More Chamber Sessions, Fewer Complications: A Signal in 168 Body-Contouring Cases

Cross-section illustration of an autologous fat graft set in subcutaneous tissue: a thin pale-amber rind of oxygenated adipocytes around the graft margin, enclosing a darker hypoxic core at its centre, with fine new capillary sprouts advancing inward from the rim into soft tissue striations

The paper’s title gives away neither its most quotable number nor the fact that a third of its patients climbed into a pressure chamber. Plastic and Reconstructive Surgery published it on 19 October: a retrospective cohort of 168 feminising body-contouring procedures performed between January 2019 and October 2024 by four surgeons, across Stanford Medicine, Align Surgical Associates in San Francisco and Rutgers. It is, by the standards of the field, a useful and fairly large series — the kind of paper written because almost nothing has been published on how these operations actually behave.

The operation in question is liposuction of the trunk with or without fat grafting to the buttocks and hips, which the authors abbreviate FBC. Nearly all of the patients — 161 of 168 — had used gender-affirming hormones for an average of 8.5 years; mean age was 37.1 and mean BMI 29.3. An average of 2.2 litres of fat was moved, harvested most often from the abdomen, the back and the medial thighs. At a mean follow-up of 318.5 days, 19.6% had experienced some complication — contour deformity in 4.2%, fat necrosis in 3.0%, cellulitis and seroma in 2.4% each — and one in five (20.2%) went back for revision because of fat loss or deformity.

A safety paper with an oxygen footnote

Then comes the sentence that makes this a hyperbaric story. A third of the patients (33.3%) attended at least one hyperbaric oxygen chamber session, with an average of 12.7 sessions across that group. And in the authors’ analysis, an increasing number of hyperbaric sessions was associated with decreased odds of any complication, at p = 0.03.

Read that against the other associations in the same model and the texture becomes clearer. Older age tracked with fat necrosis (p = 0.05). BMI did not correlate with complications at all. Graft volume trended toward more complications without reaching significance (p = 0.07). So the one variable that came out cleanly protective was the number of times a patient sat in a chamber — a variable that no surgeon randomised, no protocol fixed, and, at least in the abstract, no indication justified.

What the abstract does not supply matters as much as what it does. There is a p-value but no odds ratio. There is no statement of whether the model was adjusted, and if so for what. There is no pressure, no duration, no fraction of inspired oxygen, and no reason given for why any individual patient was sent for treatment in the first place. Those omissions are not a criticism — the authors were writing a surgical-outcomes paper, not a hyperbaric one — but they define the limits of what a secondary association can carry.

And there is a bias to hold in view. Patients who complete thirteen chamber sessions are, almost by definition, patients with the money, transport, time off work and tolerance for a daily clinical commitment that a two-hour round trip requires. Adherence of that kind correlates with better outcomes in every surgical cohort ever assembled, usually for reasons unrelated to the intervention. The direction of the confounding could also run the other way: a surgeon worried about a threatened graft may be more likely to order oxygen, which would bias the result against the treatment. Either way, the p = 0.03 is a hypothesis wearing a statistician’s coat.

Two reviews, no randomised trial

The aesthetic-surgery literature that this finding lands in is thinner than the volume of published enthusiasm suggests. A 2025 systematic review and meta-analysis by Hatan Mortada and colleagues in Aesthetic Plastic Surgery pooled eleven studies and 734 patients, 416 of whom (56.7%) received hyperbaric oxygen. Treatment was postoperative in 90.9% of cases, most often after abdominoplasty or breast surgery, delivered in sessions of 45 to 120 minutes at 2.0 to 3.0 ATA. The headline result was a pooled mean healing time of 11.30 days (95% CI 10.46 to 12.14), with patient satisfaction reaching 88.2%. The journal rated it Level of Evidence II. The authors’ own closing sentence asked for well-designed randomised controlled trials to establish standardised guidelines — because, as the abstract concedes, study designs and protocols varied too much to support anything firmer.

A pooled mean healing time is worth pausing on. It is a single number summarising how long wounds took to heal across eleven studies, with no control arm subtracted from it. It tells you what happened to patients who received oxygen. It does not tell you what would have happened to the same patients without it.

The second review, by Sean Fisher and colleagues in the same journal and the same issue, screened 591 records down to fifteen articles and reached a blunter verdict: hyperbaric oxygen “may serve a valuable adjunct in aesthetic surgery, medicine, and anti-aging,” but “the evidence to support its use, and justify its cost, is limited.” It was rated Level of Evidence V — the bottom of the scale. It is also, as far as the authors could determine, the first review to address the anti-aging claims at all, which says something about how recently that market separated from the clinical one.

Neither review identified a randomised trial. In 2025, in the aesthetic-surgery corner of this literature, there was still not one.

Two letters on adjacent pages

Something shifted this January, and it is visible in the pagination. Aesthetic Plastic Surgery volume 50, issue 1, carried two single-author letters on consecutive pages: Agostino Bruno’s “Stratifying Risk to Optimize Hyperbaric Oxygen Therapy in Aesthetic Surgery” on 517-518, and Hatan Mortada’s “Refining the Role of Hyperbaric Oxygen Therapy in Aesthetic Surgery: the Need for Stratified Evidence” on 519-520. Mortada is the first author of the meta-analysis described above — a researcher moving from his own pooled estimate toward a narrower question.

What either letter argues beyond its title, this article cannot fairly report: neither is indexed with an abstract, and both sit behind a paywall. But the titles mark a real change in the conversation. The question is no longer whether hyperbaric oxygen works in aggregate, but which patients it works for — which is also the only question a retrospective cohort like the October one can raise.

Millimetres, not atmospheres

Set the clinical argument aside for a moment and the physiology behind it is unusually specific — specific enough to be testable, which is rare in this field.

Grafted fat has no blood supply when it is placed. It survives by diffusion from the recipient bed until new vessels grow in, and diffusion has a hard geometric limit. In a 2019 Plastic and Reconstructive Surgery paper, Thomas Suszynski and colleagues built a mathematical model of that limit from four variables: the oxygen partial pressure at the recipient site, the oxygen permeability of adipose tissue, its oxygen consumption rate — which they measured directly — and the size of the graft. Working in planar geometry, the configuration that actually resembles an injected graft, they found the maximum allowable thickness of surviving fat was roughly one to two millimetres at external oxygen partial pressures of 10 to 40 mmHg. Anything thicker develops an anoxic, necrotic core. Give the graft a large enough surface area and inject it along several planes, and the maximum survivable volume reaches tens of millilitres.

That model makes the appeal of hyperbaric oxygen obvious: if survival is capped by how far oxygen diffuses in from outside, then raising the oxygen outside should push the cap outward. It also explains why fat necrosis, at 3.0% in the October cohort, is the outcome where any real effect would show up first.

But here the mechanism story complicates the commercial one. In 2014, Harunosuke Kato and colleagues tested the same premise without a chamber. They cultured aspirated human fat at 1%, 6% and 20% oxygen and found adipocytes died faster the leaner the oxygen supply. Then they autografted fat into 36 mice and housed half of them in 60% oxygen at ordinary atmospheric pressure for the first three days. The hyperoxygenated animals had significantly larger survival zones at one week and significantly better engraftment scores at twelve, with a measurable surge of regenerating preadipocytes peaking at four weeks. The benefit came from extra oxygen at one atmosphere — no pressure vessel, no two-hour session, no compression and decompression.

If that is the active ingredient, a hyperbaric session is an expensive and logistically awkward way to buy an oxygen gradient that a face mask and a concentrator can partly supply.

The animal dosing work points somewhere else again. Jianhe Liang and colleagues ran ninety rats through three arms in 2023: hyperbaric oxygen for one hour a day, for two hours a day, or not at all, for ten consecutive days. At six weeks, survival of the injected fat was 47.3% of the original volume in the one-hour group, 32.9% in the two-hour group and 16.9% in controls. The shorter schedule beat the longer one, comfortably. More oxygen was not monotonically better, which is a familiar shape in hyperbaric research and an awkward one next to a cohort finding that counts sessions.

Three lines of evidence, then, pointing three ways. A clinical series says each additional session may help. A rodent study says shorter courses are better. A mechanistic study says pressure may not be what is doing the work.

Cleared for a failing flap, not for a scheduled transfer

Which brings the regulatory question, and it is not a technicality. Hyperbaric oxygen therapy is delivered through Class II medical devices cleared by the FDA through the 510(k) pathway, searchable under Product Code CBF. In its August 2025 letter to health care providers, the agency reminded facilities that it is aware of fires in hyperbaric devices that caused serious injuries and deaths, and that providers must follow manufacturer instructions on prohibited electrical and static items, compatible clothing, staff training and continuous patient monitoring. Those requirements apply to every session in this discussion, whatever the indication.

The Undersea and Hyperbaric Medical Society’s 15th-edition indication list includes “compromised grafts and flaps.” It is the twelfth entry, and it means a graft that is failing — threatened by ischemia, infection or breakdown — not an elective fat transfer performed as planned. Medicare’s National Coverage Determination 20.29 uses narrower language again: “preparation and preservation of compromised skin grafts (not for primary management of wounds).” Coverage there is adjunctive only, and only after there are no measurable signs of healing for at least 30 days of standard therapy, with reassessment every 30 days and treatment discontinued if no healing appears within any such period. Elective body contouring appears nowhere in the determination.

So the third of the October cohort who received oxygen were, in the great majority of cases, receiving it outside any cleared indication — lawfully, since off-label use of a cleared device by a physician is permitted, but as a different kind of transaction from a reimbursed clinical treatment. Aesthetic practices commonly charge patients directly. Twelve or thirteen sessions is a real sum.

That does not make the sessions useless. It makes them unproven, and it makes the patient’s informed consent a genuine clinical act rather than a formality.

There is one aesthetic use where the comparison is at least structured. Roberta Albanese and colleagues reported in Aesthetic Surgery Journal in May on 186 patients who developed post-inflammatory hyperpigmentation after VASER ultrasound-assisted liposuction between 2019 and 2024. Ninety-three received Q-switched Nd:YAG laser alone; ninety-three received twenty hyperbaric sessions at 2 ATA for 45 minutes before laser treatment. Both groups improved, but the combined group improved significantly more (p < 0.001), tracked on a validated pigmentation index with at least six months of follow-up, and improvements were greatest on the abdomen and back and weakest on the lower limbs. It is still retrospective and still not randomised. But it has a comparator arm and an objective score, which neither of the aesthetic-surgery reviews managed — and it addresses a complication of liposuction rather than fat survival.

The commercial frame around all this has its own literature now. A 2026 review in Facial Plastic Surgery Clinics of North America by Ryan Kelm and Cameron Chesnut describes “biohacking recovery” as the replacement of the traditional rest-and-wait approach with “pre-covery”: hyperbaric oxygen bundled with pulsed electromagnetic field therapy, photobiomodulation, supplementation and “emerging regenerative peptides.” The paper is candid that this represents a “paradigm shift.” It does not claim the bundle has been validated as one.

What would settle the question is neither exotic nor expensive by surgical-research standards. Take the graft-retention question, define the endpoint before enrolling anyone — volumetric imaging at three and twelve months, say — and randomise patients to hyperbaric oxygen, to normobaric hyperoxygenation of the kind Kato’s mice received, or to neither. The normobaric arm is the one that matters, because it is the arm that would tell us whether the chamber is doing anything the oxygen is not.

Until someone runs that trial, the most defensible statement is narrow. A retrospective series of 168 gender-affirming body-contouring procedures found that patients who attended more hyperbaric sessions had fewer complications, at a p-value of 0.03, in an analysis not designed to answer the question. It is worth following up. It is not yet worth a course of thirteen sessions on the strength of it alone.

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