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Rapid Responses: Rapid Responses published:
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Air Travel at Altitude
- John M. Williams (26 April 2003)
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La Paz, Bolivia, the highest Capital City in the World
- Raquel Bravo (26 April 2003)
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Diabetes and altitude
- Louise A Browne (30 April 2003)
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Hypoxia: a provocative test to aid in diabetic control?
- Richard G Fiddian-Green (30 April 2003)
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Hyperventilatory capacity and risk of acute altitude sickness
- Maximilian Ledochowski, Dietmar Fuchs (5 May 2003)
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The Dangers of High Altitude
- Dr H Max White MRCGP (6 May 2003)
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Vitamins and Viagra for better performance at high altitude?
- A A Roger Thompson, J. Kenneth Baillie, and Matthew G. D. Bates (10 May 2003)
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Gingko biloba does not prevent altitude sickness
- Peter A. Kenrick (11 May 2003)
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Altitude sickness in the experienced climber
- Gautam P Kulkarni (6 June 2003)
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Altitude Illness
- John -- Guillebaud (11 June 2003)
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Opthalmological Effects of Altitude
- Daniel S Morris, Paul Richards (9 July 2003)
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Re: Altitude Illness
- Andrew J Pollard, Peter Barry (17 July 2003)
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Re: Altitude sickness in the experienced climber
- Vahid Ziaee (2 June 2008)
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John M. Williams, (self-employed) Markanix Co., PO Box 2697, Redwood City, CA 94064
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There is a syndrome called "jet-lag", which includes fatigue, inability to sleep, and mild lack of energy. I notice that difficulty sleeping is described for altitude sickness, as it is for "jet-lag". If I am not mistaken, long-distance airline flights often are at 10,000 m, with cabin pressurization to 3,000 m. I once travelled nonstop from San Jose to Vancouver, a distance of 1,500 km or so. When I arrived, I experienced "jet-lag", even though there was no time-zone change involved. The symptoms seemed the same, although milder, as for longer, cross-country flights across two or three time zones. I attributed this to the cabin pressurization, which would have caused some annoxia, relative to sea level, during the flight. Has anyone else noticed this? Is it possible that "jet-lag" actually might have little to do with time zones but rather with sudden mild anoxia coupled with physical inactivity for the duration of a flight? Competing interests: None declared |
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Raquel Bravo, Pediatric Hemato-Oncologist Instituto Oncologico del Oriente Boliviano
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I think this paper is very important and usefull, but I was surprised to see there was no reference from the Instituto Boliviano de Biologia de la Altura (Bolivian Institute of High Altitude Biology)IBBA. This Institute works at La Paz City, Bolivia´s capital, that is at 3600 mts above sea level. Near La Paz, we have the highest lake in the world, Lake Titicaca at aprox. 4500 mts above sea level. If any collegue is interested the web page of this institute is: http://www.umsanet.edu.bo/dipgis/institutos/ibba.html Thank you very much Competing interests: None declared |
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Louise A Browne, Project Officer Australian Podiatry Association (Vic) 26/456 St Kilda Road Melbourne VIC 3004 Australia
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I have Type 1 diabetes and was interested in reading the brief comments related to diabetes and altitude in this article. I recently spent 2 months in Peru and Boliva, much of the time at altitudes of 2000- 4000m. Before my trip I was unable to find much information about the affect of altitude on Type 1 diabetes. My normally well-controlled diabetes (HbA1c 6.8-7.2) became more unstable, it seemed in direct correlation to the altitude. As altitude increased so did by morning blood glucose levels, after 8 hours of fasting and a long acting night time insulin. Perhaps dietry change had some part to play but on return to close to sea level but still in Peru, my morning blood glucose levels returned to normal overnight. I think I had one or two minor hypoglycaemic episodes in 2 months, both at close to sea level. Perhaps the La Paz institute has some research results relating to type 1 diabetes and altitude that can explain my experience. Competing interests: None declared |
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Richard G Fiddian-Green, None None
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Bounous showed years ago that gut mucosal injury induced by ischaemia may be prevented not only by intraluminal oxygen but also by intraluminal glucose(1). An energy deficit induced by hypoxia at high altitude in a healthy subject might, therefore, be normally overcome by a compensatory increase in blood glucose or rate of glucose turnover. In a diabetic a metabloc energy deficit might, therefore, be caused by the hypoxia alone and/or by the accompanying impairment of the ability to metabolise glucose efficiently(2). In which case hypoxia might be used as a provocative test to help fine-tune diabetic management and prevent late complications. 1. Bounous G. Role of the intestinal contents in the pathophysiology of acute intestinal ischemia. Am J Surg. 1967 Sep;114(3):368-75. Review. 2. SARS and the risk of mass extinction Richard G Fiddian-Green (26 April 2003)Rapid response to: SARS virus identified, but the disease is still spreading Jane Parry BMJ 2003; 326: 897 2. Competing interests: None declared |
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Maximilian Ledochowski, Senior consultant university hospital, Dept. internal medicine Innsbruck, A-6020 Austria, Dietmar Fuchs
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With interest we read the recent review by Barra and Polard on altitude sickness (1). Especially for travellers, early risk indicators would be helpful to avoid especially the more severe forms of the syndrome. It is well known, that Tibetans and Sherpas (of Tibetan origin) have better physical performance at high altitude than caucasians (2), possibly due to genetic differences (3). Acute adaptation to high altitude and low oxygen supply primarily takes place by hyperventilation. By this means not only oxygen saturation (sO2) improves, but blood pH raises as well. It appears that the need to oxygenate tissues conflicts with the need to maintain H+ homeostasis. The result is a compromise between the respiratory adjustment aimed at increasing blood alkalosis in order to optimize the O2 transport system. The capability to correct respiratory alkalosis is thus crucial for acute adaptation to high altitude. Sherpas have been shown to have a more efficient adaptation to hypoxia, that allows to limit alkalosis through a lower ventilatory drive and to maintain arterial sO2 at the same partial oxygen pressure (pO2) by decreasing the 2,3-diphosphoglycerat/haemoglobin ratio (4). During a hiking tour at high altitude (Mt. Kailash, Tibet) we measured pO2 in 9 Austrians (all caucasians, 4 males and 5 females, aged 43–62 years) and 7 Sherpas (5 males and 2 females, aged 28-62 years). Preadaptation periods and physical fitness in Sherpas and caucasians where about the same before the test was performed. The examined Sherpas lived at Katmandu, Nepal (1500m) and caucasians in Innsbruck, Austria (550m). Basal sO2 was measured at rest and during one minute of forced hyperventilation, at altitudes of 5100m above sea level (Darchen, Mt. Kailash) and at 5600m (Dolma La, Mt. Kailash) using a small portable transdermal pulse oxymeter (NONIN Medical Inc., Plymouth, MN, USA). Sherpas had significantly lower resting sO2 but on hyperventilation they were able to rise their sO2 up to >90% while caucasians had higher basal sO2 and a significantly lower capacity to rise their sO2. In both groups the increase in sO2 over baseline values (sO2 = hyperventilation capacity) was significantly lower at 5600m compared to the HC at 5100. Subjects with a hyperventilation capacity <5% at 5100m showed mild signs of acute altitude sickness like headache, dyspnoea or subcutaneous edema when they ascended to 5600m while all others who had a HC *5% at the base camp (5100m) had no complaints. From the data we conclude that hyperventilation capacity decreases with increasing altitude and its measurement might be suitable approach to predict the development of altitude sickness. Maximilian Ledochowski M.D. Dietmar Fuchs Ph.D. Department of Internal Medicine, Institute of Medical Chemistry and Biochemistry University of Innsbruck, A-6020 Innsbruck, Austria 1. Barry PW, Pollard AJ. Altitude sickness. Brit Med J 2003;326:915- 9. 2. Chen QH, Ge RL, Wang XZ, Chen HX, Wu TY, Kobayashi T et al. Exercise performance of Tibetan and Han adolescents at altitudes of 3,417 and 4,300 m. J .Appl Physiol 1997;83:661-7. 3. Beall CM, Blangero J, Williams-Blangero S, Goldstein MC. Major gene for percent of oxygen saturation of arterial hemoglobin in Tibetan highlanders. Am J Phys Anthropol 1994;95:271-6. 4. Samaja M, Mariani C, Prestini A, Cerretelli P. Acid-base balance and O2 transport at high altitude. Acta Physiol Scand 1997;159:249-56. Competing interests: None declared |
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Dr H Max White MRCGP, Fellow BMA - Retired GP GP retired Davenal House Surgery 28 Birmingham Road Bromsgrove B61 0DD
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It is appropriate that this paper has appeared in the BMJ coninciding with the 50th anniversary of Hillary and Tensing's pioneering climb which occurred at the same time as the Queen's Coronation in 1953. I have never been a real climber myself- the conquest of Snowdon being my only achievement. However, when the BMA organised joint overseas meetings in the 60's & 70's, we had the pleasure of hearing Hillary give the inaugural lecture in Hong Kong in 1969 - his subject being an illustrated lecture on his 1967 expedition in India entitled 'From the Sea to the Sky'. He and his party (including his son) navigated the Ganges from its delta to its source (at approximately 20,000 feet) in the lower range of the Himalayas. This was by no means a straightforward exercise for these experienced climbers - they were feted by local dignatories along the whole route, only escaping their attentions when in mid-stream in their outboard-powered inflatables. On nearing their destination Hillary himself developed the full picture of mountain sickness and had to be evacuated by air. The account of this is well documented in the bood Hillary published (From the Sea to the Sky) at about the time of his BMA Hong Kong lecture. His friend, Colin Aikman, (a personal friend of mine) who was then New Zealand's High Commissioner in Delhi, was responsible for organising the helicopter resuce by the Indian Air Force. Hillary made a rapid recovery at the nearest Air Force hospital, his son and his party going on to achieve the projected summit. Edmund Hillary was by then in his 60's and had no chance of acclimatisation on his lengthy journey starting at sea level along the Ganges. The BMJ article is a warning to those ameteur trekkers who are tempted by so called walking holidays in Nepal and surrounding area, often flying in to base camp by plane. Yours sincerely H Max White MRCGP
Competing interests: None declared |
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A A Roger Thompson, Pre-registration House Officer Apex, c/o Dr F. Kristmundsdottir, College of Medicine, University of Edinburgh, EH8 9AG, J. Kenneth Baillie, and Matthew G. D. Bates
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Barry and Pollard (1) concede that medical treatments for acute mountain sickness (AMS) and the potentially fatal high altitude pulmonary oedema (HAPE) and cerebral oedema (HACE) are limited. Appropriately, they restrict their discussion to those therapies that already rest on a sound evidence base. We would like to draw attention to the potential use of a class of drugs that were once proposed to be a panacea for a broad range of pathologies, but which have so far yielded largely disappointing results: antioxidants. The best evidence for the efficacy of antioxidant therapies comes from the Medex group, in a trial conducted by Bailey & Davies, which showed a significant reduction in symptoms of AMS compared with placebo in a group of 15 climbers taking a cocktail of antioxidant vitamins (2). There is growing evidence for a role for oxidative stress, which is mitigated by antioxidants, in the pathogenesis of altitude illness. A direct consequence of hypoxia, oxidative stress may augment hypoxic pulmonary vasoconstriction (3), alter pulmonary endothelial permeability, impair red cell function (4) and lead to brain interstitial oedema. If it could be achieved, effective supplementation of antioxidant systems at tissue level is likely to be of benefit in mountain illness. The importance of raised pulmonary artery pressures in the development of HAPE in susceptible subjects is also discussed by Barry and Pollard. A recent study demonstrated that oral sildenafil, by its action on the eNOS-NO-cGMP pathway, successfully attenuates the increase in pulmonary artery pressure in humans acutely exposed to hypoxia (5). It has been postulated that Viagra may have a role in preventing pulmonary oedema at altitude. Barry and Pollard highlight the activities of Medex, a charity with a distinguished history of work in this field of research. Further to the activities mentioned in the article, Medex also helped a group of medical students found the Edinburgh-based altitude research charity, Apex. By contributing equipment and advice, they catalysed the success of this group’s first expedition, Apex Bolivia 2001. Research in this field is often very dependent on collaborative work, and we are very grateful to Medex for their continuing support. This summer, our group will test the use of antioxidant supplementation and oral sildenafil in two double-blind placebo-controlled randomised trials with 125 subjects at the Bolivian Institute of High Altitude Biology (IBBA) laboratory at Chacaltaya (5200m) in Bolivia. Reference List 1. Barry PW,.Pollard AJ. Altitude illness. BMJ 2003;326:915-9. 2. Bailey DM,.Davies B. Acute mountain sickness; prophylactic benefits of antioxidant vitamin supplementation at high altitude. High Alt.Med.Biol. 2001;2:21-9. 3. Weissmann N, Tadic A, Hanze J, Rose F, Winterhalder S, Nollen M et al. Hypoxic vasoconstriction in intact lungs: a role for NADPH oxidase- derived H(2)O(2)? [In Process Citation]. Am.J.Physiol Lung Cell Mol.Physiol 2000;279:L683-L690. 4. Celedon G, Gonzalez G, Sotomayor CP, Behn C. Membrane lipid diffusion and band 3 protein changes in human erythrocytes due to acute hypobaric hypoxia. Am.J.Physiol 1998;275:C1429-C1431. 5. Zhao L, Mason NA, Morrell NW, Kojonazarov B, Sadykov A et al. Sildenafil inhibits hypoxia-induced pulmonary hypertension. Circulation 2001;104:424-428. Competing interests: None declared |
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Peter A. Kenrick, Consultant Physician Taitung Christian Hospital, Taitung, Taiwan
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Editor-Barry & Pollard suggest in their clinical review of altitude illness that gingko biloba may be more effective than placebo in preventing symptoms of acute mountain sickness(AMS). I wish to draw attention to the PHAIT study carried out by Gertsch et al in Nepal, October to November 2002 in which gingko biloba,acetazolamide & placebo were directly compared in a randomised controlled trial of trekkers ascending from Pheriche(4250m) to Lobuche(4850m). A total of 614 subjects were enrolled and the results showed a marginal increase in AMS symptomsin the gingko biloba group (61.3%) compared w the palcebo group(53.8%), with the lowest incidence of AMS symptoms being in the acetazolamide group(21,.2%). On the basis of this study I would suggest that gingko biloba can not be recommended as prophylaxis of AMS symptoms. P.Kenrick 1 Prevention of High Altitude Illness Trial. Gertsch J,Basnyat B,et al.Personal communication of results from J.Gertsch Competing interests: I was a volunteer doctor at Himalayan Rescue Association Aid Post Pheriche during the period of the PHAIT study although not directly involved in the study. |
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Gautam P Kulkarni, SHO st Marys PICU, London W2 1NY
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As a newly qualified doctor and a trekking enthusiast, I was lucky enough to participate as the camp doctor for three high altitude Himalayan trekking expeditions. From my personal experience, even experienced climbers can suffer from high altitude sickness if they don't take the acclimatisation seriously enough. Often enough, young enthusiastic males with some experience in high altitude trekking don't take the acclimatisation seriously. The consequences in them can be extremely dangerous. Competing interests: None declared |
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John -- Guillebaud, Professor of Family Planning and Reproductive Health Dept of Obstetrics and Gynaecology, University College, London, WC1E 6HX
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EDITOR - I found the Clinical review by Drs Barry and Pollard in the BMJ of April 26th fascinating and practically informative [1] . The advice regarding pregnant women was interesting, partly for the continuing paucity of data. But I wonder what their current advice would be to young female climbers and trekkers who are not pregnant, indeed wish to avoid pregnancy (probably a larger group), with respect to the combined oral contraceptive (COC)? Fluid loss by diuresis or inadequate intake; trauma; immobility in tents when the weather closes in; all these in altitude illness can potentially increase the established risk of venous or arterial thrombosis, and moreover the leading contender to explain high altitude pulmonary oedema is patchy pulmonary hypertension. It is well recognised that high risk of either condition contraindicates the COC - the critical question is at what level of altitude the risk becomes high enough to make the contraindication "absolute" (ie WHO 4, on the 1-4 scale now recommended [2])? Autonomy is an important principle here: rock-climbing is orders of magnitude more dangerous than any risks modifiable by choice of contraceptive! The woman must have freedom to take some added risk. But the prescriber has autonomy too, if s/he considers the added risk of COC unacceptable - especially given the arrival in the UK of new highly effective alternatives to it (Implanon[tm], Cerazette[tm], banded copper IUDs and the Mirena-IUS [tm]), which are completely free of the pro- thrombotic substance, ethinylestradiol. Would Barry and Pollard agree with my current recommendation, pending further data, that women should avoid the COC (WHO 4 - 'Do not use') if planning to ascend to above 4500 metres: this being about midway in the range 3500-5800 metres where, according to their Box 1, altitude illness is "common" even if there is no rapid ascent ? In the lower range 2500 to 3500 metres, would they also agree that the additional presence of a significant venous or arterial risk factor (eg BMI above 30, heavy smoking) would raise the category to WHO 4? (Women with two such risk factors should not use the COC even at sea level!) Otherwise in the range 2500-4500 metres, in women with no known added risk factors WHO 3 (Caution) would apply. This means alternative contraceptives are preferable BUT, if these are unacceptable or contraindicated, the woman may with no promises of safety make an informed choice to continue taking the COC. J. Guillebaud 1 Barry PW, Pollard AJ. Altitude illness. BMJ 2003;326:915-19. 2 Guillebaud, J. (2001) . Medical eligibility criteria for contraceptive use. Lancet, 357, 1378-79. Competing interests: JG has received lecture fees, research grants, expenses and ad hoc consultancy fees from the manufacturers of contraceptive products. |
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Daniel S Morris, SHO Opthalmology Tennent Institute of Ophthalmology, Gartnavel General Hospital, Great Western Road, Glasgow, G12 OYN, Paul Richards
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We read with interest the review on altitude illness by Pollard and Barry1 but noted that there was no mention of the ophthalmological effects of ascending above 2500m. A good detailed review is available for specialists2 but there are several areas of interest to the general physician. Firstly the effects at altitude of LASIK surgery which is becoming increasingly popular amongst the general public. A recent study of 6 climbers on Mount Everest, 4 of whom reached the summit, showed that 3 climbers suffered transient blurring of vision which improved with descent.3 Another report of 2 climbers on Aconcagua also showed a transient myopic shift, although they were in the early post-operative period.4 So it appears that those who have had LASIK surgery should be prepared for some blurring of vision at altitude which will recover on descent. Secondly, snow blindness is a complication of failing to use protective sunglasses with sidepieces. Snow blindness is sunburn of the cornea and presents with intense pain, photophobia and itchy red eyes. It is especially common at high altitude because there is less atmosphere and pollution to absorb harmful UV radiation and often there is snow on the ground which reflects the sun’s rays. At high altitude snow blindness is potentially more serious due to a slower epithelial healing time secondary to hypobaric hypoxia, and poor hygiene which make infection more likely; in a remote environment, this can be sight threatening. Finally, high altitude retinopathy (HAR) is a pathological response by the retina to the hypoxia of altitude. It occurs in up to half of those ascending above 2500m and can be dramatic in appearance. Flame haemorrhages are most commonly seen but cotton wool spots, dot and blot, and pre-retinal haemorrhages have also been reported. Although HAR can occur in association with altitude sickness, it is usually asymptomatic and haemorrhages resolve without sequelae. Haemorrhage involving the fovea may produce a positive scotoma which may clear within a few days or last up to a year. Retinal vascular dysregualtion may be a sign of poor acclimatisation and a predictor of more serious high altitude cerebral and pulmonary oedema.5 Daniel S Morris MRCOpth.
Paul Richards, MRCGP. DFFP. MSc.
References 1. Barry PW and Pollard AJ Altitude illness BMJ 2003; 326: 915-919. 2. Karakucuk S and Mirza GE Ophthalmological effects of high altitude Ophthalmic Res 2000; 32: 30-40 3. Dimmig JW, Tabin G. The ascent of Mount Everest following laser in situ keratomileusis. J Refract Surg. 2003 Jan-Feb;19(1):48-51. 4. Boes DA, Omura AK, Hennessy MJ. Effect of high-altitude exposure on myopic laser in situ keratomileusis. J Cataract Refract Surg. 2001 Dec;27(12):1937-41. 5. Wiedman M and Tabin GC. High altitude retinopathy and altitude illness Ophthalmology 1999; 106: 1924-1927 Competing interests: DM and PR are members of Medex, a limited company which supports the activity of Medical Expeditons, a charity that promotes research and education into high altitude physiology and medicine. |
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Andrew J Pollard, Senior lecturer in Paediatrics, University of Oxford Department of Paediatrics, University of Oxford, Level 4, John Radcliffe Hospital, Oxford OX3 9DU, Peter Barry
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We are grateful to Professor Guillebaud for drawing attention to the difficulty in advising women taking the combined oral contraceptive pill (COC) who wish to ascend to altitude in his letter posted in response to our article (1). Whilst we agree with his view that there may be an increased risk of thrombosis for women travellers at high altitude who choose to take the COC, as a result of summation of risk factors, we feel that the paucity of data makes it impossible to be prescriptive about the altitudes at which use of this drug might or might not be safe. By convention high altitude starts at 2500m and it would seem reasonable that this is used as the cutoff for advising women about this issue. However, we cannot see justification for defining specific altitudes above 2500m in relation to summative risk of thrombosis for those taking the COC as there is no data on which to base these assumptions. An additional problem in defining altitudes of risk without taking other factors into consideration arises because it is possible that long periods of travel at moderate high altitude carry a similar risk of thrombosis as do shorter exposures at very high altitudes. In the absence of evidence to guide practice, we would therefore recommend that the possibility of an increased risk of thrombosis is discussed with all COC-taking travellers ascending above 2500m and that the merits of alternative methods of contraception are considered in each case. Andrew J Pollard and and Peter W Barry 1 Barry PW, Pollard AJ. Altitude illness. BMJ 2003;326:915-19 Competing interests: None declared |
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Vahid Ziaee, Sports Medicine Research Center, Tehran University of Medical Sciences Sports Medicine Research Center, Al-e-Ahmad Highway, Tehran, Iran (postcde 14195)
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My experience shows expert climbers have a lower risk for developing of AMS. In two separate studies we found that the experience of climbers has positive effect on the prevention of AMS. In both studies, we divided trekkers into 3 groups based on the number of ascents they had made to altitudes above 4000 m in the last 6 months: experienced (more than 6 ascents), semiexperienced (1–5 ascents), and inexperienced (no ascents). In teh first study, AMS developed in 41.3% of experienced climbers, 57.8% of semiexperienced, and 68.9% (131/190) inexperienced (P.value=0.001)[1]. In a recent study, AMS developed in 18.7%, 51% and 61.9%, respectively (P.value=0.001). In recent study, by logistic regression analysis and after omitting confounding factors previous trekking skills on incidence of AMS[2].
V. Ziaee MD
References: 1- Ziaee V, Yunesian M, Ahmadinejad Z, Halabchi F, Kordi R, Alizadeh R, Afsharjo HR. Acute mountain sickness in Iranian trekkers around Mount Damavand (5671m) in Iran. Wild Environ Med .2003; 14(4): 214-9. 2- Ziaee V, Alizadeh R, Mansournia MA, et al. The effect on ascending path on incdence of AMS. (under review). Competing interests: None declared |
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