Higher disease , also known as acute mountain disease ( AMS ), is a negative health effect of high altitude, caused by acute exposure to low amounts oxygen at high altitudes. It presents as a collection of nonspecific symptoms, obtained at high altitudes or low air pressure, resembling cases of "flu, carbon monoxide poisoning, or hangover".
Although minor symptoms such as shortness of breath can occur at an altitude of 1,500 meters (5,000 feet), AMS usually occurs only over 2,400 meters (8,000 feet). It is difficult to determine who will be affected by altitude sickness. Diagnosis is supported in those with moderate to severe activity reduction.
Acute mountain disease can progress to high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE), both potentially fatal, and can only be cured by descending directly to low altitudes or oxygen delivery. Chronic mountain disease is a different condition that occurs only after long-term exposure to high altitudes.
Video Altitude sickness
Signs and symptoms
People have different vulnerabilities to altitude sickness; for some healthy people, acute altitude sickness can begin to appear at about 2,000 meters (6,600 feet) above sea level, as in many mountain ski resorts, equivalent to 80 kilopascal pressure (0.79Ã, atm). This is the most common type of altitude sickness. Symptoms often show themselves six to ten hours after the climb and generally subside within one to two days, but they sometimes develop into more serious conditions. Symptoms include headache, fatigue, abdominal pain, dizziness, and sleep disorders. Exertion exacerbates symptoms.
People with the lowest initial partial pressure of end-tidal pOK 2 (lowest concentrations of carbon dioxide at the end of the respiratory cycle, higher alveolar ventilation size) and high oxygen saturation rates tend to have an incidence of acute mountain disease which is lower than that of high end tidal 2 and low oxygen saturation levels.
The main symptoms
Headaches are the main symptoms used to diagnose altitude sickness, although headache is also a symptom of dehydration. Headaches that occur at an altitude above 2,400 meters (7,900 feet) - a pressure of 76 kilopascals (0.75Ã, atm) Ã, - combined with one or more of the following symptoms, may indicate altitude sickness:
Severe symptoms
Symptoms that may indicate life-threatening altitude sickness include:
- Pulmonary edema (fluid in the lungs)
- Symptoms similar to bronchitis
- Persistent dry cough
- Fever
- Shortness of breath even when resting
- Cerebral edema (brain swelling)
- Headaches that do not respond to analgesics
- Unstable walking style
- Loss of gradual consciousness
- Increased nausea and vomiting
- Retinal bleeding
The most serious symptoms of altitude sickness arise from edema (accumulation of fluid in body tissues). At very high altitudes, humans may experience elevated pulmonary edema (HAPE), or high altitude cerebral edema (HACE). Physiological causes of altitude-induced edema are not defined. It is now believed, however, that HACE is caused by local vasodilation of the blood vessels of the brain in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressure. On the other hand, HAPE may be caused by a common vasoconstriction in the pulmonary circulation (usually a response to regional-perfusion ventilation mismatch) which, with constant cardiac output increase, also causes an increase in capillary pressure. For those who suffer from HACE, dexamethasone may provide temporary relief from symptoms to keep it down under their own strength.
HAPE can develop quickly and often fatal. Symptoms include fatigue, severe dyspnea at rest, and initially dry cough but may develop to produce foaming sputum. Descent to lower altitudes reduce HAPE symptoms.
HACE is a life-threatening condition that can lead to coma or death. Symptoms include headache, fatigue, visual impairment, bladder dysfunction, bowel dysfunction, loss of coordination, paralysis on one side of the body, and confusion. Descendants to the lowlands can save those who suffer from HACE.
Maps Altitude sickness
Cause
Altitude disease may first occur at 1,500 meters, with the effect of being severe at extreme heights (over 5,500 meters). Only a short trip over 6,000 meters is possible and extra oxygen is needed to prevent illness.
As the altitude increases, the amount of oxygen available to maintain mental and physical alertness decreases with overall air pressure, although the relative percentage of oxygen in the air, about 21%, remains practically unchanged up to 21,000 meters (70,000 feet). The speed of RMS nitrogen and diatomic oxygen is very similar so there is no change in the ratio of oxygen to nitrogen to the height of the stratosphere.
Dehydration due to higher water vapor levels lost from the lungs at higher altitudes can contribute to altitude sickness symptoms.
The level of climbing, altitude achieved, the amount of physical activity at altitude, as well as individual susceptibility, are factors that contribute to the onset and severity of high altitude sickness.
Altitude disease usually occurs after a fast ascent and can usually be prevented by rising slowly. In most of these cases, the symptoms are temporary and usually subside due to altitude acclimatization. However, in extreme cases, altitude sickness can be fatal.
High altitude
At high altitudes, 1,500 to 3,500 meters (4,900 to 11,500 feet), the physiological effects of reduced inspiratory oxygen pressure (PiO 2 ) include decreased exercise performance and increased ventilation (low arterial partial pressure of carbon dioxide - PCO 2 ). While arterial oxygen transport may be only slightly damaging to arterial oxygen saturation, SaO 2 , generally remains above 90%. Altitude diseases are common between 2,400 and 4,000 m because of the large number of people who rise rapidly to this height.
Very high altitude
At very high altitudes, 3,500 to 5,500 meters (11,500 to 18,000 feet), the maximum of SaO 2 drops below 90% as the arterial PO 2 falls below 60mmHg. Extreme hypoxemia can occur during exercise, during sleep, and the presence of high altitude pulmonary edema or other acute lung conditions. Severe altitude disease occurs most often in this range.
Extreme height
Above 5,500 meters (18,000 feet), marked hypoxemia, hypokapnia, and alkalosis are characteristic of extreme heights. The progressive decline in physiological functions ultimately goes beyond acclimatization. As a result, there is no permanent human habitation above 6,000 meters (20,000 feet). Acclimatization period is required when climbing to extreme heights; a sudden ascent without additional oxygen to other than short exposure invites severe altitude sickness.
Mechanism
The physiology of altitude sickness lies around the alveolar gas equation; low atmospheric pressure, but still there is 20.9% Oxygen, water vapor still occupies the same pressure too, this means that there is less oxygen pressure available in the lungs and blood. Compare these two equations by comparing the amount of oxygen in the blood at altitude:
Hypoxia causes increased minute ventilation (hence both low CO 2 , and then bicarbonate), Hb is increased through hemoconcentration and erythrogenesis. Alkylosis shifts the dissociation constant of hemaglobin to the left, 2,3-DPG increases to fight this. Cardiac output increases with increased heart rate.
The body's response to altitude includes the following:
- ? Erythropoietin ->? hematocrit and hemoglobin
- ? 2.3-BPG (allowing release of O 2 and right shift on the dissociation curve Hb-O 2 )
- ? excretion of renal bicarbonate (use of acetazolamide may increase treatment)
- Chronic hypoxic pulmonary vasoconstriction (may cause right ventricular hypertrophy)
People with high altitude sickness generally have a reduced hyperventilator response, disturbed gas exchange, fluid retention or an increase in sympathetic drive. There is an estimated increase in cerebral venous volume due to increased cerebral blood flow and cerebral vasoconstriction resulting in edema.
Diagnosis
Diagnosis can be helped by a number of different scoring systems.
Prevention
Falling slowly is the best way to avoid altitude sickness. Avoid strenuous activities like skiing, hiking, etc. In the first 24 hours at high altitude it reduces the symptoms of AMS. Alcohol and sleeping pills are respiratory depressants, and thus slow down the acclimatization process and should be avoided. Alcohol also tends to cause dehydration and aggravate AMS. Thus, avoiding alcohol consumption in the first 24-48 hours at higher altitudes is optimal.
Pre-acclimatization
Pre-acclimatization is when the body develops tolerance to low oxygen concentrations before rising to altitude. This significantly reduces the risk because less time should be spent in height to adapt to the traditional way. In addition, because less time should be spent on the mountain, less food and supplies should be taken. Some commercial systems exist that use altitude tents, so called because they mimic the altitude by reducing the percentage of oxygen in the air while maintaining constant air pressure around it.
Altitude acclimatization
The altitude acclimatization is a process of adjustment to lower oxygen levels at higher altitudes, to avoid altitude sickness. After being above about 3,000 meters (10,000 feet) - a pressure of 70 kilopascals (0.69Ã, atm) Ã, - most climbers and high-altitude climbers take the "high-climbing, low-sleep" approach. For highland climbers, a typical acclimatization adjustment regime may stay for a few days at base camp, climb to higher camp (slowly), and then return to the base camp. The next ascent to the higher camp then includes an overnight stay. This process is then repeated several times, each time extending the time spent in a higher place in order for the body to adjust to the oxygen level there, a process involving the production of additional red blood cells. Once the climber has adjusted to a certain height, the process is repeated with camps placed at higher altitudes. The rule of thumb is to ride no more than 300 m (1,000 ft) per day to sleep. That is, one can climb from 3,000 m (9,800 feet) (70 kPa or 0.69 atm) to 4,500 m (15,000 ft) (58 kPa or 0.57 at atm) in one day, but one then has to fall back to 3,300 m (10,800 ft) (67.5 kPa or 0.666 atm) for sleeping. This process can not be easily rushed, and this is why climbers need to spend days (or even weeks) adjusting before trying to climb a high peak. Simulation height equipment such as awning height provides hypoxic air (reduced oxygen), and is designed to allow partial pre-acclimatization to high altitudes, reducing the total time required on the mountain itself.
The altitude acclimatization is required for some people moving rapidly from low altitudes to medium altitudes (eg, by plane and ground transportation for several hours), such as from sea level to 8,000 feet (2,400 m) as in many Colorado mountain resorts USA. Stopping at medium-height overnight (for example, staying overnight in Denver, at 5,500 feet (1,700 m), when traveling to a Colorado resort mentioned above) can reduce or eliminate AMS's appearance.
Drugs
The drug acetazolamide (the Diamox trade name) can help some people make a quick climb to a sleeping height above 2,700 meters (9,000 feet), and it may also be effective if it starts at the start of the AMS journey. Acetazolamide can be taken before symptoms appear as a preventive measure with a dose of 125mg twice daily. Everest Base Camp Medical Center warns its regular use as a substitute for a reasonable climbing schedule, unless fast ascent is forced to fly to a high altitude location or due to terrain considerations. The center recommends a dose of 125mg twice daily for prophylaxis, ranging from 24 hours before rising to several days at the highest altitudes or downhill; with 250mg twice daily recommended for AMS treatment. The Centers for Disease Control and Prevention (CDC) recommend the same dose for the prevention of 125 mg of acetazolamide every 12 hours. Acetazolamide, a mild diuretic, works by stimulating the kidneys to secrete more bicarbonate in the urine, thereby moistening the blood. This pH change stimulates the respiratory center to increase the depth and frequency of respiration, thus accelerating the natural acclimatization process. An undesirable side effect of acetazolamide is a decrease in aerobic endurance performance. Other minor side effects include tingle sensation in the hands and feet. Although sulfonamide; acetazolamide is non-antibiotic and has not been shown to cause life-threatening allergic cross-reactivity in those with self-reported sulfonamide allergies. A dose of 1000 mg/day will result in a 25% reduction in performance, above reduction due to high altitude exposure. The CDC recommends that Dexamethasone be reserved for the treatment of severe AMS and HACE during descents, and noted that Nifedipine may prevent HAPE.
One randomized controlled trial found that sumatriptan may help prevent altitude sickness. Despite their popularity, antioxidant treatments have not been found as an effective drug for prevention of AMS. Interest in phosphodiesterase inhibitors such as sildenafil has been limited by the likelihood that these drugs may aggravate mountain disease headaches. A possible precaution 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 an anti-inflammatory and recommended non-steroidal pain reliever that can help relieve headache and nausea associated with AMS. This has not been studied for the prevention of cerebral edema (brain swelling) associated with extreme symptoms of AMS.
For centuries, Native Americans such as Aymaras of Altiplano, have chewed coca leaf to try to alleviate the symptoms of mild altitude sickness. In traditional Chinese and Tibetan medicine, root tissue extract Radix rhodiola is often taken to prevent the same symptoms, although none of these treatments have been shown to be effective in clinical studies.
Oxygen enrichment
In high altitude conditions, oxygen enrichment can counteract the effects of hypoxia associated with altitude sickness. A small amount of supplemental oxygen reduces equivalent altitudes in climate-controlled rooms. At 3,400 meters (11,200 feet) (67 kPa or 0.66 atm), raising the oxygen concentration level by 5% through the oxygen concentrator and the existing ventilation system provides effective 3,000 m (10,000 ft) (70 kpa or 0.69 atm) , which is more tolerable for those unfamiliar with high altitudes.
Oxygen from gas bottles or liquid containers can be directly applied through the nasal cannula or mask. The oxygen concentrator based on adsorption swing pressure (PSA), VSA, or vacuum-pressure swing adsorption (VPSA) can be used to produce oxygen if electricity is available. Stationary oxygen concentrators typically use PSA technology, which has a decrease in performance at lower barometric pressure at high altitudes. One way to offset the performance degradation is to use concentrators with more flow capacities. There are also portable oxygen concentrators that can be used on DC power vehicles or on internal batteries, and at least one commercially available system and compensate for altitude effects on performance up to 4,000 m (13,000 ft). The high purity oxygen application of one of these methods increases the partial pressure of oxygen by increasing the fiO 2 (the inspired oxygen fraction).
Other methods
Increased water intake may also be helpful in acclimatization to replace lost fluids through more severe respiration in the thin dry air found at altitude, although consuming excessive amounts ("over-hydration") has no benefit and can lead to dangerous hyponatremia.
Treatment
The only reliable treatment, and in many cases the only option available, is down. Efforts to treat or stabilize in situ patients are dangerous unless very controlled and with good medical facilities. However, the following treatments have been used when the patient's location and circumstances allow:
- Oxygen can be used for mild to moderate AMSs below 3,700 meters (12,000 feet) and is usually provided by doctors in mountain resorts. Symptoms subside within 12 to 36 hours without the need to go down.
- For more serious cases of the AMS, or where rapid declines are impractical, Gamow bags, portable plastic hyperbaric chamber pumped with foot pumps, can be used to reduce the effective height of 1,500 m (5,000 ft). Gamow bags are generally used only as an aid to evacuate severe AMS patients, not to care for them at altitude.
- Acetazolamide 250Ã, mg twice daily dosing helps the treatment of AMS by accelerating altitude acclimatization. A study by the Denali Medical Research Project concluded: "In the case of established acute mountain disease, treatment with acetazolamide relieves symptoms, increases arterial oxygenation, and prevents further interruption of lung gas exchange."
- Traditional medicine for altitude sickness in Ecuador, Peru, and Bolivia is a tea made from coca plants. See bate de coca.
- Steroids can be used to treat symptoms of pulmonary or cerebral edema, but do not treat the underlying AMS.
- Two studies in 2012 show that Ibuprofen 600 milligrams three times a day effectively decreases the severity and incidence of AMS; it is not clear whether HAPE or HACE is affected.
- Paracetamol (acetaminophen) also proved as good as ibuprofen for altitude sickness when tested on climbers who climbed Everest.
See also
- Altitude training
- Cabin pressurization
- Gas exchange
- elevation cerebral edema
- High altitude lung edema
- Climb the mountain
- Secondary polycythemia
- Hypoxic ventilation response
References
External links
- Altitude.org: what every climber should know about altitude sickness.
- An online calculator to show altitude effects on oxygen delivery
- Trip in High Height: free booklet on how to keep your health at altitude. Available in many languages.
- Merck Manual entry on altitude sickness
- Clinical Illness Clinical Guide for Doctors
- General information about altitude sickness by the Leopold Prince Tropical Institute
- Find altitude for any place to see if altitude sickness is a factor
Source of the article : Wikipedia
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