxygen exposure with or without hydrogen supplementation.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Fractional Exhaled Nitric Oxide (ΔFeNO)
Measurement of airway inflammation and oxidative stress via fractional exhaled nitric oxide (FeNO) levels measured in parts per billion (ppb).
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Exhaled Breath Particle Analysis (ΔPExA)
Change in exhaled particle count and biochemical composition (lipids, proteins, coagulation factors) reflecting epithelial lining fluid alterations.
Measured: Pre-exposure and follow-up 24-36 hours post-exposure after each intervention.
Blood and Urinary Biomarkers of Oxidative Stress and Inflammation
Analysis of venous blood and urine samples for biomarkers of oxidative stress (e.g., 8-isoprostane, MDA, 8-OHdG) and inflammation (e.g., IL-6, TNF-α) to evaluate systemic effects of hyperbaric oxygen exposure with or without hydrogen supplementation. Concentrations will be quantified in standard laboratory units, for example ng/mL, pg/mL, or other equivalent measures.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Biomarkers of Neuronal Injury
Analysis of venous plasma samples for fluid biomarkers of neuronal injury (e.g., NfL, GFAP, Tau, UCH-L1) using NULISA™ or Simoa® HD-1 assay technologies, to evaluate central nervous system effects of hyperbaric oxygen exposure with or without hydrogen supplementation. Concentrations will be quantified in pg/mL.
Measured: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Dec 2025
- Study startJan 2026 (estimated)
- Primary completionDec 2029 (estimated)
- Study completionDec 2030 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for Oxygen ToxicityStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- This is a human randomized, double-blind, crossover trial in which each participant undergoes two separate hyperbaric oxygen exposures: one with hydrogen-enriched breathing gas (1-2% H₂) and one with nitrogen-enriched breathing gas (1-2% N₂) as control. Before and after each exposure session, participants complete standardized pulmonary function tests and provide blood and urin samples for analysis of oxidative stress biomarkers. A washout period of at least two weeks is maintained between sessions to minimize carryover effects.
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 32 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Blekinge Institute of Technology
- Sponsor type
- University, hospital or other
- Collaborators
- Karolinska Institutet, Göteborg University, Lund University, Swedish Armed Forces Diving and Naval Medicine Centre
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07263399
- Sponsor's protocol ID
- BTH-6.1.1-0165-2025
- Other IDs
- 5005113/22FMV2951
- Status last verified
- Dec 2025
- First submitted
- 29 Sep 2025
- Last updated
- 4 Dec 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Publications
de Jong FJM, Wingelaar TT, van Hulst RA. Pulmonary oxygen toxicity in occupational diving. Occup Med (Lond). 2023 Jun 26;73(5):231-232. doi: 10.1093/occmed/kqad043.
PubMed 37364027Kawamura T, Wakabayashi N, Shigemura N, Huang CS, Masutani K, Tanaka Y, Noda K, Peng X, Takahashi T, Billiar TR, Okumura M, Toyoda Y, Kensler TW, Nakao A. Hydrogen gas reduces hyperoxic lung injury via the Nrf2 pathway in vivo. Am J Physiol Lung Cell Mol Physiol. 2013 May 15;304(10):L646-56. doi: 10.1152/ajplung.00164.2012. Epub 2013 Mar 8.
PubMed 23475767Yildiz F, LeBaron TW, Alwazeer D. A comprehensive review of molecular hydrogen as a novel nutrition therapy in relieving oxidative stress and diseases: Mechanisms and perspectives. Biochem Biophys Rep. 2025 Jan 25;41:101933. doi: 10.1016/j.bbrep.2025.101933. eCollection 2025 Mar.
PubMed 39911528Ohsawa I, Ishikawa M, Takahashi K, Watanabe M, Nishimaki K, Yamagata K, Katsura K, Katayama Y, Asoh S, Ohta S. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med. 2007 Jun;13(6):688-94. doi: 10.1038/nm1577. Epub 2007 May 7.
PubMed 17486089
Study at a glance
From the registry record, last updated by the sponsor on 4 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of Hydrogen Gas on Hyperbaric Oxygen Toxicity - A Randomized Controlled Cross-Over Trial
- ClinicalTrials.gov ID
- NCT07263399
- Acronym / sponsor ID
- BTH-6.1.1-0165-2025
- Conditions
- Oxygen Toxicity, Oxidative Stress, Hyperoxia, Hyperbaric Oxygen, Healthy Subjects (HS), Diving Medicine
- Keywords
- Pulmonary Oxygen Toxicity, Hydrogen Gas, Diving Physiology, Lung Function, Hyperbaric Oxygen, Human Study, Military Divers
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 32 participants (estimated)
- Lead sponsor
- Blekinge Institute of TechnologyUniversity, hospital or other
- Collaborators
- Karolinska Institutet, Göteborg University, Lund University, Swedish Armed Forces Diving and Naval Medicine Centre
- Study start
- Jan 2026 (estimated)
- Primary completion
- Dec 2029 (estimated)
- Study completion
- Dec 2030 (estimated)
- First posted
- 4 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- This is a human randomized, double-blind, crossover trial in which each participant undergoes two separate hyperbaric oxygen exposures: one with hydrogen-enriched breathing gas (1-2% H₂) and one with nitrogen-enriched breathing gas (1-2% N₂) as control. Before and after each exposure session, participants complete standardized pulmonary function tests and provide blood and urin samples for analysis of oxidative stress biomarkers. A washout period of at least two weeks is maintained between sessions to minimize carryover effects.
| Arm | Type | Receives |
|---|---|---|
| Hydrogen Gas Intervention | Experimental | Other: Inhaled Hydrogen-Enriched Oxygen Gas, Other: Inhaled Nitrogen-Enriched Oxygen GasIn this arm, participants will undergo a single hyperbaric exposure breathing a gas mixture composed of 98-99% oxygen and 1-2% hydrogen (H₂) at a partial pressure of 1.75 ATA for 240 minutes. The intervention aims to evaluate whether hydrogen gas has protective effects against pulmonary oxygen toxicity. Pulmonary function tests and blood and urin sampling for oxidative stress biomarkers will be performed both before and after the exposure session. The order of intervention and control exposures is randomized and the study is conducted in a double-blind fashion. A washout period of at least two weeks will follow before the control |
| Nitrogen Gas Control | Active comparator | Other: Inhaled Hydrogen-Enriched Oxygen Gas, Other: Inhaled Nitrogen-Enriched Oxygen GasIn this arm, participants will undergo a single hyperbaric exposure breathing a gas mixture composed of 98-99% oxygen and 1-2% nitrogen (N₂) at a partial pressure of 1.75 ATA for 240 minutes. This exposure serves as the control condition and represents the standard oxygen-enriched breathing gas currently in use. Pulmonary function tests and blood and urin sampling for oxidative stress biomarkers will be performed both before and after the exposure session. Participants will be randomized to the order of exposures, and both participants and investigators will be blinded to the gas composition. A washout period of at least two weeks will follow before the intervention. |
Who may qualify
- Ages
- 20 to 64 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (2 listed)
- Military divers actively serving, aged 20-64 years
- Meeting the Swedish Armed Forces physical standards for diving
Key exclusion criteria (6 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Inhaled Hydrogen-Enriched Oxygen GasParticipants 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. | Other | Hydrogen Gas Intervention, Nitrogen Gas Control |
| Inhaled Nitrogen-Enriched Oxygen GasParticipants 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. | Other | Hydrogen Gas Intervention, Nitrogen Gas Control |
Primary outcome
Change in Vital Capacity (ΔVC)
Time frame: 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.
15 secondary outcomes
Forced Expiratory Volume in One Second (FEV₁)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure
Change in FEV₁/FVC ratio
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure
Change in Forced Expiratory Flow 25-75% (FEF25-75%)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Peak Expiratory Flow (PEF)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Inspiratory Capacity (IC)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Total Lung Capacity (TLC)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Residual Volume (Δ RV)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Functional Residual Capacity (Δ FRC)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Diffusing Capacity for Carbon Monoxide (ΔDLCO)
Time frame: Pre-exposure, 30-120 minutes post-exposure and 24-36 hours post-exposure.
Airway Resistance (Impulse Oscillometry, Tremoflo™)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Index of Oxygen Stress (ΔiOS)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Fractional Exhaled Nitric Oxide (ΔFeNO)
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Change in Exhaled Breath Particle Analysis (ΔPExA)
Time frame: Pre-exposure and follow-up 24-36 hours post-exposure after each intervention.
Blood and Urinary Biomarkers of Oxidative Stress and Inflammation
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Biomarkers of Neuronal Injury
Time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 4 Dec 2025.
- Results publication: PubMed 37364027de Jong FJM, Wingelaar TT, van Hulst RA. Pulmonary oxygen toxicity in occupational diving. Occup Med (Lond). 2023 Jun 26;73(5):231-232. doi: 10.1093/occmed/kqad043.
- Results publication: PubMed 23475767Kawamura T, Wakabayashi N, Shigemura N, Huang CS, Masutani K, Tanaka Y, Noda K, Peng X, Takahashi T, Billiar TR, Okumura M, Toyoda Y, Kensler TW, Nakao A. Hydrogen gas reduces hyperoxic lung injury via the Nrf2 pathway in vivo. Am J Physiol Lung Cell Mol Physiol. 2013 May 15;304(10):L646-56. doi: 10.1152/ajplung.00164.2012. Epub 2013 Mar 8.
- Results publication: PubMed 39911528Yildiz F, LeBaron TW, Alwazeer D. A comprehensive review of molecular hydrogen as a novel nutrition therapy in relieving oxidative stress and diseases: Mechanisms and perspectives. Biochem Biophys Rep. 2025 Jan 25;41:101933. doi: 10.1016/j.bbrep.2025.101933. eCollection 2025 Mar.
- Results publication: PubMed 17486089Ohsawa I, Ishikawa M, Takahashi K, Watanabe M, Nishimaki K, Yamagata K, Katsura K, Katayama Y, Asoh S, Ohta S. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med. 2007 Jun;13(6):688-94. doi: 10.1038/nm1577. Epub 2007 May 7.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Swedish Armed Forces Diving and Naval Medicine Centre (DNC)
Karlskrona, Sweden
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Inhaled Hydrogen-Enriched Oxygen Gas and Inhaled Nitrogen-Enriched Oxygen Gas in people with Oxygen Toxicity and Oxidative Stress, run by Blekinge Institute of Technology at 2 sites in Sweden.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 4 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in Sweden. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Each site lists its own contact: choose the nearest one under Trial locations. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in Vital Capacity (ΔVC) (time frame: Pre-exposure, 30-120 minutes post-exposure, and 24-36 hours post-exposure.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07263399, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 4 Dec 2025.