Altitude sickness is the term for medical conditions that can happen when you move to a higher altitude too quickly. The higher up you go, the thinner the atmosphere gets. That means breathing in the same amount of air gets you less oxygen than at a lower altitude. Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen you’re getting with each breath.

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Types of this condition

Altitude sickness can refer to three distinct conditions:

• Acute mountain sickness (AMS). This is the mildest and most common form of altitude sickness that ​often feels like a bad hangover.

  • Symptoms: Headache (the hallmark), nausea, dizziness, fatigue, loss of appetite, and insomnia.

  • Onset: Usually within 2-12 hours of arriving at high altitude. 

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• High altitude pulmonary edema (HAPE). This is when altitude sickness affects your lungs, causing them to fill with fluid. It’s a medical emergency that needs immediate medical attention. While not the most severe form, it can cause death faster than other forms of altitude sickness.

  • Symptoms: Worsening shortness of breath (dyspnea), a dry cough that becomes productive (pink, frothy sputum), chest tightness, and fatigue, even at rest.

  • Action: Requires immediate descent and emergency medical care. ​

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• High altitude cerebral edema (HACE). This is the most severe form. It happens when altitude sickness causes your brain to swell. It’s a very dangerous condition that needs emergency care.

  • Symptoms: Severe headache, confusion, significant coordination problems (ataxia, difficulty walking), extreme lethargy, and altered mental status.

  • Action: Requires immediate descent and emergency medical care. 

 

How common is altitude sickness?

Altitude sickness is common among people who aren’t acclimated, meaning they’re not used to breathing at high altitudes. AMS is rare below 8,000 feet (2,438 meters) above sea level. Almost everyone who ascends quickly to 11,000 feet (3,352 meters) will develop AMS.

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Hyperbaric therapy, especially using portable pressure bags (like a Gamow bag), is a crucial, life-saving temporary treatment for severe altitude sickness (AMS, HACE, HAPE) when immediate descent isn't possible, by increasing oxygen pressure to simulate lower altitudes and relieve symptoms like headache, nausea, and fluid in the lungs/brain. While descent is key, hyperbaric oxygen (HBO) floods the body with oxygen, stabilizing patients until evacuation or acclimatization, and can even be used preventatively (preconditioning) to improve oxygenation and prevent illness, say experts at the Undersea & Hyperbaric Medical Society and Balanced Physical Therapy Telluride. 

How it works

• Simulates Descent: Portable bags create higher pressure (like 2 psi), which effectively lowers the "altitude" inside the bag, often by over 1,000 meters (thousands of feet), relieving hypoxia.

• Floods Body with Oxygen: Standard HBO delivers 100% oxygen, overwhelming the body with oxygen, counteracting low-pressure hypoxia, and reducing tissue damage. 

Types of Hyperbaric Treatment

• Portable Hyperbaric Chambers (Gamow Bags): Lightweight bags used in remote areas to stabilize severe cases (HACE/HAPE) by creating a pressurized environment until descent.

• Fixed Chambers: Administer 100% oxygen under pressure, providing rapid relief for severe symptoms.

• Preconditioning: Short sessions of HBO before high altitude exposure can improve oxygen saturation (SaO2) and reduce the risk of AMS. 

Key Takeaway

• Descent is paramount: Hyperbaric treatment is a crucial adjunct, not a replacement for descending to a lower altitude, the definitive cure for severe altitude sickness, note NCBI, Better Health Channel, and CDC.

• Stabilizes & Saves Lives: It buys time and stabilizes patients with severe symptoms (HACE/HAPE) when rescue or descent is delayed, say NCBI, Better Health Channel, and Undersea & Hyperbaric Medical Society.