The supersonic concorde cruise at altitudes between 15-20km(50,000-60,000ft). The Spacecrafts travel beyond the environment of the earth's atmosphere at altitudes above 350km, and finally, man has also landed on the moon.
This journey to high altitude has many physiological problems which affect body functions depending on the heights attained, and the speed of travel . These problems includes. A fall in the total blood pressure which causes progressive hypobaric hypoxia. Every ascent of 150m is associated with a fall in temperature of approximately 1°C . As we go high , there is a fall in relative humidity of air coupled with high wind velocities leads to insensible increase in water loss for mountainers.
The symptoms appear right from the first day ( during the first 8 - 24 hours ) but may be delayed up to 4days . person who ascend high altitude may experience anorexia, nausea and vomiting .
The pathogenesis of acute mountain sickness is not well understood , but it is believed that hypoxia , disturbances in the volume and distribution of body fluids contributes to the symptoms. Ascent to altitudes provokes increased secretion of ADH and glucocorticoids which cause fluid retention (high altitude pulmonary eodema). It also increase secretion of catecholamines , chemoreceptore, vasoconstrictors these lead to shunting of blood away from some parts of the body which lead to its accumulation in the lungs , splanchnic bed and brain . The cause of pulmonary eodema is not clear ; but there seems to be an increase in the permiability of pulmonary capillaries. Prevention of Acute Mountain Sickness can be achieved by Avoiding too rapid ascent, Administeration of drugs such as acetazolamide and dexamethasone , and then descend to lower altitude and breathe oxygen if symptoms appear.
Conclusion
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List of image references
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References for further study
Ezilo GC : Textbook of physiology, Oxford
University Press, New Delhi 2005
Ganong WF. Review of Medical
physiology, 23rd edition . Mc Graw
Hill, Singapore 2007
Guy AC and Hall JE : Textbook of Medical
Physiology , 10th edition, W.B.
Saunders Company, Philadelphia
Chamberlain G and Pipkin FB : Clinical
Physiology in Obsterics , 3rd edition ,
Blackwell Science , Oxford 1998.
Brobeck JR (Editor) : Best and Taylor's
Physiological Basis of Medical Practice
, 11th edition , Williams and Wilkins ,
Baltimore 1985
Berker KL et al.(Editors).Principles and practice of Endocrinology and Metabolism, J.P. Lippincott Company, Philadelphia 2007.