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Transcranial Doppler is a widely used noninvasive technique for assessing cerebral artery blood flow. All previous high altitude studies assessing cerebral blood flow (CBF) in the field that have used Doppler to measure arterial blood velocity have assumed vessel diameter to not alter. Here, we report two studies that demonstrate this is not the case.(More)
BACKGROUND The level of environmental hypobaric hypoxia that affects climbers at the summit of Mount Everest (8848 m [29,029 ft]) is close to the limit of tolerance by humans. We performed direct field measurements of arterial blood gases in climbers breathing ambient air on Mount Everest. METHODS We obtained samples of arterial blood from 10 climbers(More)
The time between contemplation of surgery and the procedure offers a window of opportunity to optimize patients' nutritional, functional and psychological state prior to surgery. Traditionally, preoperative pathways have focused on the underlying disease process and 'fitness for surgery' with physical pre-assessment and risk counselling late in the pathway(More)
Exposure to the underwater environment for recreational or occupational purposes is increasing. Approximately 7 million divers are active worldwide and 500,000 more are training every year. Diving related illnesses are consequently an increasingly common clinical problem with over 1000 cases of decompression illness reported annually in the USA alone.(More)
The study of healthy human volunteers ascending to high altitude provides a robust model of the complex physiological interplay that emulates human adaptation to hypoxaemia in clinical conditions. Nitric oxide (NO) metabolism may play an important role in both adaptation to high altitude and response to hypoxaemia during critical illness at sea level.(More)
We postulated that changes in cardiac high-energy phosphate metabolism may underlie the myocardial dysfunction caused by hypobaric hypoxia. Healthy volunteers (n=14) were studied immediately before, and within 4 d of return from, a 17-d trek to Mt. Everest Base Camp (5300 m). (31)P magnetic resonance (MR) spectroscopy was used to measure cardiac(More)
Ascent to high altitude is associated with a fall in the partial pressure of inspired oxygen (hypobaric hypoxia). For oxidative tissues such as skeletal muscle, resultant cellular hypoxia necessitates acclimatization to optimize energy metabolism and restrict oxidative stress, with changes in gene and protein expression that alter mitochondrial function. It(More)
We report the first direct observations of deranged microcirculatory blood flow at high altitude, using sidestream dark-field imaging. Images of the sublingual microcirculation were obtained from a group of 12 volunteers during a climbing expedition to Cho Oyu (8,201 m) in the Himalayas. Microcirculatory flow index (MFI) was calculated from the moving(More)
Lowland residents adapt to the reduced oxygen availability at high altitude through a process known as acclimatisation, but the molecular changes underpinning these functional alterations are not well understood. Using an integrated biochemical/whole-body physiology approach we here show that plasma biomarkers of NO production (nitrite, nitrate) and(More)
Many disease states are associated with regional or systemic hypoxia. The study of healthy individuals exposed to high-altitude hypoxia offers a way to explore hypoxic adaptation without the confounding effects of disease and therapeutic interventions. Using (31)P magnetic resonance spectroscopy and imaging, we investigated skeletal muscle energetics and(More)