High Altitude Physiology - Essay Example

Introduction A spirit of adventure pervades some of the contemporary recreation and vacation scenes. High altitude destinations, always popular withskiers and with climbers of all kinds, especially mountaineers, have begun to attract tourist populations unaccustomed to life at high altitudes (Peacock, 1998). The conservation movement has also contributed to the lure of heights, as increasing numbers of people wish to visit base camps of famous peaks. Most inner reaches of the Antarctic present distinct challenges of their own, as a result of the unique ecology they present. Remote mountainous areas generally lack the medical facilities which we take for granted at lower altitudes of normal habitation, and at sea level. Trekkers and climbers from the plains have therefore to be equipped with knowledge, aids, and medicines to prevent and to treat illnesses which tend to arise at unusually high altitudes (Peacock, 1998). Even medical practitioners with primary health experiences and specialist skills in unrelated areas, require orientation in the nature and ways of high altitude health care, to say nothing of the lay public which is so attracted to make sudden and quick visits to mountainous destinations. This report dwells on the prevention and treatment of common ailments at high altitudes, after defining the situation and enumerating the effects on physiology when a body is transported to a significant height where extreme atmospheric conditions prevail. It is intended for a general audience, rather than for health care professionals, and is not a substitute for personal medical consultation in specific cases. All people who travel in aircraft or visit high altitudes should consult with their primary care physicians for individual prescriptions, which this article does not seek to provide. The Nature and Implications of High Altitude The 5 thousand and 9 thousand meter marks of height above sea level are significant for people in normal states of health. This is because oxygen availability, air pressure, temperature, and wind conditions are so different at these altitudes compared to those which normally prevail at sea level. Though changes in these parameters are proportional to height gained in a climb, people in normal health who climb to less than 5 thousand meters need take no special precautions, other than to dress appropriately to combat the cold and icy and strong breeze. Conditions at the 9 thousand meter height mark deteriorate sharply from those at lower altitudes, making illnesses and medical emergencies more likely for even those who have been comfortable and in normal health below this height. Such a distinction is important for major team assaults on mountains. People who are accustomed to living at high altitudes may also have to cope with the environmental changes presented by a place of the same height in a foreign continent. People from one altitude and area can take several weeks to reach baseline levels when transported to new altitudes in a strange place (Maksimov, and Belkin, 2002); specific climatic factors in the Antarctic may delay acclimatization. Therefore even people who live in hilly and mountainous tracts should observe precautions when they cross the 5 thousand and 9 thousand meter marks at new locations. The cut-off limit for children, the geriatric, expecting mothers, and all people with respiratory and cardiac disorders, is about half that for normal adults in terms of altitude, that is about two thousand five hundred meters. Modern jet aircraft are usually pressurized to mimic the conditions of such an altitude. Passengers need take no notice of this fact during short-haul flights, as in most domestic situations, but a long transcontinental flight will require special preparations, medical checks, and emergency supplies in the form of oxygen for all the vulnerable groups mentioned in this section. It is common knowledge that extreme cold and windy conditions mark high altitudes, and the precautions needed to keep the body warm and the skin protected do not require elaboration. However, there are 5 other factors which prevail at high altitudes, which require special and detailed awareness (Peacock, 1998). The first relates to the reduction of oxygen pressure, known in medicine as hypoxia. Body tissues will be starved of normal oxygen supplies because the normal gaseous exchange which takes place between the lungs and blood is impaired at high altitudes. Not all individuals respond to hypoxia in the same way (Peacock, 1998). Some individuals can adapt faster than others, and continue to undertake strenuous physical activities at heights, without any deleterious effects. This explains the amazing ability of a few climbers to scale high mountains without oxygen support. The individual ability to deal with hypoxia can be estimated at sea level through simulated experiments in controlled conditions. However, most people will do better in real situations after acclimatization than performances recorded in simulations at sea level. A second aspect of high altitudes relates to dehydration. Fluid balances are central to the normal functioning of the body. Fluid loss from the immediate surroundings of body cells changes the conditions in which they have to operate and to survive. Dehydration has its most dramatic effect on blood, which has a large fluid component, and hence the effects of dehydration at high altitudes quickly spread to every corner of the body. Simple precautions, which can prevent illnesses at high altitudes, are the third dimension of living well at heights, and to enjoying sojourns in aircraft and journeys to high reaches. Some of these precautions are in the nature of things which people can do by themselves without professional medical help, though medical consultation before visiting a high altitude destination is always advised. Acclimatization is the most important precaution, and constitutes the fourth dimension of high altitude visits. The body must be given time to adapt. This approach is not possible when people with respiratory and cardiac conditions travel over long distances in pressurized aircraft, but it is relevant during treks and expeditions to mountain peaks. Many problems may be prevented by gaining altitude slowly with adequate breaks for rest in-between. Finally, there is the fifth dimension of treatment. This relates to carrying equipment and medicines to treat illnesses which may be encountered at high altitudes, and ensuring that as many members of the climbing party as possible are aware of how to use such aids, and to render timely medical aid. Human beings are made to function normally at altitudes below 5 thousand meters, as long as they remain protected from extremely low temperatures and from strong winds as well. However, with proper acclimatization, which can display a fair degree of variability between individuals, people can also remain physically active at higher altitudes. Since the heart and lungs are made to work much harder than usual at high altitudes, these organs must be in perfect working order when a person climbs to a significant height. Though the term high altitude is normally associated with topography, the air pressure in a commercial jet also corresponds to an altitude of well over 2 thousand meters, and while this is easily tolerated by adults with normal heart and lung functions, others may require medical support during long flights. Physiological Implications of Altitude Changes The body functions best in conditions of moderate temperature and oxygen pressure conditions as prevails at sea level in most places. Cold, and low oxygen pressure in inhaled air, affect physiology strongly at high altitudes. The skin cannot maintain its normal functions of temperature regulation and moistness without clothing and cosmetic protection. However, the effect of altitude is more telling and less easily managed at the junction of the lungs and blood, where exchange of oxygen and carbon dioxide is impaired. The paucity of oxygen is exacerbated by changes in the fluidity of blood, and by the reduced power of the heart muscles to pump blood to far reaches of the body. Physiology is therefore severely and fundamentally affected by high altitude. The most important implication of the stresses on human physiology as a result of high altitudes, relates to individual and group climbing behavior during treks and expeditions. The key is to give the body time to adjust to the temperature, air pressure, and oxygen availability for tissues which prevail at these heights (Peacock, 1998). Climbers should not gain more than 300 meters a day above 3 thousand meters, resting every few days. Anyone who feels unwell should descend by about 500 meters. A group of trekkers or climbers must put the interests of their slowest and weakest member foremost and above the expedition’s time and cost targets. Respiratory and cardio-vascular fitness of each prospective member of a climbing party should be assessed carefully at the outset. Tour operators should not be lax on this account, and should have access to the appropriate testing and evaluation resources. The normal economic and emotional considerations, with which vacation destinations are chosen, are not comprehensive for high altitudes. People who cannot exercise vigorously at sea level should not travel to altitudes-this also applies to those with open shunts in the heart, as constriction may alter the positions of these devices (Peacock, 1998). Similarly, those with impaired gas exchange in the lungs should not climb to altitudes (Peacock, 1998). Medical tests at sea level can establish lung functions in this respect. People with asthma should increase steroid doses and carry plenty of inhalers (Peacock, 1998). It is apparent that physiological considerations limit the recreation potential of visits to destinations at high altitudes, restrict the numbers of people who are fit enough for such adventures, and have deep impacts on the logistics and finances of expeditions and tours. Every expedition which has to depend on sure-footed animals and human porters, rather than on any means of mechanical transport, will be short of carrying capacities in terms of material support. There are inevitable trade-offs between alternate goods and supplies that people may wish to carry. It may be tempting, at low altitudes, to drop bulky oxygen containers, but this is a major form of support for hypoxia. Oxygen support is a partial substitute for acclimatization (Peacock and Jones, 1997), and therefore its need is more likely when trips involve rapid ascent. Flow rates affect consumption dramatically, but even reduced rates of supply will result in significant improvement in oxygen availability for tissues. Overall, an adequate supply of oxygen to meet all eventualities is essential for every project involving high altitudes (Peacock, 1998). This also applies to equipment designed to provide hyperbaric conditions inside portable chambers. However, all aspiring climbers must know that the benefits of oxygen and hyperbaric chamber support are entirely temporary, and will disappear as soon as such support is withdrawn. Therefore, acclimatization and descent are more reliable ways of dealing with hypoxia. These factors need to be kept in mind as all-terrain vehicles, mountain railways, and modern helicopters, as well as tight schedules present many means and motivations for people to ascend far more rapidly than advisable from a physiological stand point. People with poor gas exchange may need oxygen support even during long duration commercial flights (Peacock, 1998). Some airlines offer free oxygen supplies to needy passengers, while others levy separate charges. Airline policy with respect to oxygen supplies should be clarified when journeys are planned and seat reservations are confirmed. Oxygen transfer to blood is slowed down as altitude increases; the blood spends less time in the lungs when a person exercises, reducing oxygenation of blood even further (Peacock, 1998). The maximum heart rate which a body can reach falls at high altitudes, and cardiac output decreases as well (Peacock, 1998). The blood thickens at altitudes-this is partly because of dehydration, and also because the body is stimulated to produce more hemoglobin (Peacock, 1998); this may cause clots and strokes. Thus, physical exertion is difficult at high altitudes, and there are serious health risks as well. Climbers who pride themselves on levels of physical fitness may be unpleasantly surprised when they find it difficult to complete even routine tasks at high altitudes. All casual vacationers should be aware of the risks they take on sudden visits to places at high altitudes. Fluid intake has to be increased to deal with the dehydration effect of extreme heights. Overall physiology is severely affected at high altitudes. Some individuals may react differently from the norm. These effects limit the kinds of people who can visit high altitudes and even undertake long flights in aircraft pressurized to meet air conditions at about two thousand five hundred meters. People with impaired heart and lung functions should not visit high altitudes. Oxygen supplies and portable hyperbaric chambers should have priorities when teams plan for supplies to be carried on expeditions to significant heights. Effects of Altitude on Physiology High altitude affects physiology by disrupting essential fluid balances, reducing oxygen availability for body cells, thickening blood, and reducing the rate of its circulation. These effects combine to produce some typical medical conditions, which can be both debilitating and life-threatening. Everyone who climbs to a high altitude should be assessed for tendencies to develop such conditions, and should have access to professional help throughout the climb. Acute mountain sickness is the most common medical condition encountered at high altitudes. Fortunately, it mostly resolves on its own. Descent hastens recovery, and the condition can be prevented by proper acclimatization. Headache, loss of appetite, insomnia, and breathlessness are the most telling symptoms of this malaise (Peacock, 1998) Acute mountain sickness, if ignored, may result in loss of consciousness due to fluid accumulation in the cerebral region, and deteriorate in to drop in body temperature and ultimately, even to death. A hyperbaric chamber will provide immediate relief, but it is nearly impossible to lower a person in such a chamber to a lower elevation. Acute discomfort and relapse will set in almost as soon as a person with acute mountain sickness is taken out of a hyperbaric chamber at a high altitude. Acetazolamide and steroids may be administered by doctors for more lasting relief from the most distressing symptoms of acute mountain sickness. Pulmonary edema, or the accumulation of fluid in the lungs, is a more serious medical risk at high altitudes than acute mountain sickness. Altitudes cause vessels inside the lungs to narrow, driving up the pressure within the lungs, which in turn leads to accumulation of fluid in the lungs (Peacock, 1998). A victim will have a productive cough, and the phlegm will be tinged with blood. A spell of acute mountain sickness is likely before this serious condition develops. It is likely that a person with pulmonary edema has ignored earlier symptoms of acute mountain sickness, and has not descended in response. Pulmonary edema needs immediate medical attention. Prescription medicines to widen the blood vessels of the heart and to reduce muscular contractions are used to treat pulmonary edema (Peacock, 1998). Though serious illnesses can threaten a climb, the body has an efficient system to cope with the physiological demands of high altitude. The adaptive responses may remain indefinitely long after a climb is over and the person has returned to a normal altitude. This is importantly reflected in the blood picture (Magalhaes et al, 2005). Hypoxia at high altitudes causes changes in counts and functioning of red blood corpuscles (RBCs). This is a major response to the paucity of oxygen, and reduced rate of blood circulation, as the body tries to compensate for the duress. Climbers who believe that they have adapted well to high altitudes may show the most marked and durable changes in RBC counts. Similarly, blood flow to the brain increases at high altitudes (Berre, Vachiery, Moraine, and Naeije, 1999). Since the blood thickens and becomes viscous, the possibilities of clots and strokes are also higher. These dangers come without attendant benefits, since hypoxia remains a threat even with the increased blood supply. Brain cells are starved of oxygen, and climbers may display long term effects in terms of changes in brain functioning and capabilities (Peacock, 1998). Musculature responds to hypoxia in the same way as the brain. Fatigue sets in with bouts of physical activity which are easily within the fitness levels of people at ground level (Felici et al, 2001). However, muscle tissue also adapts to high altitude conditions over time, and people who put in the time for acclimatization should be able to continue essential tasks, including climbing, if they are in normal health, and if they gain height gradually and with adequate rest. Accomplished climbers undergo relatively permanent changes in physiology. This makes them more suitable for spending time at high altitudes than at sea level, though it also deprives them of some normal capabilities, such as those related to mental faculties. However, strong adaptation to high altitude conditions in other continents do not necessarily prepare people for the harsh and unusual desolation faced at heights in the Antarctic (Maksimov, and Belkin, 2002): each environment may demand its own type of adaptive response. People with chronic disorders, on the other hand, may not be able to cope with even the simple demands of travel in airliners. Patients with cystic fibrosis for example, who function normally at sea level, are likely to require oxygen support during long flights (Thews, Fleck, Kamin, and Rose, 2004). Conclusions All individuals do not have the same physiological response to high altitudes. The latter has such different connotations for people with lung, heart, and circulatory disorders, compared to others, that even a long flight in an aircraft can constitute a significant high altitude episode for them. High altitude physiology has both acute and long term implications, which means that regular climbers may display long term changes in the functioning and capabilities of their bodies and minds. High altitude conditions in the Antarctic are known to be different from those at the same elevations in other continents. Everyone who intends to climb, even if in normal health, should be assessed for response to the challenges of high altitudes, through simulated experiments at sea level. They can perform better during actual climbs if they gain height gradually (Peacock and Jones, 1997), which proves the universal efficacy of submitting to the discipline of acclimatization. The conditions in the cabin of a commercial aircraft simulate high altitude stress for people with lung, heart, and circulatory disorders, so they should travel by air over long distances only after considered medical advice, and after notifying airlines at the time of buying their tickets, so that oxygen and related medical supplies are at hand. References Berre, J. Vachiery, J. L. Moraine, J. J. and Naeije, R 1999 Cerebral blood flow velocity responses to hypoxia in subjects who are susceptible to high altitude pulmonary edema, European Journal of Applied Physiology, 80: 260 -263. Felici, F. Raponi, A. Sbriccoli, P. Scarcia, M. Bazzucchi, I. and Iannttone, M. 2001 Effect of Human Exposure to altitude on muscle endurance during isometric contraction, European Journal of Applied Physiology, 85, 507-512 Magalhaes, J. Ascensa, A. Marques, F. Soares, J. M. C. Ferreira, R. Neuparth, M. J. and Duarte, J. A. 2005 Effect of a high-altitude expedition to a Himalayan peak (Pumori, 7,161 m) on plasma and erythrocyte antioxidant profile, European Journal of Physiology, 93: 726–732 Maksimov, A.and Belkin, V. Sh. 2002 Characteristics of Human Adaptation in High Altitude of Central Asia and the Antarctic, Journal of Human Physiology, Vol. 28, No 6, pp 640-646 Peacock, A. J. 1998 ABC of Oxygen: Oxygen at High Altitude British Journal of Medicine, 317:1063-1066 Peacock, A. J. and Jones, P. L. 1997 Gas exchange at extreme altitude: results from the British 40th Anniversary Everest Expedition, European Respiratory Journal, 10: 1439–1444 Thews, O. Fleck, B. Kamin, W. E. S. and Rose, D. M. 2004 Respiratory function and blood gas variables in cystic fibrosis patients during reduced environmental pressure, European Journal of Applied Physiology, 92: 493–497 Read More