High altitude sickness is a serious and potentially life-threatening condition that can occur when people ascend too quickly to high altitudes. One of the most common forms of this sickness is HACE (high-altitude cerebral edema) and HAPE (high-altitude pulmonary edema).

This blog post will discuss the differences between these two forms of high altitude sickness and how to recognize them.

What is AMS?

Acute Mountain Sickness (AMS) is the most common and mild form of altitude sickness. It occurs at high altitudes and is characterized by various symptoms, including headache, dizziness, nausea, fatigue, and difficulty sleeping.

The exact cause of AMS is unclear, but it is believed to be related to a lack of oxygen at higher altitudes. To prevent AMS, it is important to slowly acclimate to the altitude by ascending slowly and drinking enough fluids.

Treatment for AMS includes rest and medications such as ibuprofen or acetazolamide. If left untreated, AMS can progress to more serious conditions such as high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE).

What is HACE?

High Altitude Cerebral Edema (HACE) is a serious and life-threatening altitude sickness that occurs when the brain swells due to fluid. It is caused by a rapid ascent to high altitudes, particularly those over 8,000 feet, and is more likely to occur in people who are unacclimatized to the environment.

Symptoms of HACE include confusion, clumsiness, stumbling, and severe headache. If left untreated, HACE can lead to coma or even death.

To diagnose HACE, a doctor may order blood tests, CT scans, and other tests to determine the level of brain swelling.

Treatment for HACE typically includes oxygen therapy and medications that reduce brain swelling. Sometimes, patients may need to be transferred to lower altitudes to alleviate the symptoms.

What is HAPE?

High-altitude pulmonary edema (HAPE) is a fluid buildup in the lungs that can be very dangerous and even life-threatening. This is the result of a cascade of events that occur when ascending quickly to high altitudes. The air pressure drops, which causes the alveoli in the lungs to fill with fluid. This can lead to difficulty breathing, fatigue, coughing up pink, frothy sputum, rapid heartbeat, and an increased breathing rate. In severe cases, it can lead to death.

HAPE is most common in people who are unacclimatized to high altitudes or ascend too quickly. It can also be caused by extreme physical exertion at high altitudes or certain medications and medical conditions. People at the highest risk are those who have had HAPE before, those with a history of heart or lung problems, and those who are pregnant.

If untreated, HAPE can have serious complications, including coma and death. Since it is a medical emergency, it is important to seek medical help as soon as possible if any signs or symptoms of HAPE appear.

Comparison Between AMS, HACE, and HAPE

Acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) are the three main forms of altitude illness. These conditions are caused by the decrease in air pressure and oxygen levels as you ascend to higher altitudes.

AMS is the most common and mildest form of altitude illness, while HACE and HAPE are very serious and can be life-threatening.

AMS is characterized by headache, fatigue, nausea, or lack of appetite. It is important to recognize the symptoms of AMS early and take the necessary precautions to avoid progression to HACE or HAPE. If the symptoms are not managed on time, it can lead to a more severe form of altitude illness such as HACE or HAPE.

HACE is a severe altitude sickness marked by confusion, clumsiness, stumbling, and fluid on the brain. It is caused by brain swelling due to hypoxia. This can be very dangerous, and it is important to descend back to a lower altitude as soon as possible.

HAPE is a life-threatening condition caused by fluid accumulation in the lungs due to high altitudes. Symptoms include shortness of breath, cough with frothy sputum, fast breathing and heart rate, chest tightness or pain, weakness or fatigue, and decreased exercise performance. It is important to seek medical attention immediately if these symptoms appear.

Causes of AMS, HACE, and HAPE

AMS , HACE, and HAPE are illnesses that occur most commonly in mountain areas due to the lower oxygen levels at higher elevations.

The main cause of both conditions is the same: rapid ascent to high altitudes with limited time for acclimatization.

Other factors that may increase the risk of either condition include physical exertion at high altitudes, dehydration, and pre-existing medical conditions such as heart disease. Additionally, some medications, such as those used to treat asthma, may increase the risk of HAPE.

Symptoms of AMS, HACE and HAPE

HACE and HAPE are serious illnesses that can occur at high altitudes and manifest in various ways.

  • Acute mountain sickness (AMS) is the most common and mild altitude sickness. The symptoms of AMS are similar to those of the flu, such as headache, fatigue, dizziness, loss of appetite, nausea, and difficulty sleeping. Other symptoms include shortness of breath, rapid heart rate, and swelling in the hands and face. In severe cases, AMS can lead to confusion and disorientation.
  • The symptoms of HACE include confusion, clumsiness, and stumbling.
  • HAPE produces excess fluid in the lungs that cause difficulty breathing, chest pain, and a persistent cough that may produce white or pink frothy sputum. Other symptoms associated with HAPE include fatigue, dizziness, shortness of breath, and rapid heart rate.

It is important to note that symptoms may vary from person to person and may worsen with elevation. If left untreated, these conditions can become life-threatening. It is essential to seek medical attention immediately if these symptoms are experienced at high altitudes.

Risk Factors of HACE and HAPE

High altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) are two types of altitude sickness that can occur when someone ascends to a high altitude too quickly. Unacclimatized people and those who ascend to altitudes higher than 8,000 feet are at risk of developing HAPE or HACE.

Additionally, those in poor physical condition or suffering from certain medical conditions may be at an increased risk. Some medical conditions that can increase the risk of developing HACE and HAPE include obesity, heart disease, COPD, smoking, diabetes, asthma, anemia, and certain medications. It is also possible for women to be more susceptible to altitude sickness than men due to their lower red blood cell concentrations.

Diagnosis of AMS, HACE, and HAPE

Diagnosing acute mountain sickness (AMS) can be difficult because the symptoms are often very similar to other illnesses, such as the common cold or influenza. 

Diagnosis typically involves a physical exam and a review of your travel and health history. Your doctor may also order tests to check for low oxygen levels in your blood or conduct a CT scan to check for fluid accumulation in your lungs.

The diagnosis of HACE and HAPE can also be difficult and requires a thorough medical examination. The doctor will ask questions about the person’s medical history, symptoms, and recent activities, such as hiking or skiing. A physical examination is also necessary to check for signs of fluid in the lungs or brain.

Sometimes, blood tests, chest X-rays, or computed tomography (CT) scans may be used to confirm the diagnosis. Other tests may include an electrocardiogram (ECG) to measure heart rate and rhythm, a pulse oximetry test to measure oxygen levels in the blood or an echocardiogram to assess heart function.

HACE and HAPE must be diagnosed quickly so treatment can be started as soon as possible. Delays in diagnosis can increase the risk of complications or death.

Treatment for AMS, HACE, and HAPE Conditions

Treatment for acute mountain sickness (AMS) starts with the person descending to lower altitudes as soon as possible. If descent is not possible, oxygen, rest, and medications may be used to treat the symptoms.

Pain relievers like ibuprofen can be used to reduce headache pain. Acetazolamide (also known as Diamox) is a medication that can help reduce the symptoms of AMS by decreasing the amount of fluid in the body and increasing the rate of breathing.

It is important to note that acetazolamide does not speed up the acclimatization process, but it can relieve the symptoms of AMS. In some cases, supplemental oxygen may be necessary to reduce severe symptoms.

Treatment for HACE and HAPE is similar and should begin as soon as possible. The first step is to descend to a lower altitude as quickly and safely as possible. Oxygen therapy is also used to help increase the amount of oxygen in the bloodstream, and medications such as acetazolamide can reduce symptoms.

In more severe cases, hospitalization may be necessary, and patients may need to be put on a ventilator. It is important to note that while these treatments can help reduce symptoms, they do not cure the condition, so it is important to take steps to prevent HACE and HAPE in the future.

Prevention Tips for AMS, HACE, and HAPE Conditions

Preventing AMS, HACE and HAPE can be done by slowing down the rate of ascent, allowing for acclimatization, and avoiding intense physical activity. Additionally, one should avoid alcohol and sleeping pills when traveling to high altitudes as these can impair the body’s functioning and increase the risk of altitude sickness.

It is also important to stay hydrated, as dehydration can lead to HACE and HAPE. To maximize one’s chances of avoiding altitude sickness, it is recommended to ascend slowly and not increase elevation by more than 500 m per day. Finally, carrying a portable oxygen tank is a good idea if traveling to high altitudes. This can help prevent altitude sickness in case of an emergency.

Complications that Can Result from Not Treating These Conditions Quickly Enough

When HACE or HAPE is left untreated, it can lead to serious complications.

  • In the case of HACE, the swelling on the brain can cause confusion, coma, or even death.
  • For HAPE, the fluid in the lungs can lead to difficulty breathing, impaired oxygen absorption, and in some cases, cardiac arrest.

If left untreated for a long enough period, both conditions can be fatal. Therefore, it is important to seek medical attention as soon as possible if you are experiencing any symptoms of HACE or HAPE.

If you are in a remote area and cannot access medical care, descending to a lower altitude may be necessary to reduce the symptoms and prevent further complications from occurring.

The Prognosis for Those Who Are Diagnosed with Either Condition

The prognosis for those diagnosed with HACE or HAPE is generally good if proper medical attention is sought and treatment is followed. Both conditions can be treated with oxygen and medications such as diuretics, steroids, and bronchodilators. Sometimes, people may need to be hospitalized and treated with a mechanical ventilator.

If untreated, HACE and HAPE can cause significant organ damage or even death. It is important to seek medical help as soon as possible if any of the symptoms of these conditions are present. With prompt and proper treatment, the prognosis for those diagnosed with HACE or HAPE is usually good.

How to Cope With the Symptoms of Either Condition

When dealing with either HACE or HAPE, it is important to take steps to manage the symptoms. This includes getting plenty of rest and drinking plenty of fluids to help increase the oxygen flow in the body. It is also important to stay at the same altitude or lower, as going higher can worsen the symptoms.

Your doctor may also prescribe medications such as acetazolamide or nifedipine to help reduce swelling and improve oxygen flow. If you experience any signs of distress, such as chest pain, shortness of breath, confusion, or other worrying symptoms, seek medical attention immediately.

Exercise Restrictions During an Episode of Either Condition

Regarding both HACE and HAPE, exercise restrictions are a must. As both conditions are caused by high altitude, it is important to reduce the strain on the body while the body is trying to adjust to the change in elevation. Doctors may advise that trekkers either remain at a lower altitude or take an extended rest break until the symptoms have subsided.

It is also important to avoid strenuous activities such as climbing or running during an episode of either HACE or HAPE. High-intensity activities can cause further strain on the lungs and heart, leading to further complications.

For those trekking at high altitudes, it is important to take regular breaks and stay hydrated to prevent either condition from developing. Regular exercise is beneficial, but it should be done at a lower intensity to prevent further strain on the body.

Diet Restrictions During an Episode of Either Condition

When suffering from either HACE or HAPE, it is important to pay attention to your diet. Eating too much or too little can hurt your symptoms, as can certain types of food. Eating light but nutritious meals and snacks throughout the day is important. Avoiding salt, alcohol, and caffeine is also recommended, as these can worsen the symptoms of both conditions.

Eating small meals more often can help reduce any nausea you may experience. Drinking plenty of fluids is also essential for keeping your body hydrated and helping to reduce the risk of dehydration. Contact your doctor for advice and further treatment if you cannot keep food or fluids down.

Long-Term Effects of Acute Mountain Sickness (AMS)

Acute mountain sickness (AMS) can have long-term effects on the body and cause permanent damage. Some of the possible long-term effects of AMS include:

  • Brain damage due to lack of oxygen to the brain. This can cause memory loss, confusion, and difficulty concentrating.
  • Pulmonary edema is a potentially life-threatening condition in which fluid accumulates in the lungs.
  • High altitude cerebral edema (HACE) is a life-threatening condition that causes brain swelling due to a lack of oxygen.
  • High altitude retinal hemorrhage is an eye disorder caused by a lack of oxygen to the eyes. It can lead to poor vision, scarring, and even blindness.

Taking AMS seriously and taking steps to prevent it is important, as the long-term effects can be severe and even deadly. If you plan on climbing to high altitudes, take the proper precautions and acclimatize properly to avoid any long-term health complications.

Long-Term Effects of HACE and HAPE

Early symptoms include a nonproductive cough, dyspnoea on exertion, and reduced exercise performance. If HAPE is not treated promptly, it can lead to dyspnoea, incapacitating fatigue, chest tightness, orthopnoea, and cough with pink, frothy sputum.

In severe cases, HAPE can cause rapid clearing of air sacs in the lungs (alveoli) and severe pulmonary hypertension with uneven distribution, leading to areas of hyperperfusion and hypertension. Left untreated, HAPE can result in mortality in 50% of cases. Those who recover from HAPE have long-term effects, such as breathing difficulties due to hemoptysis, in an estimated 20% of cases. Therefore, it is important for anyone experiencing the symptoms of HAPE to seek medical attention immediately.

High-altitude cerebral edema (HACE) is a life-threatening medical condition in which the brain swells with fluid due to the physiological effects of traveling to high altitudes. It is characterized by ataxia, fatigue, and altered mental status and generally takes 3-5 days to develop after acute mountain sickness (AMS).

In advanced cases of altitude sickness, HACE can be accompanied by high-altitude pulmonary edema (HAPE). Patients may experience symptoms such as headache, loss of coordination, confusion, and in extreme cases, death. 


High altitude sickness is a serious condition affecting anyone who ascends to high altitudes too quickly. It is important to be aware of the symptoms and to take steps to prevent and treat them. Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE) are the three main forms of high altitude sickness, and they differ in terms of their symptoms and severity.

AMS is the most common and mild form, while HAPE and HACE are more serious and can be life-threatening if not treated promptly. It is important to know each condition’s signs and symptoms and take steps to prevent and treat them accordingly.