Pictured above is the highest hyperbaric chamber in the world at the Bolivian Naval Station at Lake Titicaca.

If you’ve ever climbed high enough to feel short of breath, dizzy, or just “off,” you’ve likely experienced the effects of high altitude on the human body. Once you get above about 2,500 meters (8,200 feet), the air gets “thinner”—not because oxygen disappears, but because there’s less pressure pushing oxygen into your body. This particular problem is termed hypobaric hypoxia, and it can turn a beautiful mountain adventure into a medical problem quickly.

Why Altitude Hits So Hard

At elevation, your body is forced to adapt fast—and sometimes it isn’t able to keep up. That’s when altitude illness can develop, ranging from mild to life-threatening ailments:

• Acute Mountain Sickness (AMS): headache, nausea, fatigue
• High-Altitude Pulmonary Edema (HAPE): fluid in the lungs, causing shortness of breath
• High-Altitude Cerebral Edema (HACE): brain swelling, confusion, and potentially coma

These aren’t separate diseases so much as a continuum of worsening hypoxia. Most severe cases can start as mild symptoms and can later progress to more severe presentations. The quicker you can recognize the more subtle symptoms, the better you may be in avoding severe illness. 

What’s Happening Inside the Body?

When oxygen levels drop, the body goes into survival mode:

• Blood vessels in the lungs constrict → raising pressure (risk of HAPE)
• Blood vessels in the brain become leaky → swelling (risk of HACE)
• Inflammatory and hormonal systems ramp up → causing AMS symptoms

In short: your body is trying to compensate in response to the change in environment, but sometimes those compensations backfire.

Enter Hyperbaric Oxygen Therapy (HBOT)…

Now imagine flipping the script. Instead of struggling in thin air, what if you could flood your body with oxygen under pressure? That’s exactly what Hyperbaric Oxygen Therapy (HBOT) does. Inside a pressurized chamber, you breathe 100% oxygen, dramatically increasing how much oxygen dissolves into your blood. In a way you have artificially placed yourself in a lower altitude. 

How HBOT Helps at Altitude

HBOT essentially acts like a “simulated descent”—one of the most important treatments for altitude illness.

It can:

• Boost oxygen levels in your blood and tissues
• Improve brain function in hypoxic states
• Reduce inflammation and oxidative stress
• Potentially stabilize the blood–brain barrier

In wilderness medicine and EMS settings, portable hyperbaric chambers are already used when immediate descent isn’t possible. They can be lifesaving.

But there’s a catch: The benefits are temporary. Once the pressure is removed, symptoms can return if the person is still at altitude where their symptoms first started.

A New Idea: Can HBOT Be Used Before You Climb?

Here’s where things get interesting. Researchers are now exploring whether HBOT could be used not just as treatment—but as preparation.

The concept: preconditioning

The idea is that repeated exposure to hyperbaric oxygen before ascent might “train” the body to handle low-oxygen environments better—similar to acclimatization.

Potential effects include:

• Activation of hypoxia-response pathways (like HIF)
• Improved mitochondrial efficiency (better energy use)
• Increased antioxidant defenses
• Enhanced microcirculation

In theory, this could mean: fewer symptoms, better performance, and lower risk of severe altitude illness

What Does the Evidence Say?

Early research is promising, but not definitive.

Some studies suggest:

• Reduced incidence and severity of AMS
• Better oxygen saturation at altitude
• Possible protection against brain and lung edema

But there are still big unknowns:

• What pressure and duration work best?
• How long before ascent should HBOT be done?
• Who benefits most—athletes, mountaineers, or everyone?

For now, HBOT preconditioning is an exciting idea—not standard practice.

What About Athletes and High Performers?

Altitude is a major challenge for:

• Endurance athletes
• Military personnel
• Search and rescue teams
• Mountaineers

Performance drops quickly due to:

• Lower VO₂ max
• Faster fatigue
• Impaired decision-making

HBOT might help by:

• Improving oxygen efficiency
• Preserving cognitive function
• Delaying fatigue

But again—this is still being studied, and access to HBOT can be limited and expensive.

How Does HBOT Compare to Proven Strategies?

Right now, the gold standard hasn’t changed:

• Gradual ascent → still the most effective prevention
• Acetazolamide → helps your body acclimate faster
• Dexamethasone → used in higher-risk situations

HBOT (for prevention) is still catching up in terms of evidence.

Is HBOT Risk-Free?

Not entirely. While generally safe, it can cause: ear or lung barotrauma (due to pressure-related injury), oxygen toxicity (rare but serious), and can lead to increased oxidative stress with overuse. These risks matter more when using HBOT proactively rather than as a rescue therapy.

Where This Is Headed

HBOT sits at a fascinating intersection of performance, medicine, and physiology.

Future research is looking to focus on finding optimal preconditioning protocols like treatment duration and number of set times. Some other areas also include identifying which patient populations would benefit most from this form of treatment and combining HBOT with other strategies like hypoxic training.

Bottom Line…

Hyperbaric oxygen therapy is already a powerful tool for treating severe altitude illness, especially when descent from altitude isn’t immediately possible.

As a preventive strategy, it shows real promise, but it’s not ready to replace the fundamentals.

For now, your best defense at altitude is still:

• Climb gradually
• Know the symptoms and have a buddy!
• Use proven medications when appropriate (like Acetazolamide)

HBOT may one day become part of the toolkit—but for now, it’s a high-potential frontier, not a first-line solution.

References 

Centers for Disease Control and Prevention. (2023). High-altitude travel and altitude illness. https://www.cdc.gov/travel/page/high-altitude-travel

National Center for Biotechnology Information. (2023). High-altitude illness. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK430716/

National Center for Biotechnology Information. (2023). Hyperbaric oxygen therapy. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK459172/

PubMed Central. (2020). Hyperbaric oxygen therapy: Mechanisms and clinical applications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMCPubMed Central. (2018). Pathophysiology, prevention, and treatment of high-altitude illness. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC

Wilderness Medical Society. (2019). Wilderness Medical Society clinical practice guidelines for the prevention and treatment of acute altitude illness. Wilderness & Environmental Medicine, 30(4), S3–S18. https://doi.org/10.1016/j.wem.2019.04.006

Hackett, Peter H., & Roach, Robert C.. (2001). High-altitude illness. New England Journal of Medicine, 345(2), 107–114. https://doi.org/10.1056/NEJM200107123450206

Bärtsch, Peter, & Swenson, Erik R.. (2013). Acute high-altitude illnesses. New England Journal of Medicine, 368(24), 2294–2302. https://doi.org/10.1056/NEJMra1214870

Moon, Richard E.. (2019). Hyperbaric oxygen therapy indications. Undersea & Hyperbaric Medicine, 46(3), 425–430.

Milledge, James S., West, John B., & Schoene, Robert B.. (2013). High altitude medicine and physiology (5th ed.). CRC Press.

Dylan Raulie was born and raised in Colorado Springs, Colorado and went out of state for his undergraduate years at Creighton University in Omaha, Nebraska, trading mountains for cornfields and altitude for attitude … from the wind. He got a Bachelor’s of Science in Emergency Medical Services majoring in sirens, stress, and 2 a.m. calls. After studying and learning about what could go wrong with future patients, he would often times avoid trying to become one on his interscholastic rugby team. He worked as a 911 paramedic in Colorado Springs. Between brutal call volumes, lack of sufficient ambulances on the streets, and extreme variety in patient presentations, no day was the same.  He later earned his Master’s in Biomedical Sciences at Rocky Vista University where he developed into being a better student and lifelong learner, which directly influenced his approach as a medical student. On his days off, he is a part-time grappler (in BJJ), but a full-time adventurer, always in motion—physically and mentally.