Articles
Research at High Altitudes
Field studies in the mountains are challenging to design and undertake and need to balance practicalities (such as limited power supply) with scientific objectives. This article examines the history and rationale for high altitude research and discusses the challenges of organising a field study.
Introduction
Science and mountain exploration are closely linked throughout history. A large array of studies of varying complexity have been performed conditions of hypobaric hypoxia, some on field studies, some in hypobaric chambers. The military has contributed greatly to this body of evidence both through operations in high altitude regions of the world, hypobaric chamber studies and through field studies as part of adventurous training expeditions. The hope is that by investigating hypoxia in fit participants in field or chamber studies insights may be gained into the adaptation to hypoxia during critical illness and novel approaches for treatment developed.
History of association of science and mountaineering
Anecdotal accounts of medical problems at high altitude go back to the Chinese in the time of Emperor Ching-Te (32-7 BC) and mountain exploration and scientific enquiry have always gone hand in hand. The first team to climb Mont Blanc, the physician Michel Gabriel Paccard (1757–1827) and local crystal hunter Jacques Balmat, (1762–1834) were motivated by the ambition to make scientific observations on the summit (including barometric pressure) when they climbed the mountain in 1786. The first scientific work on altitude related physiology was published by Paul Bert in Paris in 1878, “La Pression Barometrique”[2]. Bert’s work was primarily performed in hypobaric chambers and demonstrated that hypoxia was the prime danger of hypobaric conditions. High altitude observatories and laboratories where built on the two highest mountains in the Alps (Mont Blanc and Mont Rosa) during the late 1800’s [3]. Significant events occurred at the laboratory including work on the ventilator response to hypoxia and what is probably the first recorded case of high altitude pulmonary oedema. Expeditions with a significant medical aim (rather than science as a secondary aim of the expedition) began with a Pike’s Peak Expedition in 1911. This expedition was led by J.S. Haldane (the famous Scottish physiologist) and was the first to measure the fall in alveolar carbon dioxide during two weeks at altitude[4]. The landmark field study was the “Silver hut” study in 1960-1. A laboratory was built at 5800m in the Everest area and inhabited for 6 months and data collected up to 7440m on Makalu (8481m)[5]. This project lead on to the American Medical Research Everest Expedition in 1981 (led by Professor John B West), barometric pressure was measured on the summit of Everest for the first time and alveolar gas samples taken [6]. In the very recent past the Caudwell Extreme Everest expedition took 208 trekkers to Everest base camp, 15 climbers onto Everest and 8 to the summit in a 21/2 month long expedition[7]. Data was collected on blood flow, Doppler and arterial blood gases were taken at 8400m showing profound hypoxia and hypocarbia (mean (range)KPa PaO2 3.28 (2.55 – 3.93) and PaCO2 1.77 (1.37-2.1) [8].
Association with military mountaineering
The Joint Services Expeditions Trust was set up in September 1969 to encourage Joint Service adventurous expeditions which have a significant scientific element. The Trust give grants to support scientific research of all kinds (not ex clusively medical) during adventurous training expeditions. The purpose of the grants are “to further the efficiency of Her Majesty’s Armed Forces through the development of personal and leadership qualities by supporting adventurous and arduous expeditions for the purpose of carrying out research of a scientific nature (including social sciences), and disseminating the knowledge gained as a result thereof” [9]. The work of Sqn Ldr Pask GE during World War II is outlined elsewhere in the Journal of the Royal Army Medical Corps[10]. Military expeditions have had a history of including medical research, performing some quality field studies, notably the first measurement of Brain Naturetic Peptide at altitude and early work on the hypoxic ventilatory response [11-13]. Mountains are natural borders between countries and therefore potentially areas of conflict. During the early 60’s the Chinese and Indian armies faced each other across the Himalayas when China invaded in 1964. The Indians realised that their troops were at a great disadvantage when compared to the Chinese who were resident at high altitude on the Tibetan plateau. During the conflict the Indian troops suffered greatly with high altitude illness and much work was published during that period by the Indians[14-15]. Other potential high altitude flash points exist, India and Pakistan have high altitude military posts on the Siachen glacier in the Karakorum Himalayas and a significant proportion of Afghanistan and northern Pakistan is over 3000 m. Future conflicts are likely to be fuelled by a lack of resources (e.g. oil and gas) and climatic changes[16] this is likely to result in conflict in high altitude regions as populations migrate and exploit currently untapped resources. Shock and hypoxia is a part of all critical illness, even with good pre-hospital airway care and ventilation, trauma patients frequently present to the Emergency Department in the hospital in Camp Bastion with a profound base deficit indicating end-organ tissue hypoxia. In 22 major ballistic injuries there was a median base deficit of 7 despite a median SpO2 of 99.5% (Authors unpublished data). Inducing shock in healthy subjects is ethically difficult, however, enabling individuals to take part in an expedition during which they will inevitably become profoundly hypoxaemic may provide an acceptable approach for both investigators and subject. Chamber studies have been used to replicate the altitude profiles of Everest ascents[17]. These studies are immensely costly and ethically challenging: to run a hypobaric chamber requires two operators and medical cover around the clock over the typical Everest ascent of 8 weeks. The ethics of subjecting individuals to 8 weeks of enforced captivity during which they are very likely to become unwell is questionable. Chamber studies can only replicate the hypobaric elements of mountaineering and not the relationship of hypoxia to exercise, dehydration or dietary changes. Contrast this with expeditions where those taking part do so of their own free will and would often undertake the trek with or without the science element - there are far fewer ethical conflicts. Furthermore through combining a few days of research (as planned days throughout the expedition) and still being able to achieve other aims, in terms of trekking or climbing, individuals will contribute financially to the overall costs of scientific expeditions. In many ways the military is ideally placed to lead scientific expeditions and has a long history of doing so. The Joint Services Adventurous Training (JSAT) scheme supports adventurous training financially with costs typically split equally between contributions from public funds, non-public funds and personal contributions) and further grants are available to expeditions fulfilling suitable scientific aims through the Joint Services Expeditions Trust. Richard Feynman eloquently observed that “nature uses only the longest threads to weave her patterns, so that each small piece of her fabric reveals the organization of the entire tapestry”[18]. Whilst the leap from high altitude research in healthy subjects to critically ill octogenarians on an intensive care unit is not immediately apparent by adding strands to the tapestry the whole picture is more likely to emerge.
Challenges of high altitude field research
Mountainous regions of the world are generally poorly developed in terms of road, rail, telephone and power supplies. This lack of resource produces significant challenges to the planning and execution of field research. Temperature falls in a predictable way with altitude and is referred to as the lapse rate. Typically, in clear skies the lapse rate is 1deg C per 100m of altitude which leads to very cold temperatures at high altitude. However due to the thinner atmosphere the radiated solar energy is very high leading to a huge difference in temperature between that in direct sunlight and shade, with almost inevitable sub-zero temperatures after dark. The consequence of this is that maintaining samples or equipment within a reasonable temperature range is difficult. This large temperature range has implications for power supplies. Cold batteries rapidly loose charge or do not generate sufficient power for operating equipment, thus batteries need to be kept warm, usually in a pocket by day or sleeping bag overnight, if they are to have the predicted output. Even in use, equipment can cool rapidly and thought must be given tomaintaining a working temperature for example, by placing equipment on a hot water bottle or inside a down jacket. Despite the small size and relative portability of modern medical equipment power remains a real issue. Even in well travelled areas such as the Khumbu valley on the Everest Base Camp trail there is relatively little reliable electricity. Most tea houses allow trekkers to recharge from a solar panel or their domestic system, which is usually a solar charged battery rather than generator, for a fee. This supply may not be adequate to charge medical equipment. Solar panel technology has improved dramatically over the last few years but the supply may still be of inadequate potential difference to power a lap-top computer; in addition solar panels are most effective when left stationary but on many expeditions most of the day light hours are spent trekking. Compact generators can be used but are heavy, usually weighing at least 25Kg, which is a full porter load where they have to be carried on foot and sufficient clean fuel may be difficult to obtain. Disposal of waste such as sharps and contaminated clinical waste will be difficult in remote areas and at least require carrying in and out. Undertaking research is often not seen by all the expedition members as the most important aspect of an expedition. During the Defence Medical Services expedition to Vellicitos and Aconcagua in 2007, few subjects felt able to perform a step test at 0400 in the morning, when it was -5 deg C and oxygen saturations were in the low 80’s, however all the team managed to find motivation to climb the 100m to the summit of Vellicitos later that morning!
Careful planning of the expedition itinerary is required in order to ensure that individual expectation is matched to the scientific aims especially if the subjects are financially contributing to the expedition. An expedition needs to be planned to have time for the research elements. Scheduling days for investigation when a rest day is required for acclimatisation allows work to be carried out in sun light, with functioning batteries or solar power, rather than trying to perform measurements at the end of a long days trekking, in the dark when it’s well below freezing. Caudwell Extreme Everest (CXE) overcame this problem by having 4 fixed “laboratories” carrying out investigation along the trek to base camp. This provides an ideal solution but can only be used by large scale expeditions such as CXE which had 208 trekkers and was the largest project of it’s kind ever undertaken).
Conclusion
There is some truth in Sir Edmund Hilary’s quote at the introduction to this article. The appetite for performing science in the mountain environment would arguably not be so great if the opportunity for travel to beautiful, remote regions of the world and climbing were not there. That said with careful planning and preparation the objective of carrying out good science can work together with the other aims of adventurous training (for the military) or trekking and climbing. References with the author. First published in the Journal of the Royal Army Medical Corps. With kind permission by the Editor JRAMC.
Surgeon Commander Adrian Mellor FRCA RN
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