Altitude sickness, also known as acute mountain sickness (AMS), is a condition that can affect travellers ascending to high altitudes, typically above 2,500 meters (8,200 feet). Whether you’re planning a hiking expedition, a ski trip, or a visit to high-altitude cities, understanding altitude sickness is crucial for a safe and enjoyable journey. 

This ultimate guide by e-Surgery explores the causes, symptoms, prevention and treatment of altitude sickness, providing valuable information for anyone planning a trip to high-altitude destinations.  

Whether you’re a seasoned mountaineer or a first-time high-altitude traveller, this guide will equip you with the knowledge to tackle the challenges of high-altitude environments safely. 

Understanding Altitude Sickness

Altitude sickness occurs when the body struggles to adapt to lower oxygen levels at high altitudes. As you ascend to higher elevations, the air pressure decreases, making it harder for your body to get the oxygen it needs. This reduction in oxygen saturation can lead to various symptoms and, in severe cases, potentially life-threatening complications. 

There are three main types of altitude sickness, each varying in severity: 

  • Acute Mountain Sickness (AMS): This is the most common and mildest form of altitude sickness. The symptoms typically resemble those of a hangover, including headache, fatigue, and nausea.
  • High-Altitude Cerebral Edema (HACE): A severe and potentially fatal condition involving swelling of the brain. It is often considered an advanced form of AMS.
  • High-Altitude Pulmonary Edema (HAPE): Another serious condition where fluid accumulates in the lungs, impeding oxygen exchange. It can occur either in conjunction with or independently of HACE.

Understanding these different forms can help travellers recognise and respond to symptoms more effectively. It’s important to note that altitude sickness can affect anyone, regardless of age, fitness level, or previous experience at high altitudes.

Causes Of Altitude Sickness

The primary cause of altitude sickness is rapid ascent to high altitudes without proper acclimatisation. When you climb too quickly, your body doesn’t have enough time to adjust to the decrease in oxygen levels. This rapid change can lead to a cascade of psychological responses that manifest as the symptoms of altitude sickness. 

There are several specific factors that contribute to the development of altitude sickness: 

  • Reduced Partial Pressure Of Oxygen: As altitude increases, the partial pressure of oxygen in the air decreases. This means that even though the percentage of oxygen in the air remains constant, the number of oxygen molecules in each breath is reduced.
  • Hypoxia: The reduced oxygen levels in the blood (hypoxemia) lead to hypoxia – a state where body issues don’t receive enough oxygen.
  • Changes In Blood pH: The body’s initial response to the lower oxygen levels is to breathe faster and deeper. While this helps to increase oxygen intake, it also leads to the expulsion of more carbon dioxide.
  • Fluid Shifts: At high altitudes, fluid tends to leak from the capillaries into the lungs and brain tissue.
  • Increased Sympathetic Nervous System Activity: The body’s stress response to low oxygen levels includes increased activity of the sympathetic nervous system. This leads to increased heart rate and blood pressure, which can exacerbate symptoms.
  • Increased Cerebral Blood Flow: In response to hypoxia, blood flow to the brain increases. While this is a compensatory mechanism to deliver more oxygen, it can also contribute to headaches.
  • Impaired Fluid Regulation: High altitudes can affect the body’s ability to regulate fluids properly.
  • Genetic Factors: Some individuals may be genetically predisposed to developing altitude sickness more easily than others.

It’s important to note that the rate of ascent is a crucial factor in the development of altitude sickness. The faster the ascent, the less time the body has to acclimatise, and the more likely altitude sickness becomes. This is why gradual ascent and proper acclimatisation are key strategies in preventing altitude sickness.

Symptoms & Warning Signs

Recognizing the symptoms of altitude sickness is crucial for early intervention. Symptoms can range from mild to severe and may appear within hours or days of reaching high altitude. It’s important to pay attention to your body and take any symptoms seriously, especially if they worsen over time. 

Acute Mountain Sickness (AMS) 

AMS is the most common form of altitude sickness. The symptoms typically appear within 6-24 hours of ascending to high altitude. 

They include headache (often the first symptom), dizziness or light-headedness, fatigue or weakness, shortness of breath (especially during exertion), loss of appetite, nausea and sometimes vomiting, difficulty sleeping, rapid heart rate, and a general feeling of malaise. 

These symptoms often resemble a bad hangover or flu. If you experience these symptoms at high altitude, it’s important to stop ascending and allow time for acclimatisation. 

High-Altitude Cerebral Edema (HACE) 

HACE is a severe form of altitude sickness involving swelling of the brain. It’s rare but potentially fatal if not treated properly. 

The warning signs of HACE include a severe headache that doesn’t respond to pain medication, confusion or altered mental status, difficulty with balance and co-ordination, stumbling or inability to walk in a straight line, extreme fatigue, and hallucinations. 

HACE can progress rapidly, so it’s critical to recognise these symptoms early and descend immediately if they occur. 

High-Altitude Pulmonary Edema (HAPE) 

HAPE involves fluid accumulation in the lungs and is another severe, potentially fatal form of altitude sickness. 

The symptoms of HAPE include a persistent dry cough (which may progress to a wet cough with pink, frothy sputum), severe shortness of breath, chest tightness or congestion, rapid breathing and heart rate, weakness and decreased exercise performance, blue or grey lips or fingernails, crackling or wheezing sounds in the lungs, or fever. 

Like HACE, HAPE requires immediate descent and medical attention. 

Risk Factors

While anyone can experience altitude sickness, certain factors may increase your risk: 

  • Rapid Ascent: The faster you climb to high altitude, the more likely to you are to experience altitude sickness.
  • Altitude Reached: The higher you go, the greater the risk.
  • Previous History Of Altitude Sickness: If you’ve experienced altitude sickness before, you’re more likely to get it again. 
  • Age: While altitude sickness can affect anyone, younger people tend to be more susceptible.
  • Physical Exertion: Overexertion at high altitudes, especially in the first 24 hours, can increase your risk. 
  • Certain Medication Conditions: Pre-existing heart, lung, or blood disorders can increase your risk. 
  • Dehydration: Being dehydrated can exacerbate the effects of high altitude and increase your risk of altitude sickness. 

It’s important to note that physical fitness does not necessarily protect against altitude sickness. Even very fit individuals can experience altitude sickness if they ascend too quickly or don’t take proper precautions. 

If you have any pre-existing medical conditions or concerns about your risk factors, it’s essential to consult with a doctor before travelling.

Medications For Altitude Sickness

While proper acclimatisation is the best way to prevent altitude sickness, medications can play a crucial role in both prevention and treatment. Always consult with a healthcare professional before taking any medications, especially if you have pre-existing medical conditions. 

  • Acetazolamide: Primarily used for the prevention and treatment of AMS, Acetazolamide works by increasing the breathing rate, which boosts blood oxygen levels and speeds up acclimatisation. 
  • Dexamethasone: This medication is used to treat moderate to severe AMS and HACE. It works by reducing brain swelling and inflammation. 
  • Nifedipine: Nifedipine is mainly used for the prevention and treatment of HAPE. It functions by dilating pulmonary blood vessels, which lowers pressure in the lungs. 
  • Ibuprofen: Commonly used for treating altitude-related headaches, Ibuprofen helps by reducing pain and inflammation. 
  • Paracetamol: This medication is used to treat altitude-related headaches by reducing pain. 
  • Sumatriptan: Used for the treatment of severe altitude-related headaches, Sumatriptan works by constricting blood vessels in the brain. 

Remember, while these medications can be helpful, the most effective treatment for altitude sickness is descent to a lower altitude. You should always prioritise safety and be prepared to change your plans if altitude sickness occurs. 

Next Steps

Altitude sickness is a real concern for travellers venturing to high-altitude destinations, but with proper preparation and precautions, it can be prevented or managed effectively. By understanding the causes, recognising the symptoms, and implementing prevention strategies, you can significantly reduce your risk and enjoy your high-altitude adventures safely. 

At e-Surgery, we understand the challenges of dealing with altitude sickness and are here to support you. Our ‘Ask-a-Pharmacist‘ service provides advice from trained UK healthcare professionals regarding altitude sickness.

With proper preparation and respect for the challenges of high-altitude environments, you can push your boundaries and experience some of the world’s most breathtaking locations.