Abstract
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Each of the research groups present at the conference gave an account of their recent activities. Edward Gilbert-Kawai (CASE) gave an overview of the recent “Xtreme Everest 2” project, which studied different groups on route to Everest Base Camp. These groups included identical twins, children, experienced mountaineers, and the local Sherpa population. Initial findings included Sherpas having different cardiac metabolism and increased NO activity. Damian Bailey (University of South Wales) presented recent work on oxidative stress at altitude in lowlander and highlander populations, with evidence of increased oxidative stress in maladapted highlanders. An overview of how children born from artificial reproductive techniques have increased oxidative stress and impaired endothelial function at altitude compared to controls was also presented. Sam Oliver (Extremes Research Group, University of Bangor) gave an overview of observational skin antigen work, which suggests that altitude may impair immunity, and also presented MRI studies during hypoxia demonstrating increases in total brain volume, possibly grey matter, at 10 hours hypoxia. Kenny Baillie (APEX) described their 2013 Bolivia expedition whereby their gene expression microarray data will be freely available to other interested parties, and described their website altitude.org and its value as a public health resource, as well as their increasing HAPE database. Chris Imray (BMRES) highlighted observations at Testa Grigia describing the effect of acetazolamide on exercise at acute altitude exposure and recent MRI studies of the cerebral vascular effects of 22 h at 12% O2. Adam Booth gave a brief overview of the Diploma of Mountain Medicine (DIMM) and encouraged involvement of junior doctors, and highlighted the possible use of the DIMM e-mail forum to altitude researchers requiring advice.
Invited speakers discussed aspects of adaptation to hypoxia. Sam Lucas (University of Birmingham) discussed sleep and brain blood flow, and central sleep apnea during sleep recordings near Everest Base Camp. Changes in vascular reactivity and oscillations in middle cerebral artery velocity were associated with cyclical apnea, changes in heart rate, and oxygen saturations. These could be reduced or enhanced with IV acetazolamide or indomethacin, respectively. Kenny Baillie (APEX) presented compelling evidence that acute mountain sickness (AMS) (as currently defined by Lake Louise score) probably describes at least two distinct clinical syndromes. This sparked a lively debate as to the best way to categorize and grade altitude illness, and whether sleep should be excluded from diagnosing AMS. It was generally agreed that headache is the key symptom, with nausea very variable. Andrew Murray (University of Cambridge) presented studies on mitochondria in the mountains showing how cardiac energy buffer is decreased at altitude (also seen in heart failure) but recovers by 6 months. Muscle biopsies demonstrated dramatic reduction in numbers of mitochondria after ascent above Everest Base Camp, but not in individuals trekking to Base Camp. Possible mechanisms behind this, including mitochondrial uncoupling, were presented.
The morning concluded with a well-illustrated account of a recent Everest ascent by Adam Booth.
The short reports in the afternoon sessions included data showing no benefit of beetroot juice on elite 10 km altitude running performance, implications of inspiratory muscle training pre altitude exposure to improve oxygen saturations, and data illustrating the considerably increased work rate of “rush and rest” over “slow plod” at altitude with no difference in time to complete a set distance. Useful discussions on safe oxygen saturations for pilots and crew at altitude, and the use of a hypoxicating tent for prolonged exposure to hypoxia where serial MRI scans showed early peaks in cerebral artery velocity. Saccadic latencies were unaffected at acute exposure to moderate altitude, although a significant increase of saccadic latency was noted in subject on acetazolamide at altitude. A meta-analysis concluded that previous AMS history was not a sufficiently sensitive or specific risk factor to predict recurrent AMS (with lively discussion from members of the audience). Skin changes with ultraviolet exposure at altitude, practical use of portable lactate meters, the possible adverse effect of acetazolamide on exercise performance at moderate altitude, and the induction of extravascular lung water on strenuous exercise at altitude were also presented.
Posters included a review of high altitude pulmonary edema prophylaxis, immunological consequences of high altitude, hypoxia and myoblasts, and a study of effects of an 18-day sojourn at altitude on energy expenditure.
Kyle Pattinson (University of Oxford) discussed the sensation of breathlessness, in particularly focusing on how breathlessness in mountaineers and COPD patients is perceived differently, and this can be visualized using fMRI. Areas of brain activity corresponding with anxiety show less activation after pulmonary rehabilitation, which may explain its impact on quality of life. Mark Wilson (Imperial College, London) reviewed cerebral circulation and hypoxia, focusing on the venous aspect of headache. Translational aspects were presented with implications for idiopathic intracranial haemorrhage and headaches seen in individuals in space.
The day was concluded with an inspiring talk by Harriet Tuckey, discussing the huge impact her father, Griffith Pugh, had on the success of the 1953 Everest expedition. As an exercise physiologist, he revolutionized supplementary oxygen use, fluid intake, clothing, diet, and acclimatization schedules, all of which ultimately helped to make the ascent possible. His later contributions to high altitude in the Silver Hut were also covered.
This day brought many of the UK altitude research groups together to focus on their latest work and highlighted upcoming debates in how we diagnose AMS, increased use of ultrasound and MRI in furthering altitude medicine research, and possible translational benefits of high altitude physiology research into clinical medicine. Alex Wright was thanked for his hard work in organizing a successful conference.