Altitude sickness primary prevention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Altitude sickness is largely preventable. Potential factors that influence altitude sickness prevention include: avoiding alcohol ingestion and strenuous activity within 24 hours of traveling to a different altitude and actively preparing for altitude acclimatization.
Primary Prevention
Avoiding Alcohol Ingestion
As alcohol tends to dehydrate, avoidance in the first 24 hours at a higher altitude is optimal.
Strenous Activity
People with recurrent AMS note that by avoiding strenuous activity such as skiing, hiking, etc in the first 24 hours at altitude reduces their problems.
Altitude Acclimatization
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 meters (10,000 feet), most climbers and high altitude trekkers follow the "golden rule" - climb high, sleep low. For high altitude climbers, a typical acclimatization regime might be to stay a few days at a base camp, climb up to a higher camp (slowly), then return to base camp. A subsequent climb to the higher camp would then include an overnight stay. This process is then repeated a few times, each time extending the time spent at higher altitudes to let the body "get used" 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 general rule of thumb is to not ascend more than 300 metres (1,000 feet) per day to sleep. That is, one can climb from 3,000 (10,000 feet) to 4,500 meters (15,000 feet) in one day, but one should then descend back to 3,300 meters (11,000 feet) to sleep. This process cannot safely be rushed, and this explains why climbers need to spend days (or even weeks at times) acclimatizing before attempting to climb a high peak. Simulated altitude equipment that produce hypoxic (reduced oxygen) air can be used to acclimate to altitude, reducing the total time required on the mountain itself.
Patients can sometimes control mild altitude sickness by consciously taking ten to twelve large, rapid breaths every five minutes. If overdone, this can remove too much carbon dioxide and cause tingling in the extremities of the body. Other treatments include injectable steroids to reduce pulmonary edema, and inflatable pressure vessels to relieve and evacuate severe mountain-sick persons.
The only real cure once symptoms appear is for the sufferer to move to a lower altitude as quickly as possible. For serious cases of AMS, a Gamow bag can be used to reduce the effective altitude by as much as 1,500 meters (5,000 feet). A Gamow bag is a portable plastic pressure bag inflated with a foot pump.
In Peru hotels on the shore of Lake Titicaca at 3,812 m (12,507 feet) offer oxygenated bedrooms at a premium charge. The same is true at the Monasterio hotel in Cuzco at the lower elevation of 3,500 m (11,500 feet). The folk remedy for altitude sickness in Peru and Bolivia is a tea made from the coca plant.
Altitude acclimatization is necessary for some people who rapidly move from lower altitudes to more moderate altitudes, usually by aircraft and ground transportation over a few hours, such as from sea level to 7000 feet of many Colorado, USA mountain resorts. Stopping at an intermediate altitude overnight can reduce or eliminate a repeat episode of AMS.
Drugs
Acetazolamide may help some people to speed up the acclimatization process when taken before arriving at altitude, and can treat mild cases of altitude sickness. Ibuprofen and acetazolamide are similarly effective in preventing high altitude headache and other symptoms of acute mountain sickness.[1]
A typical dose is started the day before moving to altitude. A dose of 125 mg bd of acetazolamide has been found to be similar 375 mg bd in the prevention of acute mountain sickness; 125 mg bd should be considered the preferred dosage when indicated for persons ascending to altitudes above 2500 m.[2]
A single randomized controlled trial found that sumatriptan may help prevent altitude sickness.[3]
Over the last 20 years a number of small trials have reported that spironolactone effectively prevents acute mountain sickness. Spironolactone (50 mg BID) was ineffective in comparison to acetazolamide (250 mg BID) in the prevention of Acute Mountain Sickness in partially acclimatized western trekkers ascending to 5000 m in the Nepali Himalaya. [4]
Steroids are also used to prevent and treat high-altitude illnesses. Cases have been reported with altered mental status, gastrointestinal bleeding, skin rash, and avascular necrosis in climbers taking prophylactic dexamethasone prior to an attempt to climb Mt Everest. High-altitude cerebral edema and acute adrenal crisis can present similarly. Hence, differentiation of such life-threatening conditions at high altitude is essential for successful treatment.
For centuries, indigenous cultures of the Altiplano, such as the Aymaras, have used coca leaves to treat mild altitude sickness.
Oxygen Enrichment
In high-altitude conditions, oxygen enrichment can counteract the effects of altitude sickness, or hypoxia. A small amount of supplemental oxygen reduces the equivalent altitude in climate-controlled rooms. At 3,400 m (67 kPa), raising the oxygen concentration level by 5 percent via an oxygen concentrator and an existing ventilation system provides an effective altitude of 3,000 m (70 kPa), which is more tolerable for surface-dwellers.[5]
One of the effective source of supplemental oxygen at high altitude are oxygen concentrators that use vacuum swing adsorption (VSA) technology. As opposed to generators that use pressure swing adsorption (PSA), VSA technology does not suffer from performance degradation at increased altitude. The lower air density actually facilitates the vacuum step process.
Other Methods
Drinking plenty of water will also help in acclimatisation[6] 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 lead to hyponatremia.
Oxygen from gas bottles or liquid containers can be applied directly via a nasal cannula or mask. Oxygen concentrators based upon PSA, VSA, or 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 utilize a concentrator with more flow capacity. There are also portable oxygen concentrators that can be used on vehicle 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 meters (13,123 feet). 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).
References
- ↑ Gertsch JH, Lipman GS, Holck PS, Merritt A, Mulcahy A, Fisher RS; et al. (2010). "Prospective, double-blind, randomized, placebo-controlled comparison of acetazolamide versus ibuprofen for prophylaxis against high altitude headache: the Headache Evaluation at Altitude Trial (HEAT)". Wilderness Environ Med. 21 (3): 236–43. doi:10.1016/j.wem.2010.06.009. PMID 20832701.
- ↑ Basnyat B, Gertsch JH, Holck PS, Johnson EW, Luks AM, Donham BP; et al. (2006). "Acetazolamide 125 mg BD is not significantly different from 375 mg BD in the prevention of acute mountain sickness: the prophylactic acetazolamide dosage comparison for efficacy (PACE) trial". High Alt Med Biol. 7 (1): 17–27. doi:10.1089/ham.2006.7.17. PMID 16544963.
- ↑ Jafarian S, Gorouhi F, Salimi S, Lotfi J (2007). "Sumatriptan for prevention of acute mountain sickness: randomized clinical trial". Ann. Neurol. 62 (3): 273–7. doi:10.1002/ana.21162. PMID 17557349.
- ↑ Basnyat B, Holck PS, Pun M, Halverson S, Szawarski P, Gertsch J; et al. (2011). "Spironolactone does not prevent acute mountain sickness: a prospective, double-blind, randomized, placebo-controlled trial by SPACE Trial Group (spironolactone and acetazolamide trial in the prevention of acute mountain sickness group)". Wilderness Environ Med. 22 (1): 15–22. doi:10.1016/j.wem.2010.10.009. PMID 21377114.
- ↑ West, John B. (1995), "Oxygen Enrichment of Room Air to Relieve the Hypoxia of High Altitude", Respiration Physiology 99(2):230.
- ↑ Dannen, Kent (2002). Rocky Mountain National Park. Globe Pequot. p. 9. ISBN 0762722452.
Visitors unaccustomed to high elevations may experience symptoms of Acute Mountain Sickness (AMS)[...s]uggestions for alleviating symptoms include drinking plenty of water[.]
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