Design and conduct of Xtreme Everest 2: An observational cohort study of Sherpa and lowlander responses to graduated hypobaric hypoxia.

OBJECTIVE: Oxygen availability falls with ascent to altitude and also as a consequence of critical illness. Because cellular sequelae and adaptive processes may be shared in both circumstances, high altitude exposure ('physiological hypoxia') assists in the exploration of the response to pathological hypoxia. We therefore studied the response of healthy participants to progressive hypobaric hypoxia at altitude. The primary objective of the study was to identify differences between high altitude inhabitants (Sherpas) and lowland comparators. METHODS: We performed an observational cohort study of human responses to progressive hypobaric hypoxia (during ascent) and subsequent normoxia (following descent) comparing Sherpas with lowlanders. Studies were conducted in London (35m), Kathmandu (1300m), Namche Bazaar (3500m) and Everest Base Camp (5300m). Of 180 healthy volunteers departing from Kathmandu, 64 were Sherpas and 116 were lowlanders. Physiological, biochemical, genetic and epigenetic data were collected. Core studies focused on nitric oxide metabolism, microcirculatory blood flow and exercise performance. Additional studies performed in nested subgroups examined mitochondrial and metabolic function, and ventilatory and cardiac variables. Of the 180 healthy participants who left Kathmandu, 178 (99%) completed the planned trek. Overall, more than 90% of planned testing was completed. Forty-four study protocols were successfully completed at altitudes up to and including 5300m. A subgroup of identical twins (all lowlanders) was also studied in detail. CONCLUSION: This programme of study (Xtreme Everest 2) will provide a rich dataset relating to human adaptation to hypoxia, and the responses seen on re-exposure to normoxia. It is the largest comprehensive high altitude study of Sherpas yet performed. Translational data generated from this study will be of relevance to diseases in which oxygenation is a major factor.

A paradigm of fragile Earth in Priestley's bell jar.

BACKGROUND: Photosynthesis maintains aerobic life on Earth, and Joseph Priestly first demonstrated this in his eighteenth-century bell jar experiments using mice and mint plants. In order to demonstrate the fragility of life on Earth, Priestley's experiment was recreated using a human subject placed within a modern-day bell jar. METHODS: A single male subject was placed within a sealed, oxygen-depleted enclosure (12.4% oxygen), which contained 274 C3 and C4 plants for a total of 48 h. A combination of natural and artificial light was used to ensure continuous photosynthesis during the experiment. Atmospheric gas composition within the enclosure was recorded throughout the study, and physiological responses in the subject were monitored. RESULTS: After 48 h, the oxygen concentration within the container had risen to 18.1%, and hypoxaemia in the subject was alleviated (arterial oxygen saturation rose from 86% at commencement of the experiment to 99% at its end). The concentration of carbon dioxide rose to a maximum of 0.66% during the experiment. CONCLUSIONS: This simple but unique experiment highlights the importance of plant life within the Earth's ecosystem by demonstrating our dependence upon it to restore and sustain an oxygen concentration that supports aerobic metabolism. Without the presence of plants within the sealed enclosure, the concentration of oxygen would have fallen, and carbon dioxide concentration would have risen to a point at which human life could no longer be supported.

Knowledge and exposure to complementary and alternative medicine in paediatric doctors: a questionnaire survey.

BACKGROUND: Complementary and alternative medicines are increasingly used by the general population. A survey was conducted to ascertain the knowledge of Complementary and Alternative Medicines (CAMs) amongst paediatric physicians, and whether seniority increases the likelihood of its use being considered in consultations, or of families discussing it. METHODS: Anonymous survey of general paediatric doctors in a large inner-city district general hospital (DGH) and tertiary children's centre (TC) using a questionnaire. Statistical analysis was calculated using Minitab. RESULTS: 43/49 (88%) questionnaires were returned correctly. 13 (30%, CI 17 - 46%) doctors had personally used CAMs. 24 (56%, CI 40 - 71%) of their families had used CAMs. 13 (30%, CI 17 - 46%) had received formal CAMs education. 21 (49%, CI 40 - 71%) could name a total of 5 types of CAMs. Consultants were significantly more likely to ask about CAM use than middle-grades and juniors (p < 0.05, CI 48 - 93%, 35 - 90%, 8 - 33% respectively) and have had a clinical encounter where they felt it was significant. 32 (74%, CI 59 - 86%) of the clinicians had been asked about CAMs. 33 (77%, CI 61 - 88%) of doctors had successful CAM use reported to them, and 20 (47%, CI 31 - 62%) had failure of CAMs reported to them. CONCLUSION: CAM use is relatively common in paediatric doctors and their families. They have received little formal CAMs education. Consultants were more likely than juniors to ask about CAM use and have had a clinical encounter where it played a significant part. Around half of all doctors irrespective of grade have been asked about CAMs in a clinical encounter.