A Clinical Guide to Patient Selection, Pressure-Related Injury, Oxygen Toxicity, Medication Considerations, and Risk Reduction
Hyperbaric oxygen therapy is generally well tolerated when it is prescribed appropriately and delivered by trained personnel in a medically supervised setting. Most adverse effects are mild, temporary, and manageable. However, HBOT exposes the body to increased ambient pressure and elevated oxygen partial pressure, creating risks that require careful screening and monitoring.
A contraindication does not always mean that treatment can never be performed. In many cases, it identifies a condition that must be stabilized, investigated, or managed before the patient enters the chamber. The decision should consider the urgency of the indication, the expected clinical benefit, the available chamber system, and the facility’s ability to manage the patient safely.
The Absolute Contraindication to Hyperbaric Oxygen Therapy
An untreated pneumothorax is generally recognized as the primary absolute contraindication to HBOT.
A pneumothorax occurs when gas enters the pleural space between the lung and chest wall. During decompression, trapped pleural gas can expand as ambient pressure falls. If the gas cannot escape, it may compress the affected lung, shift mediastinal structures, impair venous return, and develop into a life-threatening tension pneumothorax.
A patient with a known pneumothorax generally requires appropriate chest drainage before hyperbaric exposure. In an emergency where HBOT is urgently indicated, such as severe arterial gas embolism or carbon monoxide poisoning, the clinical team must address the pneumothorax while coordinating treatment with specialists experienced in critical care and hyperbaric medicine. (NCBI)
A remote history of pneumothorax is not automatically an absolute contraindication. It does warrant evaluation of the underlying cause, recurrence risk, previous treatment, current pulmonary status, and available imaging.
Relative Contraindications Require Individual Assessment
Most other HBOT contraindications are relative rather than absolute. A relative contraindication means that treatment may carry an increased risk, but the risk may be reduced through additional testing, treatment modification, consultation, or closer monitoring.
Common relative contraindications and precautions include:
- Pulmonary blebs, bullae, or significant air trapping
- Chronic obstructive pulmonary disease with carbon dioxide retention
- Active upper respiratory or sinus infection
- Inability to equalize middle-ear pressure
- Uncontrolled fever
- Poorly controlled seizure disorder
- Severe claustrophobia or confinement anxiety
- Unstable cardiovascular disease
- Decompensated heart failure
- Uncontrolled blood glucose
- Pregnancy, depending on the indication
- Certain current or previous medications
- Implanted medical devices without a verified pressure rating
These conditions should not be treated as a universal list of automatic exclusions. Their importance depends on the individual patient and the reason HBOT is being considered.
For example, pregnancy may lead clinicians to avoid elective or nonurgent HBOT when maternal and fetal benefit is uncertain. In severe carbon monoxide poisoning, however, hyperbaric treatment may be considered because carbon monoxide presents a significant risk to both the pregnant patient and fetus. (NCBI)
Middle-Ear Barotrauma
Middle-ear barotrauma is the most frequently reported adverse effect of HBOT. It occurs when pressure in the middle ear does not equalize with the rising chamber pressure during compression. (PubMed Central (PMC))
Patients may experience:
- Ear fullness or pressure
- Increasing ear pain
- Reduced hearing
- Tinnitus
- Dizziness
- Fluid or bleeding behind the tympanic membrane
- Tympanic membrane injury in more severe cases
The risk is greater in patients with eustachian tube dysfunction, congestion, previous ear surgery, radiation-related tissue changes, altered mental status, or an inability to understand and perform equalization techniques.
Before treatment, patients should be taught how to equalize pressure by swallowing, yawning, moving the jaw, or performing an appropriate pressure-equalization maneuver. Compression should be slowed or paused when discomfort develops. Continuing compression through significant pain increases the likelihood of injury.
Patients who repeatedly cannot equalize may require evaluation by an otolaryngologist. Tympanostomy tubes may be considered when a prolonged HBOT course is necessary and conservative strategies are unsuccessful.
Children, sedated patients, intubated patients, and individuals with cognitive impairment may be unable to report symptoms promptly. These patients require a plan that accounts for their limited ability to participate in equalization.
Sinus and Dental Barotrauma
The paranasal sinuses are also vulnerable to pressure-related injury. Swelling, infection, polyps, mucosal inflammation, or structural obstruction can prevent gas from moving freely between a sinus cavity and the surrounding environment.
Sinus barotrauma may cause facial pressure, localized pain, headache, dental discomfort, or nasal bleeding. Symptoms often occur during compression, but reverse-block symptoms can develop during decompression if gas becomes trapped within a sinus.
Patients should report new congestion or respiratory illness before each treatment. Delaying a nonurgent session may be safer than attempting treatment when pressure equalization is likely to be impaired.
Dental barotrauma is less common. It may occur when gas becomes trapped beneath a restoration, within a damaged tooth, or near recent dental work. Significant unexplained dental pain should be evaluated rather than attributed automatically to normal chamber pressure.
Pulmonary Barotrauma and Air Trapping
Pulmonary barotrauma is rare during routine clinical HBOT, but it can be serious. The greatest concern occurs when gas becomes trapped in a region of the lung and expands during decompression.
Potential complications include:
- Pneumothorax
- Pneumomediastinum
- Subcutaneous emphysema
- Pulmonary tissue injury
- Arterial gas embolism
Patients with severe obstructive lung disease, active bronchospasm, bullous lung disease, pulmonary cysts, previous spontaneous pneumothorax, or recent thoracic surgery may require pulmonary assessment and imaging before treatment.
Mechanical ventilation adds further complexity. Ventilator settings, endotracheal tube cuffs, airway pressures, breathing circuits, and device performance can be affected by changes in ambient pressure. Critically ill patients should be treated only in facilities equipped and staffed for hyperbaric critical care.
Patients should never hold their breath during decompression. Conscious patients are generally instructed to breathe normally so expanding gas can leave the lungs.
Central Nervous System Oxygen Toxicity
Breathing oxygen at elevated partial pressure can produce central nervous system oxygen toxicity. The most recognized manifestation is a generalized tonic-clonic seizure.
Oxygen-induced seizures are uncommon during standard clinical treatments and are typically self-limited after oxygen exposure is discontinued. They remain important because a seizure inside a chamber creates risks related to patient positioning, airway protection, aspiration, and the controlled management of chamber pressure. (UHMS)
Possible warning symptoms may include:
- Facial or lip twitching
- Nausea
- Visual changes
- Auditory changes
- Dizziness
- Irritability or unusual behavior
- Tingling sensations
- Confusion
These symptoms are not always present before a seizure.
Factors that may increase susceptibility include fever, hypoglycemia, carbon dioxide retention, certain medications, stimulant use, withdrawal states, a history of seizures, acute brain injury, and prolonged or higher-pressure oxygen exposure.
A previous seizure disorder is not necessarily an absolute contraindication. Clinicians should assess seizure control, medication adherence, recent events, fever, metabolic abnormalities, and other factors that may lower the seizure threshold. Treatment pressure, oxygen duration, and air-break scheduling may be adjusted when clinically appropriate. (NCBI)
If a seizure occurs, staff typically discontinue oxygen exposure when possible, protect the patient from injury, maintain airway safety, and follow the facility’s emergency protocol. Immediate uncontrolled decompression is generally avoided because rapid pressure reduction can introduce additional risk.
Pulmonary Oxygen Toxicity
Pulmonary oxygen toxicity is associated with excessive cumulative oxygen exposure. It is more relevant during prolonged treatment tables, repeated high-dose exposures, or unusually intensive treatment schedules than during many routine outpatient protocols.
Symptoms may include:
- Dry cough
- Substernal discomfort
- Chest tightness
- Shortness of breath
- Airway irritation
- Reduced pulmonary function
Routine clinical HBOT protocols are designed to limit this risk through controlled pressure, defined oxygen-breathing periods, air breaks when indicated, and limits on treatment duration. Pulmonary symptoms should still be evaluated, particularly in patients with underlying lung disease or previous exposure to pulmonary-toxic therapies. (PubMed Central (PMC))
Temporary Vision Changes and Ocular Risks
Repeated HBOT sessions can produce a temporary myopic shift. Patients may notice that distance vision becomes blurred while near vision remains stable or improves.
This change is believed to result primarily from oxygen-related alterations within the lens. It often develops gradually during a multiweek treatment course and commonly improves after treatment ends, although recovery may take several weeks or months. (UHMS)
Patients should be informed about this possibility before beginning a prolonged course. Purchasing new prescription lenses during treatment is often discouraged unless the visual change creates a significant functional or safety problem.
Cataract progression has also been reported, particularly with extensive cumulative oxygen exposure. Patients with significant preexisting ocular disease may require individualized assessment. The presence of an intraocular lens after cataract surgery does not create the same lens-related myopic response as a natural crystalline lens, but other ocular considerations may still apply.
New eye pain, visual field loss, flashes, floaters, or sudden major visual deterioration should not be assumed to be a routine HBOT effect. These symptoms require prompt ophthalmic evaluation.
Cardiovascular Risks and Heart Failure
Hyperbaric oxygen causes systemic vasoconstriction and can increase systemic vascular resistance. Heart rate and cardiac output may decrease during exposure. Many patients tolerate these changes without difficulty, but individuals with limited cardiac reserve require additional caution.
Patients with decompensated heart failure may be at increased risk of pulmonary congestion or pulmonary edema. HBOT may still be considered in selected patients after optimization of volume status, cardiac medications, and monitoring, particularly when the treatment indication is urgent or strongly supported.
The pre-treatment assessment should consider:
- Current dyspnea or orthopnea
- Recent weight gain or edema
- Left ventricular function
- Arrhythmias
- Blood pressure control
- Recent acute coronary syndrome
- Valvular disease
- Diuretic use
- Baseline oxygen and ventilation requirements
Chest pain, acute respiratory distress, new hypoxemia, or signs of pulmonary edema require immediate clinical assessment. Cardiovascular disease is not a single yes-or-no contraindication. Risk depends on stability, severity, treatment urgency, and the resources available within the hyperbaric facility.
Blood Glucose Changes During HBOT
Patients with diabetes may experience changes in blood glucose during the treatment period. Reduced food intake, insulin timing, oral medications, infection, treatment duration, and individual metabolic response can contribute to hypoglycemia.
Symptoms such as sweating, confusion, tremor, visual disturbance, or behavioral change may be difficult to distinguish from anxiety or oxygen-related neurologic symptoms inside the chamber.
Hyperbaric programs commonly establish protocols for:
- Pre-treatment glucose testing
- Meal and medication timing
- Minimum glucose thresholds
- Approved in-chamber glucose treatment
- Post-treatment reassessment
- Management of insulin pumps and continuous glucose monitors
A universal glucose cutoff is not appropriate for every patient. Decisions should account for the patient’s usual control, current trend, medication regimen, treatment length, chamber type, and ability to communicate symptoms. Blood glucose concerns should be addressed before compression whenever possible. (UHMS)
Medication and Chemotherapy Considerations
A complete medication history is essential before HBOT. The review should include current prescriptions, recently discontinued medications, chemotherapy history, over-the-counter products, supplements, substance use, and medication withdrawal.
Several medications have historically raised concern because of potential interactions with hyperoxia or pressure. Frequently discussed agents include:
- Doxorubicin
- Bleomycin
- Cisplatin
- Disulfiram
- Mafenide acetate
These medications should not be treated as a simple permanent exclusion list. The evidence, proposed mechanism, timing, dose, treatment indication, and patient condition differ for each agent.
Concurrent doxorubicin exposure has raised concern about enhanced cardiotoxicity. Previous bleomycin exposure requires assessment of pulmonary toxicity, cumulative dose, time since treatment, symptoms, and lung function. Cisplatin may raise concerns related to wound healing when HBOT is being used for a chronic wound. (PubMed)
In urgent situations, the risk of delaying HBOT may exceed the theoretical or known interaction risk. The decision should be made jointly by the hyperbaric physician and relevant specialists, such as oncology, pulmonology, cardiology, infectious disease, or clinical pharmacy.
Medication should not be stopped solely because a patient sees it on a general contraindication list. Unsupervised discontinuation can create greater harm than the potential interaction.
Claustrophobia, Anxiety, and Behavioral Considerations
Some patients experience significant anxiety in an enclosed chamber. Symptoms may include panic, rapid breathing, agitation, a sense of entrapment, or an urgent desire to end treatment.
Mild confinement anxiety can often be managed through education, chamber orientation, clear communication, visual contact, relaxation techniques, and gradual exposure. In some cases, medication may be considered after evaluating its effects on respiratory status, mental status, and seizure threshold.
Severe claustrophobia may prevent safe treatment if the patient cannot remain still, follow instructions, or communicate reliably. Chamber type can influence tolerance. A patient who cannot tolerate a monoplace chamber may feel more comfortable in a larger multiplace system, although the oxygen hood or mask used in a multiplace chamber can create a different form of confinement discomfort.
Anxiety should not be dismissed as a lack of cooperation. A patient who understands what will happen and trusts that the team will respond to distress is more likely to complete treatment safely.
Implanted and External Medical Devices
Pacemakers, implantable cardioverter-defibrillators, infusion pumps, neurostimulators, glucose-management devices, ventilators, and other medical equipment must be evaluated for use under pressure.
The exact manufacturer and model matter. A device approved for one pressure range may not be appropriate at another. Pressure can affect gas-filled components, seals, flow rates, alarms, battery performance, displays, and mechanical operation.
The facility should verify:
- The manufacturer’s pressure limit
- Compatibility with the prescribed treatment pressure
- Whether the device can remain active
- Whether programming changes are required
- Whether external equipment can remain outside the chamber
- The consequences of device failure
- The emergency plan if the device malfunctions
A device should not be cleared based solely on prior uneventful use in another patient. Evaluation and documentation must be specific to the device and treatment profile.
Fire and Chamber-Environment Risks
The oxygen-rich hyperbaric environment increases the ease and intensity of combustion. Oxygen is not itself flammable, but it supports rapid burning when fuel and an ignition source are present.
Potential hazards include unapproved electronics, batteries, synthetic clothing, petroleum-based products, hand warmers, lighters, aerosols, skin products, dressings, and medical equipment that has not been assessed for hyperbaric use.
In August 2025, the FDA emphasized proper grounding, fire prevention, staff training, equipment maintenance, and adherence to manufacturer instructions following reports of serious injuries and deaths involving HBOT devices. (U.S. Food and Drug Administration)
These environmental hazards are not patient contraindications in the traditional medical sense, but they can make treatment unsafe until the prohibited material is removed or replaced. Every item entering the chamber should be approved under the facility’s safety program.
Balancing HBOT Risks Against Clinical Benefit
HBOT risk assessment should be tied to the clinical indication. The acceptable level of risk may be different for an elective course treating delayed radiation injury than for an emergency involving arterial gas embolism, decompression sickness, or severe carbon monoxide poisoning.
A careful evaluation asks:
- Is HBOT supported for this diagnosis?
- How urgent is treatment?
- What is the expected benefit?
- Can the identified risks be corrected or reduced?
- Is additional imaging or specialist consultation needed?
- Does the patient require monoplace or multiplace capability?
- Can the facility provide the necessary monitoring?
- What are the risks of not treating?
Most HBOT complications can be reduced through appropriate patient selection, pressure-equalization coaching, controlled oxygen dosing, glucose management, medication review, equipment verification, and continuous observation.
The presence of a relative contraindication should prompt clinical reasoning, not automatic rejection. The goal is to determine whether HBOT can be delivered with a favorable risk-benefit balance and a safety plan tailored to the patient.
