How Hyperbaric Oxygen Therapy May Support Healing in Selected Complex Diabetic Foot Wounds
A diabetic foot ulcer is rarely caused by one problem alone. Peripheral neuropathy may prevent a person from feeling repetitive pressure or minor trauma. Foot deformity can concentrate mechanical stress in a small area. Peripheral artery disease may reduce blood flow, while impaired immune function, infection, edema, and metabolic dysfunction further limit tissue repair.
Once an ulcer develops, these factors can reinforce one another. Continued pressure causes additional tissue damage, ischemia limits oxygen delivery, and infection increases local oxygen demand. The result may be a wound that remains open despite appropriate care and places the patient at risk for hospitalization, osteomyelitis, tissue loss, or amputation.
Hyperbaric oxygen therapy, or HBOT, may be considered for a carefully selected subset of these wounds. It is not intended for every diabetic foot ulcer, and it does not replace revascularization, debridement, offloading, antimicrobial therapy, or diabetes management. Its role is adjunctive: to improve oxygen availability within viable but hypoxic tissue while the underlying causes of the wound are addressed.
Why Diabetic Foot Ulcers Become Hypoxic
Wound healing depends on an adequate supply of oxygen. Oxygen supports cellular energy production, collagen synthesis, fibroblast activity, angiogenesis, epithelial migration, and the oxidative mechanisms used by leukocytes to kill certain microorganisms.
In a diabetic foot ulcer, oxygen delivery may be impaired at several levels. Peripheral artery disease can reduce blood flow into the foot. Microvascular dysfunction can affect the distribution of oxygen within tissue. Edema can increase the distance oxygen must diffuse between functioning capillaries and cells. Infection and inflammation can raise metabolic demand at the same time that supply is falling.
Neuropathy creates an additional challenge. Because protective sensation is diminished, the patient may continue to walk on the injured area without experiencing the pain that would normally limit activity. Repeated pressure and shear can damage newly forming tissue faster than the wound can repair itself.
A normal pulse oximetry reading does not rule out local wound hypoxia. Pulse oximetry measures hemoglobin saturation in arterial blood, not oxygen tension in the tissue surrounding a foot ulcer. A patient may have normal systemic oxygen saturation while the wound bed and adjacent tissue remain poorly oxygenated.
How Hyperbaric Oxygen Therapy Affects a Diabetic Foot Wound
During HBOT, the patient breathes oxygen while exposed to increased atmospheric pressure inside a medical hyperbaric chamber. Increased pressure raises the partial pressure of oxygen in the lungs and substantially increases the amount of oxygen dissolved directly in plasma.
This oxygen-rich plasma can reach functioning microvessels and create a stronger diffusion gradient between capillary blood and hypoxic tissue. Oxygen may then travel farther from the capillary than it can under normal atmospheric conditions.
For a diabetic foot ulcer, the relevant physiologic effects may include:
- Temporary elevation of oxygen tension in hypoxic tissue
- Support for oxygen-dependent fibroblast and collagen activity
- Promotion of angiogenic signaling and capillary development
- Improved oxygen-dependent leukocyte function
- Modulation of inflammation and leukocyte-endothelial adhesion
- Hyperoxic vasoconstriction that may help reduce edema
- Support for metabolically stressed but still viable tissue
The treatment does not force blood through a completely obstructed artery. Some degree of perfusion is still necessary to transport oxygen toward the wound. Significant arterial disease must therefore be identified and corrected when feasible before HBOT is expected to support healing.
The International Working Group on the Diabetic Foot notes that oxygen is involved in angiogenesis, collagen deposition, and epithelialization. Its 2023 wound-healing guideline conditionally recommends considering HBOT for neuro-ischemic or ischemic diabetes-related foot ulcers when standard care has failed and appropriate treatment resources already exist. The certainty of evidence supporting that recommendation was rated low. (IWGDF Guidelines)
Which Diabetic Foot Ulcers May Be Appropriate for HBOT?
The presence of diabetes and an open foot wound does not, by itself, establish an indication for HBOT. The wound should be thoroughly evaluated to determine its depth, perfusion, infection status, mechanical causes, healing trajectory, and response to standard care.
In the United States, Medicare coverage for diabetic lower-extremity wounds generally requires all three of the following:
- The patient has type 1 or type 2 diabetes and a lower-extremity wound caused by diabetes
- The wound is classified as Wagner grade 3 or higher
- The wound has failed an adequate course of standard wound therapy
For coverage purposes, failure of standard care is defined as no measurable signs of healing for at least 30 consecutive days. HBOT must be provided in addition to continued standard wound care, and the wound must be reassessed at least every 30 days during treatment. (Centers for Medicare & Medicaid Services)
A Wagner grade 3 ulcer typically extends into deeper structures and may involve an abscess, tendon, joint, or bone infection. Grade 4 describes localized gangrene, while grade 5 describes extensive gangrene of the foot.
The Wagner system is useful for describing wound depth and tissue loss, but it does not fully characterize ischemia or infection severity. Clinicians may also use the Wound, Ischemia, and foot Infection classification, known as WIfI, and the IWGDF/IDSA infection classification to guide vascular, surgical, and infectious-disease decisions.
The Undersea and Hyperbaric Medical Society clinical practice guideline suggests HBOT for Wagner grade 3 or higher ulcers that have not shown significant improvement after 30 days of standard care. It also addresses selected acute postoperative wounds following surgical treatment of an infected diabetic foot. HBOT is not generally suggested for Wagner grade 2 or lower ulcers solely to promote healing. (UHMS)
Standard Diabetic Foot Ulcer Care Must Come First
HBOT is most appropriately considered after the fundamentals of diabetic foot care have been implemented and any correctable barriers to healing have been addressed.
Standard care should include:
- Vascular assessment and revascularization when indicated
- Effective offloading of the ulcerated area
- Debridement of devitalized or infected tissue
- Diagnosis and treatment of clinically significant infection
- Moisture-balanced wound management
- Optimization of glucose management
- Nutritional assessment and support
- Management of edema and other comorbid conditions
- Regular measurement and documentation of wound progress
CMS specifically identifies vascular assessment, correction of vascular problems when possible, nutritional optimization, glucose management, debridement, moist wound care, offloading, and infection treatment as components of standard diabetic wound care. (Centers for Medicare & Medicaid Services)
Offloading is particularly important. Even an advanced wound product or adjunctive therapy may fail when the patient continues to place excessive pressure on a plantar ulcer. The offloading plan must be clinically effective and realistic for the patient’s mobility, balance, home environment, and daily responsibilities.
Similarly, HBOT should not delay revascularization. A patient with clinically significant ischemia requires prompt vascular evaluation. Oxygen delivered under pressure may improve diffusion from vessels that are still functioning, but it cannot substitute for restoring adequate macroscopic blood flow.
HBOT Is Not a Stand-Alone Treatment for Infection
Many advanced diabetic foot ulcers are complicated by soft-tissue infection or osteomyelitis. HBOT may improve tissue oxygenation and support oxygen-dependent leukocyte activity, but it is not a substitute for infection source control.
An infected diabetic foot may require urgent:
- Surgical drainage
- Excisional debridement
- Bone resection or limited amputation
- Culture-directed antimicrobial therapy
- Vascular intervention
- Hospitalization and systemic support
The IWGDF/IDSA guideline recommends diagnosing diabetic foot infection clinically, based on local or systemic signs of inflammation, and grading its severity using the IWGDF/IDSA system. It also advises against using antibiotics for clinically uninfected ulcers solely to prevent infection or promote healing. (OUP Academic)
HBOT should not be prescribed simply because an ulcer culture contains bacteria. Chronic wounds are commonly colonized, and a positive culture alone does not establish invasive infection. The clinical team must distinguish colonization from infection and determine whether soft tissue, bone, or systemic structures are involved.
Vascular Assessment and Tissue Oxygen Testing
Peripheral artery disease is common in patients with diabetes-related foot ulcers and strongly influences healing potential. Assessment may include pedal pulse examination, Doppler waveforms, ankle pressures, toe pressures, ankle-brachial index, skin perfusion pressure, transcutaneous oxygen measurement, or vascular imaging.
The ankle-brachial index can be difficult to interpret in diabetes because medial arterial calcification may make vessels poorly compressible and produce falsely elevated measurements. Toe pressure and waveform-based assessment may provide additional information.
Transcutaneous oxygen measurement, often abbreviated TcPO₂ or TCOM, may be used by some programs to assess local tissue oxygenation and the wound’s response to supplemental or hyperbaric oxygen. Measurements can help clinicians understand whether the surrounding tissue is severely hypoxic and whether oxygen delivery improves under test conditions.
No single oxygen measurement should be interpreted in isolation. Results must be considered alongside vascular anatomy, wound characteristics, infection status, edema, temperature, technical quality, and the overall clinical picture. A favorable oxygen response does not correct inadequate offloading or untreated infection, while a poor result may prompt further vascular evaluation before an HBOT course is started.
What a Course of HBOT May Involve
Treatment protocols are prescribed by a hyperbaric physician according to the wound, patient risk factors, chamber system, and clinical response.
Many chronic-wound protocols use pressures between approximately 2.0 and 2.5 atmospheres absolute, with 60 to 90 minutes of oxygen breathing at treatment pressure. Treatments are often scheduled five days per week over several weeks, although the pressure, duration, air breaks, and total number of sessions vary. (UHMS)
A typical visit includes:
- Pre-treatment assessment, including review of symptoms, medications, glucose status, and ear-clearing ability.
- Removal of prohibited items and preparation according to hyperbaric fire-safety requirements.
- Gradual chamber compression.
- Oxygen exposure at the prescribed treatment pressure.
- Air breaks when included in the protocol.
- Controlled decompression and post-treatment assessment.
Patients with diabetes commonly require blood glucose testing before treatment. Depending on their medication regimen and clinical risk, glucose may also be checked after treatment. Meal timing, insulin administration, glucose trends, and symptoms of hypoglycemia should be reviewed throughout the course.
The wound should continue to be measured regularly. HBOT should not continue automatically because a predetermined number of sessions was ordered. The team should reassess perfusion, infection, offloading adherence, wound area, tissue quality, and overall progress.
What the Evidence Shows About Healing and Amputation
The evidence for HBOT in diabetic foot ulcers remains clinically promising but methodologically mixed. Trials have used different ulcer classifications, levels of ischemia, treatment protocols, definitions of healing, follow-up periods, and amputation outcomes. Some studies have been small or at high risk of bias.
The 2023 IWGDF review found conflicting results. The studies with the lowest risk of bias suggested possible improvement in complete wound healing and ulcer-area reduction, but the guideline found insufficient evidence to establish a reliable reduction in amputation. It therefore issued a conditional recommendation based on low-certainty evidence. (IWGDF Guidelines)
A 2024 systematic review and meta-analysis reported improved complete healing with HBOT but did not find a statistically significant effect on major or minor amputation rates. These findings illustrate why outcomes should not be presented as guaranteed and why careful patient selection remains essential. (PubMed)
Differences in the evidence do not mean HBOT has no clinical role. They indicate that benefit is unlikely to be uniform across all diabetic foot ulcers. A deeply infected or ischemic wound that remains hypoxic despite optimized care is clinically different from a superficial neuropathic ulcer that has not been adequately offloaded.
Risks and Practical Barriers to Treatment
HBOT is generally well tolerated in appropriately screened patients, but it is not risk free. Potential adverse effects include:
- Middle-ear or sinus barotrauma
- Temporary myopic vision changes
- Blood glucose instability
- Claustrophobia or anxiety
- Pulmonary oxygen effects
- Rare oxygen-induced seizure
An untreated pneumothorax is generally considered an absolute contraindication. Pulmonary disease, inability to equalize ear pressure, seizure risk, heart failure, implanted devices, medication interactions, and severe confinement anxiety require individual assessment.
The treatment course may also be demanding. Patients may need transportation to a hyperbaric center five days per week while simultaneously attending wound-care, vascular, infectious-disease, surgical, endocrinology, or rehabilitation appointments. Mobility limitations, caregiver responsibilities, work schedules, and financial strain can affect completion.
These barriers should be discussed honestly before treatment. A compassionate care plan considers not only whether a patient is medically eligible, but whether the complete wound-healing strategy is practical and sustainable.
Measuring Whether HBOT Is Helping
The purpose of HBOT is not simply to complete a series of chamber sessions. It is to contribute to measurable clinical progress.
Indicators of improvement may include:
- Reduction in wound area, depth, or volume
- Improved granulation tissue
- Reduced devitalized tissue
- Stabilization of wound margins
- Improved control of edema or local inflammation
- Progress toward reconstructive closure
- Preservation of viable tissue after surgery
- Avoidance of further tissue loss
A wound that is not progressing requires renewed assessment. Persistent failure may reflect inadequate perfusion, continued pressure, residual infection, unrecognized osteomyelitis, poor glucose control, malnutrition, tobacco exposure, edema, or an incorrect diagnosis.
HBOT should remain one component of a coordinated limb-preservation strategy. The best candidate is not simply a person with diabetes and a difficult wound. It is a patient with an appropriately classified, viable, hypoxic or ischemic ulcer for whom standard care has been optimized, correctable vascular problems have been addressed, and adjunctive oxygen therapy offers a clinically reasonable opportunity to support healing.
