M. Martinez endured 18 months with long COVID before being directed to emergency medicine specialist Craig Lindsey’s hyperbaric center in Santa Fe, N.M. At 49, the court professional faced severe cognitive decline, leaving him unable to work full-time or drive, and fearing a potential move to a memory care facility.
Remarkably, after an eight-week course of hyperbaric oxygen therapy (HBOT)—a process of inhaling pure oxygen at high pressure in a specialized chamber—two-thirds of his neurocognitive test scores returned to normal, enabling him to work and drive again.
Such experiences are sparking increased interest in HBOT as a potential treatment for long COVID, a complex array of symptoms like brain fog and extreme fatigue affecting millions globally without a definitive cure.
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HBOT has shown its effectiveness in treating various conditions, including decompression sickness, carbon monoxide poisoning, and diabetic wounds. However, its efficacy as a treatment for long COVID remains uncertain.
Proposed Mechanisms
Several plausible biological explanations for the effects of hyperbaric therapy on long COVID have been suggested, though none are confirmed.
Some long COVID sufferers seem to have difficulty with oxygen extraction at the tissue level, possibly due to thickened capillary membranes. HBOT might counteract this by increasing the oxygen dissolved in the blood.
Long COVID is also associated with blood clotting, chronic inflammation, and dysfunctional mitochondria, the cellular powerhouses. Advocates of HBOT claim it operates by addressing blood vessel lining issues that lead to clotting, encouraging new blood vessel growth, reducing inflammatory cytokines, and enhancing mitochondrial function.
HBOT might also stimulate the release of growth factors like brain-derived neurotrophic factor, potentially aiding neuron repair in long COVID patients experiencing neuroinflammation.
A Mixed Evidence Base
The clinical evidence is both promising and inconsistent. A placebo-controlled phase 2 trial at Shamir Medical Center in Israel involving 73 long COVID patients reported lasting improvements in cognition, energy, and sleep. Participants attended daily sessions for 40 days over two months, and in a follow-up study, the benefits persisted for at least a year. However, a Swedish trial with 80 subjects found no placebo benefit; that study involved only 10 sessions across six weeks. “These treatments are really meant to be a Monday-through-Friday daily session,” notes Lindsey, who was not involved in these studies. “That’s where you get the benefit.”
Long COVID’s origins could span a wide range of underlying causes, from persistent viral presence to immune system dysregulation or vascular damage, with individuals potentially requiring “vastly different treatments,” according to David Putrino, a rehabilitation and human performance professor at Mount Sinai in New York City, also uninvolved in the trials. HBOT might be most suitable for long COVID patients with vascular dysfunction or neuroinflammation, but “more studies are needed to figure out which [type of patient] will have the most benefit at what dosage,” says Monica Verduzco-Gutierrez, who leads the multidisciplinary long COVID clinic at UT Health San Antonio.
While controlled trials suggest the therapy is generally safe, “it should not be considered risk‑free,” warns Mark Faghy, a clinical exercise physiology professor at Loughborough University, England. A study in the Netherlands on long COVID patients showed that although 56 to 63 percent experienced significant quality-of-life improvements following HBOT, 13 to 19 percent reported declines in mental or physical health.
Individuals with postexertional malaise, a condition where symptoms worsen after minimal exertion, might face higher risks from the therapy, Faghy and Putrino emphasize. The treatment involves being in a high-pressure chamber for 90 minutes daily, breathing against the pressure. “If your patients are not carefully selected, you can cause more harm than good by exerting them to that degree,” Putrino explains.
HBOT can also cause tissue damage due to pressure differences and poses a fire risk, particularly outside of a clinical setting. Hyperbaric chambers in unregulated “medical spas” often operate at ineffective low pressures and are staffed by individuals who “are not certified, and that makes it dangerous as well as ineffective,” Lindsey cautions.
Barriers to Access
Neither the U.S. Food and Drug Administration nor the Undersea and Hyperbaric Medical Society (UHMS), which accredits hyperbaric oxygen facilities, currently endorse HBOT for long COVID. However, the American Academy of Physical Medicine and Rehabilitation lists it as an emerging therapy.
HBOT faces significant challenges for widespread adoption. Lindell Weaver, a hyperbaric medicine specialist who has conducted phase 2 trials on traumatic brain injury, suggests U.S. insurers and Medicare are unlikely to cover HBOT for long COVID and brain injury without large, FDA-regulated phase 3 trials. Currently, no such trials are being funded.
Without insurance coverage, HBOT remains financially inaccessible for many. Hospitals charge approximately $5,000 per session, with a complete 40-session course costing $200,000. “This creates significant equity concerns, as access is largely limited to people who can afford to self-fund treatment,” Faghy notes.
There are practical obstacles as well. “These are big devices that take up a lot of space,” Putrino comments. In the U.S., there are only about 1,000 hospital-based hyperbaric facilities, insufficient to meet the needs of the millions with long COVID, Lindsey observes.
Sandra Wainwright, a hyperbaric physician with Yale New Haven Health System and incoming UHMS president, plans to create a committee to assess the evidence for the therapy’s new brain-related applications, including long COVID. She is hopeful UHMS may act before the FDA, but even with UHMS approval, insurance coverage may still be five to 10 years away, she anticipates.
For now, Verduzco-Gutierrez states, the therapy will likely remain an option only for those who can afford it.
