Arterielle Hypertonie unter Höheneinfluss

Oxygen comfort evaluation method based on symptom index for short-term internal migrants to Tibet

In Tibet, the hypobaric-hypoxic environment found at high altitudes leads to dysfunction in short-term internal migrants and has noticeable effects on physiology, psychological health, and comfort level. Therefore, it is essential to accurately determine the degree of hypoxia and improve the hypoxic environment of plateaus. Despite advances in the medical diagnosis and treatment of pathological hypoxic injuries, there are some limitations in the oxygenic evaluation of internal migrants with mild hypoxia. An oxygen comfort evaluation method (OCEM) based on typical anoxic symptomatology and physiological indices is proposed in this study. Experiments with different oxygen concentrations were conducted to measure anoxic symptomatology and physiological indices. Using item and exploratory factor analyses, 19 symptom indices were screened to predict oxygen sensation in humans. Finally, the OCEM was established using an artificial neural network and fuzzy mathematics method and its accuracy was verified through a field survey. The results showed that the artificial neural network model using symptomatologic indices could predict human oxygen sensation, with an area under the receiver operating characteristic curve of 0.630-0.913 and prediction accuracy of 93 %. Oxygen comfort can be predicted from the oxygen sensation and typical physiological indices using the fuzzy mathematics method; the weighted kappa coefficient was 0.825, indicating a strong correlation between the predicted and actual values. The proposed OCEM can help determine the oxygen comfort conditions of high-altitude internal migrants and provide a basis for indoor oxygen environment regulation in high-altitude buildings.

Altitude and cold weather: are they vascular risks?

PURPOSE OF REVIEW

The relationship of altitude and cold to cardiovascular risk is complex. Cold is hard to separate from altitude. This review highlights the latest information on cardiovascular disease associated with high altitude and cold; both represent unique clinical situations.

RECENT FINDINGS

Evolution and genetics are relevant to high altitude, with much new information available. Specific physiology explains some congenital heart disease at altitude. New reports of hematological changes associated with altitude and cold help clarify thrombosis, which is relevant to reports of very late in-stent thrombosis at altitude. Multiple cardiovascular risk factors are affected by altitude and cold, and an increased incidence of myocardial infarction occurs. There is new research on acute mountain sickness associated with inflammation with relevance for clinical study of pulmonary edema. Socioeconomics plays a part in altitude and cold effects on cardiovascular disease. In addition to acute disease, high altitude involves chronic mountain sickness with new knowledge of associated cardiovascular endothelial abnormalities.

SUMMARY

High altitude and cold involve acute disease, chronic disease, and public health issues. Continued research is essential to enable the best clinical management in this era of rapid worldwide travel.

Short-term exposure to hypoxia for work and leisure activities in health and disease: which level of hypoxia is safe?

INTRODUCTION

Exposures to natural and simulated altitudes entail reduced oxygen availability and thus hypoxia. Depending on the level of hypoxia, the duration of exposure, the individual susceptibility, and preexisting diseases, health problems of variable severity may arise. Although millions of people are regularly or occasionally performing mountain sport activities, are transported by airplanes, and are more and more frequently exposed to short-term hypoxia in athletic training facilities or at their workplace, e.g., with fire control systems, there is no clear consensus on the level of hypoxia which is generally well tolerated by human beings when acutely exposed for short durations (hours to several days).

CONCLUSIONS

Available data from peer-reviewed literature report adaptive responses even to altitudes below 2,000 m or corresponding normobaric hypoxia (F(i)O(2) > 16.4%), but they also suggest that most of exposed subjects without severe preexisting diseases can tolerate altitudes up to 3,000 m (F(i)O(2) > 14.5%) well. However, physical activity and unusual environmental conditions may increase the risk to get sick. Large interindividual variations of responses to hypoxia have to be expected, especially in persons with preexisting diseases. Thus, the assessment of those responses by hypoxic challenge testing may be helpful whenever possible.