Materiały źródłowe

• #1 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #2 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://wwwnc.cdc.gov/travel/yellowbook/2024/environmental-hazards-risks/high-elevation-travel-and-altitude-illness

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #3 Altitude sickness – Wikipedia

  https://en.wikipedia.org/wiki/Altitude_sickness

  Altitude sickness can first occur at 1,500 metres (4,900 ft), with the effects becoming severe at extreme altitudes (greater than 5,500 metres (18,000 ft)). Only brief trips above 6,000 metres (20,000 ft) are possible and supplemental oxygen is needed to avert sickness. […] As altitude increases, the available amount of oxygen to sustain mental and physical alertness decreases with the overall air pressure, though the relative percentage of oxygen in air, at about 21%, remains practically unchanged up to 21,000 metres (69,000 ft). […] The rate of ascent, altitude attained, amount of physical activity at high altitude, as well as individual susceptibility, are contributing factors to the onset and severity of high-altitude illness. […] Altitude sickness usually occurs following a rapid ascent and can usually be prevented by ascending slowly.

• #4 Altitude Sickness – Harvard Health

  https://www.health.harvard.edu/a_to_z/altitude-sickness-a-to-z

  At higher altitudes, the pressure of the air around you (barometric pressure) decreases so there is less oxygen in surrounding air. […] Altitude sickness is more likely to occur in people who have a previous history of altitude sickness. It is more likely if you climb quickly, if you exercise vigorously during your first few days of altitude exposure, and if you have been living at low elevation prior to your climb. Obesity appears to increase the risk for altitude sickness. Genetics may also put some people at increased risk, particularly for high altitude pulmonary edema (HAPE). […] Symptoms that develop at high altitude should be taken very seriously, since some altitude problems can develop into fatal illnesses. One dangerous reaction to high altitude is a condition called high-altitude cerebral edema (HACE), in which the brain accumulates extra fluid, swells and stops working properly. A related illness, high-altitude pulmonary edema (HAPE), can occur with or without warning symptoms that signal altitude sickness. […] Acute mountain sickness is the least dangerous of several kinds of altitude illnesses that can occur. This sickness affects close to half of all people who begin near to sea level and climb to 14,000 feet of elevation without scheduling enough rest time.

• #5 Causes of Altitude sickness | Hospital Clínic Barcelona

  https://www.clinicbarcelona.org/en/assistance/be-healthy/altitude-sickness/causes

  Altitude sickness is a consequence of a lack of oxygen in the body. This lack of oxygen occurs because as the altitude increases, the atmospheric pressure decreases and there is less oxygen and nitrogen, meaning that the alveoli in the lungs cannot transport the necessary amount of oxygen to the blood. […] There are some people who are more susceptible to altitude sickness, and there are also factors that affect it such as physical activity, speed of ascension or the initial altitude at departure.

• #6 Altitude Sickness

  https://mentalhealth.networkofcare.org/Bucks-pa/HealthLibrary/Article?docType=na&articleId=ug3357

  Altitude sickness occurs when you cannot get enough oxygen from the air at high altitudes. This causes symptoms such as a headache, loss of appetite, and trouble sleeping. It happens most often when people who are not used to high altitudes go quickly from lower altitudes to 8000 ft (2500 m) or higher. […] Mild altitude sickness is common. Experts do not know who will get it and who will not. Neither your fitness level nor being male or female plays a role in whether you get altitude sickness. […] Air is „thinner” at high altitudes. When you go too high too fast, your body cannot get as much oxygen as it needs. So you need to breathe faster. This causes the headache and other symptoms of altitude sickness. As your body gets used to the altitude, the symptoms go away. […] You may be able to prevent altitude sickness by taking your time when you go to high altitudes and using medicine in advance.

• #7 What Causes Altitude Sickness?

  https://www.ukmeds.co.uk/blog/what-causes-altitude-sickness

  Altitude sickness, also known as acute mountain sickness (AMS), occurs when your body struggles to adjust to lower oxygen levels at high elevations. This condition is most common when ascending to altitudes over 2,500 metres (8,000 feet) too quickly, preventing your body from acclimatising properly. […] The air becomes thinner as you go higher above sea level, meaning there is less oxygen available with each breath. Your body is accustomed to a certain level of oxygen at lower altitudes, and when you ascend too quickly, it doesn’t have enough time to adapt. This oxygen deprivation can cause symptoms such as headaches, nausea, dizziness, and shortness of breath. […] Altitude sickness can affect anyone, regardless of age, sex, or fitness level. However, certain factors increase the likelihood of experiencing symptoms: Rapid Ascent, Climbing too quickly without allowing time to acclimatise.

• #8 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #9 Acute Mountain Sickness – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK430716/

  Acute Mountain Sickness is caused by the bodys reaction to the reduced oxygen level in respired air and resultant tissue hypoxia. […] At baseline metabolic levels, the brain is the most sensitive organ regarding hypoxia and oxygen stress. Thus, the symptoms of Acute Mountain Sickness (discussed below) are mediated by the central nervous system (CNS). […] In many travelers at altitude, respirations during sleep develop a periodic pattern that may contribute to the development of symptoms.

• #10 Acute Mountain Sickness – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK430716/

  Acute Mountain Sickness is caused by the bodys reaction to the reduced oxygen level in respired air and resultant tissue hypoxia. […] At baseline metabolic levels, the brain is the most sensitive organ regarding hypoxia and oxygen stress. Thus, the symptoms of Acute Mountain Sickness (discussed below) are mediated by the central nervous system (CNS). […] In many travelers at altitude, respirations during sleep develop a periodic pattern that may contribute to the development of symptoms.

• #11 Altitude sickness – Wikipedia

  https://en.wikipedia.org/wiki/Altitude_sickness

  Altitude sickness can first occur at 1,500 metres (4,900 ft), with the effects becoming severe at extreme altitudes (greater than 5,500 metres (18,000 ft)). Only brief trips above 6,000 metres (20,000 ft) are possible and supplemental oxygen is needed to avert sickness. […] As altitude increases, the available amount of oxygen to sustain mental and physical alertness decreases with the overall air pressure, though the relative percentage of oxygen in air, at about 21%, remains practically unchanged up to 21,000 metres (69,000 ft). […] The rate of ascent, altitude attained, amount of physical activity at high altitude, as well as individual susceptibility, are contributing factors to the onset and severity of high-altitude illness. […] Altitude sickness usually occurs following a rapid ascent and can usually be prevented by ascending slowly.

• #12 Patient education: High-altitude illness (including mountain sickness) (Beyond the Basics) – UpToDate

  https://www.uptodate.com/contents/high-altitude-illness-including-mountain-sickness-beyond-the-basics/print

  Ascending to or being at a new high altitude may cause high-altitude illness (HAI). HAI includes acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). HAI is caused by lower oxygen levels in the air and thus the blood. […] It is impossible to know if you will get sick when traveling to a high altitude. Being physically fit does not lower your chances of developing a high-altitude illness. However, certain groups are at increased risk, including people who: […] Acute mountain sickness (AMS) is the most common of the altitude illnesses; it occurs in approximately 40 to 50 percent of people who live at a low altitude and travel to sleep at an altitude above 10,000 feet (3000 m), and in approximately 25 percent of those sleeping above 8000 feet (2400 m). […] High-altitude pulmonary edema (HAPE) is a potentially fatal condition in which lung capillaries leak and fluid accumulates in the lungs. HAPE is uncommon but can occur in people who rapidly ascend to altitudes above 8200 feet (2500 m).

• #13 Altitude sickness – symptoms, treatments and causes | healthdirect

  https://www.healthdirect.gov.au/altitude-sickness

  Altitude sickness can happen if you travel to a high elevation such as up a mountain. […] It happens when your body has not had time to adjust to the lower amount of oxygen. […] Altitude sickness is caused by low oxygen levels in the air. This happens at altitudes above about 2,500 metres. It happens when your body has not had time to adjust to the lower amount of oxygen. Your body is not able to get enough oxygen to work properly.

• #14 Patient education: High-altitude illness (including mountain sickness) (Beyond the Basics) – UpToDate

  https://www.uptodate.com/contents/high-altitude-illness-including-mountain-sickness-beyond-the-basics/print

  Ascending to or being at a new high altitude may cause high-altitude illness (HAI). HAI includes acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). HAI is caused by lower oxygen levels in the air and thus the blood. […] It is impossible to know if you will get sick when traveling to a high altitude. Being physically fit does not lower your chances of developing a high-altitude illness. However, certain groups are at increased risk, including people who: […] Acute mountain sickness (AMS) is the most common of the altitude illnesses; it occurs in approximately 40 to 50 percent of people who live at a low altitude and travel to sleep at an altitude above 10,000 feet (3000 m), and in approximately 25 percent of those sleeping above 8000 feet (2400 m). […] High-altitude pulmonary edema (HAPE) is a potentially fatal condition in which lung capillaries leak and fluid accumulates in the lungs. HAPE is uncommon but can occur in people who rapidly ascend to altitudes above 8200 feet (2500 m).

• #15 Altitude Sickness Is Typically Mild But Can Sometimes Turn Very Serious − a High-Altitude Medicine Physician Explains How to Safely Prepare

  https://news.cuanschutz.edu/news-stories/altitude-sickness-is-typically-mild-but-can-sometimes-turn-very-serious-a-high-altitude-medicine-physician-explains-how-to-safely-prepare

  Altitude sickness is rare at elevations of less than 8,200 feet but becomes much more common at higher altitudes. […] Altitude sickness, which most commonly refers to acute mountain sickness, presents a significant challenge to those traveling to and adventuring in high-altitude destinations. […] The risk rapidly increases with higher ascents. Above 9,800 feet (3,000 meters), up to 75% of travelers may develop symptoms. […] When travelers do not properly acclimatize, they can be susceptible to life-threatening altitude illnesses, such as high-altitude pulmonary edema or high-altitude cerebral edema. […] Altitude sickness symptoms are thought to be caused by increased pressure surrounding the brain, which results from the failure of the body to acclimatize to higher elevations. […] People who skip this step and travel directly to high elevations are up to four times more likely to develop altitude sickness symptoms.

• #16 Altitude Sickness | APEX | Altitude.org

  https://www.altitude.org/altitude-sickness

  Altitude sickness has three forms. […] What causes altitude sickness? […] Two things are certain to make altitude sickness very likely – ascending faster than 500m per day, and exercising vigorously. […] Altitude sickness happens because there is less oxygen in the air that you breathe at high altitudes. […] There is so much less oxygen in the high mountains that it is not surprising that travelling to high altitude causes people to feel unwell, but how this shortage of oxygen actually leads to altitude sickness is still not fully understood. […] Some scientists believe that it is due to swelling of the brain but the evidence for this hypothesis is not conclusive. […] The theory is that in susceptible individuals, swelling could cause a small increase in the pressure inside the skull and lead to symptoms of acute mountain sickness.

• #17 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #18 Altitude Sickness – Harvard Health

  https://www.health.harvard.edu/a_to_z/altitude-sickness-a-to-z

  At higher altitudes, the pressure of the air around you (barometric pressure) decreases so there is less oxygen in surrounding air. […] Altitude sickness is more likely to occur in people who have a previous history of altitude sickness. It is more likely if you climb quickly, if you exercise vigorously during your first few days of altitude exposure, and if you have been living at low elevation prior to your climb. Obesity appears to increase the risk for altitude sickness. Genetics may also put some people at increased risk, particularly for high altitude pulmonary edema (HAPE). […] Symptoms that develop at high altitude should be taken very seriously, since some altitude problems can develop into fatal illnesses. One dangerous reaction to high altitude is a condition called high-altitude cerebral edema (HACE), in which the brain accumulates extra fluid, swells and stops working properly. A related illness, high-altitude pulmonary edema (HAPE), can occur with or without warning symptoms that signal altitude sickness. […] Acute mountain sickness is the least dangerous of several kinds of altitude illnesses that can occur. This sickness affects close to half of all people who begin near to sea level and climb to 14,000 feet of elevation without scheduling enough rest time.

• #19 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #20 Altitude Sickness: What It Is, Symptoms, Treatment & Prevention

  https://my.clevelandclinic.org/health/diseases/15111-altitude-sickness

  Altitude sickness is when your body doesnt have time to adjust to lower oxygen availability higher up in the atmosphere. […] Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen youre getting with each breath. […] Given time, your body can usually adapt to altitude-related changes that affect how much oxygen you get with each breath. Without enough time to adapt, altitude sickness is the result. […] The risk factors for altitude sickness often relate to the altitude itself or how you get there. […] A common misconception is that your physical health is a risk factor for developing altitude sickness. It isnt, but altitude sickness can make symptoms of some existing conditions worse. […] Altitude sickness can become deadly if AMS turns into HAPE or HACE. HAPE can be deadly within 12 hours. HACE can be deadly within 24 hours. […] The outlook for altitude sickness depends on the severity, how you react to the symptoms and how you respond to treatment. If you ignore symptoms and keep ascending, youll likely experience worsening symptoms.

• #21 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #22 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  High-altitude illnesses encompass the pulmonary and cerebral syndromes that occur in non-acclimatized individuals after rapid ascent to high altitude. […] Risk factors include home elevation, maximum altitude, sleeping altitude, rate of ascent, latitude, age, gender, physical condition, intensity of exercise, pre-acclimatization, genetic make-up, and pre-existing diseases. […] Acute mountain sickness has been recognized for centuries. […] Although high altitude is defined as beginning at an elevation of 1,500 m (5,000 feet), symptoms are rarely present at 1,500 m but become increasingly common with rapid ascent to higher elevations. […] AMS is typically associated with headache variably accompanied by loss of appetite, disturbed sleep, nausea, fatigue, and dizziness beginning within 12 hours of ascent in two-thirds of susceptible subjects and within 36 hours in the remaining third.

• #23 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  High-altitude illnesses encompass the pulmonary and cerebral syndromes that occur in non-acclimatized individuals after rapid ascent to high altitude. […] Risk factors include home elevation, maximum altitude, sleeping altitude, rate of ascent, latitude, age, gender, physical condition, intensity of exercise, pre-acclimatization, genetic make-up, and pre-existing diseases. […] Acute mountain sickness has been recognized for centuries. […] Although high altitude is defined as beginning at an elevation of 1,500 m (5,000 feet), symptoms are rarely present at 1,500 m but become increasingly common with rapid ascent to higher elevations. […] AMS is typically associated with headache variably accompanied by loss of appetite, disturbed sleep, nausea, fatigue, and dizziness beginning within 12 hours of ascent in two-thirds of susceptible subjects and within 36 hours in the remaining third.

• #24 Altitude Sickness, What causes altitude sickness?, What are the risk factors for altitude sickness?, What are the symptoms and treatment of altitude sickness?, Physiological adaptation to altitude sickness

  https://reference.jrank.org/diseases/Altitude_Sickness.html

  Previous episodes of altitude sickness and living at low altitudes predispose individuals to have an episode. […] The amount of physical exertion placed on the body affects how much oxygen the body needs, making greater exertion a risk factor for altitude sickness when individuals are ascending. […] In order to maximize the ability of the blood to carry oxygen to the tissues, the amount of hemoglobin present in the blood increases. […] The more red blood cells present in the blood, the greater the oxygen-carrying capacity of the blood. […] The best way to prevent altitude sickness is to ascend to high altitude gradually. […] Acetazolamide is sometimes used preventively to avoid the occurrence of altitude sickness.

• #25 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The goal for the traveler might not be to avoid all symptoms of altitude illness but to have no more than mild illness, thereby avoiding itinerary changes or the need for medical assistance or evacuation. […] Some common high-altitude destinations require rapid ascent by airplane to 11,150 ft (3,400 m), placing travelers in a high-risk category for AMS. […] With rates of altitude illness approaching 50% in these situations, a low threshold for chemoprophylaxis is advised. […] The condition is typically self-limited, developing and resolving over 1-3 days. […] AMS improves rapidly with a descent of 300 m (1,000 ft) or more, especially if exertion is minimal. […] If symptoms worsen while the traveler is at the same altitude and despite treatment, descent is mandatory. […] The main point of instructing travelers about altitude illness is not to eliminate the possibility of mild illness but to prevent severe illness, need for evacuation, or death.

• #26 Altitude Illness – Injuries and Poisoning – Merck Manual Consumer Version

  https://www.merckmanuals.com/home/injuries-and-poisoning/altitude-illness/altitude-illness

  Altitude illness occurs because of a lack of oxygen at high altitudes and affects mountain climbers, recreational hikers, skiers, and others who travel to high altitude. […] As altitude increases, the percentage of oxygen in air remains constant, but the atmospheric pressure decreases, thinning the air so that less oxygen is available. […] Most people can ascend to 5,000 to 6,500 feet (1,500 to 2,000 meters) in 1 day without problems, but about 25% of people who ascend to 8,000 feet (2,500 meters) and 40% who ascend to 14,000 feet (4,340 meters) develop some form of altitude illness. […] Other factors that contribute to developing altitude illness are the maximum altitude reached and the sleeping altitude. […] The risk of developing altitude illness varies greatly among individuals. But generally, risk is increased in people who ascend to more than 2000 m (5000 to 6500 ft) and meet at least 1 of the following conditions: Have had previous altitude illness, Live at sea level or very low altitude, Go too high too fast, Overexert themselves, Sleep at too high an altitude.

• #27 Altitude Sickness – Causes, Symptoms, Treatment, Diagnosis – MedBroadcast.com

  https://medbroadcast.com/condition/getcondition/altitude-sickness

  Children are especially vulnerable, and can experience high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) below 2,500 metres (8,000 feet). Limited evidence seems to suggest men may be affected by HAPE more than women, but acute mountain sickness (AMS) and HACE affect men and women equally. If someone has had altitude sickness before, they have a 3 times greater risk. If someone usually lives below 3,000 metres, they are at more than 3 times the risk of those who reside at higher altitudes. However, if someone lives at a high altitude, an increased risk can develop even after a brief stay at lower elevations. Being in better physical condition does not protect you against altitude sickness.

• #28 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #29 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS can afflict any visitor sleeping higher than 6000 feet. […] We have to admit that the exact cause of AMS is still not clear. Of course, AMS is due to low oxygen, but the steps between low oxygen and AMS are fuzzy. […] Current thinking is that hypoxia (low oxygen) in the air and blood causes the blood vessels of the brain to dilate in an attempt to get more oxygen. […] Some researchers think that AMS is more like a migraine headache, and indeed, AMS and migraine have some similarities, but they are not identical. […] If you have had altitude illness in the past you may be at risk to get it again, since there is a significant genetic component to altitude illness. […] Several factors increase your risk for getting AMS: Your genetic makeup, a history of previous AMS, residence at an altitude below 3000 ft, obesity, current respiratory infection, most importantly, fast rate of ascent, over-exertion the first day or two at altitude, alcohol the first night at altitude.

• #30 Altitude Sickness – Harvard Health

  https://www.health.harvard.edu/a_to_z/altitude-sickness-a-to-z

  At higher altitudes, the pressure of the air around you (barometric pressure) decreases so there is less oxygen in surrounding air. […] Altitude sickness is more likely to occur in people who have a previous history of altitude sickness. It is more likely if you climb quickly, if you exercise vigorously during your first few days of altitude exposure, and if you have been living at low elevation prior to your climb. Obesity appears to increase the risk for altitude sickness. Genetics may also put some people at increased risk, particularly for high altitude pulmonary edema (HAPE). […] Symptoms that develop at high altitude should be taken very seriously, since some altitude problems can develop into fatal illnesses. One dangerous reaction to high altitude is a condition called high-altitude cerebral edema (HACE), in which the brain accumulates extra fluid, swells and stops working properly. A related illness, high-altitude pulmonary edema (HAPE), can occur with or without warning symptoms that signal altitude sickness. […] Acute mountain sickness is the least dangerous of several kinds of altitude illnesses that can occur. This sickness affects close to half of all people who begin near to sea level and climb to 14,000 feet of elevation without scheduling enough rest time.

• #31 Altitude sickness Guide: Causes, Symptoms and Treatment Options

  https://www.drugs.com/health-guide/altitude-sickness.html

  At higher altitudes, the pressure of the air around you (barometric pressure) decreases so there is less oxygen in surrounding air. […] Altitude sickness is more likely to occur in people who have a previous history of altitude sickness. It is more likely if you climb quickly, if you exercise vigorously during your first few days of altitude exposure, and if you have been living at low elevation prior to your climb. Obesity appears to increase the risk for altitude sickness. Genetics may also put some people at increased risk, particularly for high altitude pulmonary edema (HAPE).

• #32 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #33 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #34 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://wwwnc.cdc.gov/travel/yellowbook/2024/environmental-hazards-risks/high-elevation-travel-and-altitude-illness

  Diagnosis of AMS is based on a history of recent ascent to high altitude and the presence of subjective symptoms. […] The condition is typically self-limited, developing and resolving over 1-3 days. […] Travelers with preexisting medical conditions must optimize their treatment and have their conditions stable before departure. […] Travelers with underlying medical conditions (e.g., coronary artery disease, any form of chronic pulmonary disease or preexisting hypoxemia, obstructive sleep apnea [OSA], or sickle cell trait) even if well-controlled should consult a physician familiar with high-altitude medical issues before undertaking such travel.

• #35 Altitude sickness causes and prevention – Discovery World Trekking

  https://www.discoveryworldtrekking.com/blog/altitude-sickness-causes-and-prevention

  However, the chance of catching altitude sickness depends on factors like elevation, ascending rate, and at what altitude you sleep. […] People with medical conditions such as sickle cell anemia, pregnancy, heart failure, unstable angina, or cystic fibrosis are more prone to altitude sickness symptoms.

• #36 Altitude Sickness: Symptoms, Treatment & Medication, Prevention

  https://www.webmd.com/a-to-z-guides/altitude-sickness

  Sometimes called mountain sickness, altitude sickness is a group of symptoms that can strike if you walk or climb to a higher elevation, or altitude, too quickly. […] The pressure of the air that surrounds you is called barometric or atmospheric pressure. When you go to higher altitudes, this pressure drops and there is less oxygen available. […] Any time you go above 8,000 feet, you can be at risk for altitude sickness. […] Your chance of getting altitude sickness depends on a few other things: how quickly you move to a higher elevation, how high you go up, the altitude where you sleep, and other factors. […] Your risk also depends on where you live and the altitude there, your age (young people are more likely to get it), and whether you’ve had altitude sickness before. […] Having certain illnesses like diabetes or lung disease doesn’t automatically make you more likely to develop altitude sickness. People who have sickle cell anemia, COPD, unstable angina, a high-risk pregnancy, heart failure, or cystic fibrosis are less likely to be able to tolerate the change in altitude. So are people who have had recent heart attacks or strokes.

• #37 Altitude Sickness: What It Is, Symptoms, Treatment & Prevention

  https://my.clevelandclinic.org/health/diseases/15111-altitude-sickness

  Altitude sickness is when your body doesnt have time to adjust to lower oxygen availability higher up in the atmosphere. […] Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen youre getting with each breath. […] Given time, your body can usually adapt to altitude-related changes that affect how much oxygen you get with each breath. Without enough time to adapt, altitude sickness is the result. […] The risk factors for altitude sickness often relate to the altitude itself or how you get there. […] A common misconception is that your physical health is a risk factor for developing altitude sickness. It isnt, but altitude sickness can make symptoms of some existing conditions worse. […] Altitude sickness can become deadly if AMS turns into HAPE or HACE. HAPE can be deadly within 12 hours. HACE can be deadly within 24 hours. […] The outlook for altitude sickness depends on the severity, how you react to the symptoms and how you respond to treatment. If you ignore symptoms and keep ascending, youll likely experience worsening symptoms.

• #38 Understanding Altitude Sickness | A Guide to Elevation Illness

  https://lastingadventures.com/blog/understanding-altitude-sickness/

  Altitude sickness, also known as elevation illness or mountain sickness, occurs in areas with lower oxygen levels and can be exasperated by dehydration, both of which coincide with higher altitudes. […] Altitude sickness occurs when our bodies intake less oxygen than they’re used to. At higher altitudes where the air is “thinner,” less oxygen is present in the air. […] With less oxygen, your body can not function nearly as well, producing symptoms like a lack of energy, nausea and insomnia. Another factor in these symptoms is dehydration. […] Altitude sickness most commonly occurs at elevations above 8,000 feet, with high altitude ranging from 8,000 to 12,000 feet. […] Anyone can be susceptible to altitude sickness, and factors like age, sex and general health often don’t affect who gets it.

• #39 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #40 Altitude Sickness – Causes, Symptoms, Treatment, Diagnosis – MedBroadcast.com

  https://medbroadcast.com/condition/getcondition/altitude-sickness

  Children are especially vulnerable, and can experience high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) below 2,500 metres (8,000 feet). Limited evidence seems to suggest men may be affected by HAPE more than women, but acute mountain sickness (AMS) and HACE affect men and women equally. If someone has had altitude sickness before, they have a 3 times greater risk. If someone usually lives below 3,000 metres, they are at more than 3 times the risk of those who reside at higher altitudes. However, if someone lives at a high altitude, an increased risk can develop even after a brief stay at lower elevations. Being in better physical condition does not protect you against altitude sickness.

• #41 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #42 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS can afflict any visitor sleeping higher than 6000 feet. […] We have to admit that the exact cause of AMS is still not clear. Of course, AMS is due to low oxygen, but the steps between low oxygen and AMS are fuzzy. […] Current thinking is that hypoxia (low oxygen) in the air and blood causes the blood vessels of the brain to dilate in an attempt to get more oxygen. […] Some researchers think that AMS is more like a migraine headache, and indeed, AMS and migraine have some similarities, but they are not identical. […] If you have had altitude illness in the past you may be at risk to get it again, since there is a significant genetic component to altitude illness. […] Several factors increase your risk for getting AMS: Your genetic makeup, a history of previous AMS, residence at an altitude below 3000 ft, obesity, current respiratory infection, most importantly, fast rate of ascent, over-exertion the first day or two at altitude, alcohol the first night at altitude.

• #43 What Causes Altitude Sickness?

  https://www.ukmeds.co.uk/blog/what-causes-altitude-sickness

  Lack of Acclimatisation, Not giving your body enough time to adjust to higher altitudes. […] Previous Experience, If you have had altitude sickness before, you are more likely to get it again. […] Dehydration, Not drinking enough fluids can make symptoms worse. […] Alcohol or Smoking, Both can affect oxygen levels and worsen symptoms. […] Strenuous Activity, Overexerting yourself at high altitudes increases the risk of developing symptoms.

• #44 Altitude Illness – Injuries; Poisoning – MSD Manual Professional Edition

  https://www.msdmanuals.com/professional/injuries-poisoning/altitude-illness/altitude-illness

  Altitude illness is caused by the decreased availability of oxygen at high altitudes. […] The pathogenesis of acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) remain unclear despite considerable research in this area. […] High-altitude pulmonary edema (HAPE) is caused by hypoxia-induced elevation of pulmonary artery pressure, which causes interstitial and alveolar pulmonary edema, resulting in impaired oxygenation. […] Other factors that contribute to developing altitude illness are the maximum altitude reached and the sleeping altitude. […] The most important measure is a slow ascent. […] Acetazolamide 125 mg orally every 12 hours reduces the incidence of altitude illness.

• #45 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #46 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #47 Altitude sickness – Wikipedia

  https://en.wikipedia.org/wiki/Altitude_sickness

  High altitude illness can be classified according to the altitude: high (1,500-3,500 metres (4,900-11,500 ft)), very high (3,500-5,500 metres (11,500-18,000 ft)) and extreme (above 5,500 metres (18,000 ft)). […] The physiological cause of altitude-induced edema is not conclusively established. It is currently believed, however, that HACE is caused by local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressures. […] The body’s response to high altitude includes the following: Erythropoietin hematocrit and haemoglobin, 2,3-BPG (allows release of O2 and a right shift on the Hb-O2 disassociation curve), kidney excretion of bicarbonate (use of acetazolamide can augment for treatment), Chronic hypoxic pulmonary vasoconstriction (can cause right ventricular hypertrophy).

• #48 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS can afflict any visitor sleeping higher than 6000 feet. […] We have to admit that the exact cause of AMS is still not clear. Of course, AMS is due to low oxygen, but the steps between low oxygen and AMS are fuzzy. […] Current thinking is that hypoxia (low oxygen) in the air and blood causes the blood vessels of the brain to dilate in an attempt to get more oxygen. […] Some researchers think that AMS is more like a migraine headache, and indeed, AMS and migraine have some similarities, but they are not identical. […] If you have had altitude illness in the past you may be at risk to get it again, since there is a significant genetic component to altitude illness. […] Several factors increase your risk for getting AMS: Your genetic makeup, a history of previous AMS, residence at an altitude below 3000 ft, obesity, current respiratory infection, most importantly, fast rate of ascent, over-exertion the first day or two at altitude, alcohol the first night at altitude.

• #49 Altitude Sickness | APEX | Altitude.org

  https://www.altitude.org/altitude-sickness

  Altitude sickness has three forms. […] What causes altitude sickness? […] Two things are certain to make altitude sickness very likely – ascending faster than 500m per day, and exercising vigorously. […] Altitude sickness happens because there is less oxygen in the air that you breathe at high altitudes. […] There is so much less oxygen in the high mountains that it is not surprising that travelling to high altitude causes people to feel unwell, but how this shortage of oxygen actually leads to altitude sickness is still not fully understood. […] Some scientists believe that it is due to swelling of the brain but the evidence for this hypothesis is not conclusive. […] The theory is that in susceptible individuals, swelling could cause a small increase in the pressure inside the skull and lead to symptoms of acute mountain sickness.

• #50 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #51 Altitude Illness – Injuries; Poisoning – MSD Manual Professional Edition

  https://www.msdmanuals.com/professional/injuries-poisoning/altitude-illness/altitude-illness

  Altitude illness is caused by the decreased availability of oxygen at high altitudes. […] The pathogenesis of acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) remain unclear despite considerable research in this area. […] High-altitude pulmonary edema (HAPE) is caused by hypoxia-induced elevation of pulmonary artery pressure, which causes interstitial and alveolar pulmonary edema, resulting in impaired oxygenation. […] Other factors that contribute to developing altitude illness are the maximum altitude reached and the sleeping altitude. […] The most important measure is a slow ascent. […] Acetazolamide 125 mg orally every 12 hours reduces the incidence of altitude illness.

• #52 Altitude Sickness | Concise Medical Knowledge

  https://www.lecturio.com/concepts/altitude-sickness/

  All symptomatology of AMS and HACE is related to hypoxia. The central nervous system is the most sensitive organ to hypoxia. […] Hypobaric hypoxia from high altitude decreased nitric oxide and increased endothelin 1 in pulmonary vasculature causing vasoconstriction. […] Increased pulmonary capillary pressure interstitial fluid leak causes HAPE.

• #53 Altitude sickness – Wikipedia

  https://en.wikipedia.org/wiki/Altitude_sickness

  High altitude illness can be classified according to the altitude: high (1,500-3,500 metres (4,900-11,500 ft)), very high (3,500-5,500 metres (11,500-18,000 ft)) and extreme (above 5,500 metres (18,000 ft)). […] The physiological cause of altitude-induced edema is not conclusively established. It is currently believed, however, that HACE is caused by local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressures. […] The body’s response to high altitude includes the following: Erythropoietin hematocrit and haemoglobin, 2,3-BPG (allows release of O2 and a right shift on the Hb-O2 disassociation curve), kidney excretion of bicarbonate (use of acetazolamide can augment for treatment), Chronic hypoxic pulmonary vasoconstriction (can cause right ventricular hypertrophy).

• #54 Altitude and Travel – Fit for Travel

  https://www.fitfortravel.nhs.uk/advice/general-travel-health-advice/altitude-and-travel

  At altitude the air pressure is lower and this means there is less oxygen available to your body when you breath. […] The process of your body adapting to the lower oxygen levels is called acclimatisation and it takes about 3 to 5 days. […] If your body does not get enough time to acclimatise to being at high altitude, you can develop altitude sickness (sometimes called mountain sickness). […] Altitude sickness usually happens at levels above 2,500m. […] The major cause of AMS is going too high too quickly. […] If the signs of AMS are ignored and you continue to go higher, you are at risk of developing life threatening altitude sickness, High Altitude Cerebral Oedema (HACE) and/or High Altitude Pulmonary Oedema (HAPE). […] HACE is due to swelling of the brain. […] HAPE is caused by fluid gathering in your lungs. […] Both conditions are an emergency and can quickly result in death; descending to a lower altitude must be carried out immediately.

• #55 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #56 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS can afflict any visitor sleeping higher than 6000 feet. […] We have to admit that the exact cause of AMS is still not clear. Of course, AMS is due to low oxygen, but the steps between low oxygen and AMS are fuzzy. […] Current thinking is that hypoxia (low oxygen) in the air and blood causes the blood vessels of the brain to dilate in an attempt to get more oxygen. […] Some researchers think that AMS is more like a migraine headache, and indeed, AMS and migraine have some similarities, but they are not identical. […] If you have had altitude illness in the past you may be at risk to get it again, since there is a significant genetic component to altitude illness. […] Several factors increase your risk for getting AMS: Your genetic makeup, a history of previous AMS, residence at an altitude below 3000 ft, obesity, current respiratory infection, most importantly, fast rate of ascent, over-exertion the first day or two at altitude, alcohol the first night at altitude.

• #57 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS can afflict any visitor sleeping higher than 6000 feet. […] We have to admit that the exact cause of AMS is still not clear. Of course, AMS is due to low oxygen, but the steps between low oxygen and AMS are fuzzy. […] Current thinking is that hypoxia (low oxygen) in the air and blood causes the blood vessels of the brain to dilate in an attempt to get more oxygen. […] Some researchers think that AMS is more like a migraine headache, and indeed, AMS and migraine have some similarities, but they are not identical. […] If you have had altitude illness in the past you may be at risk to get it again, since there is a significant genetic component to altitude illness. […] Several factors increase your risk for getting AMS: Your genetic makeup, a history of previous AMS, residence at an altitude below 3000 ft, obesity, current respiratory infection, most importantly, fast rate of ascent, over-exertion the first day or two at altitude, alcohol the first night at altitude.

• #58 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #59 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #60 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-Makes-Different-People-More-or-Less-Susceptible-to-Altitude-Sickness.aspx

  Altitude sickness encompasses a range of pulmonary and cerebral conditions caused by hypoxia, which is oxygen deprivation, due to rapid ascent and poor pre-acclimatization to high altitudes. […] The incidence rate of altitude sickness depends on various factors, including an individuals age, gender, rate of ascent, home elevation, overall physical health, previous experience at altitude, and their individual susceptibility to altitude sickness. […] While the main cause of altitude sickness is poor pre-acclimatization and rapid ascent to high altitudes, there is little to suggest that any particular demographic is significantly more susceptible than the other. No significant differences between men and women or ages have currently been identified, and genetic reasons for suffering from AMS are being actively investigated.

• #61 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #62 Altitude Sickness: Signs, Symptoms, Treatment, Medications, Death, Prevention

  https://www.emedicinehealth.com/mountain_sickness/article_em.htm

  Altitude sickness is due to a rapid ascent to higher altitudes (4800 to 11,200 ft or more) due to the decreasing amount of oxygen (low PO2) that occurs at high altitudes. […] The cause of altitude sickness is the decreasing amount of oxygen available as altitude increases. […] Altitude sickness develops when the rate of ascent into higher altitudes outpaces the body’s ability to adjust to those altitudes due to the decreasing levels of oxygen in the air as altitude increases. This results in abnormally low blood levels of oxygen. […] Altitude sickness generally develops at elevations higher than 8,000 feet (about 2,400 meters) above sea level and when the rate of ascent exceeds 1,000 feet (300 meters) per day. […] The following actions can trigger altitude sickness: Ascending too rapidly (not allowing enough time for the body to compensate for decreased oxygen in the air), Overexertion within 24 hours of ascent, Inadequate fluid intake, Hypothermia, Consumption of alcohol or other sedatives. […] It is possible, depending on the person’s health, that an individual can rapidly go through symptoms of acute mountain sickness and then progress to high-altitude pulmonary edema or high-altitude cerebral edema at moderate to high altitudes.

• #63 Acute mountain sickness: MedlinePlus Medical EncyclopediaLock

  https://medlineplus.gov/ency/article/000133.htm

  Acute mountain sickness is caused by reduced air pressure and lower oxygen levels at high altitudes. […] The faster you climb to a high altitude, the more likely you will get acute mountain sickness. […] You are at higher risk for acute mountain sickness if: […] You have not acclimatized appropriately to the altitude. […] Alcohol or other substances have interfered with acclimatization. […] If you have anemia.

• #64 Altitude Sickness: Symptoms, causes and treatment

  https://www.medicalnewstoday.com/articles/179819

  Altitude sickness occurs when a person travels to a high altitude usually above 8,000 feet without gradually acclimatizing. […] The condition generally occurs at altitudes higher than 8,000 feet (ft), or 2,500 meters (m), and is usually due to a lack of oxygen. […] The leading cause of altitude sickness is ascending to a great height too rapidly. Staying at high altitudes for extended periods may also cause forms of altitude sickness. […] At higher altitudes, the oxygen concentration remains the same, but air pressure is much lower. […] The average human body needs from 1 to 3 days to become acclimatized to a change in altitude. […] Rising to higher altitudes can also cause fluid to leak from tiny blood vessels, resulting in a potentially dangerous fluid buildup in the lungs and the brain. […] Both of these conditions are uncommon, but may occur if a person ascends to a very high altitude too rapidly and stays there.

• #65 Altitude Sickness | APEX | Altitude.org

  https://www.altitude.org/altitude-sickness

  Altitude sickness has three forms. […] What causes altitude sickness? […] Two things are certain to make altitude sickness very likely – ascending faster than 500m per day, and exercising vigorously. […] Altitude sickness happens because there is less oxygen in the air that you breathe at high altitudes. […] There is so much less oxygen in the high mountains that it is not surprising that travelling to high altitude causes people to feel unwell, but how this shortage of oxygen actually leads to altitude sickness is still not fully understood. […] Some scientists believe that it is due to swelling of the brain but the evidence for this hypothesis is not conclusive. […] The theory is that in susceptible individuals, swelling could cause a small increase in the pressure inside the skull and lead to symptoms of acute mountain sickness.

• #66 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The goal for the traveler might not be to avoid all symptoms of altitude illness but to have no more than mild illness, thereby avoiding itinerary changes or the need for medical assistance or evacuation. […] Some common high-altitude destinations require rapid ascent by airplane to 11,150 ft (3,400 m), placing travelers in a high-risk category for AMS. […] With rates of altitude illness approaching 50% in these situations, a low threshold for chemoprophylaxis is advised. […] The condition is typically self-limited, developing and resolving over 1-3 days. […] AMS improves rapidly with a descent of 300 m (1,000 ft) or more, especially if exertion is minimal. […] If symptoms worsen while the traveler is at the same altitude and despite treatment, descent is mandatory. […] The main point of instructing travelers about altitude illness is not to eliminate the possibility of mild illness but to prevent severe illness, need for evacuation, or death.

• #67 Altitude and Travel – Fit for Travel

  https://www.fitfortravel.nhs.uk/advice/general-travel-health-advice/altitude-and-travel

  At altitude the air pressure is lower and this means there is less oxygen available to your body when you breath. […] The process of your body adapting to the lower oxygen levels is called acclimatisation and it takes about 3 to 5 days. […] If your body does not get enough time to acclimatise to being at high altitude, you can develop altitude sickness (sometimes called mountain sickness). […] Altitude sickness usually happens at levels above 2,500m. […] The major cause of AMS is going too high too quickly. […] If the signs of AMS are ignored and you continue to go higher, you are at risk of developing life threatening altitude sickness, High Altitude Cerebral Oedema (HACE) and/or High Altitude Pulmonary Oedema (HAPE). […] HACE is due to swelling of the brain. […] HAPE is caused by fluid gathering in your lungs. […] Both conditions are an emergency and can quickly result in death; descending to a lower altitude must be carried out immediately.

• #68 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #69 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #70 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #71 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-Causes-Altitude-Sickness.aspx

  There are many reasons why people ascend to high altitudes, from travel, leisure and sport to making permanent homes at altitude. Some people are more susceptible to altitude sickness, a condition caused by exposure to low oxygen levels at high altitudes. […] The exact cause of HACE is unknown, but it is hypothesized that hypoxia (oxygen deprivation) leads to neurohumoral and hemodynamic responses in the brain, causing leaks from microvascular beds and edema. […] This occurs because of a leak in the alveolar-capillary membrane caused by excessive hypoxia. […] Ascending to high altitudes too quickly remains the main risk factor for developing altitude sickness. […] Getting used to conditions at altitude by spending time at moderate altitudes can decrease the incidence of altitude sickness. […] Medication to prevent altitude sickness is not necessary for low-risk circumstances.

• #72 Altitude Sickness Is Typically Mild But Can Sometimes Turn Very Serious − a High-Altitude Medicine Physician Explains How to Safely Prepare

  https://news.cuanschutz.edu/news-stories/altitude-sickness-is-typically-mild-but-can-sometimes-turn-very-serious-a-high-altitude-medicine-physician-explains-how-to-safely-prepare

  Altitude sickness is rare at elevations of less than 8,200 feet but becomes much more common at higher altitudes. […] Altitude sickness, which most commonly refers to acute mountain sickness, presents a significant challenge to those traveling to and adventuring in high-altitude destinations. […] The risk rapidly increases with higher ascents. Above 9,800 feet (3,000 meters), up to 75% of travelers may develop symptoms. […] When travelers do not properly acclimatize, they can be susceptible to life-threatening altitude illnesses, such as high-altitude pulmonary edema or high-altitude cerebral edema. […] Altitude sickness symptoms are thought to be caused by increased pressure surrounding the brain, which results from the failure of the body to acclimatize to higher elevations. […] People who skip this step and travel directly to high elevations are up to four times more likely to develop altitude sickness symptoms.

• #73 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://wwwnc.cdc.gov/travel/yellowbook/2024/environmental-hazards-risks/high-elevation-travel-and-altitude-illness

  The goal for the traveler might not be to avoid all symptoms of altitude illness but to have no more than mild illness, thereby avoiding itinerary changes or the need for medical assistance or evacuation. […] Some common high-altitude destinations require rapid ascent by airplane to 11,150 ft (3,400 m), placing travelers in a high-risk category for AMS. […] With rates of altitude illness approaching 50% in these situations, a low threshold for chemoprophylaxis is advised. […] Whenever possible, adding extra days to the trek can make for a more enjoyable and safer trip. […] Altitude illness is divided into 3 syndromes: AMS; high-altitude cerebral edema (HACE); and high-altitude pulmonary edema (HAPE). […] AMS is the most common form of altitude illness, affecting, for example, 25% of all visitors sleeping at altitudes 2,450 m (8,000 ft) in Colorado.

• #74 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The goal for the traveler might not be to avoid all symptoms of altitude illness but to have no more than mild illness, thereby avoiding itinerary changes or the need for medical assistance or evacuation. […] Some common high-altitude destinations require rapid ascent by airplane to 11,150 ft (3,400 m), placing travelers in a high-risk category for AMS. […] With rates of altitude illness approaching 50% in these situations, a low threshold for chemoprophylaxis is advised. […] The condition is typically self-limited, developing and resolving over 1-3 days. […] AMS improves rapidly with a descent of 300 m (1,000 ft) or more, especially if exertion is minimal. […] If symptoms worsen while the traveler is at the same altitude and despite treatment, descent is mandatory. […] The main point of instructing travelers about altitude illness is not to eliminate the possibility of mild illness but to prevent severe illness, need for evacuation, or death.

• #75 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-Causes-Altitude-Sickness.aspx

  There are many reasons why people ascend to high altitudes, from travel, leisure and sport to making permanent homes at altitude. Some people are more susceptible to altitude sickness, a condition caused by exposure to low oxygen levels at high altitudes. […] The exact cause of HACE is unknown, but it is hypothesized that hypoxia (oxygen deprivation) leads to neurohumoral and hemodynamic responses in the brain, causing leaks from microvascular beds and edema. […] This occurs because of a leak in the alveolar-capillary membrane caused by excessive hypoxia. […] Ascending to high altitudes too quickly remains the main risk factor for developing altitude sickness. […] Getting used to conditions at altitude by spending time at moderate altitudes can decrease the incidence of altitude sickness. […] Medication to prevent altitude sickness is not necessary for low-risk circumstances.

• #76 Altitude sickness – Wikipedia

  https://en.wikipedia.org/wiki/Altitude_sickness

  High altitude illness can be classified according to the altitude: high (1,500-3,500 metres (4,900-11,500 ft)), very high (3,500-5,500 metres (11,500-18,000 ft)) and extreme (above 5,500 metres (18,000 ft)). […] The physiological cause of altitude-induced edema is not conclusively established. It is currently believed, however, that HACE is caused by local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressures. […] The body’s response to high altitude includes the following: Erythropoietin hematocrit and haemoglobin, 2,3-BPG (allows release of O2 and a right shift on the Hb-O2 disassociation curve), kidney excretion of bicarbonate (use of acetazolamide can augment for treatment), Chronic hypoxic pulmonary vasoconstriction (can cause right ventricular hypertrophy).

• #77 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #78 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #79 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #80 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #81 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #82 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #83 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #84 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #85 High-Altitude Pulmonary Edema (HAPE): Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/300716-overview

  High-altitude pulmonary edema (HAPE) generally occurs 2-4 days after rapid ascent to altitudes in excess of 2500 m (8202 ft). Young people and previously acclimatized people reascending to a high altitude following a short stay at low altitude seem more predisposed to HAPE. Other predisposing factors include the following: […] Preexisting conditions that may predispose toward the development of high-altitude pulmonary edema include the following:

• #86 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #87 Azthena logo with the word Azthena

  https://www.news-medical.net/health/What-Causes-Altitude-Sickness.aspx

  There are many reasons why people ascend to high altitudes, from travel, leisure and sport to making permanent homes at altitude. Some people are more susceptible to altitude sickness, a condition caused by exposure to low oxygen levels at high altitudes. […] The exact cause of HACE is unknown, but it is hypothesized that hypoxia (oxygen deprivation) leads to neurohumoral and hemodynamic responses in the brain, causing leaks from microvascular beds and edema. […] This occurs because of a leak in the alveolar-capillary membrane caused by excessive hypoxia. […] Ascending to high altitudes too quickly remains the main risk factor for developing altitude sickness. […] Getting used to conditions at altitude by spending time at moderate altitudes can decrease the incidence of altitude sickness. […] Medication to prevent altitude sickness is not necessary for low-risk circumstances.

• #88 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  The pathophysiology of high-altitude pulmonary edema is not completely understood, but the primary mechanism is thought to be exaggerated hypoxic pulmonary vasoconstriction that causes increased pulmonary capillary pressure. […] The incidence of high-altitude pulmonary edema in unacclimatized mountaineers at 15,000 ft (4,600 m) is approximately 4 percent. […] Acute mountain sickness is not a prerequisite for the development of high-altitude pulmonary edema. […] High-altitude pulmonary edema is the leading cause of death from altitude illness, but it is avoidable with careful ascent and reversible with early recognition and treatment.

• #89 Altitude Illness – Injuries; Poisoning – MSD Manual Professional Edition

  https://www.msdmanuals.com/professional/injuries-poisoning/altitude-illness/altitude-illness

  Altitude illness is caused by the decreased availability of oxygen at high altitudes. […] The pathogenesis of acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) remain unclear despite considerable research in this area. […] High-altitude pulmonary edema (HAPE) is caused by hypoxia-induced elevation of pulmonary artery pressure, which causes interstitial and alveolar pulmonary edema, resulting in impaired oxygenation. […] Other factors that contribute to developing altitude illness are the maximum altitude reached and the sleeping altitude. […] The most important measure is a slow ascent. […] Acetazolamide 125 mg orally every 12 hours reduces the incidence of altitude illness.

• #90 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  The pathophysiology of high-altitude pulmonary edema is not completely understood, but the primary mechanism is thought to be exaggerated hypoxic pulmonary vasoconstriction that causes increased pulmonary capillary pressure. […] The incidence of high-altitude pulmonary edema in unacclimatized mountaineers at 15,000 ft (4,600 m) is approximately 4 percent. […] Acute mountain sickness is not a prerequisite for the development of high-altitude pulmonary edema. […] High-altitude pulmonary edema is the leading cause of death from altitude illness, but it is avoidable with careful ascent and reversible with early recognition and treatment.

• #91 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  The pathophysiology of high-altitude pulmonary edema is not completely understood, but the primary mechanism is thought to be exaggerated hypoxic pulmonary vasoconstriction that causes increased pulmonary capillary pressure. […] The incidence of high-altitude pulmonary edema in unacclimatized mountaineers at 15,000 ft (4,600 m) is approximately 4 percent. […] Acute mountain sickness is not a prerequisite for the development of high-altitude pulmonary edema. […] High-altitude pulmonary edema is the leading cause of death from altitude illness, but it is avoidable with careful ascent and reversible with early recognition and treatment.

• #92 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS usually resolves by itself, within 6 to 48 hours. […] The headache of AMS improves with rest, and medications such as ibuprofen (Motrin) or acetaminophen (Tylenol) are often sufficient. […] Acetazolamide (Diamox) is a prescription medication that increases breathing, raises the blood oxygen level, speeds up acclimatization and therefore resolves AMS. […] Altitude illness is a general term referring to the three problems that can occur on ascent to altitude: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE). […] AMS and HACE are considered a spectrum of the same altitude illness. […] Any condition that takes up space in the brain such as a brain tumor, hydrocephalus, or recent bleeding increases the risk for HACE as there is less room for brain swelling. […] Risk factors for HAPE include: genetic makeup, a prior history of HAPE, certain preexisting lung and heart conditions, history of high pulmonary artery pressure, men tend to get HAPE more frequently than women, coming to high altitude with a respiratory infection, especially children.

• #93 High-Altitude Pulmonary Edema (HAPE): Causes & Treatment

  https://my.clevelandclinic.org/health/diseases/high-altitude-pulmonary-edema

  What causes HAPE? As you get higher in altitude, the air pressure and oxygen levels are lower than at or near sea level. Your body can eventually adjust to the lower oxygen level, but it takes time. If you increase your altitude too quickly, not enough oxygen will get into your bloodstream and out to your tissues and organs. This can make you sick and eventually be fatal. If part of your lungs isnt getting enough oxygen, the blood vessels in your lungs will narrow. This is an effort to push blood to other parts of your lungs that are working better. It increases the pressure on the vessels, causing them to leak fluid. The fluid will sit in your lungs and make it hard to breathe. Eventually, blood may leak into your lungs, causing you to cough up blood-tinged mucus. […] The biggest risk factor is ascending too quickly, regardless of how healthy or in shape you are. Other risk factors for HAPE include having a history of HAPE, preexisting pulmonary hypertension, differences in the structures of your heart, including intracardiac shunts and blood vessel abnormalities, cold temperatures, and respiratory infections.

• #94 Altitude Illness – Cerebral Syndromes: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/768478-overview

  Altitude illness refers to a group of syndromes that result from hypoxia. […] Rapid ascent to altitudes greater than 2,500 m can cause AMS. […] The risk of HACE or AMS increases with altitude. […] Continued ascent despite symptoms of AMS is a major risk factor for developing HACE. At altitudes over 5,000 m, ascents of as little as 200 m for individuals with moderate AMS have precipitated HACE. […] HACE frequently is seen secondary to HAPE, presumably because of rapidly worsening hypoxia, which is equivalent to continued ascent.

• #95 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS usually resolves by itself, within 6 to 48 hours. […] The headache of AMS improves with rest, and medications such as ibuprofen (Motrin) or acetaminophen (Tylenol) are often sufficient. […] Acetazolamide (Diamox) is a prescription medication that increases breathing, raises the blood oxygen level, speeds up acclimatization and therefore resolves AMS. […] Altitude illness is a general term referring to the three problems that can occur on ascent to altitude: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE). […] AMS and HACE are considered a spectrum of the same altitude illness. […] Any condition that takes up space in the brain such as a brain tumor, hydrocephalus, or recent bleeding increases the risk for HACE as there is less room for brain swelling. […] Risk factors for HAPE include: genetic makeup, a prior history of HAPE, certain preexisting lung and heart conditions, history of high pulmonary artery pressure, men tend to get HAPE more frequently than women, coming to high altitude with a respiratory infection, especially children.

• #96 Altitude Sickness: What It Is, Symptoms, Treatment & Prevention

  https://my.clevelandclinic.org/health/diseases/15111-altitude-sickness

  Altitude sickness is when your body doesnt have time to adjust to lower oxygen availability higher up in the atmosphere. […] Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen youre getting with each breath. […] Given time, your body can usually adapt to altitude-related changes that affect how much oxygen you get with each breath. Without enough time to adapt, altitude sickness is the result. […] The risk factors for altitude sickness often relate to the altitude itself or how you get there. […] A common misconception is that your physical health is a risk factor for developing altitude sickness. It isnt, but altitude sickness can make symptoms of some existing conditions worse. […] Altitude sickness can become deadly if AMS turns into HAPE or HACE. HAPE can be deadly within 12 hours. HACE can be deadly within 24 hours. […] The outlook for altitude sickness depends on the severity, how you react to the symptoms and how you respond to treatment. If you ignore symptoms and keep ascending, youll likely experience worsening symptoms.

• #97 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html

  The biggest concern, however, is hypoxia, due to the decreased partial pressure of oxygen (PO2). […] The magnitude and consequences of hypoxic stress depend on the altitude, rate of ascent, and duration of exposure; host genetic factors may also contribute. […] Altitude illness can develop before the acute acclimatization process is complete, but not afterward. […] Any unacclimatized traveler proceeding to a sleeping altitude of 2,450 m (8,000 ft) and sometimes lower is at risk for altitude illness. […] In addition, travelers who have successfully adjusted to an altitude are at risk when moving to higher sleeping altitudes, especially if the altitude gain is 600-900 m (2,000-3,000 ft). […] How a traveler previously responded to high altitude is the most reliable guide for future trips but only if the altitude and rate of ascent are similar, and even then, this is not an infallible predictor.

• #98 Altitude Illness: Risk Factors, Prevention, Presentation, and Treatment | AAFP

  https://www.aafp.org/pubs/afp/issues/2010/1101/p1103.html

  Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. […] Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. […] High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. […] Risk factors for altitude illness include rapid ascent, strenuous physical exertion, young age, living at a low altitude, and a history of altitude illness. […] Rapid ascent is the most important and modifiable risk factor. […] Although the pathophysiology of acute mountain sickness and high-altitude cerebral edema is not completely understood, current evidence suggests that hypobaric hypoxemia leads to relative fluid retention, in contrast with the usual response of marked diuresis in nonaffected climbers.

• #99 Altitude Sickness | APEX | Altitude.org

  https://www.altitude.org/altitude-sickness

  Altitude sickness has three forms. […] What causes altitude sickness? […] Two things are certain to make altitude sickness very likely – ascending faster than 500m per day, and exercising vigorously. […] Altitude sickness happens because there is less oxygen in the air that you breathe at high altitudes. […] There is so much less oxygen in the high mountains that it is not surprising that travelling to high altitude causes people to feel unwell, but how this shortage of oxygen actually leads to altitude sickness is still not fully understood. […] Some scientists believe that it is due to swelling of the brain but the evidence for this hypothesis is not conclusive. […] The theory is that in susceptible individuals, swelling could cause a small increase in the pressure inside the skull and lead to symptoms of acute mountain sickness.

• #100 Altitude sickness | Better Health Channel

  https://www.betterhealth.vic.gov.au/health/healthyliving/altitude-sickness

  Mountain climbers are at risk of developing altitude sickness. […] Altitude sickness is caused by ascending too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure. […] It is caused by gaining altitude too rapidly, which doesn’t allow the body enough time to adjust to reduced oxygen and changes in air pressure, and causes hypobaric hypoxia (a lack of oxygen reaching the tissues of the body). […] Men are at greater risk of altitude sickness than women, for reasons unknown. […] The only sure method of prevention is to take plenty of time to ascend. […] The best way to prevent altitude sickness is to ascend slowly. […] Considerable evidence exists for the effectiveness of acetazolamide as a preventative. […] Be aware that you are at increased risk of altitude sickness if you have experienced it before.

• #101 Altitude Illness — Institute For Altitude Medicine

  http://www.highaltitudedoctor.org/altitude-illness

  AMS usually resolves by itself, within 6 to 48 hours. […] The headache of AMS improves with rest, and medications such as ibuprofen (Motrin) or acetaminophen (Tylenol) are often sufficient. […] Acetazolamide (Diamox) is a prescription medication that increases breathing, raises the blood oxygen level, speeds up acclimatization and therefore resolves AMS. […] Altitude illness is a general term referring to the three problems that can occur on ascent to altitude: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE). […] AMS and HACE are considered a spectrum of the same altitude illness. […] Any condition that takes up space in the brain such as a brain tumor, hydrocephalus, or recent bleeding increases the risk for HACE as there is less room for brain swelling. […] Risk factors for HAPE include: genetic makeup, a prior history of HAPE, certain preexisting lung and heart conditions, history of high pulmonary artery pressure, men tend to get HAPE more frequently than women, coming to high altitude with a respiratory infection, especially children.

• #102 High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

  A rapid rate of ascent is an important contributor to the development of AMS. […] Early hypoxemia, a decrease in the SaO2 greater than that expected for a given altitude, is a risk factor for developing AMS. […] A prior history of AMS is an important predictor for developing AMS on subsequent exposures to comparable altitudes. […] The exact processes leading to high-altitude cerebral edema are unknown although the edema is probably extracellular, due to blood-brain barrier leakage (vasogenic edema), rather than intracellular, due to cellular swelling (cytotoxic edema). […] High-altitude pulmonary edema (HAPE) is a potentially fatal consequence of rapid ascent to high altitude. […] The pathogenesis of high-altitude pulmonary edema is still a subject for investigation; however, it is probably triggered by an increase in pulmonary artery pressure due to the normal pulmonary vasoconstriction induced by hypoxia.

• #103 High-altitude cerebral edema – Wikipedia

  https://en.wikipedia.org/wiki/High-altitude_cerebral_edema

  Hypoxia increases extracellular fluid, which passes through the vasogenic endothelium in the brain. […] It has been hypothesized that vascular endothelial growth factor may cause the vascular permeability at the root of HACE. […] While there is strong evidence that vasogenic edema plays a major role in HACE, cytotoxic edema, cellular retention of fluids, may contribute as well. […] Cytotoxic edema may be caused by the failure of cellular ion pumps, which results from hypoxia. […] It is not known why some are more vulnerable to HACE than others. […] One theory is that variations in brain size play a role, but the increase in brain volume from edema does not likely cause cranial vault impingement. […] Another theory about the cause of HACE is that hypoxia may induce nitrous oxide synthase. […] Vasodilation is caused by the release of nitric oxide and adenosine. […] This in turn can increase vascular permeability and causes edema.

• #104 Altitude and Travel – Fit for Travel

  https://www.fitfortravel.nhs.uk/advice/general-travel-health-advice/altitude-and-travel

  At altitude the air pressure is lower and this means there is less oxygen available to your body when you breath. […] The process of your body adapting to the lower oxygen levels is called acclimatisation and it takes about 3 to 5 days. […] If your body does not get enough time to acclimatise to being at high altitude, you can develop altitude sickness (sometimes called mountain sickness). […] Altitude sickness usually happens at levels above 2,500m. […] The major cause of AMS is going too high too quickly. […] If the signs of AMS are ignored and you continue to go higher, you are at risk of developing life threatening altitude sickness, High Altitude Cerebral Oedema (HACE) and/or High Altitude Pulmonary Oedema (HAPE). […] HACE is due to swelling of the brain. […] HAPE is caused by fluid gathering in your lungs. […] Both conditions are an emergency and can quickly result in death; descending to a lower altitude must be carried out immediately.

• #105 High-Altitude Travel and Altitude Illness | Yellow Book | CDC

  https://wwwnc.cdc.gov/travel/yellowbook/2024/environmental-hazards-risks/high-elevation-travel-and-altitude-illness

  The goal for the traveler might not be to avoid all symptoms of altitude illness but to have no more than mild illness, thereby avoiding itinerary changes or the need for medical assistance or evacuation. […] Some common high-altitude destinations require rapid ascent by airplane to 11,150 ft (3,400 m), placing travelers in a high-risk category for AMS. […] With rates of altitude illness approaching 50% in these situations, a low threshold for chemoprophylaxis is advised. […] Whenever possible, adding extra days to the trek can make for a more enjoyable and safer trip. […] Altitude illness is divided into 3 syndromes: AMS; high-altitude cerebral edema (HACE); and high-altitude pulmonary edema (HAPE). […] AMS is the most common form of altitude illness, affecting, for example, 25% of all visitors sleeping at altitudes 2,450 m (8,000 ft) in Colorado.

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