Every medical intervention carries risk. Hyperbaric oxygen therapy, despite its reputation as a non-invasive treatment with broad therapeutic potential, is no exception. A comprehensive review published in the second quarter of 2026 in the Undersea and Hyperbaric Medicine Journal by Dr. Marvin Heyboer and William Santiago provides the most current clinical accounting of HBOT’s adverse effects—quantifying their incidence, explaining their mechanisms, and underscoring why they remain manageable when proper protocols are followed.
The timing is significant. As HBOT expands beyond traditional hospital settings into outpatient clinics, wellness centers, and even home environments, understanding the therapy’s risk profile has never been more critical. The FDA’s August 2025 safety communication, which highlighted serious injuries and deaths associated with HBOT device misuse, makes this clinical review essential reading for practitioners and patients alike.
The Fundamental Mechanism: Benefit and Risk Share a Source
Hyperbaric oxygen therapy delivers 100% oxygen at pressures typically ranging from 2.0 to 2.4 atmospheres absolute (ATA). The therapeutic benefits emerge from two primary mechanisms: hyperoxia (elevated oxygen levels in plasma and tissues) and hyperbaric pressure itself. These same mechanisms, however, generate the therapy’s principal risks.
The increased pressure can cause barotrauma—physical injury to gas-containing spaces in the body as they compress or expand. The elevated oxygen exposure can trigger oxygen toxicity—a spectrum of dose-dependent toxic effects on the lungs, central nervous system, and other tissues. Understanding that benefits and risks stem from identical physiological principles helps clinicians optimize treatment protocols: sufficient pressure and oxygen to achieve therapeutic goals, but not more than necessary.
Barotrauma: Pressure’s Physical Toll
The human body contains gas-filled spaces—middle ears, sinuses, lungs, and teeth with trapped air—that respond to pressure changes according to Boyle’s Law. As external pressure increases during chamber compression, these spaces must equalize or risk tissue damage.
Middle ear barotrauma represents the most common HBOT complication, occurring in approximately 5–10% of treated patients. The Eustachian tube, which normally equalizes pressure between the middle ear and nasopharynx, can fail to open adequately—particularly in patients with upper respiratory congestion, allergies, or anatomical variations. Symptoms range from mild fullness and discomfort to severe pain, hearing loss, and tympanic membrane perforation. Pre-treatment screening, patient education on equalization techniques, and temporary treatment pauses for decongestant administration reduce incidence significantly.
Sinus barotrauma follows similar mechanics, affecting the paranasal sinuses when ostial obstruction prevents pressure equalization. Patients with active sinusitis or recent upper respiratory infections face elevated risk. The frontal and maxillary sinuses are most commonly affected, producing facial pain, pressure, and occasionally epistaxis.
Pulmonary barotrauma, though rare, carries the greatest potential severity. If a patient holds their breath during decompression, expanding gas can cause alveolar rupture, leading to pneumothorax, pneumomediastinum, or arterial gas embolism. Modern protocols emphasize continuous breathing coaching, and the incidence of serious pulmonary barotrauma has fallen to less than 0.01% in accredited facilities.
Dental barotrauma affects teeth with trapped gas beneath fillings, crowns, or within necrotic pulp chambers. The condition, known as barodontalgia, produces sharp pain during compression or decompression and resolves when the underlying dental issue is addressed.
Oxygen Toxicity: When the Cure Becomes the Poison
Oxygen, essential for aerobic life, becomes toxic at elevated partial pressures. The 2026 UHMS review details three principal manifestations of oxygen toxicity in clinical HBOT practice.
Central nervous system oxygen toxicity presents the most dramatic risk. At oxygen partial pressures exceeding approximately 1.3 ATA (achieved at 2.0 ATA breathing 100% oxygen), susceptible individuals may experience seizures—typically tonic-clonic convulsions indistinguishable from epileptic seizures. The incidence in routine clinical practice ranges from 1 in 5,000 to 1 in 10,000 treatments. Importantly, CNS oxygen toxicity seizures are self-limiting: they resolve when oxygen delivery stops, and they produce no lasting neurological sequelae when managed properly. Risk factors include hyperthyroidism, certain medications (particularly penicillin and disulfiram), fever, and hypoglycemia.
Pulmonary oxygen toxicity develops with prolonged exposure to elevated oxygen partial pressures. Symptoms—substernal discomfort, cough, and dyspnea—typically require many hours of continuous exposure far exceeding standard HBOT protocols. The condition is essentially never seen in routine clinical HBOT, where treatment sessions last 60–120 minutes with air breaks that allow pulmonary recovery.
Ocular effects represent a unique category of oxygen toxicity relevant to HBOT. Myopic shift—temporary nearsightedness caused by oxygen-induced lens changes—can occur after extended treatment courses, particularly in protocols exceeding 20–30 sessions. The effect is fully reversible, typically resolving within weeks to months after treatment completion. Cataract progression has been reported with very prolonged exposure but remains rare in standard therapeutic protocols.
Other Documented Adverse Effects
The UHMS review catalogs additional, less common complications. Claustrophobia affects approximately 1–5% of patients, ranging from mild anxiety to panic attacks requiring treatment interruption. Modern chambers with improved visibility, communication systems, and patient coaching have reduced this incidence.
Oxygen-induced vasoconstriction, while contributing to therapeutic effects in certain conditions (such as reducing edema in compartment syndrome), can transiently reduce tissue perfusion. This effect is generally benign but requires consideration in patients with marginal cardiac output or peripheral vascular disease.
Reactive oxygen species-mediated effects include transient fatigue, headache, and malaise following treatment sessions. These symptoms, attributed to oxidative stress and inflammatory responses, typically resolve within hours and may actually indicate that the therapy’s intended biological mechanisms are active.
Fire risk, though not a physiological side effect, represents the most serious safety concern in hyperbaric medicine. The 2025 FDA safety communication specifically addressed this risk, noting reports of serious injuries and deaths from chamber fires. Pure oxygen environments, combined with ignition sources and combustible materials, create inherently hazardous conditions. Accredited facilities follow strict protocols: cotton-only clothing, prohibition of static-generating materials, grounded equipment, and continuous fire suppression systems.
The Safety Record: Context Matters
When properly administered in accredited facilities, HBOT maintains an excellent safety profile. The UHMS review emphasizes that serious adverse events are rare—occurring in less than 0.1% of treatments—while minor, self-limited complications (primarily ear barotrauma) affect fewer than 10% of patients.
This safety record, however, depends critically on proper patient selection, appropriate protocols, and qualified personnel. The FDA’s 2025 warning highlighted that adverse events often occur when devices are used outside established guidelines, when staff lack proper training, or when safety protocols are compromised.
The contrast between hospital-based hyperbaric medicine departments and the expanding wellness clinic market illustrates this point. UHMS-accredited facilities undergo rigorous evaluation of equipment, protocols, and personnel. The same cannot be said for all commercial operations offering HBOT for anti-aging, cognitive enhancement, or general wellness—applications for which the FDA has not cleared the therapy.
Risk Mitigation: Evidence-Based Protocols
The 2026 review outlines established strategies for minimizing HBOT complications. Pre-treatment screening identifies contraindications (untreated pneumothorax, certain chemotherapy agents, uncontrolled fever) and risk factors (sinus congestion, Eustachian tube dysfunction, claustrophobia history). Patient education ensures proper equalization techniques and breathing patterns. Treatment protocols incorporate air breaks that reduce CNS oxygen toxicity risk without compromising therapeutic efficacy.
For patients with recurrent ear barotrauma, interventions range from topical nasal decongestants to temporary tympanostomy tubes that bypass the Eustachian tube entirely. For those with claustrophobia, pre-treatment anxiolytics, relaxation techniques, or selection of larger multiplace chambers may enable successful therapy completion.
The Regulatory Context: FDA’s Watchful Eye
The FDA’s August 2025 safety communication serves as both warning and guidance. The agency reminded healthcare providers that HBOT devices are Class II medical devices requiring 510(k) clearance, and that manufacturer instructions for use must be followed precisely. Specific recommendations included ensuring fire prevention measures, proper grounding equipment, staff training, continuous patient monitoring, and use of hyperbaric-compatible materials.
The communication also highlighted that the FDA “is aware of recent reports of fires that occurred with HBOT devices that resulted in serious injuries and deaths.” While the root causes remain under investigation, the agency emphasized that serious adverse events, though rare, can and do occur—underscoring the importance of vigilant safety practices.
For consumers, the FDA maintains clear guidance: HBOT is cleared for specific medical indications including decompression sickness, carbon monoxide poisoning, certain non-healing wounds, and late radiation tissue injury. Uses for autism, Alzheimer’s disease, cancer, cerebral palsy, multiple sclerosis, and general wellness are not FDA-cleared, and the agency explicitly warns against using HBOT for these purposes.
Conclusion: Informed Risk Assessment
The 2026 UHMS review provides clinicians and patients with a clear-eyed assessment of HBOT’s adverse effect profile. The therapy is not risk-free—barotrauma, oxygen toxicity, and fire hazards are real concerns requiring respect and preparation. Yet when administered in accredited facilities by trained personnel following established protocols, serious complications are rare, and most adverse effects are minor and self-limited.
As hyperbaric medicine continues expanding into new clinical areas and commercial markets, this risk-benefit calculus becomes increasingly important. The evidence supports HBOT’s use for established indications where benefits demonstrably outweigh risks. For unproven applications, particularly in non-medical settings, the same risk profile may be harder to justify—especially when the FDA has explicitly declined to clear such uses.
Patients considering HBOT should seek treatment at UHMS-accredited facilities, ensure their condition represents an established indication, and discuss potential side effects with qualified hyperbaric physicians. The therapy’s benefits are substantial for appropriate candidates—but only when the risks are properly understood and managed.