therapies · education ·
Hyperbaric Oxygen Helps Some Wounds & Not Others. The Dividing Line Is A Grade
A guideline draws its line at Wagner grade 3. A Cochrane pool found a six-week advantage that was gone by one year. One good trial found nothing at all.
Ask whether hyperbaric oxygen heals wounds and you will get a yes or a no, delivered with confidence, from someone who has picked a side.
The literature does not answer that question, because it is the wrong question. It answers a narrower one: which wound, at what grade, and measured when.
Get specific and the mess resolves into something surprisingly clear.
The guideline draws a line, and it is a number
The Undersea and Hyperbaric Medical Society ran a systematic review using GRADE methodology and produced an actual clinical practice guideline, which this field had gone decades without (Huang et al., Undersea and Hyperbaric Medicine, 2015).
They sorted the evidence by Wagner wound classification, which is a measure of how deep a diabetic foot ulcer runs, and by how old the wound is. Their conclusions:
- Wagner grade 3 or greater, just after surgical debridement: hyperbaric oxygen is beneficial for preventing amputation and promoting complete healing
- Wagner grade 3 or greater, showing no significant improvement after 30 or more days: same conclusion
- Wagner grade 2 or lower: inadequate evidence to justify it as an adjunctive treatment
That last line is the one nobody quotes, and it is the most useful sentence in the paper. It is not that shallower ulcers were shown not to respond. It is that the evidence is not there, and the guideline declines to pretend otherwise.
The authors grade their own overall body of evidence as moderate, and they call explicitly for shared decision-making between clinicians, patients and policy-makers. That is what honest looks like when a field is genuinely mixed.
In patients with Wagner Grade 2 or lower DFUs, there was inadequate evidence to justify the use of HBO2 as an adjunctive treatment.
Huang et al., Undersea and Hyperbaric Medicine, 2015
Then the pool, and the part about timing
Cochrane gathered the randomized trials of hyperbaric oxygen for chronic wounds: twelve trials, 577 participants, of which ten trials and 531 participants had diabetic foot ulcers (Kranke et al., Cochrane Database of Systematic Reviews, 2015).
Pooling five of those trials, 205 participants, ulcers healed at a higher rate with hyperbaric oxygen at six weeks: risk ratio 2.35 (95% CI 1.19 to 4.62, P = 0.01).
Then the sentence that matters just as much: that benefit was not evident at one-year follow-up.
Major amputation across five trials and 312 participants showed no statistically significant difference, risk ratio 0.36 (95% CI 0.11 to 1.18). That interval crosses 1, so it did not reach significance, though it is worth noticing which direction it points.
And the reviewers’ own verdict on the trials they pooled: they had various flaws in design and reporting, which left the authors not confident in the results and calling for adequately powered trials.
So: a real short-term advantage, on a body of work the people who assembled it do not fully trust, that they could not find again a year later.
The trial that found nothing
We keep these. A therapy’s null trials are part of its evidence, not an inconvenience to route around.
Patients with diabetic foot lesions at Wagner grade 2 to 4, open at least four weeks, were randomized to 30 daily 90-minute sessions of hyperbaric oxygen at 244 kPa or a sham breathing air at 125 kPa. Patients, physicians and researchers were all blinded. One hundred and seven were randomized and 103 were available for adjudication (Fedorko et al., Diabetes Care, 2016).
At 12 weeks, criteria for major amputation were met in 11 of 49 on hyperbaric oxygen against 13 of 54 on sham (odds ratio 0.91, 95% CI 0.37 to 2.28, P = 0.846).
Healed: 10 of 49, or 20%, against 12 of 54, or 22% on sham (odds ratio 0.90, P = 0.823).
Every other index of wound healing also failed to separate. The authors’ conclusion is one sentence long and worth reading slowly: hyperbaric oxygen does not offer an additional advantage to comprehensive wound care in reducing the indication for amputation or facilitating wound healing in patients with chronic diabetic foot ulcers.
Notice the population. Wagner grade 2 to 4, which mixes the grades the guideline says are supported with the grade it says are not. That is not a criticism of the trial, it is an illustration of why the guideline sorted by grade in the first place.
How to hold three answers at once
They are not really in conflict.
The guideline says the benefit lives at grade 3 and above. The Cochrane pool says the healing advantage shows up early and does not persist to a year. Fedorko says that across a mixed-grade population with excellent standard wound care, the addition does not separate at 12 weeks.
Put together, our reading: hyperbaric oxygen has moderate-quality support in deep, non-healing diabetic foot ulcers, measured over weeks, on top of good wound care and never instead of it. Everything beyond that sentence is being sold ahead of its data.
The older supportive trials are part of the record too, and we will name them rather than lean on them. A 1996 randomized study in severe, mostly ischemic diabetic foot ulcers reported major amputation in 3 of 35 (8.6%) with adjunctive hyperbaric oxygen against 11 of 33 (33.3%) without (Faglia et al., Diabetes Care, 1996). Striking numbers, small trial, thirty years old, and exactly the kind of result that later and larger work keeps failing to reproduce cleanly.
The dose question nobody asks
Everything above ran near 2 atmospheres, breathing high-concentration oxygen, in clinical chambers.
That is not what most people can buy. Researchers measured transcutaneous tissue oxygen in chronic ulcer patients breathing 100% oxygen and found it averaged about 161 mmHg at 1.4 atmospheres against about 333 mmHg at 2 atmospheres (Sack et al., Undersea and Hyperbaric Medicine, 2024).
Roughly half the tissue oxygen. Not zero, and not the dose these wound trials used.
So when somebody points at the wound literature to sell a session, the question is not whether hyperbaric oxygen works. It is whether the thing being sold is the thing that was studied. Ask for the atmospheres and the oxygen fraction, in writing.
We cover that whole continuum in hard chamber or soft, and why the pressure range is the real question.
What we are and are not saying
| Claim | Our line |
|---|---|
| Hyperbaric oxygen treats, cures or heals disease | Never |
| A guideline supports it for Wagner grade 3 and above diabetic foot ulcers | Yes, on moderate-quality evidence, as an adjunct |
| It is supported for shallower ulcers | No. The guideline calls that evidence inadequate |
| Pooled trials found better healing at six weeks | Yes, risk ratio 2.35 |
| That advantage held at one year | No. It was not evident at one-year follow-up |
| It reduces major amputation | Unproven. The pooled estimate did not reach significance |
| A good trial found nothing | Yes, and we report it. 12 weeks, double blind, no separation |
| A soft chamber delivers the studied dose | No. About 161 mmHg against 333 mmHg on tissue oxygen |
Where the design shows up
Under pressure, oxygen stops depending on your red blood cells and dissolves straight into the plasma. That is the entire mechanism, and it is the reason this therapy exists: tissue that has lost its blood supply can still be reached by the fluid around it.
Which is worth sitting with. The delivery system most wounds need is a working artery, and no chamber builds one. What pressure buys is time, a window in which tissue that would have starved gets fed by a second route while the repair machinery does what it already knows how to do.
The chamber does not heal anything. It keeps the crew supplied.
“The plans of the diligent certainly lead to advantage, but everyone who is hasty certainly comes to poverty.” Proverbs 21:5, NASB
The verse carries the conviction. One guideline, twelve pooled trials and one honest null carry the evidence.
What to do this week
If this is your wound, the grade is the first thing to find out.
Ask whoever is managing it where it sits on the Wagner scale, and whether the standard of care has been fully run: debridement, offloading, infection control, blood supply assessment, glucose control. Every trial above added hyperbaric oxygen on top of comprehensive wound care, and none of them tested it instead.
If a centre offers you sessions, ask two questions before paying: what pressure, and what oxygen fraction. Then compare that to the roughly 2 atmospheres the trials used.
Read this next: the broader question and the trial that makes the strongest case: does hyperbaric oxygen work. What a course actually asks of you, and the one thing that bothers people: does hyperbaric oxygen work. And the dose continuum in full: hard chamber or soft.
Sources
- Huang ET, Mansouri J, Murad MH, et al. “A clinical practice guideline for the use of hyperbaric oxygen therapy in the treatment of diabetic foot ulcers.” Undersea and Hyperbaric Medicine, 2015;42(3):205-247. https://pubmed.ncbi.nlm.nih.gov/26152105/
- Kranke P, Bennett MH, Martyn-St James M, et al. “Hyperbaric oxygen therapy for chronic wounds.” Cochrane Database of Systematic Reviews, 2015;6:CD004123. https://pubmed.ncbi.nlm.nih.gov/26106870/
- Fedorko L, Bowen JM, Jones W, et al. “Hyperbaric Oxygen Therapy Does Not Reduce Indications for Amputation in Patients With Diabetes With Nonhealing Ulcers of the Lower Limb.” Diabetes Care, 2016;39(3):392-399. https://pubmed.ncbi.nlm.nih.gov/26740639/
- Faglia E, Favales F, Aldeghi A, et al. “Adjunctive systemic hyperbaric oxygen therapy in treatment of severe prevalently ischemic diabetic foot ulcer. A randomized study.” Diabetes Care, 1996;19(12):1338-1343. https://pubmed.ncbi.nlm.nih.gov/8941460/
- Sack RA, Pikkel YY, Shemy OL, Ramon Y, Ullmann Y, Zeltzer AA. “Transcutaneous oximetry values in chronic ulcer patients during hyperbaric treatment at 1.4 ATA compared to 2 ATA.” Undersea and Hyperbaric Medicine, 2024;51(1):1-5. https://pubmed.ncbi.nlm.nih.gov/38615347/
Article metadata retrieved from PubMed. Photograph from Pexels. Scripture quoted from the New American Standard Bible.
Educational content from True Health Solutions. We do not diagnose or prescribe, and nothing here is a substitute for care from someone who knows your history. The body heals. We write about what supports that design.
Questions people ask
- Does hyperbaric oxygen heal wounds?
- It depends entirely on which wound. The Undersea and Hyperbaric Medical Society guideline found it beneficial for diabetic foot ulcers at Wagner grade 3 or greater, and found the evidence inadequate to justify it at Wagner grade 2 or lower. The grade is the dividing line, not the word wound.
- What is a Wagner grade?
- A classification of how deep a diabetic foot ulcer goes. Grades 1 and 2 are surface and deeper ulcers without abscess or bone involvement. Grade 3 and above add abscess, bone infection, or tissue death. The guideline's recommendation starts at grade 3.
- How strong is the evidence?
- The guideline rates its own body of evidence as moderate. A 2015 Cochrane review pooled five diabetic foot ulcer trials and found higher healing at six weeks, risk ratio 2.35, but that advantage was not evident at one year, and the reviewers said design and reporting flaws left them not confident in the results.
- Are there trials that found nothing?
- Yes, and it is a good one. A double-blind randomized trial gave 30 daily sessions and found no significant difference from sham on amputation criteria or on healing at 12 weeks. We report it because a therapy's null trials are part of its evidence.
- Is a soft home chamber the same as the wound trials?
- No. Those wound protocols ran near 2 atmospheres breathing high-concentration oxygen. Measured in chronic ulcer patients breathing 100% oxygen, tissue oxygen averaged about 161 mmHg at 1.4 atmospheres against about 333 mmHg at 2. Different dose, different literature.
