Are Seizures a Side Effect of Hyperbaric Oxygen Therapy?
Yes, seizures are a recognized but extremely rare side effect of hyperbaric oxygen therapy (HBOT), occurring due to central nervous system oxygen toxicity, with an incidence of approximately 1 in 8,000 to 1 in 60,000 treatments depending on treatment pressure and patient factors.
Incidence and Risk Profile
The overall risk of oxygen toxicity seizures during HBOT is very low when appropriate protocols are followed:
The most recent large-scale study found an overall seizure incidence of 0.011% (1:8,945 treatments), with only one clear oxygen toxicity-induced seizure out of 62,614 sessions (1:62,614). 1
Multiple guidelines acknowledge this risk but characterize it as minimal, with the American College of Emergency Physicians reporting seizure rates of 0% to 8% in older studies, but only 1 seizure in 1,037 CO poisoning patients treated with HBOT (0.10%) in more recent trials. 2
Another large retrospective analysis of 80,679 treatments documented only 2 seizures, yielding an incidence of 2.4 per 100,000 patient-treatments. 3
Pressure-Dependent Risk
The risk of seizures increases significantly with higher treatment pressures:
- At 2.0 atmospheres absolute (atm abs): 0 per 10,000 treatments 4
- At 2.4-2.5 atm abs: 15 per 10,000 treatments 4
- At 2.8 atm abs: 51 per 10,000 treatments 4
This pressure-dependent relationship is statistically significant (p < .001), meaning treatment protocols using higher pressures carry demonstrably increased seizure risk. 4
Patient-Specific Risk Factors
Certain medical conditions and medications may lower the seizure threshold and contribute to oxygen toxicity seizures:
- Hypercapnia secondary to chronic obstructive pulmonary disease 5
- Narcotic or alcohol withdrawal 5
- Use of antidepressants, tramadol, or cephalosporins/ceftriaxone 5
- Morbid obesity and obesity hypoventilation syndrome 6
- Uncontrolled epilepsy is the primary contraindication 1
Safety in Neurological Populations
Patients with chronic neurological disorders (traumatic brain injury, stroke) are NOT at increased risk for oxygen toxicity seizures compared to other patient populations, except for those with uncontrolled epilepsy. 1
This finding is clinically important because it confirms that HBOT can be considered safe for the growing population of patients with chronic neurological conditions. 1
Clinical Outcomes
While seizures during HBOT are typically self-limited and resolve without long-term consequences, rare fatal outcomes have been reported:
One case report documented sudden death after an oxygen toxicity seizure in a 37-year-old patient with morbid obesity, likely related to airway compromise and physiologic changes associated with extreme obesity. 6
The American Heart Association notes that hyperbaric oxygen therapy has a "low incidence of severe side effects" when used for carbon monoxide poisoning. 2
Practical Implications
Guidelines consistently characterize HBOT as "generally safe" despite the seizure risk:
The American Journal of Respiratory and Critical Care Medicine states that "HBO2 has been administered safely" across various patient populations. 2
The 2020 American Heart Association guidelines note that "hyperbaric oxygen therapy has a low incidence of side effects." 2
Multiple sources confirm that the most common complications are anxiety and middle ear barotrauma (0-8%), not seizures. 2, 7, 8, 9
Common Pitfalls to Avoid
Do not withhold HBOT from patients with chronic neurological disorders solely due to seizure concerns, as they are not at increased risk unless they have uncontrolled epilepsy. 1
Screen for medications that lower seizure threshold (antidepressants, tramadol, cephalosporins) and consider risk-benefit analysis. 5
Use the lowest effective treatment pressure to minimize seizure risk while achieving therapeutic goals. 4
Ensure appropriate airway management capabilities are immediately available, particularly in patients with morbid obesity or other conditions that may complicate emergency response. 6