Hyperbaric Oxygen Therapy in Veterinary Patients: Evidence and Applications

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Hyperbaric oxygen therapy (HBOT) involves intermittent inhalation of 100% oxygen at pressures exceeding 1 atmosphere absolute (ATA), primarily modulating cell signaling through intracellular reactive oxygen and nitrogen species.
• The strongest evidence for HBOT in veterinary patients is extrapolated from human medicine, supporting its use in refractory wound healing, radiation tissue injury, and compromised skin flaps/grafts due to enhanced angiogenesis and fibroblast function.
• Arterial hyperoxia, a risk of HBOT, is associated with increased mortality in subsets of critically ill human patients (e.g., cardiac arrest, TBI), necessitating careful patient selection and risk stratification in veterinary practice.
• Evidence for HBOT in neurological conditions like stroke and traumatic brain injury is limited, with human trials failing to demonstrate efficacy, likely due to critical timing windows and pressure protocol issues.
• Principal risks of HBOT include barotrauma (most commonly otic) and oxygen toxicity (neurologic and pulmonary), managed through careful patient selection, pre-treatment assessment (e.g., otoscopic exams), and controlled decompression.
• Veterinary-specific outcome data for HBOT are scarce, with current applications largely based on human clinical trials and animal models, underscoring the need for cautious extrapolation and further research.

Hyperbaric oxygen therapy (HBOT) delivers 100% oxygen to a patient enclosed in a chamber pressurized above one atmosphere absolute (ATA). The therapy has been used in human medicine for over a century, yet it remains controversial despite progressive clarification of its mechanisms and appropriate indications. This article reviews the current evidence base for HBOT in veterinary patients, with emphasis on the physiological principles that govern clinical response, the conditions for which evidence supports use, and the safety considerations that constrain patient selection. It is written for practicing veterinarians who are evaluating HBOT as an adjunctive treatment option or who encounter patients referred for hyperbaric medicine.

The clinical question this article addresses is direct: for which veterinary conditions does HBOT offer documented benefit, and how should the practitioner weigh that evidence against the physiological risks of hyperoxia? The evidence set draws primarily from human medicine, where randomized trials and systematic reviews exist, and from animal models that inform mechanism. Veterinary-specific outcome data remain limited, and this review identifies those gaps explicitly instead of extrapolating beyond what the literature supports.

At a Glance

Physiological Basis of Hyperbaric Oxygen Therapy

The therapeutic effects of HBOT arise from the delivery of oxygen at partial pressures far exceeding those achievable with normobaric supplementation. At 2 to 3 ATA, the partial pressure of oxygen in arterial blood rises sufficiently to drive oxygen diffusion into tissues with compromised perfusion, including regions where hemoglobin-bound transport is ineffective. This physical effect is straightforward. The biological consequences are more complex.

Reactive oxygen and nitrogen species generated under hyperbaric conditions function as signaling molecules instead of merely as oxidant stressors. These species participate in cell signal transduction cascades that influence angiogenesis, fibroblast proliferation, collagen synthesis, and leukocyte function. The recognition that reactive species serve as second messengers has reframed HBOT from a purely oxygen-delivery intervention to a modulator of cellular repair programs. This mechanistic understanding, articulated in reviews of hyperbaric oxygen mechanisms and efficacy, explains why the therapy may benefit conditions where simple oxygen supplementation fails.

The dose-response relationship for HBOT is not linear. Excessive chamber pressure or prolonged exposure can shift the balance from therapeutic signaling to oxidative injury. This principle underlies the caution with which pressure protocols are selected and explains why clinical trials using high pressures have sometimes produced worse outcomes than those using moderate pressures.

Oxygen Toxicity and the Hyperoxia Paradox

The same reactive species that mediate therapeutic benefit can produce cellular damage when present in excess. This duality is central to understanding HBOT risk. In critically ill patients, arterial hyperoxia has been associated with increased mortality across several diagnostic categories, including cardiac arrest, traumatic brain injury, and stroke. A systematic review and meta-analysis of cohort studies in critically ill adults found consistent associations between hyperoxia and worse outcomes, although the authors noted substantial heterogeneity and the absence of dedicated studies in sepsis, acute lung injury, and multiple trauma.

The relevance of these findings to veterinary patients is twofold. First, they establish that oxygen is not benign at any dose. Second, they suggest that patient selection for HBOT must account for baseline critical illness severity. A patient with sepsis-induced vasoplegia may respond differently to hyperbaric oxygen than a stable patient with a nonhealing wound. The veterinary literature does not yet provide species-specific outcome data to refine this risk stratification, and practitioners should extrapolate from human critical care data with appropriate caution.

Evidence for Wound Healing and Tissue Salvage

The strongest clinical evidence for HBOT in human medicine concerns refractory diabetic wounds and radiation tissue injury. Systematic reviews and randomized trials support its use in these settings, and the mechanisms identified in animal models align with the observed clinical responses. Hyperbaric oxygen enhances angiogenesis in hypoxic tissue beds, improves leukocyte bactericidal activity, and supports fibroblast function in wounds where oxygen tension is the limiting factor.

For compromised flaps and grafts, the evidence base rests on animal studies and a small number of clinical trials. The physiological rationale is sound: a marginally perfused flap exists in a state where oxygen delivery is inadequate for viability, and hyperbaric oxygen can maintain tissue oxygenation until neovascularization occurs. However, the clinical trials are few, and patient selection criteria remain imprecise. Veterinary practitioners considering HBOT for flap salvage should recognize that the evidence supports a biological rationale instead of a proven outcome guarantee.

Neurological Applications and the Timing Problem

The use of HBOT in stroke and traumatic brain injury illustrates the importance of treatment timing. Hyperbaric oxygen can salvage acutely ischemic brain tissue through multiple mechanisms, including improved oxygen delivery to the penumbra and modulation of inflammatory cascades. Yet three human clinical trials failed to demonstrate efficacy. The likely explanations are delayed time to therapy, inadequate sample sizes, and excessive chamber pressures. Previous trials also did not assess long-term benefit in patients with confirmed tissue reperfusion.

This pattern carries a specific lesson for veterinary practice. If HBOT is considered for acute neurological injury, the window for intervention is narrow, and the pressure protocol must be selected with reference to the failed human trials. The evidence does not support the use of HBOT as a salvage intervention for chronic neurological deficits. Reviews of traumatic brain injury treatment note marginal benefit with prolonged treatment courses, a finding that should temper expectations for veterinary patients with chronic post-traumatic encephalopathy.

Retinal Oxygen Environment and Photoreceptor Survival

The retina presents a unique therapeutic target because its oxygen environment can be modulated systemically. In animal models of photoreceptor degeneration, manipulation of environmental oxygen levels alters the rate of cell loss. The balance between retinal oxygen supply and consumption is critical for homeostasis, and disruption of this balance contributes to disease progression in inherited retinal degenerations.

Hyperbaric oxygen has been used clinically in human patients with retinitis pigmentosa, and the rationale for this application rests on the observation that photoreceptor degeneration may be accelerated by local hypoxia. The evidence is preliminary, and the optimal oxygen dose and treatment duration remain undefined. For veterinary patients with suspected inherited retinal disease, HBOT should be regarded as experimental, with outcomes that are unpredictable and potentially dependent on the specific genetic mutation involved.

Patient Selection and Pretreatment Assessment

Candidate selection begins with a complete physical examination, baseline blood work, and imaging appropriate to the presenting condition. Thoracic radiographs or point-of-care ultrasound are advisable before chamber exposure because pulmonary pathology alters both the risk of barotrauma and the efficiency of oxygen delivery. Patients with pneumothorax, bullous emphysema, or untreated thoracic trauma should be excluded until those conditions are resolved, as gas trapping expands during compression and decompression.

Cardiovascular status requires particular attention. Patients with congestive heart failure may not tolerate the increased systemic vascular resistance that accompanies hyperbaric exposure. Conversely, the vasoconstrictive effects of hyperbaric oxygen can be therapeutically useful in reducing edema, but this same mechanism can compromise perfusion in patients with marginal cardiac output. Assess hydration status and perfusion parameters before treatment, and correct hypovolemia prior to chamber entry. The RECOVER veterinary CPR guidelines provide relevant context for hemodynamic assessment in critically ill patients, though they do not address hyperbaric therapy directly.

Auricular barotrauma is the most common complication in veterinary patients. Examine both tympanic membranes and the external ear canals before each session. Patients with otitis externa, stenotic canals, or ruptured tympanic membranes require myringotomy or tympanostomy tubes before treatment. The same consideration applies to patients with sinusitis or nasal masses, where pressure equilibration may fail.

Pregnancy is a relative contraindication in veterinary patients, as in human medicine, though data in companion animals are sparse. The MSD Veterinary Manual notes that the physiologic changes of pregnancy complicate anesthetic and oxygen management across species, and this caution extends to hyperbaric exposure.

Monitoring During Treatment

Continuous visual monitoring through chamber viewports is mandatory. Sedation requirements vary by species and temperament, but the goal is a calm, nonstruggling patient. Struggling increases oxygen consumption and carbon dioxide production, which can precipitate respiratory acidosis inside the chamber.

Physiologic monitoring during treatment typically includes heart rate, respiratory rate, and mucous membrane color. Pulse oximetry readings are unreliable during hyperbaric exposure because the elevated partial pressure of oxygen saturates hemoglobin regardless of true tissue oxygenation, and the sensor itself may be affected by pressure. Capnography, where available, provides more useful information about ventilation, particularly in sedated patients.

Blood pressure monitoring is valuable in patients with cardiovascular disease, as the vasoconstrictive response to hyperoxia can raise afterload. Temperature should be monitored in prolonged sessions, as chamber temperature rises with compression and patients may become hyperthermic.

Document each session with a standardized record that includes chamber pressure, duration, fraction of inspired oxygen, patient positioning, sedation drugs and doses, physiologic parameters at five-minute intervals, and any adverse events. Serial photographs of wounds before, during, and after the treatment course provide objective documentation of progress.

Evidence Levels by Condition

The veterinary evidence base for hyperbaric oxygen therapy is largely extrapolated from human medicine and experimental animal models. The table below summarizes the current evidence level for common veterinary applications.

The distinction between evidence levels matters clinically. Conditions with moderate to high evidence support a primary therapeutic role. Conditions with low evidence may still warrant a trial of therapy when conventional options are exhausted, but the owner should understand the uncertainty. Thom's review of hyperbaric oxygen mechanisms and efficacy provides the mechanistic framework for these applications, while Grim and colleagues' earlier review outlines the indications considered appropriate and the controversy surrounding them.

Contraindications and Complication Management

Absolute contraindications include untreated pneumothorax, current treatment with bleomycin or cisplatin, and concurrent doxorubicin therapy, as these agents potentiate oxygen toxicity. Patients with a history of seizures require careful risk assessment, as central nervous system oxygen toxicity can trigger convulsions at pressure.

Relative contraindications include:

• Chronic obstructive pulmonary disease with air trapping
• Uncontrolled hyperthermia
• Recent thoracic or ophthalmic surgery
• Severe anemia, which limits oxygen-carrying capacity
• Active upper respiratory infection with impaired pressure equilibration
• Cardiac pacemakers, which may malfunction under pressure

Complications fall into three categories. Barotrauma affects the ears, sinuses, and lungs. Middle ear effusion and tympanic membrane rupture are the most frequent events. Pulmonary barotrauma is rare but potentially fatal, and it is prevented by excluding patients with bullous disease and by controlling the rate of pressure change.

Oxygen toxicity manifests as pulmonary and neurologic forms. Pulmonary toxicity presents with coughing, dyspnea, and reduced lung compliance after prolonged exposure. Neurologic toxicity presents as twitching, nausea, and generalized seizures. Both are managed by terminating the session, decompressing to ambient pressure, and providing supportive care. Seizures typically resolve without anticonvulsant therapy once the patient is removed from hyperbaric conditions.

Claustrophobia and anxiety are common in veterinary patients and may require sedation. The AAHA/AAFP fluid therapy guidelines remind practitioners that fluid shifts occur with pressure changes, and hydration status should be reassessed between sessions.

Species and Setting Considerations

Small animal practice dominates veterinary hyperbaric medicine, and most published experience involves dogs and cats. Exotic species, birds, and reptiles present additional challenges. Birds have air sacs that communicate with the respiratory system and may not equilibrate pressure effectively. Reptiles have variable metabolic rates and may not tolerate the oxygen-rich environment. No species-specific safety data exist for these patients, and treatment should proceed cautiously, if at all.

Production animals are rarely treated with hyperbaric oxygen because of chamber size limitations and cost. The WOAH terrestrial animal health standards address oxygen therapy only in the context of transport and welfare, not as a therapeutic modality.

Equipment availability determines practice patterns. Single-patient chambers are suitable for small animals but cannot accommodate large breeds. Multiplace chambers allow attendant access but require more staff and infrastructure. The AVMA practice resources provide guidance on facility planning and safety standards for veterinary procedures generally, though specific hyperbaric chamber regulations vary by region and should be verified locally.

The hyperoxia paradox described in the physiological basis section has direct clinical implications. Brief, intermittent hyperbaric exposure appears to precondition tissues and reduce subsequent injury, while prolonged continuous exposure produces toxicity. This supports the clinical practice of short sessions repeated over days instead of single prolonged exposures. The systematic review of arterial hyperoxia in critical illness reinforces this concern, showing that excessive oxygenation in critically ill patients is associated with worse outcomes across multiple diagnostic categories.

Recognized Complications and Early Detection

The principal complications of hyperbaric oxygen therapy fall into three categories: pressure-related barotrauma, oxygen toxicity, and cardiovascular or pulmonary decompensation during compression. Barotrauma affects gas-filled spaces, most commonly the middle ear, tympanic cavity, and paranasal sinuses. In veterinary patients, the inability to equalise pressure through voluntary swallowing or yawning makes middle ear barotrauma the most frequent adverse event. Early detection relies on observing distress during the compression phase, head shaking, pawing at the ears, or vocalisation. In dogs and cats under sedation or anesthesia, otoscopic examination before treatment identifies patients with pre-existing otitis, stenosis, or masses that impair pressure equalisation.

Pulmonary barotrauma, including pneumothorax and pneumomediastinum, occurs when gas trapping develops during decompression. Patients with bullous emphysema, pre-existing pneumothorax, or recent thoracic surgery carry the highest risk. Detection during treatment relies on continuous monitoring of respiratory rate, end-tidal carbon dioxide, and thoracic auscultation where feasible. After treatment, persistent tachypnoea, reduced lung sounds, or subcutaneous emphysema should prompt immediate thoracic imaging.

Oxygen toxicity manifests in two forms. Central nervous system toxicity presents as twitching, tremors, or seizures, typically at pressures above 2.5 atm absolute. Pulmonary oxygen toxicity develops more insidiously with prolonged exposure and presents as progressive dyspnoea, cough, and reduced compliance. The risk of both forms increases with treatment pressure and duration, and the underlying mechanisms involve reactive oxygen and nitrogen species generated during hyperbaric exposure Thom 2011, hyperbaric oxygen mechanisms and efficacy. Early detection requires vigilance for subtle behavioral change, particularly in patients that cannot report subjective symptoms. Capnography and pulse oximetry remain useful, although pulse oximetry cannot distinguish hyperoxia from normoxia once saturation exceeds 100%.

Common Errors and Corrective Actions

Less experienced clinicians frequently misjudge the interaction between hyperbaric oxygen therapy and concurrent critical illness. The association between arterial hyperoxia and worsened outcomes in some subsets of critically ill adults, particularly after cardiac arrest and traumatic brain injury, argues against reflexive oxygen administration in all patients systematic review of arterial hyperoxia in critical illness. The corrective action is to establish a clear treatment target, document baseline oxygenation, and avoid treating patients whose primary problem is not oxygen-responsive.

A second recurring error involves undertreating the underlying condition while focusing on the chamber. Hyperbaric oxygen does not replace surgical debridement, antimicrobial therapy, or definitive wound management. The evidence supporting its use in compromised flaps and grafts derives from animal studies and a limited number of clinical trials, and patient selection criteria remain imperfect Thom 2011, hyperbaric oxygen mechanisms and efficacy. The corrective action is to treat hyperbaric oxygen as an adjunct, not a substitute, and to maintain conventional standards of care throughout the treatment course.

A third error concerns the timing of therapy. In neurological applications, delayed treatment substantially reduces the likelihood of benefit. Clinical trials of hyperbaric oxygen in human ischemic stroke failed to show efficacy, with delayed time to therapy and excessive chamber pressures identified as probable contributors Singhal 2007, oxygen therapy in ischemic stroke. The corrective action is to define a therapeutic window before initiating treatment and to avoid offering hyperbaric oxygen when that window has closed.

Limitations of the Current Evidence

The veterinary evidence base for hyperbaric oxygen therapy remains largely extrapolated from human medicine and experimental animal models. Randomised controlled trials in clinical veterinary patients are scarce, and most published experience consists of case series and retrospective reports. The mechanisms of action, particularly the role of reactive species in cell signal transduction, are increasingly well characterized, but the translation of these mechanisms to clinical benefit in specific veterinary conditions remains uncertain Grim et al 1990, hyperbaric oxygen therapy review.

Expert opinion still differs on several points. The optimal pressure and duration for different conditions are not established, and protocols vary substantially between institutions. Whether hyperbaric oxygen provides meaningful benefit in chronic conditions such as degenerative myelopathy or cognitive dysfunction is contested, with available literature suggesting at most marginal benefit after prolonged treatment courses Morries et al 2015, treatments for traumatic brain injury. The role of hyperbaric oxygen in retinal disease is similarly unresolved, although manipulation of the retinal oxygen environment can modulate photoreceptor degeneration in animal models Yu and Cringle 2005, retinal degeneration and local oxygen metabolism.

Referral, Consultation, and Escalation

Referral to a facility with hyperbaric capability is appropriate when the suspected benefit outweighs the risks of transport and delayed definitive care. Patients with progressive wound necrosis, compromised grafts, or gas gangrene may warrant referral, provided they are stable for transfer. Specialist consultation with a veterinary anesthetist or criticalist is advisable before treating patients with cardiac disease, seizure disorders, or severe pulmonary pathology, because these conditions modify both the risk profile and the monitoring requirements.

Laboratory involvement is indicated when baseline assessment reveals anemia, coagulopathy, or electrolyte derangements that could influence oxygen carriage or seizure threshold. Serial hematology and biochemistry may be warranted during prolonged treatment courses, although no universal monitoring schedule exists. Regulatory reporting obligations vary by jurisdiction, and practitioners should consult their local veterinary board or professional body for guidance on adverse event reporting. The AVMA practice resources and MSD Veterinary Manual provide additional context on professional standards and species-specific considerations.

Frequently Asked Questions

How should I triage a patient for HBOT when chamber access is limited or delayed?

Prioritize conditions with the strongest evidence for time-sensitive benefit, particularly compromised flaps or grafts and ischemia-reperfusion injuries, where animal studies support early intervention. Wound healing indications such as refractory diabetic ulcers can tolerate longer delays while stabilization proceeds. If the chamber is unavailable, optimize conventional care: surgical debridement, infection control, and careful fluid therapy guided by current consensus recommendations such as the AAHA/AAFP fluid therapy guidelines. Document the clinical rationale for deferral and revisit the decision if the patient deteriorates. Avoid using normobaric oxygen as a substitute, since its mechanisms and tissue effects differ substantially from hyperbaric delivery.

What documentation is advisable when administering HBOT in practice?

Record the indication, pretreatment assessment findings, chamber pressure and duration, number of sessions, and any adverse events observed during or after each treatment. Note the patient's oxygenation status and ventilatory parameters where relevant, since hyperoxia carries recognized risks in critically ill patients, as summarized in systematic reviews of arterial hyperoxia and outcomes in critical illness. Document client consent, including discussion of expected benefits and potential complications. Maintain a treatment log that permits retrospective review of outcomes and complications. This record supports both clinical decision-making and any future referral discussions.

How do I explain HBOT to an owner who expects a guaranteed cure?

Frame HBOT as an adjunctive therapy with condition-specific evidence, not a universal remedy. Explain that clinical and mechanistic data support its use for selected disorders, but that responses vary and some conditions lack robust clinical trials. Describe the physiological rationale in accessible terms: increased dissolved oxygen delivery to hypoxic tissues and modulation of cellular signaling pathways. Be explicit about the number of sessions planned, the monitoring involved, and the possibility of complications such as barotrauma or oxygen toxicity. Provide written information and invite questions. If the owner asks about cost, direct them to the practice's administrative team instead of making promises about outcomes.

When is HBOT inappropriate in a small animal patient despite a potential indication?

Exclude patients with uncontrolled pneumothorax, recent thoracic surgery, or known bullous lung disease, since pressure changes risk gas trapping and rupture. Severe respiratory compromise, uncontrolled seizures, and certain otologic conditions also warrant caution. Review the patient's full medication list, as some drugs lower seizure threshold. For pregnant patients, weigh potential fetal effects against maternal benefit. The MSD Veterinary Manual provides species-specific guidance on contraindications relevant to common companion animal comorbidities. When uncertainty remains, consult a colleague experienced in veterinary hyperbaric medicine before proceeding.

Does HBOT have a role in food animal or equine practice?

Evidence is largely extrapolated from small animal and human medicine, so exercise caution. In horses, HBOT has been used for wound healing and musculoskeletal conditions, but peer-reviewed veterinary data are limited. For food animals, practical constraints include chamber size, anesthesia requirements, withdrawal considerations, and cost relative to animal value. Production animal practitioners should consult regional veterinary standards and trade-related guidance, such as the WOAH terrestrial animal health standards, when considering advanced therapies. In all cases, document the evidence basis for the decision and prioritize conventional, proven treatments first.

How should I respond when a colleague dismisses HBOT as unproven?

Acknowledge that controversy has surrounded hyperbaric oxygen throughout its history, and that evidence quality varies by condition. Point to the clarified mechanisms of action involving reactive oxygen and nitrogen species in cell signaling, and to systematic reviews supporting specific indications such as refractory wound healing and radiation injuries. Concede that some applications rest on animal studies or small trials, and that patient selection criteria continue to evolve. Offer to review the relevant literature together and suggest a case-based discussion. This approach maintains professional collegiality while grounding the conversation in the current evidence base.

Related Clinical & Scientific Guides

• Toxicology in Emergency Practice: Common Poisons and Diagnostic Approach
• Veterinary Cardiopulmonary Resuscitation: Post-Cardiac Arrest Care
• Fluid Therapy Guidelines for Dogs and Cats: A Practical Update

References and Further Reading

• Hyperbaric oxygen therapy.. 1990.
• Hyperbaric oxygen: its mechanisms and efficacy.. 2011.
• A review of oxygen therapy in ischemic stroke.. 2007.
• Retinal degeneration and local oxygen metabolism.. 2005.
• Association Between Arterial Hyperoxia and Outcome in Subsets of Critical Illness: A Systematic Review, Meta-Analysis, and Meta-Regression of Cohort Studies.. 2015.
• Treatments for traumatic brain injury with emphasis on transcranial near-infrared laser phototherapy.. 2015.
• RECOVER Initiative Veterinary CPR Guidelines. Veterinary Emergency and Critical Care Society.
• AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats. AAHA.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.

Related Articles

• Complications of Oxygen Therapy in Veterinary Patients
• Oxygen Therapy Delivery Methods in Veterinary Critical Care
• Veterinary Oxygen Therapy: Flow Rates and Delivery Devices
• Veterinary Fluid Therapy: Crystalloids vs Colloids
• Failure Modes in Mechanical Ventilation of Veterinary Patients

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.