Editorial: Working at high altitude (p. 307)

This issue of the Journal includes a Pro/Con feature on possible ways of identifying subjects who will remain fit and who are able to work effectively at high altitude. The Editorial discusses three areas where people are working at increasingly high altitudes and the conditions are therefore very challenging.

Sightings, Edited by Peter Bärtsch and Erik Swenson (p. 311)

Pro and Con, Edited by Erik Swenson

Hypoxic cardiopulmonary exercise testing identifies subjects at risk for severe high altitude illnesses

Increasingly lowlanders are finding it necessary to work at higher and higher altitudes. An important but difficult issue is how to identify subjects who will do well under these challenging conditions. Jean-Paul Richalet (p. 315) takes the Pro side while Peter Bärtsch (p. 318) takes the Con. Each debater also contributes a short rebuttal.

Review

Hypoxia and environmental epigenetics

Brown and Rupert (p. 323) provide a timely review on an emerging important area related to tolerance to hypoxia. Epigenetics refers to modifications of gene activity that are not caused by changes in the primary base sequence of the DNA. This is a rapidly growing topic and this authoritative review is welcome.

Scientific Articles

Ventilatory chemosensitivity, cerebral and muscle oxygenation, and total hemoglobin mass before and after a 72-day Mt. Everest expedition

Cheung and colleagues (p. 331) studied subjects before and after an expedition to Mt. Everest lasting 72 days. A treadmill test under progressive hypoxic conditions showed that exercise under hypoxic conditions improved significantly post-expedition. An interesting finding was that the ventilatory response to acute hypoxia was significantly elevated. A measure of cerebral oxygenation during hypoxic exercise improved post-expedition, but this was not true of muscle oxygenation.

Early adaptation in the Antarctic environment at Dome C: Consequences on stress-sensitive innate immune functions

Antarctica provides a very challenging environment and in this study Feurecker and colleagues (p. 341) studied the health of 9 males at CONCORDIA Station Dome C, altitude 3233 m. The extreme conditions include severe cold, hypoxia and the remote location. They found an increase in blood catecholamines which was thought to down-regulate innate immune functions.

Impact of hypoxic versus normoxic training on physical fitness and vasculature in diabetes

Schreuder et al (p. 349) studied the effect of exercise training including hypoxia on the fitness of patients with Type II diabetes. They found, as expected, that exercise training improved physical fitness but were surprised that this was not potentiated by combining the exercise with hypoxia caused by inhaling 16.5% oxygen.

Age-related arrhythmogenesis on ascent and descent; “Autonomic conflicts” on hypoxia/reoxygenation at high altitude?

Behn and colleagues (p. 356) studied heart rate variations using Holter monitoring in both old and young male subjects while ascending or descending between 2950 and 5050 m as car passengers in north Chile. Arrhythmic events defined as an increased R-R interval occurred more frequently on descent than ascent. The frequency increased with previous time spent at the highest altitude. It was suggested that age-dependent changes of autonomic activity played a role in the development of arrhythmias.

No evidence of intracranial hypertension in trekkers with acute mountain sickness when assessed non-invasively with distortion product otoacoustic emissions

The possible role of increased intracranial pressure in the development of acute mountain sickness is still debated. In this study (p. 364) intracranial pressure was estimated non-invasively by distortion product otoacoustic emission. Results in 187 subjects up to altitudes of 2610 m showed that those with symptoms of acute mountain sickness did not have higher intracranial pressures than normal subjects.

Rhodiola crenulata and Cordyceps sinensis based supplements boost aerobic exercise performance after short-term high altitude training

In this study from Taiwan, Chen and colleagues (p. 371) studied whether two dietary supplements improved aerobic exercise performance during two weeks of training at an altitude of 2200 m. Measurements included time to exhaustion, and blood changes such as red cell count and erythropoietin. The conclusion was that the supplements did provide an advantage, and this was attributed to a reduction in parasympathetic activity in the group taking the supplements.

Changes in the levels of cytokines in both diabetic/non-diabetic Type I children living in a moderate altitude area in Saudi Arabia

Allam and coworkers (p. 380) measured hemoglobin A1c and inflammatory cytokines in children with Type I diabetes and control children at altitudes of 1800 to 2000 m compared with sea level. The study included 600 children. It was found that hemoglobin A1c (a reflection of increased blood glucose levels) was significantly higher in children living at the moderate altitude compared with those at sea level. The Type I diabetes patients had higher values of serum cytokine levels than non-diabetics. Glycemic control in patients with Type I diabetes was more difficult at the moderate altitude.

Plasma and liver lipid profile in rats exposed to chronic hypobaric hypoxia: Changes in metabolic pathways

Siques and coworkers (p. 388) studied lipid metabolism in rats exposed to chronic hypoxia equivalent to an altitude of 4600 m for 30 days. Compared to control animals the hypoxic group had an increase in total cholesterol, LDL cholesterol, and triglycerides. Howevern HDL cholesterol decreased. The results may be relevant to cardiovascular risk.

Hypergravity and hypobaric hypoxic conditions promote endothelial cell and platelet activation

Rubenstein and Yin (p. 396) note that previous work has suggested that both hypoxia and increased acceleration can alter endothelial cell function affecting blood platelet activity and potentially exaggerating cardiovascular disease. In this study, endothelial cells and platelets were exposed to half normal barometric pressure on the one hand, and 8 G acceleration on the other. Both insults were found to enhance cardiovascular disease responses although the presence of platelets tended to inhibit the responses of the endothelial cells.

Brief Reports

Hematological changes in an elite climber over 18 years

Mejuto and colleagues (p. 406) studied an elite climber over a period of 18 years including measurements of red cell and hemoglobin concentration and hematocrit. As expected there was an increase in red cell parameters following ascent to altitude, but the responses decreased with increasing age.

Chronic intermittent high altitude exposure, occupation, and body mass index in workers of mining industry

Esenamanova and colleagues (p. 412) looked at obesity in miners working at altitudes of 3800 to 4500 m. They documented high obesity rates with increased blood pressure, cholesterol and glucose levels in miners exposed to intermittent high altitude hypoxia.

Gestational and early postnatal exposure to simulated high altitude does not modify postnatal body mass growth trajectory in the rat

Bozzini and colleagues (p. 418) tested whether hypoxia during the gestational and early postnatal period blunts growth when the offspring are raised in normoxia. This study in rats indicated that this is not the case.

Letters to the Editor

Pupil dynamics in hypoxic conditions: Caudwell Xtreme Everest results

A previous report showed a reduction in pupil aperture change and constriction velocity within one hour of arrival at high altitude although the changes reverted to normal over subsequent days. Here (p. 422) the relationship to peripheral arterial oxygen saturation was determined and it was argued that the pupil dynamics may be due to a direct hypoxic effect.

Seizures at high altitude—still a mystery?

Küpper (p. 424) notes reports of occasional seizures at high altitude but argues that the cause is still unclear.