This article is part of the HBOT Radar series, where we summarize the latest published hyperbaric oxygen therapy research.
Disclaimer: This article is intended for educational and informational purposes only. It summarizes published medical research conducted in clinical settings and does not evaluate Brain Spa Hyperbaric products. The hyperbaric chambers offered on this website are non-medical wellness devices and are not intended to diagnose, treat, cure, or prevent any disease. Do not make medical decisions based on this article — consult a qualified healthcare professional.
Title:
Prospective registry finds 56–63% of long COVID patients show meaningful improvement 3 months after HBOT, especially in cognition
What this study examined
Long COVID has created a huge unmet need for treatments that improve:
- chronic fatigue
- brain fog
- cognitive dysfunction
- reduced physical capacity
- reduced quality of life
Clinical demand for HBOT has grown quickly, but formal guidelines are still lacking.
To better understand real-world outcomes, researchers established a prospective registry tracking long COVID patients undergoing HBOT.
This publication reports the 3-month results.
HBOT treatment details
The protocol was 40 daily sessions at 2.4–2.5 ATA, 90 to 110 minutes each with five-minute air breaks every 20 minutes, five days a week for eight weeks, in multiplace chambers with 100% oxygen by mask or hood. Patients paid for this themselves — hyperbaric oxygen for long COVID is off-label in the Netherlands.
These patients were treated in hospital hyperbaric units under medical supervision. Results from clinical research cannot be directly applied to other settings or devices — always consult a healthcare professional.
Who was included?
Patients with long-term symptoms after COVID infection.
Patient-reported outcomes were collected:
- at baseline
- after HBOT
- at 3 months (this publication)
- with 1-year data coming later
Key findings at 3 months
1. 56–63% of patients had clinically meaningful improvement
A ≥10-point increase in physical or mental health scores on the SF-36 questionnaire was considered meaningful.
2. Cognitive symptoms improved the most
Patients commonly reported:
- clearer thinking
- reduced brain fog
- improved memory
- better concentration
3. 13–19% of patients worsened
A minority experienced clinically meaningful deterioration in their SF-36 scores.
This highlights the need for careful pacing and individualized protocols.
4. Secondary outcomes improved for many patients
Including:
- overall quality of life
- symptom burden
- ability to work
Why this matters
This is one of the largest real-world datasets for long COVID HBOT so far.
It shows a strong trend toward improvement — especially cognitively — but also makes it clear that not everyone tolerates standard protocols well.
The 13–19% who got worse is the most important number in this study
Most reporting on hyperbaric oxygen skips the people who deteriorate. This registry did not, and that is what makes it worth reading. Of 137 patients analysed at three months, 76 improved meaningfully, 43 stayed roughly where they were, and 18 got meaningfully worse.
Buried in the discussion is a finding that deserves more attention than it has had. Some patients had their treatment extended to 50 or 60 sessions. In that group, 63% responded — but 19% deteriorated. In the standard 40-session group the numbers were 53% and 11%.
More treatment produced more improvement and more harm. Those two lines diverge rather than rising together, which is not what a simple "more is better" model predicts. It is what you would expect if the right dose differs sharply between individuals, and if overshooting has a cost.
The authors' explanation for the deterioration is that the treatment was simply too much for some of these patients — that in a population defined by post-exertional malaise, an intensive eight-week course can push people past what they can absorb. Ten patients stopped early for exactly this reason, reporting worsening fatigue during treatment.
That clinical description and the oxidative-stress account are not competing explanations. They are the same event described at two levels. Hyperbaric oxygen is a physiological load, not a neutral input. In a body where mitochondrial function and redox balance are already impaired — which is the working picture of long COVID and of ME/CFS — the capacity to absorb that load is reduced, and the point at which it stops being useful and starts being harmful arrives earlier. Post-exertional malaise is what exceeding that point looks like from the outside.
Which is why severity matters here. The sicker the patient, the lower the threshold. The centres recognised this in practice rather than in theory: patients now need at least four hours of upright activity a day to be accepted for treatment, a rough proxy for whether their system can take the load at all.
There is a second dose signal in the safety data. One patient developed early cataracts after 40 sessions. Cataract induction has long been associated with hyperbaric courses over a hundred sessions, but the authors point to unpublished trial data suggesting it may occur in around 2% of patients at 20 to 40 sessions — meaning the threshold may be lower than assumed. Alongside that, 65% reported fatigue and 27% blurry vision during treatment.
This is why the dose question in hyperbaric medicine is not academic. Paul Harch has argued for years that neurological conditions follow an inverted-U curve — too little does nothing, too much does harm — and that pressures around 1.3 to 1.5 ATA may suit fragile nervous systems better than the 2.0 to 2.5 ATA that clinical protocols default to. This registry did not test that. It did not compare pressures, and without a control group it cannot establish cause for anything. What it does is put real numbers on the cost of a high-dose protocol in a population that may not tolerate one: a fifth of the extended-treatment group ended up worse than when they started.
For anyone with post-exertional malaise or dysautonomia, the case for starting gentle and going slowly rests on that observation plus mechanism and clinical experience. It does not yet rest on a trial comparing the two. That trial has not been run.
Takeaway for the community
In this prospective registry:
- 56–63% improved meaningfully three months after treatment, with the largest gains in cognitive symptoms, energy and social functioning
- 13–19% got worse — a safety signal the authors note had not been reported in earlier research
- deterioration was more common in patients who received extended treatment (19% vs 11%), at the same time as improvement was more common (63% vs 53%)
- the authors attribute the worsening to the treatment exceeding what some patients could absorb — a load problem in a population whose physiology is already strained — and have since tightened eligibility criteria
- one patient developed early cataracts after 40 sessions, and the authors suggest this risk may be underestimated at standard session counts
- there was no control group, patients self-funded an off-label treatment, and causality cannot be established
Starting lower and building slowly is a conservative response to a study where a meaningful minority ended up worse. This registry does not prove that a gentler protocol would have served them better — but it is the clearest published evidence so far that the standard high-dose protocol does not suit everyone in this population.
HBOT Radar continues to follow long COVID research and the emerging science guiding safer, more effective hyperbaric treatment strategies.
Study link: https://pubmed.ncbi.nlm.nih.gov/40759992/
Educational disclaimer
This content summarizes findings from published medical research for educational purposes only.
The hyperbaric chambers sold on this website are non-medical wellness devices and are not intended to diagnose, treat, cure, or prevent any disease.
The studies discussed here were conducted in clinical medical settings using medical-grade interventions. The inclusion of research summaries does not imply that similar outcomes can be achieved using non-medical wellness devices.
