Реферат: Hypoxia Essay Research Paper HypoxiaHypoxia is a

Hypoxia Essay, Research Paper


Hypoxia is a condition in humans that is caused by the reduction in partial pressure of oxygen, inadequate oxygen transport, or when tissues are simply unable to make use of the oxygen provided. This disease occurs in the tissues and brain. It results in a shortness of breath, and an overall impairment of function.

Anoxia is the extreme form of hypoxia, and it occurs when there is absolutely no oxygen at all in the body that the brain and tissues can make proper use of.

There are five different types of hypoxia. These types are hypoxemic hypoxia, anemic hypoxia, stagnant hypoxia, histoxic hypoxia, and pemic hypoxia.

Hypoxemic hypoxia happens when there is a reduction in the amount of oxygen passing into the blood, resulting in too much hemoglobin and not enough oxygen. Therefore the oxygen pressure in the blood that is traveling to the tissues is too low to saturate the large amounts of hemoglobin. Hypoxemic hypoxia is caused by a reduced gas exchange area, exposure to high altitude, or by lung disease. Hypoxemic hypoxia has also been proven to be hazardous to aviators, mountain climbers, and generally in people living at high altitudes because the lowered barometric pressure causes the supply of oxygen to decrease.

Anemic hypoxia occurs when there is not enough hemoglobin that is functional, and so the capacity of blood capable to carry oxygen is too low. In anemic hypoxia either the entire amount of the hemoglobin is too small to supply the body s oxygen requirements-as in anemia or after severe bleeding-or the hemoglobin that is present is useless-such as in carbon monoxide poisoning and metho-globinuria. In both of the latter cases the hemoglobin is so altered by toxic agents that it becomes unavailable for any oxygen transport, and therefore is no longer useful to the respiratory system.

Anemia is one of the most frequent cases of anemic hypoxia. It is a condition due to the healthy red blood cell amount falling way below normal.

Stagnant hypoxia is an oxygen deficiency when there is poor blood circulation or poor blood flow. The blood flow through the capillaries is insufficient to properly supply the tissues. There, the blood itself is normal, but the blood flow is so reduced that there is not enough blood reaching the tissues. Stagnant hypoxia may be general or local. In a general case, it may result from heart disease, impairing the circulation; an impairment of the return of the blood through the veins; or trauma-induced shock. In a local case of stagnant hypoxia, it may be due to any condition that reduces or prevents blood circulation anywhere in the body. Both Raynaud s disease and Buerger s disease are examples of local stagnant hypoxia. Examples of causes of stagnant hypoxia are high G forces, prolonged sitting in the same position or hanging in a harness, cold temperatures, and positive pressure breathing. If a person sits in the same position for long hours, such as in a classroom, stagnant hypoxia can be experienced.

Histoxic hypoxia is when the tissues and cells of the body-even if the amount in the blood may be normal and under normal tension-are unable to use the oxygen because the tissues were poisoned. Carbon monoxide and cyanide poisoning, certain narcotics, chewing tobacco, and alcohol will all prevent oxygen use by the tissues. Usually, histoxic hypoxia is experienced after an over dosage of alcohol.

It is assumed by most people that there are only four types of hypoxia, but this is not so. There is a fifth type of hypoxia that is not so frequently diagnosed as the other four types. This type is known as pemic hypoxia. Pemic hypoxia is a reduction of the oxygen carrying capacity of the blood. It is caused by a reduced amount of hemoglobin or a reduced amount of red blood cells. A reduction in oxygen transport capacity of the blood occurs through blood donation, hemorrhage, or anemia. A reduction in the oxygen carrying capacity of the blood occurs through drugs, chemicals, or carbon monoxide.

In general, hypoxia can be caused by anything that lowers cellular respiration. It can be caused by agents such as narcotics, alcohol, formaldehyde, acetone, and specified anesthetic agents. Diseases of the blood, heart, circulation, or the lungs can also cause it.

Hypoxia is often confused with altitude sickness, or mountain sickness. Although altitude sickness is associated with hypoxia, especially with hypoxemic hypoxia, they are not the same thing. Altitude sickness occurs only in people who are associated with high altitudes; such as mountain climbers, aviators, and people living at high altitudes. Hypoxemic hypoxia occurs in those same people, but for the aforementioned reasons. Altitude sickness is a condition in which the body is starved of oxygen because of the thinness of air at high altitudes. That is why altitude sickness is not the same thing as hypoxia; it is caused by the air and therefore affects the oxygen of the body whereas hypoxia directly affects the blood and oxygen of the body.

The symptoms of altitude sickness fall into four main categories; respiratory, mental/muscular, cardiac, and gastrointestinal.

Symptoms associated with respiratory are shortness of breath upon any exertion at all, and deeper and more rapid breathing.

Symptoms that fall into the mental/muscular category are weakness, fatigue, dizziness, lassitude, headache, sleepiness, less mental activity, decreased muscle coordination, and impaired sight and hearing.

Cardiac symptoms are pain in the chest, palpitations, and an irregular heartbeat.

Finally, the symptoms of the gastrointestinal category are nausea and vomiting.

Altitude sickness symptoms occur six hours to four days after the arrival at high altitude, and after two to five days they disappear. Altitude sickness can be fatal if one does not return to a low altitude in time; symptoms only disappear if one descends from the high altitude.

Altitude sickness occurs because at high altitudes the air becomes much thinner, and therefore the amount of breathable oxygen drastically decreases. Also, the lower barometric pressures of high altitudes lead to lower partial pressure of oxygen in the alveoli in the lungs, which in turn decreases how much oxygen the red blood cells absorb from the alveoli for transport to the body s tissues. It can result in insufficient quantities of oxygen in the arterial blood supply, and therefore causes the symptoms of altitude sickness.

A popular method of training came about for serious athletes long ago, known as high altitude training. High altitude training is when athletes ascend to high altitudes (such as on a mountain) to train there during their off season. As they train there, because there is a lower amount of oxygen available at the higher altitude, the body is forced to adapt by generating more oxygen-carrying red blood cells. This allows the athlete to perform normally even though he/she is at a high altitude with a lack of oxygen to be provided. Once an individual s body is finally capable of performing well at the high altitude, he/she descends back to sea level, where they can retain the higher concentration of oxygen-carrying red blood cells, allowing their body to absorb and transport oxygen much more efficiently than ever before. This greatly benefits the athlete because it allows for a better performance in any activity-from jogs along the road to the one hundred meter sprint at the Olympics, now that his/her endurance is so significantly increased.

Hypoxia affects more than just the blood and hemoglobin; a prolonged hypoxia causes a low rise in the red blood cell count (polycythaemia). This increase in the rate of red blood cell production is produced by hypoxia s effect on the kidney. It causes the kidney to secrete a substance known as enythrogenin into the blood stream. There, it acts upon a plasma protein called erythropoietinogen, which produces erythropoietin, stimulating the red bone marrow to make more red blood cells.

Hypoxia also affects the brain-especially the respiratory center of the brain. Even a brief lack of oxygen has effects on this area in the brain, such as a loss of consciousness. When hypoxia causes a shortage of oxygen it affects the respiratory center of the brain because the brain struggles to recover from the shortage of oxygen by causing the breathing rate to increase. If one becomes so starved of oxygen that he/she loses consciousness this causes him/her to lose many of his/her brain cells.

That is just one example of the many different effects hypoxia can have on the brain. Any effect on the brain can be dangerous, because it is such a crucial organ of the body. That is why hypoxia is so dangerous, and why people should be extremely careful about avoiding it. Hypoxia is a mystery to most people, because they were never educated about its harmful effects on the body. This disease should be taught to people everywhere, because it can be caused by habitual activities such as sitting in the same position too long, or even by drugs such as alcohol which are wreaking havoc everywhere across the world. Hypoxia is not something to be joked about, it has the potential to seriously harm someone or even be fatal. That is why hypoxia should be considered a probable enemy to today s society.

Bibliography March 11, 2001

A Text Source:

The World Book Encyclopedia (A: Volume 1). By World Book, Inc. (2000). World Book, Inc. Chicago

An Article Source:

Early Effects of Hypoxia on Brain Cell Function By Kmjeviee, K. (1999). Anesthesia Research Department, Montreal

Intranet Source:

Hypoxia (2000). (On-line). Available: www.eb.com:180/ bol/search?type=topic&query=hypoxia&Dbases=Articles by Britannica, Inc.

Internet Source:

What is High Altitude Training? (2000). (On-line). Available: www.altitude-training.com/whatis.htm by Greska, B.

*excerpt from an air force manual

Hypoxia (1999). (On-line). Available: www.batnet.com/

mtwright/hypoxia.html by Wright, M.


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