Editing Altitude sickness (section)

== Prevention ==
Ascending slowly is the best way to avoid altitude sickness.<ref name=Thompson/> 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 are respiratory depressants, and thus slow down the acclimatization process and should be avoided. Alcohol also tends to cause dehydration and exacerbates AMS. Thus, avoiding alcohol consumption in the first 24–48 hours at a higher altitude is optimal.

=== Pre-acclimatization ===
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. Additionally, because less time has to be spent on the mountain, less food and supplies have to be taken up. Several commercial systems exist that use [[altitude tent]]s, 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 [[Ischemic preconditioning|ischaemic preconditioning]], using [[Hypobaric chamber|hypobaric]] air breathing in order to simulate altitude, and [[positive end-expiratory pressure]].<ref name=":1" />

=== Altitude acclimatization ===<!-- This section is linked from [[Mount Kilimanjaro]] -->
Altitude acclimatization is the process of adjusting to decreasing [[oxygen]] levels at higher elevations, in order to avoid altitude sickness.<ref name=Acclimatization>{{Cite journal |last1=Muza |first1=S.R. |last2=Fulco |first2=C.S. |last3=Cymerman |first3=A. |title=Altitude Acclimatization Guide |journal=U.S. Army Research Inst. Of Environmental Medicine Thermal and Mountain Medicine Division Technical Report |issue=USARIEM–TN–04–05 |year=2004 |url=http://archive.rubicon-foundation.org/7616 |access-date=5 March 2009 |archive-url=https://web.archive.org/web/20090423042451/http://archive.rubicon-foundation.org/7616 |archive-date=23 April 2009 |url-status=usurped}}</ref> Once above approximately {{convert|3000|m|-3}}{{snd}}a pressure of {{convert|70|kPa|atm}}{{snd}}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 [[Homeostasis#Blood oxygen content|red blood cells]].<ref name=tortora>{{cite book |vauthors=Tortora GJ, Anagnostakos NP |title=Principles of anatomy and physiology |url=https://archive.org/details/principlesofanat05tort |url-access=registration |pages=[https://archive.org/details/principlesofanat05tort/page/444 444]–445|edition= Fifth |location=New York |publisher=Harper & Row, Publishers |date=1987 |isbn=978-0-06-350729-6}}</ref> 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 {{convert|300|m|-2|abbr=on}} per day to sleep. That is, one can climb from {{convert|3000|m|abbr=on}} ({{convert|70|kPa|atm|abbr=on|disp=or}}) to {{convert|4500|m|-3|abbr=on}} ({{convert|58|kPa|atm|abbr=on|disp=or}}) in one day, but one should then descend back to {{convert|3300|m|abbr=on}} ({{convert|67.5|kPa|atm|abbr=on|disp=or}}) to sleep. This process cannot safely be rushed, and this is why climbers need to spend days (or even weeks at times) acclimatizing before attempting to climb a high peak. Simulated altitude equipment such as [[altitude tent]]s provide hypoxic (reduced oxygen) air, and are designed to allow partial pre-acclimation to high altitude, reducing the total time required on the mountain itself.

Altitude acclimatization is necessary for some people who move rapidly from lower altitudes to higher altitudes.<ref>{{Cite web |url=http://www.altitudemedicine.org/altitude-illness/ |title=Altitude Illness |publisher=[[Institute for Altitude Medicine]] |location=Telluride, Colorado}}</ref>

=== Medications ===
The drug [[acetazolamide]] (trade name Diamox) may help some people making a rapid ascent to sleeping altitude above {{convert|2700|m|ft|sigfig=1}}, and it may also be effective if started early in the course of AMS.<ref>{{Cite book |author=[[World Health Organization]] |title=International travel and health |chapter=Chapter 3: Environmental health risks |chapter-url=http://whqlibdoc.who.int/publications/2007/9789241580397_3_eng.pdf |page=31 |date=1 January 2007 |access-date=21 November 2009}}</ref> Acetazolamide can be taken before symptoms appear as a preventive measure at a dose of 125&nbsp;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.<ref name="BaseCampMD_prophylaxis">{{Cite web |title=Prophylaxis |url=http://www.basecampmd.com/expguide/amspremed.shtml |publisher=Everest BC Clinic, BaseCampMD.com |access-date=21 November 2009}}</ref> The Centre suggests a dosage of 125&nbsp;mg twice daily for prophylaxis, starting from 24 hours before ascending until a few days at the highest altitude or on descending;<ref name="BaseCampMD_prophylaxis"/> with 250&nbsp;mg twice daily recommended for treatment of AMS.<ref>{{Cite web |title=Treating AMS |url=http://www.basecampmd.com/expguide/diamox.shtml |publisher=Everest BC Clinic, BaseCampMD.com |access-date=21 November 2009}}</ref> The [[Centers for Disease Control and Prevention]] (CDC) suggest the same dose for prevention of 125&nbsp;mg acetazolamide every 12 hours.<ref name="CDC_Yellow Book">{{Cite book |title=CDC Health Information for International Travel 2010 "The Yellow Book" |veditors=Turell D, Brunette G, Kozarsky P, Lefor A |chapter=Chapter 2 The Pre-Travel Consultation – Self-Treatable Diseases – Altitude Illness |vauthors=Hackett P, Shlim D |chapter-url=http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/altitude-illness.aspx |publisher=Mosby |location=St. Louis |year=2009 |isbn=978-0-7020-3481-7|url-access=registration |url=https://archive.org/details/cdchealthinforma0000unse_f7v6}}</ref> 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. Although a [[sulfonamide]], acetazolamide is a non-antibiotic and has not been shown to cause life-threatening allergic cross-reactivity in those with a self-reported sulfonamide allergy.<ref>{{cite journal |vauthors=Platt D, Griggs RC |title=Use of acetazolamide in sulfonamide-allergic patients with neurologic channelopathies |journal=[[Archives of Neurology]] |volume=69 |issue=4 |pages=527–9 |date=April 2012 |pmid=22158718 |pmc=3785308 |doi=10.1001/archneurol.2011.2723}}</ref><ref>{{cite journal |vauthors=Kelly TE, Hackett PH |title=Acetazolamide and sulfonamide allergy: a not so simple story |journal=[[High Altitude Medicine & Biology]] |volume=11 |issue=4 |pages=319–23 |year=2010 |pmid=21190500 |doi=10.1089/ham.2010.1051}}</ref><ref>{{cite journal |vauthors=Lee AG, Anderson R, Kardon RH, Wall M | title = Presumed "sulfa allergy" in patients with intracranial hypertension treated with acetazolamide or furosemide: cross-reactivity, myth or reality? |journal=[[American Journal of Ophthalmology]] |volume=138 |issue=1 |pages=114–8 |date=July 2004 |pmid=15234289 |doi=10.1016/j.ajo.2004.02.019 |url=http://www.ajo.com/article/S0002-9394(04)00145-X/abstract|url-access=subscription }}</ref> Dosage of 1000&nbsp;mg/day will produce a 25% decrease in performance, on top of the reduction due to high-altitude exposure.<ref>{{cite web |url=http://www.usariem.army.mil/pages/download/altitudeacclimatizationguide.pdf |title=Altitude Acclimatization Guide |url-status=dead |archive-url=https://web.archive.org/web/20120324235011/http://www.usariem.army.mil/Pages/download/altitudeacclimatizationguide.pdf |archive-date=24 March 2012}}</ref> The CDC advises that [[Dexamethasone]] be reserved for treatment of severe AMS and HACE during descents, and notes that [[Nifedipine]] may prevent HAPE.<ref name="CDC_Yellow Book"/>

There is insufficient evidence to determine the safety of [[sumatriptan]] and if it may help prevent altitude sickness.<ref>{{Cite journal |last1=Gonzalez Garay |first1=Alejandro |last2=Molano Franco |first2=Daniel |last3=Nieto Estrada |first3=Víctor H. |last4=Martí-Carvajal |first4=Arturo J. |last5=Arevalo-Rodriguez |first5=Ingrid |date=March 2018 |title=Interventions for preventing high altitude illness: Part 2. Less commonly-used drugs |journal=The Cochrane Database of Systematic Reviews |volume=3 |issue=12 |pages=CD012983 |doi=10.1002/14651858.CD012983 |issn=1469-493X |pmc=6494375 |pmid=29529715}}</ref> Despite their popularity, [[antioxidant]] treatments have not been found to be effective medications for prevention of AMS.<ref name="pmid19273551">{{cite journal |vauthors=Baillie JK, Thompson AA, Irving JB, Bates MG, Sutherland AI, Macnee W, Maxwell SR, Webb DJ |display-authors=6 |title=Oral antioxidant supplementation does not prevent acute mountain sickness: double blind, randomized placebo-controlled trial |journal=[[QJM]] |volume=102 |issue=5 |pages=341–8 |date=May 2009 |pmid=19273551 |doi=10.1093/qjmed/hcp026 |doi-access=free}}</ref> Interest in phosphodiesterase inhibitors such as [[sildenafil]] has been limited by the possibility that these drugs might worsen the headache of mountain sickness.<ref name="pmid17408118">{{cite journal |vauthors=Bates MG, Thompson AA, Baillie JK |title=Phosphodiesterase type 5 inhibitors in the treatment and prevention of high altitude pulmonary edema |journal=Current Opinion in Investigational Drugs |volume=8 |issue=3 |pages=226–31 |date=March 2007 |pmid=17408118}}</ref> 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.<ref>{{Cite web |url=http://med.stanford.edu/ism/2012/march/altitude.html |title=Ibuprofen decreases likelihood of altitude sickness, researchers find |first=John |last=Sanford |date=March 2012 |access-date=19 September 2012 |archive-url=https://web.archive.org/web/20120424180422/http://med.stanford.edu/ism/2012/march/altitude.html |archive-date=24 April 2012 |url-status=dead}}</ref>

=== Over-the-counter herbal supplements and traditional medicines ===
Herbal supplements and traditional medicines are sometimes suggested to prevent high altitude sickness including [[ginkgo biloba]], ''R crenulata'', minerals such as [[iron]], [[antacid]]s, and [[Hormone|hormonal]]-based supplements such as [[medroxyprogesterone]] and [[erythropoietin]].<ref name=":1" /> Medical evidence to support the effectiveness and safety of these approaches is often contradictory or lacking.<ref name=":1" /> [[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 yet been proven effective in a clinical study.<ref>{{cite journal |vauthors=Bauer I |title=Erythroxylum – a comprehensive review |journal=[[Tropical Diseases, Travel Medicine and Vaccines]] |volume=5 |issue=1 |pages=20 |date=2019-11-26 |pmid=31798934 |pmc=6880514 |doi=10.1186/s40794-019-0095-7 |doi-access=free }}</ref> In Chinese and Tibetan traditional medicine, an extract of the root tissue of ''[[Rhodiola rosea|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.<ref>{{cite journal |vauthors=Wang J, Xiong X, Xing Y, Liu Z, Jiang W, Huang J, Feng B |title=Chinese herbal medicine for acute mountain sickness: a systematic review of randomized controlled trials |journal=[[Evidence-Based Complementary and Alternative Medicine]] |volume=2013 |pages=732562 |date=2013 |pmid=24454510 |pmc=3881533 |doi=10.1155/2013/732562 |doi-access=free}}</ref>

=== Oxygen enrichment ===
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 {{convert|3400|m}} ({{convert|67|kPa|atm|abbr=on|disp=or}}), raising the oxygen concentration level by 5% via an [[oxygen concentrator]] and an existing ventilation system provides an effective altitude of {{convert|3000|m|-3|abbr=on}} ({{convert|70|kPa|atm|abbr=on|disp=or}}), which is more tolerable for those unaccustomed to high altitudes.<ref name="pmid7777705">{{cite journal |vauthors=West JB |title=Oxygen enrichment of room air to relieve the hypoxia of high altitude |journal=Respiration Physiology |volume=99 |issue=2 |pages=225–32 |date=February 1995 |pmid=7777705 |doi=10.1016/0034-5687(94)00094-G}}</ref>

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 {{convert|4000|m|abbr=on}}. The application of high-purity oxygen from one of these methods increases the partial pressure of oxygen by raising the [[FIO2|FiO<sub>2</sub>]] (fraction of inspired oxygen).

=== Other methods ===
Increased water intake may also help in acclimatization<ref name="dannen">{{Cite book |vauthors=Dannen K, Dannen D |title=Rocky Mountain National Park |publisher=Globe Pequot |year=2002 |pages=9 |url=https://books.google.com/books?id=txzevi145t8C&q=%22drinking+plenty+of+water%22+%22altitude+sickness%22&pg=PA9 |isbn=978-0-7627-2245-7 |quote=Visitors unaccustomed to high elevations may experience symptoms of Acute Mountain Sickness (AMS)[...s]uggestions for alleviating symptoms include drinking plenty of water[.] |via=[[Google Books]]}}</ref> 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]].