SafekipediaAltitude sickness
Adapted from Wikipedia · Discoverer experience
Altitude sickness is a problem that can happen when people go to very high places where there is less oxygen. When someone climbs quickly to a high altitude, their body may not have enough time to adjust, and this can cause symptoms like headaches, tiredness, trouble sleeping, dizziness, and sometimes vomiting.
This kind of sickness usually happens above 2,500 metres, which is about 8,000 feet, but some people can feel it even at lower heights. Having had altitude sickness before, moving up very quickly, or being very active can increase the risk. Being in good physical shape does not protect someone from getting it.
To prevent altitude sickness, it is best to climb slowly, increasing elevation by no more than 300 metres (1,000 feet) each day. If symptoms appear, resting and drinking plenty of fluids can help. For mild cases, certain medicines may be used, and severe cases need immediate descent to lower altitudes. The only sure way to get better from serious altitude sickness is to go down until the symptoms go away.
Signs and symptoms
People can get altitude sickness when they go up very high mountains quickly. This happens because there is less oxygen in the air at high places. Some people might feel sick even at heights around 2,000 metres, like at ski resorts. Symptoms usually start showing up within ten hours of climbing and often get better in a couple of days. But sometimes, they can become more serious.
Common symptoms include headaches, feeling tired, stomach trouble, dizziness, and trouble sleeping. Moving around can make these feelings worse. Headaches are a main sign of altitude sickness, especially if they happen above 2,400 metres and come with other symptoms like feeling very tired or dizzy.
More serious symptoms can include fluid building up in the lungs, coughing, fever, and feeling short of breath even when resting. There can also be swelling in the brain, which causes headaches that don’t go away, trouble walking, and confusion. These serious symptoms need quick help, like moving to a lower altitude, to get better.
| Disordered system | Symptoms |
|---|---|
| Gastrointestinal | Loss of appetite, nausea, vomiting, excessive flatulation |
| Nervous | Fatigue or weakness, headache with or without dizziness or lightheadedness, insomnia, "pins and needles" sensation |
| Locomotory | Peripheral edema (swelling of hands, feet, and face) |
| Respiratory | Nose bleeding, shortness of breath upon exertion |
| Cardiovascular | Persistent rapid pulse |
| Other | General malaise |
Cause
See also: Breathing § Breathing at altitude, and Effects of high altitude on humans
Altitude sickness can start when you go up to about 1,500 metres (4,900 ft). The problem gets worse the higher you go, especially above 5,500 metres (18,000 ft), where you might need extra oxygen to stay safe.
When you climb high up, there is less air pressure and less oxygen to help you think and move. Even though the air still has about the same amount of oxygen, your body finds it harder to get enough. This can make you feel unwell. How fast you climb, how high you go, and how active you are all affect how likely you are to get altitude sickness.
Usually, if you climb slowly, your body can get used to the height, and the bad feelings will go away. But if you climb too fast to very high places, it can be very dangerous.
High altitude
At heights between 1,500 to 3,500 metres (4,900 to 11,500 ft), you might notice you get tired more quickly and need to breathe more. Your blood still carries enough oxygen, but you might feel the effects more.
Very high altitude
Between 3,500 to 5,500 metres (11,500 to 18,000 ft), getting enough oxygen gets much harder. This can cause serious problems, especially when you’re active or sleeping.
Extreme altitude
Above 5,500 metres (18,000 ft), there isn’t enough oxygen to keep your body working well. People can’t live permanently above this height. If you climb here too fast without extra oxygen, you could get very sick.
Mechanism
When you go very high up in the mountains, there is less oxygen in the air. This can make it hard for your body to get enough oxygen, which can cause problems. Your body tries to adjust by making more red blood cells to carry oxygen and by changing how your blood works.
People can feel sick from this kind of air, with symptoms like headaches or feeling tired. Their bodies might not respond well to the change, and extra fluid can build up in important parts like the brain. This is why it's important to take it easy when moving to high places.
| Type | At Sea Level | At 8400 m (The Balcony of Everest) | Formula |
|---|---|---|---|
| Pressure of oxygen in the alveolus | 21 % × ( 101.3 kPa − 6.3 kPa ) − ( 5.3 kPa 0.8 ) = 13.3 kPa O 2 {\textstyle 21\%\times (101.3{\text{ kPa}}-6.3{\text{ kPa}})-\left({\frac {5.3{\text{ kPa}}}{0.8}}\right)=13.3{\text{ kPa O}}_{2}} | 21 % × ( 36.3 kPa − 6.3 kPa ) − ( 1.8 kPa 0.74 ) = 3.9 kPa O 2 {\textstyle 21\%\times (36.3{\text{ kPa}}-6.3{\text{ kPa}})-\left({\frac {1.8{\text{ kPa}}}{0.74}}\right)=3.9{\text{ kPa O}}_{2}} | F I O 2 × ( P B − P H 2 O ) − ( P CO 2 RQ ) {\textstyle F_{I}{\text{O}}_{2}\times (P_{\text{B}}-P_{{\text{H}}_{2}{\text{O}}})-\left({\frac {P_{{\text{CO}}_{2}}}{\text{RQ}}}\right)} |
| Oxygen carriage in the blood | ( 0.98 × 1.34 × 14 g dL ) + ( 0.023 × 12 kPa ) = 17.3 mL O 2 100 mL blood {\textstyle \left(0.98\times 1.34\times 14{\frac {\text{g}}{\text{dL}}}\right)+(0.023\times 12{\text{ kPa}})={\frac {17.3{\text{ mL O}}_{2}}{100{\text{ mL blood}}}}} | ( 0.54 × 1.34 × 19.3 g dL ) + ( 0.023 × 3.3 kPa ) = 14.0 mL O 2 100 mL blood {\textstyle \left(0.54\times 1.34\times 19.3{\frac {\text{g}}{\text{dL}}}\right)+(0.023\times 3.3{\text{ kPa}})={\frac {14.0{\text{ mL O}}_{2}}{100{\text{ mL blood}}}}} | ( Sa O 2 × 1.34 mL g Hb × Hb ) + ( O 2 carriage in blood × Pa O 2 ) {\textstyle ({\text{Sa}}_{{\text{O}}_{2}}\times 1.34{\tfrac {\text{mL}}{\text{g Hb}}}\times {\text{Hb}})+({\text{O}}_{2}{\text{ carriage in blood}}\times {\text{Pa}}_{{\text{O}}_{2}})} |
Diagnosis
Altitude sickness is usually figured out by yourself because the signs are clear, like feeling sick to your stomach, throwing up, or having a headache. These signs often happen when you quickly go up a mountain or to a place with less air. But, sometimes these signs can look like dehydration. In serious cases, a doctor might use special machines like an MRI or CT scan to see if there is extra fluid in the lungs or brain.
Prevention
Ascending slowly is the best way to avoid altitude sickness. Avoiding strenuous activity such as skiing, hiking, etc. in the first 24 hours at high altitude may reduce the symptoms of AMS. Alcohol and sleeping pills slow down the acclimatization process and should be avoided. Alcohol also tends to cause dehydration and makes AMS worse. Thus, avoiding alcohol consumption in the first 24–48 hours at a higher altitude is optimal.
Pre-acclimatization is when the body develops tolerance to low oxygen concentrations before ascending to an altitude. It significantly reduces risk because less time has to be spent at altitude to acclimatize in the traditional way. Several commercial systems exist that use altitude tents, so called because they mimic altitude by reducing the percentage of oxygen in the air while keeping air pressure constant to the surroundings. Examples of pre-acclimation measures include remote ischaemic preconditioning, using hypobaric air breathing in order to simulate altitude, and positive end-expiratory pressure.
Altitude acclimatization is the process of adjusting to decreasing oxygen levels at higher elevations, in order to avoid altitude sickness. Once above approximately 3,000 metres (10,000 ft) – a pressure of 70 kilopascals (0.69 atm) – most climbers and high-altitude trekkers take the "climb-high, sleep-low" approach. For high-altitude climbers, a typical acclimatization regimen might be to stay a few days at a base camp, climb up to a higher camp (slowly), and then return to base camp. A subsequent climb to the higher camp then includes an overnight stay. This process is then repeated a few times, each time extending the time spent at higher altitudes to let the body adjust to the oxygen level there, a process that involves the production of additional red blood cells. Once the climber has acclimatized to a given altitude, the process is repeated with camps placed at progressively higher elevations. The rule of thumb is to ascend no more than 300 m (1,000 ft) per day to sleep.
The drug acetazolamide (trade name Diamox) may help some people making a rapid ascent to sleeping altitude above 2,700 metres (9,000 ft), and it may also be effective if started early in the course of AMS. Acetazolamide can be taken before symptoms appear as a preventive measure at a dose of 125 mg twice daily. The Everest Base Camp Medical Centre cautions against its routine use as a substitute for a reasonable ascent schedule, except where rapid ascent is forced by flying into high altitude locations or due to terrain considerations. The Centre suggests a dosage of 125 mg twice daily for prophylaxis, starting from 24 hours before ascending until a few days at the highest altitude or on descending; with 250 mg twice daily recommended for treatment of AMS. The Centers for Disease Control and Prevention (CDC) suggest the same dose for prevention of 125 mg acetazolamide every 12 hours. Acetazolamide, a mild diuretic, works by stimulating the kidneys to secrete more bicarbonate in the urine, thereby acidifying the blood. This change in pH stimulates the respiratory center to increase the depth and frequency of respiration, thus speeding the natural acclimatization process. An undesirable side-effect of acetazolamide is a reduction in aerobic endurance performance. Other minor side effects include a tingle-sensation in hands and feet.
There is insufficient evidence to determine the safety of sumatriptan and if it may help prevent altitude sickness. Despite their popularity, antioxidant treatments have not been found to be effective medications for prevention of AMS. Interest in phosphodiesterase inhibitors such as sildenafil has been limited by the possibility that these drugs might worsen the headache of mountain sickness. A promising possible preventive for altitude sickness is myo-inositol trispyrophosphate (ITPP), which increases the amount of oxygen released by hemoglobin.
Prior to the onset of altitude sickness, ibuprofen is a suggested non-steroidal anti-inflammatory and painkiller that can help alleviate both the headache and nausea associated with AMS. It has not been studied for the prevention of cerebral edema (swelling of the brain) associated with extreme symptoms of AMS.
Herbal supplements and traditional medicines are sometimes suggested to prevent high altitude sickness including ginkgo biloba, R crenulata, minerals such as iron, antacids, and hormonal-based supplements such as medroxyprogesterone and erythropoietin. Medical evidence to support the effectiveness and safety of these approaches is often contradictory or lacking. Indigenous peoples of the Americas, such as the Aymaras of the Altiplano, have for centuries chewed coca leaves to try to alleviate the symptoms of mild altitude sickness. This therapy has not been proven effective in a clinical study. In Chinese and Tibetan traditional medicine, an extract of the root tissue of Radix rhodiola is often taken in order to prevent the symptoms of high altitude sickness, however, no clear medical studies have confirmed the effectiveness or safety of this extract.
In high-altitude conditions, oxygen enrichment can counteract the hypoxia related effects of altitude sickness. A small amount of supplemental oxygen reduces the equivalent altitude in climate-controlled rooms. At 3,400 metres (11,200 ft) (67 kPa or 0.66 atm), raising the oxygen concentration level by 5% via an oxygen concentrator and an existing ventilation system provides an effective altitude of 3,000 m (10,000 ft) (70 kPa or 0.69 atm), which is more tolerable for those unaccustomed to high altitudes.
Oxygen from gas bottles or liquid containers can be applied directly via a nasal cannula or mask. Oxygen concentrators based upon pressure swing adsorption (PSA), VSA, or vacuum-pressure swing adsorption (VPSA) can be used to generate the oxygen if electricity is available. Stationary oxygen concentrators typically use PSA technology, which has performance degradations at the lower barometric pressures at high altitudes. One way to compensate for the performance degradation is to use a concentrator with more flow capacity. There are also portable oxygen concentrators that can be used on vehicular DC power or on internal batteries, and at least one system commercially available measures and compensates for the altitude effect on its performance up to 4,000 m (13,000 ft). The application of high-purity oxygen from one of these methods increases the partial pressure of oxygen by raising the FiO2 (fraction of inspired oxygen).
Increased water intake may also help in acclimatization to replace the fluids lost through heavier breathing in the thin, dry air found at altitude, although consuming excessive quantities ("over-hydration") has no benefits and may cause dangerous hyponatremia.
Treatment
If someone has severe altitude sickness, the best way to get better is to go down to a lower altitude until they feel well again.
There are some ways doctors can help if going down right away is not possible. Giving oxygen can help with milder cases of altitude sickness. A special bag called a Gamow bag can also help by making it feel like the person is at a lower altitude. Some medicines, like acetazolamide, can help the body adjust to high altitudes faster. In some places, people use tea made from the coca plant to help with symptoms. Steroids can help with certain serious symptoms but do not fix the main problem of altitude sickness. Certain pain relievers like ibuprofen or paracetamol may also help reduce some symptoms.
Epidemiology
José de Acosta, SJ (1539 or 1540 in Medina del Campo, Spain – February 15, 1600 in Salamanca, Spain) was a sixteenth-century Spanish Jesuit missionary and naturalist in Latin America. His ideas about the health problems people face when crossing the Andes in 1570 helped us understand altitude sickness better, now sometimes called Acosta's disease.
Tourists and mountain climbers often get altitude sickness. Who gets it more depends on things like age, health, how active they usually are, and how fast they go up the mountain. People with certain health issues, like anemia or problems with their lungs, heart, or nervous system, are more likely to get altitude sickness.
Altitude sickness is also common for workers in mines in the Chilean Andes. Because these workers often live at lower elevations and then work very high up, they can get sick. Chilean law requires tests to make sure workers can handle working at high altitudes and moves those who can't to lower places, still paying their usual salary. Unlike Chile, the United States and Peru did not have such laws for mining workers as of 2017.
We still don’t know much about how working at high altitudes, but only visiting them sometimes, affects miners’ health.
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