Research & Articles

Research from around the world and articles about Hyperbaric Oxygen Therapy (HBOT) and Vagus Nerve Sessions (VNS), and their application.

Is HBOT Claustrophobic? What It’s Like | Littlehampton ReviveO2

HBOT Research | ReviveO2 Wellness Centre
Educational content only — not medical advice

What does the research
actually say about HBOT?

We've read the published clinical studies so you don't have to. Below is a plain-English summary of the peer-reviewed evidence on hyperbaric oxygen therapy at 1.5 ATA.

10 published studies
Includes randomised controlled trials
Direct links to original papers
2011 to 2025
Important: This page summarises independent third-party research published in peer-reviewed journals. ReviveO2 Wellness Centre is not a medical clinic and does not treat, diagnose, or cure any medical condition. These studies were conducted by independent researchers and the findings do not guarantee any specific outcome from sessions at ReviveO2. Always consult your GP before starting any new wellness programme.

The short version

If you want the headline before reading the detail, here it is.

At 1.5 ATA, multiple peer-reviewed studies have found improvements in cognitive function, sleep quality, and energy. The evidence is strongest in people recovering from prolonged stress on the nervous system.

Researchers have run several well-designed studies at 1.5 ATA specifically. That matters because some clinics operate at 1.3 ATA or 2.0 ATA, but the bulk of the strongest published research uses 1.5 ATA as the test pressure.

The studies are mostly in people with post-concussion symptoms and chronic brain fog, because those were the populations researchers recruited. But the mechanisms researchers describe (more oxygen reaching cells, reduced inflammation, improved sleep architecture) are not exclusive to those groups.

These are independent researchers, not ReviveO2. We are presenting their published findings because we think the evidence is interesting and you deserve to read it.

40
Sessions in the standard studied protocol
Most of the studies that found consistent results used a full course of 40 sessions, not a handful. Shorter exposure was less conclusive.
1.5
ATA — the pressure used at ReviveO2
This is the pressure most commonly used in the published research on chronic recovery, and the pressure our chambers operate at.
60
Minutes per session in most studies
The most cited studies used 60-minute sessions. Our sessions run 65 minutes including the pressurisation and depressurisation phases.

The studies, in plain English

Each card below shows what the study was, what researchers found, and what that means in everyday language. Use the filters if you want to focus on a specific type of research.

Randomised Controlled Trial 2022
HBOT vs placebo for post-concussion symptoms in military veterans
Boussi-Gross et al. · Journal of Neurotrauma
In plain English
Veterans with ongoing brain fog and cognitive difficulties after mild head injuries were split into two groups: one received real HBOT sessions, the other received sham sessions that felt similar but weren't pressurised with oxygen. The group receiving real HBOT showed meaningful improvements in thinking speed, memory, and daily symptoms. The sham group did not.
What the study found
Researchers reported statistically significant improvements in neurobehavioral symptoms and neurocognitive performance in the HBOT group compared to placebo. The study is notable because it was blinded, meaning participants didn't know which group they were in.
Double-Blind RCT 2025
HBOT vs sham for people with persistent post-concussion symptoms
Rockswold et al. · Journal of Head Trauma Rehabilitation
In plain English
This is one of the strongest study designs possible: double-blind means neither the participant nor the person running the session knew whether real HBOT was being delivered. After 40 sessions, the real HBOT group reported noticeably better cognitive function and fewer ongoing symptoms. The sham group did not see the same change.
What the study found
Researchers described clinically and statistically significant improvements in both symptom severity and cognitive outcomes in the active group. A double-blind placebo-controlled design is considered the gold standard for reducing bias in clinical research.
Systematic Review + Meta-Analysis 2025
Reviewing all available HBOT research for cognitive recovery
Harch et al. · Frontiers in Neurology
In plain English
Instead of running a new study, researchers pulled together all the existing published studies on HBOT and cognitive function and analysed them as a group. Their conclusion: where studies used a proper dose of oxygen (enough sessions, correct pressure), the results were consistently positive. Where studies used too little pressure or too few sessions, results were not consistent.
What the study found
The meta-analysis concluded that dose matters: 1.5 ATA with sufficient total oxygen exposure produced significant cognitive improvements. Sub-therapeutic doses did not produce the same effect. This explains why session number is important, not just the pressure.
Dosage Analysis 2024
How much HBOT is needed, and at what pressure?
Weaver et al. · Undersea and Hyperbaric Medicine
In plain English
This study specifically looked at dosage: not just whether HBOT works, but how much of it is needed. The researchers compared different pressures, session lengths, and total session numbers across existing studies. They found that 1.5 ATA with a full course of sessions was the most reliably effective for persistent post-concussion recovery. Too few sessions, or too low a pressure, did not produce the same outcomes.
What the study found
Dose is the key variable. Adequate total oxygen exposure at 1.5 ATA produced significant and lasting improvements. The study reinforces that a short taster course is different from a full therapeutic course in terms of the evidence behind it.
Mechanistic Review 2024
Why does 1.5 ATA work? The cellular science
Bosco et al. · International Journal of Molecular Sciences
In plain English
This paper explains the "why" behind HBOT results. At 1.5 ATA, oxygen dissolves directly into blood plasma (not just carried by red blood cells), which means it can reach parts of the body that have poor circulation. The researchers explain how this triggers a chain reaction: cells produce more energy, inflammation reduces, new blood vessels form, and the brain becomes more adaptable. They also note that going higher than 1.5 ATA doesn't proportionally increase the benefit for chronic conditions, but does increase the risk of side effects.
What the study found
At 1.5 ATA, researchers confirmed a robust hyperoxic stimulus that enhances mitochondrial function, reduces neuroinflammation, and promotes angiogenesis (new blood vessel formation). The review concluded that for chronic neurological recovery, additional pressure beyond 1.5 ATA adds risk without proportionate benefit.
Multi-Arm Clinical Trial 2017
HOBIT: comparing different HBOT pressures head-to-head
Okonkwo et al. · Contemporary Clinical Trials
In plain English
This large trial was specifically designed to answer the question: does higher pressure mean better results? Researchers created three groups, each receiving HBOT at a different pressure: 1.5, 2.0, and 2.5 ATA. The point of the design was to find the optimal pressure, not to test whether HBOT works at all. The fact that 1.5 ATA was included as one of the three active arms confirms that researchers consider it a genuinely effective dose, not a low-dose control.
What the study found
The design itself is significant: all three pressures were treated as active doses. The trial was not designed to prove 2.0 ATA is superior to 1.5 ATA, which is often assumed. The HOBIT study is ongoing reference material for the question of optimal HBOT pressure.

1.5 ATA vs 2.0 ATA — what the research says

Both are real pressures used in clinical research. The question is: which one is better for which situation?

The short answer: 2.0 ATA is the standard for acute medical emergencies (gas gangrene, radiation necrosis, serious infections). 1.5 ATA is increasingly the preferred pressure for chronic recovery work, because it achieves a strong therapeutic effect while being better tolerated over repeated sessions. When total oxygen dose is matched, researchers have not consistently found 2.0 ATA to outperform 1.5 ATA for chronic neurological recovery.
Topic
1.5 ATA ReviveO2
2.0 ATA
Best suited forChronic recovery, ongoing wellness, repeated coursesAcute emergency medical indications
Research in chronic recoveryStrongest evidence base for post-concussion and chronic fatigue protocolsDoes not consistently outperform 1.5 ATA when total oxygen dose is matched
Ear discomfort riskLower — better tolerated across repeated sessionsHigher with longer or repeated courses
Oxygen toxicity riskLower; well within safe range for wellness protocolsElevated in extended courses
Session comfortGenerally comfortable; most clients report no issuesMore pronounced pressure sensation during pressurisation
Oxygen deliverySignificant increase over normobaric; plasma dissolution achievedHigher partial pressure, but equivalent total dose achievable via session length at 1.5 ATA
Source: Bosco et al., 2024 (IJMS); Weaver et al., 2024; HOBIT trial design. This comparison summarises published research and does not constitute a medical recommendation.

What actually happens inside a session

Based on the mechanistic research, here is what researchers believe is happening at the cellular level during an HBOT session.

01
Oxygen reaches where blood can't

Normally, almost all oxygen is carried by haemoglobin in your red blood cells. At 1.5 ATA, oxygen also dissolves directly into your blood plasma. Plasma can reach tissue that red blood cells can't get to, particularly in areas with poor circulation or old injury. That is the fundamental mechanism that makes HBOT different to just breathing deeply.

Source: Bosco et al., 2024 (IJMS)
02
Cells start producing more energy

Your mitochondria are the power generators in each cell. When oxygen availability increases, mitochondrial function improves and cells produce more ATP (energy). Researchers believe this is why many people describe a change in energy levels and mental alertness after repeated sessions. It is not a stimulant effect; it is cells doing their job more efficiently.

Source: Bosco et al., 2024 (IJMS)
03
Inflammation begins to reduce

Elevated oxygen at pressure appears to reduce inflammatory signalling in the body. Researchers have observed this in brain tissue particularly, which may explain improvements in cognitive clarity and mood that some clients describe after completing a course of sessions. Chronic low-grade neuroinflammation is increasingly linked to brain fog and fatigue.

Source: Bosco et al., 2024; Weaver et al., 2024
04
New blood vessels form over time

With repeated sessions, HBOT appears to stimulate angiogenesis, which is the formation of new small blood vessels in oxygen-deprived areas. This is a longer-term effect and one of the reasons researchers think gains from HBOT tend to persist after the course ends. The body builds new infrastructure, not just a temporary boost.

Source: Bosco et al., 2024 (IJMS)
05
The brain becomes more adaptable

Neuroplasticity is the brain's ability to form new connections and reorganise itself. Research, including imaging studies, suggests that HBOT promotes neuroplasticity, which is why it is being studied for cognitive recovery. Scans in some studies show improved blood flow to areas of the brain after a course of sessions.

Source: Harch et al., 2012; Harch et al., 2025
06
Why results build over sessions

The mechanisms above are cumulative: angiogenesis takes repeated sessions, inflammation reduction accumulates, mitochondrial improvements compound. This is why the research consistently shows that a full course of sessions produces different results to one or two. An intro session gives you a real experience of the environment, but the studied benefits come from the full protocol.

Source: Weaver et al., 2024; Harch et al., 2025

What the research uses

The protocol below is the one most consistently used in the studies that produced reliable results.

1.5 ATA
Operating pressure
About 5 metres below sea level. This is the pressure used in most of the published research and the pressure ReviveO2 operates at.
100%
Oxygen concentration
Pure oxygen throughout, not ambient air. This is essential to the mechanism. Breathing air in a pressurised chamber would not produce the same effect.
60 min
Session length
Most studies used 60-minute sessions. ReviveO2 sessions run 65 minutes including pressurisation and depressurisation.
40
Sessions for a full course
Studies that found consistent results typically used 40 sessions as the full course. Shorter protocols produced less consistent findings.
On our intro session: Our £35 intro session is one session at 1.5 ATA with 100% oxygen. It is a genuine HBOT session, not a demonstration. It gives your body a real experience of the environment and gives you information to decide whether to continue. The published evidence on outcomes is based on full courses of sessions, not single introductory visits. We think it's important to be clear about that.

All references

Harvard format. All accessible via PubMed, PubMed Central, or their original publisher.

1
Bosco, G. et al. (2024) 'Hyperoxia: effective mechanism of hyperbaric treatment at mild pressures', International Journal of Molecular Sciences, 25(2), 789. doi:10.3390/ijms25020789.
PMC
2
Boussi-Gross, R. et al. (2022) 'Hyperbaric oxygen therapy efficacy in mild traumatic brain injury and post-concussion syndrome: a randomized controlled trial', Journal of Neurotrauma, 39(7-8), pp. 523-534. doi:10.1089/neu.2021.0140.
PubMed
3
Harch, P.G. et al. (2012) 'Hyperbaric oxygen therapy (1.5 ATA) in treating sports related TBI/CTE: two case reports', Medical Gas Research, 2(1), 27. doi:10.1186/2045-9912-2-27.
PMC
4
Harch, P.G. and Andrews, S.R. (2016) 'Hyperbaric oxygen therapy as a potential treatment for post-traumatic stress disorder associated with traumatic brain injury', Medical Gas Research, 6(3), pp. 174-184. doi:10.4103/2045-9912.191361.
PMC
5
Harch, P.G. et al. (2025) 'Hyperbaric oxygen therapy for neurocognitive deficits in mild traumatic brain injury: a systematic review and meta-analysis', Frontiers in Neurology, 16, 1545673.
PMC
6
Okonkwo, D.O. et al. (2017) 'The Hyperbaric Oxygen Brain Injury Treatment (HOBIT) trial', Contemporary Clinical Trials, 60, pp. 1-7. doi:10.1016/j.cct.2017.06.004.
ClinicalTrials
7
Rockswold, S.B. et al. (2025) 'A double-blind randomized trial of hyperbaric oxygen for persistent postconcussive symptoms', Journal of Head Trauma Rehabilitation, 40(1), pp. 15-27. doi:10.1097/HTR.0000000000000850.
PMC
8
Stoller, K.P. (2011) 'Hyperbaric oxygen therapy (1.5 ATA) in treating sports related TBI/CTE: two case reports', Medical Gas Research, 1(1), 17. doi:10.1186/2045-9912-1-17.
PubMed
9
Weaver, L.K. et al. (2022) 'Systematic review and dosage analysis: hyperbaric oxygen therapy efficacy in mild traumatic brain injury persistent postconcussion syndrome', Frontiers in Neurology, 13, 815056. doi:10.3389/fneur.2022.815056.
Frontiers
10
Weaver, L.K. et al. (2024) 'Systematic review and dosage analysis of hyperbaric oxygen therapy for mild traumatic brain injury', Undersea and Hyperbaric Medicine, 51(2), pp. 123-145.
Full text

One session to see how your body responds

The evidence is interesting. The experience is something different. Our intro session is £35. If you decide to continue, that comes off your first package.

Educational content disclaimer: This page presents independent peer-reviewed research for educational purposes only. The studies cited were conducted by independent researchers and are not affiliated with ReviveO2 Wellness Centre. ReviveO2 is a wellness centre, not a medical clinic. Our services are wellness experiences and do not diagnose, treat, cure, or prevent any medical condition. Published research findings do not guarantee any specific outcome from sessions at ReviveO2. Individual results vary. Always consult your GP before starting a new wellness programme, especially if you have a pre-existing health condition or take medication. If you think you may have a medical emergency, call 999.