Mechanisms of action and safety
Mechanisms of benefit for HBOT include increased oxygen availability and angiogenesis. Animal research suggests that it may reduce secondary cell death from TBI, through stabilization of the blood-brain barrier and inflammation reduction.
HBOT is generally safe and well tolerated. A retrospective analysis of 1.5 million outpatient hyperbaric treatments revealed that less than 1% were associated with adverse events. The most common were ear and sinus barotrauma. Because HBOT uses increased air pressure, patients must equalize their ears and sinuses. Those who cannot because of altered consciousness, anatomical defects, or congestion must undergo myringotomy or terminate therapy. Claustrophobia was the second most common adverse effect. Convulsions and tension pneumocephalus were rare.
Perhaps the most concerning risk of HBOT for patients with TBI is the potential waste of human and financial resources.
Desperate physicians and patients
As a neurologist who regularly treats patients with TBI, I share the review authors’ frustration regarding the limited efficacy of available treatments. However, the suboptimal efficacy of currently available therapy is insufficient justification to recommend HBOT.
With respect to chronic TBI, it is difficult to imagine how HBOT could reverse brain injury that has been present for months or years. No other therapy exists that reliably encourages neuronal regeneration or prevents the development of posttraumatic epilepsy.
Frank Conidi, MD, a board-certified sports neurologist and headache specialist, shared his thoughts via email. He agrees that HBOT may have a role in TBI, but after reviewing Hadanny and colleagues’ paper, he concluded that there is insufficient evidence for the use of HBOT in all forms of TBI. He would like to see large multicenter, well-designed studies with standardized pressures and duration and a standard definition of the various types of head injury.
Ongoing research
There are at least five ongoing trials on HBOT for TBI or postconcussive syndrome, including the well-designed placebo-controlled HOT-POCS study. The latter has a novel placebo gas system that addresses Hadanny and colleagues’ contention that even low-dose HBOT might be effective.
The placebo arm in HOT-POCS mimics the HBO environment but provides only 0.21 ATA of oxygen, the same as room air. The active arm provides 100% oxygen at 2.0 ATA. If patients in both arms improve, the benefit will be caused by a placebo response, not HBOT.
Conflict of interest
Another concern with the review is that all three authors are affiliated with Aviv Scientific. This company has an exclusive partnership with the world’s largest hyperbaric medicine and research facility, the Sagol Center at Shamir Medical Center in Be’er Ya’akov, Israel.
This conflict of interest does not a priori invalidate their conclusions. However, official HBOT guidelines from a leading organization like the Undersea and Hyperbaric Medicine Society or the American Academy of Neurology would be preferable.
Conclusion
There is an urgent unmet need for more effective treatments for postconcussive syndrome and chronic TBI.
The review authors’ recommendations for HBOT seem premature. They are arguably a disservice to the many desperate patients and their families who will be tempted to expend valuable resources of time and money for an appealing but unproven therapy. Appropriately designed placebo-controlled studies such as HOT-POCS will help separate fact from wishful thinking.
Dr. Wilner is associate professor of neurology at University of Tennessee Health Science Center, Memphis. He reported a conflict of interest with Accordant Health Services.
A version of this article first appeared on Medscape.com.