Hypoxia is a condition in which the body or body of the body lacks sufficient oxygen supply at the tissue level. Hypoxia can be classified as general , affecting the whole body, or local , affecting a body region. Although hypoxia is often a pathological condition, variations in arterial oxygen concentration may be part of normal physiology, for example, during hypoventilation training or severe physical exercise.
Hypoxia differs from hypoxaemia and anoxemia in hypoxia which refers to a situation in which oxygen supply is insufficient, whereas hypoxaemia and anoxemia refer specifically to situations that have low or zero arterial oxygen supply. Hypoxia in which there is a complete lack of oxygen supply is referred to as anoxia .
General hypoxia occurs in healthy people as they rise to high altitudes, where it causes altitude sickness leading to potentially fatal complications: high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Hypoxia also occurs in healthy individuals when inhaling gas mixtures with low oxygen content, such as underwater dives, especially when using a closed-circuit rebreather system that controls the amount of oxygen in the air provided. Mild and non-destructive intermittent hypoxia is used intentionally during altitude training to develop athletic performance adaptation at systemic and cellular levels.
Hypoxia is a common complication of premature birth in newborns. Because the lungs develop at the end of pregnancy, premature infants often have undeveloped lungs. To improve lung function, doctors often place babies at risk of hypoxia in the incubator (also known as humidicribs) that provide continuous positive air pressure.
Video Hypoxia (medical)
Thorough hypoxia
The symptoms of complete hypoxia depend on the severity and acceleration of the onset.
In the case of altitude sickness, where hypoxia develops gradually, symptoms include fatigue, numbness/tingling of the extremities, nausea, and anoxia. In severe hypoxia, or rapid onset hypoxia, ataxia, confusion/disorientation/hallucinations/behavioral changes, severe headache/decreased level of consciousness, papilloedema, shortness of breath, pallor, tachycardia, and pulmonary hypertension leading to ultimate signs cyanosis, slow heart rate/cor pulmonale, and low blood pressure followed by death.
Because the hemoglobin is dark red when it is not attached to oxygen (deoxyhemoglobin), as opposed to the rich red color that it has when bound to oxygen (oxyhemoglobin), when viewed through the skin it has an increased tendency to reflect blue light back into the eye. In cases where oxygen is transferred by other molecules, such as carbon monoxide, the skin may appear 'cherry red' instead of cyanosis. Hypoxia can cause premature birth, and injure the liver, among other damaging effects.
Maps Hypoxia (medical)
Local hypoxia
If the tissue is not absorbed properly, it may feel cold and look pale; If severe, hypoxia can cause cyanosis, a blue discoloration of the skin. If hypoxia is severe, the tissue may eventually become gangrene. Incredible pain can also be felt in or around the site.
Hypoxia tissue from low oxygen delivery may be caused by low hemoglobin concentrations (anemic hypoxia), low cardiac output (stagnant hypoxia) or low hemoglobin saturation (hypoxic hypoxia). The consequences of oxygen deprivation in tissues are anaerobic metabolic changes at the cellular level. Thus, a decrease in systemic blood flow may lead to an increase in serum lactate. Serum lactate levels have been correlated with disease severity and mortality in critically ill adults and in ventilated neonates with respiratory distress.
Cause
Oxygen passively diffuses in the pulmonary alveoli according to the pressure gradient. Oxygen diffuses from inhaled air, mixed with water vapor, into arterial blood, where its partial pressure is about 100 mmHg (13.3 kPa). In the blood, oxygen is bound to hemoglobin, a protein in red blood cells. The hemoglobin binding capacity is affected by the partial pressure of oxygen in the environment, as described in the oxygen-hemoglobin dissociation curve. Small amounts of oxygen are transported in solution in the blood.
In peripheral tissues, oxygen once again diffuses to lower the pressure gradient into their cells and mitochondria, where it is used to generate energy in relation to the breakdown of glucose, fats, and some amino acids.
Hypoxia can result from failure at any stage in the delivery of oxygen to the cell. These can include a decrease in the partial pressure of oxygen, problems of oxygen diffusion in the lungs, lack of available hemoglobin, problems with blood flow to the end tissue, and problems with respiratory rhythm.
Experimently, oxygen diffusion becomes the rate limit (and off) when the partial pressure of arterial oxygen decreases to 60 mmHg (5.3 kPa) or below.
Almost all oxygen in the blood is bound to hemoglobin, thus disrupting this carrier molecule limiting oxygen delivery to the periphery. Hemoglobin increases the oxygen carrying capacity of blood by about 40-fold, with the ability of hemoglobin to carry oxygen to be affected by the oxygen partial pressure in the environment, the relationship described in the oxygen-hemoglobin dissociation curve. When the ability of hemoglobin to carry oxygen is disrupted, the state of hypoxia can occur.
Ischemia
Ischemia, which means inadequate blood flow to the tissues, can also cause hypoxia. This is called 'ischemic hypoxia'. These may include embolic events, heart attacks that decrease overall blood flow, or trauma to the tissues that cause damage. Examples of insufficient blood flow cause local hypoxia is gangrene that occurs in diabetes.
Diseases such as peripheral vascular disease can also cause local hypoxia. For this reason, the symptoms get worse when the limb is used. Pain can also be felt as a result of increased hydrogen ions leading to a decrease in blood pH (acidity) created as a result of anaerobic metabolism.
Hypoxia hypoxemia
This refers specifically to the state of hypoxia in which the arterial oxygen content is insufficient. This may be due to changes in respiration, such as in respiratory alkalosis, physiological or pathological shifts of blood, diseases that interfere with lung function resulting in perfusion-ventilation mismatches, such as pulmonary embolus, or changes in partial pressure of oxygen. in the environment or the lungs of the alveoli, as can occur at altitudes or while diving.
Carbon monoxide poisoning
Carbon monoxide competes with oxygen to bind the site to the hemoglobin molecule. Because carbon monoxide is bound up with hemoglobin hundreds of times tighter than oxygen, it can prevent the transport of oxygen. Carbon monoxide poisoning can occur acutely, such as smoke poisoning, or over a period of time, such as smoking. Due to the physiological process, carbon monoxide is maintained at a 4-6 ppm break rate. This increases in urban areas (7-13 ppm) and in smokers (20-40 ppm). A carbon monoxide level of 40 ppm is equivalent to a 10 g/L hemoglobin decrease.
CO has a second toxic effect, which displaces the allosteric shift of the oxygen dissociation curve and shifts the left leg curve. Thus, hemoglobin tends to release oxygen in peripheral tissues. Some variants of abnormal hemoglobin also have a higher than normal oxygen affinity, and are also bad in sending oxygen to the periphery.
Altitude
Hypoxic breathing gas
Respiratory gas in scuba diving may contain insufficient oxygen partial pressures, particularly in the impaired function of rebreathers. Such situations can cause unconscious unconsciousness because of normal levels of carbon dioxide and the human body perceives pure hypoxia poorly.
A similar problem occurs when breathing in an odorless asphyxia gas. Asphyxiant gas reduces/replaces normal oxygen concentrations in air respiration, where prolonged exposure to respiratory hypoxic gas leads to unconsciousness, followed by death by inert asphyxiation gas. When the oxygen level falls below 19.5% v/v, air is considered oxygen deprived, where oxygen concentrations below 16% by volume are considered very harmful to humans. Since asphyxiant gases are relatively inert and odorless, their presence may be overlooked until the effects of increased carbon dioxide (hypercapnia) by the body. Inert asphyxia gas may be intentional by using a suicide bag. Unintentional deaths have occurred in cases where the concentration of controlled atmospheric nitrogen, or methane in the mine, has not been detected or appreciated.
More
The function of hemoglobin can also be lost by chemically oxidizing the iron atoms to the iron form. This inactive form of hemoglobin is called methemoglobin and can be made by swallowing sodium nitrite as well as certain drugs and other chemicals.
Anemia
Hemoglobin plays an important role in carrying oxygen throughout the body, and when it is deficient, anemia can occur, causing 'anemic hypoxia' if tissue perfusion decreases. Iron deficiency is the most common cause of anemia. Because iron is used in the synthesis of hemoglobin, less hemoglobin will be synthesized when there is less iron, due to inadequate intake, or poor absorption.
Anemia is usually a chronic process that is compensated over time by elevated levels of red blood cells via regulated erythropoietin. Chronic hypoxia may result from poor compensatory anemia.
Histotoxic hypoxia
Cyanide poisoning
Histotoxic hypoxia occurs when the amount of oxygen reaching a normal cell, but the cell can not use oxygen effectively, because the oxidative phosphorylation enzyme is disabled. This may be the case with Cyanide poisoning.
Physiological compensation
Acute
If the oxygen delivery to the cell is insufficient for demand (hypoxia), electrons will be diverted to pyruvic acid in the lactic acid fermentation process. This temporary measure (anaerobic metabolism) allows a small amount of energy to be released. The formation of lactic acid (in tissue and blood) is an inadequate mark of mitochondrial oxygenation, which may be caused by hypoxemia, poor blood flow (eg, shock) or a combination of both. If severe or prolonged it can cause cell death.
In humans, hypoxia is detected by peripheral chemoreceptors in the carotid and aortic bodies, with carotid body chemoreceptors being the main mediator of the reflex response to hypoxia. This response does not control the ventilation rate at p O
2 , but below normal the activity of neurons that conserve these receptors increases dramatically, so much so as to override signals from the chemoreceptor center in the hypothalamus, increasing p O
2 even though pCO falls 2
This is seen in some humans (encountered with hypoxia), there is a loss of words in their speech due to confusion and cell damage in the brain.
In most body tissues, the response to hypoxia is vasodilatation. By widening the blood vessels, the tissue allows greater perfusion.
In contrast, in the lungs, the response to hypoxia is vasoconstriction. This is known as lung vasoconstriction of hypoxia, or "HPV".
Chronic
When pulmonary capillary pressure remains chronically elevated (at least for 2 weeks), the lungs become more resistant to pulmonary edema because the lymph vessels dilate, increasing the ability to carry fluids away from interstitial space perhaps as much as 10-fold.. Therefore, in patients with chronic mitral stenosis, pulmonary capillary pressures from 40 to 45 mm Hg have been measured without the development of lethal pulmonary edema. [Guytun and Hall physiology]
Hypoxia exists when there is a decreased amount of oxygen in the tissues of the body. Hypoxemia refers to a decrease in PO2 below the normal range, regardless of whether gas exchange is impaired in the lungs, adequate CaO2, or tissue hypoxia exists. There are several potential physiological mechanisms for hypoxemia, but in patients with dominant COPD is unsuitable V/Q, with or without alveolar hypoventilation, as indicated by PaCO2. Hypoxemia caused by a V/Q discrepancy as seen in COPD is relatively easy to repair, so only a relatively small amount of additional oxygen (less than 3 L/min for most patients) is required for LTOT. Although hypoxemia usually stimulates ventilation and produces dyspnea, these symptoms and other hypoxic signs and symptoms are quite variable in patients with COPD, thus being of limited value in patient assessment. Chronic alveolar hypoxia is a major factor leading to pulmonary coronary development - right ventricular hypertrophy with or without apparent right ventricular failure - in patients with COPD. Pulmonary hypertension may affect survival in COPD, to levels parallel to the degree to which resting pulmonary artery pressure is increased. Although the level of airflow obstruction measured by FEV1 is the best correlation with overall prognosis in patients with COPD, chronic hypoxaemia increases mortality and morbidity for each disease severity. Large-scale studies of LTOT in patients with COPD have shown a dose-response relationship between the daily hours of oxygen use and survival. There is reason to believe that persistent 24-hour daily use of oxygen in properly selected patients will result in even greater survival benefits than the studies indicated in NOTT and MRC.
Treatment
To overcome the effects of high altitude sickness, the body should return p
2 to normal. Acclimatization, the means by which the body adapts to higher heights, only partially returns p O
2 to the standard level. Hyperventilation, the most common body response for high altitude conditions, increases p O
2 by increasing the depth and rate of breathing. However, while p O
2 improved with hyperventilation, did not return to normal. The study of miners and astronomers working at 3000 meters and above shows an increase in p
alveolar O
2 with full acclimation , but p O
2 remain the same or even below the threshold for continuous oxygen therapy for patients with chronic obstructive pulmonary disease (COPD). In addition, there are complications involved with acclimatization. Polycythemia, in which the body increases the number of red blood cells in circulation, thickens the blood, increasing the danger that the heart can not pump it.
In high altitude conditions, only oxygen enrichment can counteract the effects of hypoxia. By increasing the concentration of oxygen in the air, the effect of lower barometric pressure is offset and the level of
2 returned to normal capacity. A small amount of supplemental oxygen reduces equivalent altitudes in climate-controlled rooms. At 4000 m, raising the oxygen concentration level by 5 percent through the oxygen concentrator and the existing ventilation system gives a height of 3000 m equivalent, which is much more tolerable for the increasing number of low landers working at high altitudes. In a study of astronomers working in Chile in 5050 m, oxygen concentrators increased the oxygen concentration level by nearly 30 percent (ie, from 21 percent to 27 percent). This results in increased worker productivity, less fatigue, and better sleep.
Oxygen concentrators are uniquely suited for this purpose. They require little maintenance and electricity, provide a constant source of oxygen, and eliminate the costly and often dangerous task of transporting oxygen cylinders to remote areas. Offices and housing already have climate-controlled rooms, where temperature and humidity are kept at a constant level. Oxygen can be added to this system easily and relatively cheaply.
Renewal of prescriptions for home oxygen after hospitalization requires assessment of the patient for ongoing hypoxemia.
See also
- Asphyxia
- Autoerotic hypoxia or erotic asphyxia, deliberate oxygen restriction to the brain for sexual arousal
- Cerebral hypoxia or cerebral anoxia, decreased oxygen supply to the brain
- The fink effect, or the diffusion hypoxia, the factors affecting the partial pressure of oxygen in the pulmonary alveolus
- G-LOC brain hypoxia caused by excessive g-forces
- Histotoxic hypoxia, the inability of cells to take or exploit oxygen from the bloodstream
- Hyperoxia
- Hypoventilation training
- Hypoxic drive, breathing drive where the body uses oxygen chemoreceptor to regulate the respiratory cycle
- Hypoxemia or hypoxia hypoxemia, oxygen deficiency in arterial blood
- Hypoxic hypoxia, due to lack of oxygen available to the lungs
- Hypoxia in fish, fish response to hypoxia
- Hypoxic ventilation response
- Hypoxicator tool aimed at acclimatizing hypoxia in a controlled manner
- Intrauterine hypoxia, when the fetus lacks sufficient oxygen supply
- Intermittent hypoxia training
- Latent hypoxia or deep water blackouts, loss of consciousness while rising from deep freedives
- Pseudohypoxia, increasing the ratio of free NADH cytosol to NAD in cells
- Sleep apnea
- Useful awareness time
- Hypoxic tumor, a situation in which tumor cells have lost oxygen
- Rinomanometry
References
External links
Source of the article : Wikipedia
0 Comments