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For other uses of the term "hypoxia", see hypoxia.

Hypoxia is a pathological condition in which the body as a whole (generalized hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Hypoxia in which there is complete deprivation of oxygen supply is referred to as anoxia.

Hypoxia is distinguished from apoxemia, which is an abnormally low concentration of oxygen in arterial blood. [1] A frequent error is to use the term hypoxia to mean low oxygen content in arterial blood. The correct term for low oxygen content in arterial blood is hypoxemia. Hypoxaemia (or hypoxemia is a deficiency in the concentration of dissolved oxygen in Arterial blood It is possible to have a low oxygen content (e. g. , due to anemia) but a high PO2. Incorrect use of these terms can lead to confusion.

Generalized hypoxia occurs in healthy people when they ascend to high altitude, where it causes altitude sickness and its potentially fatal complications, high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). High altitude are regions on the Earth 's surface (or in its atmosphere) that are high above Mean sea level. Altitude sickness, also known as acute mountain sickness ( AMS) altitude illness, or soroche, is a pathological condition that is caused by acute High altitude pulmonary edema (HAPE is a life-threatening form of non-cardiogenic Pulmonary edema that occurs in otherwise healthy Mountaineers at altitudes above High altitude pulmonary edema (HAPE is a life-threatening form of non-cardiogenic Pulmonary edema that occurs in otherwise healthy Mountaineers at altitudes above High altitude cerebral edema (or HACE) is a severe (frequently fatal form of Altitude sickness. High altitude cerebral edema (or HACE) is a severe (frequently fatal form of Altitude sickness. Hypoxia also occurs in healthy individuals when breathing mixtures of gases with a low oxygen content, such as while diving underwater, especially when using closed-circuit rebreather systems that control the amount of oxygen in the supplied air. A rebreather is a type of Breathing set that provides a Breathing gas containing Oxygen and recycled exhaled gas Altitude training intentionally uses mild hypoxia to increase the concentration of red blood cells in the body for increased athletic performance. Altitude training traditionally referred to as altitude camp, is the practice by some Endurance athletes of training for several weeks at high Altitude

Contents

Symptoms

Symptoms of generalized hypoxia depend on its severity and acceleration of onset. In the case of altitude sickness, where hypoxia develops gradually, the symptoms include headaches, fatigue, shortness of breath, a feeling of euphoria and nausea. Altitude sickness, also known as acute mountain sickness ( AMS) altitude illness, or soroche, is a pathological condition that is caused by acute A headache ( cephalalgia in medical terminology is a condition of pain in the Head; sometimes Neck or upper back pain may also be interpreted Nausea ( Latin: Nausea, Greek:, " Sea-sickness " also called wamble) is the sensation of unease and discomfort In severe hypoxia, or hypoxia of very rapid onset, changes in levels of consciousness, seizures, coma and death occur. An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting In Medicine, a coma (from the Greek koma, meaning deep sleep is a profound state of Unconsciousness. Severe hypoxia induces a blue discolouration of the skin, called cyanosis. Cyanosis is a blue coloration of the Skin and mucous membranes due to the presence of deoxygenated Hemoglobin in Blood vessels near the skin surface Because haemoglobin is a darker red when it is not bound to oxygen (deoxyhemoglobin), as opposed to the rich red colour that it has when bound to oxygen (oxyhaemoglobin), when seen through the skin it has an increased tendency to reflect blue light back to the eye. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein In cases where the oxygen is displaced by another molecule, such as carbon monoxide, the skin may appear 'cherry red' instead of cyanotic.

Types of hypoxia

Pathophysiology

After mixing with water vapour and expired CO2 in the lungs, oxygen diffuses down a pressure gradient to enter arterial blood around where its partial pressure is 100mmHg (13. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Arteries are Blood vessels that carry blood away from the Heart. 3kPa). [2] Arterial blood flow delivers oxygen to the peripheral tissues, where it again diffuses down a pressure gradient into the cells and into their mitochondria. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. These bacteria-like cytoplasmic structures strip hydrogen from fuels (glucose, fats and some amino acids) to burn with oxygen to form water. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Water is a common Chemical substance that is essential for the survival of all known forms of Life. Released energy (originally from the sun and photosynthesis) is stored as ATP, to be later used for energy requiring metabolism. The Sun (Sol is the Star at the center of the Solar System. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy The fuel's carbon is oxidized to CO2, which diffuses down its partial pressure gradient out of the cells into venous blood to finally be exhaled by the lungs. Experimentally, oxygen diffusion becomes rate limiting (and lethal) when arterial oxygen partial pressure falls to 40mmHg or below.

If oxygen delivery to cells is insufficient for the demand (hypoxia), hydrogen will be shifted to pyruvic acid converting it to lactic acid. Pyruvic acid (CH3COCO2H is an alpha-keto acid. The Carboxylate Anion of pyruvic acid is known as pyruvate. Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role This temporary measure (anaerobic metabolism) allows small amounts of energy to be produced. Lactic acid build up in tissues and blood is a sign of inadequate mitochondrial oxygenation, which may be due to hypoxemia, poor blood flow (e. g. , shock) or a combination of both. [4] If severe or prolonged it could lead to cell death.

Vasoconstriction and vasodilation

In most tissues of the body, the response to hypoxia is vasodilation. By widening the blood vessels, the tissue allows greater perfusion.

By contrast, in the lungs, the response to hypoxia is vasoconstriction. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels particularly the large Arteries, Arterioles This is known as "Hypoxic pulmonary vasoconstriction", or "HPV".

Treatment

To counter the effects of high-altitude diseases, the body must return arterial PO2 toward normal. Acclimatization, the means by which the body adapts to higher altitudes, only partially restores PO2 to standard levels. Acclimatization is the process of an organism adjusting to chronic change in its environment, often involving temperature moisture food often relating to seasonal Climate Hyperventilation, the body’s most common response to high-altitude conditions, increases alveolar PO2 by raising the depth and rate of breathing. In Medicine, hyperventilation (or overbreathing) is the state of Breathing faster and/or deeper than necessary bringing about lightheadedness and other However, while PO2 does improve with hyperventilation, it does not return to normal. Studies of miners and astronomers working at 3000 meters and above show improved alveolar PO2 with full acclimatization, yet the PO2 level remains equal to or even below the threshold for continuous oxygen therapy for patients with chronic obstructive pulmonary disease (COPD). Chronic obstructive pulmonary disease ( COPD) is a Disease of the lungs in which the Airways become narrowed [5] 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, raising the danger that the heart can’t pump it. Polycythemia (or polycythaemia or erythrocytosis) is a condition in which there is a net increase in the total number of Blood cells, primarily Red

In high-altitude conditions, only oxygen enrichment can counteract the effects of hypoxia. By increasing the concentration of oxygen in the air, the effects of lower barometric pressure are countered and the level of arterial PO2 is restored toward normal capacity. A small amount of supplemental oxygen reduces the equivalent altitude in climate-controlled rooms. At 4000 m, raising the oxygen concentration level by 5 percent via an oxygen concentrator and an existing ventilation system provides an altitude equivalent of 3000 m, which is much more tolerable for the increasing number of low-landers who work in high altitude. [6] In a study of astronomers working in Chile at 5050 m, oxygen concentrators increased the level of oxygen concentration by 6 percent (that is, from 21 percent to 27 percent). This resulted in increased worker productivity, less fatigue, and improved sleep. [7]

Oxygen concentrators are uniquely suited for this purpose. An oxygen concentrator is a device used to provide Oxygen therapy to a Patient at substantially higher concentrations than those of ambient air used as They require little maintenance and electricity, provide a constant source of oxygen, and eliminate the expensive, and often dangerous, task of transporting oxygen cylinders to remote areas. Offices and housing already have climate-controlled rooms, in which temperature and humidity are kept at a constant level. Oxygen can be added to this system easily and relatively cheaply.

See also

For aircraft decompression incidents at altitude see:

Footnotes

  1. ^ West, John B. Altitude training traditionally referred to as altitude camp, is the practice by some Endurance athletes of training for several weeks at high Altitude For other uses of the term "hypoxia" see Hypoxia. Cerebral hypoxia refers to deprivation of Oxygen supply to brain tissue A deep water blackout is a loss of consciousness caused by Cerebral hypoxia on ascending from a deep Freedive or breath-hold dive typically of ten metres or more Drowning is Death as caused by suffocation when a liquid causes interruption of the body's absorption of oxygen from the air leading to Asphyxia. G-LOC, abbreviated from G-force induced Loss Of Consciousness, is a term generally used in Aerospace physiology to describe a loss of consciousness arising from Tumor hypoxia is the situation where Tumor cells have been deprived of Oxygen. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused A shallow water blackout is a loss of consciousness caused by Cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five Time of useful consciousness (TUC is defined as the amount of time an individual is able to perform flying duties efficiently in an environment of inadequate Oxygen The 1999 South Dakota Learjet crash involved a chartered Learjet 35 flying between Orlando, Florida, and Dallas, Texas. Helios Airways Flight 522 (HCY 522 or ZU522 was a Helios Airways Boeing 737-31S flight that crashed on 14 August 2005 at 1204 EEST into a mountain Soyuz 11 was the first successful visit to the world's first Space station, Salyut 1. (1977). Pulmonary Pathophysiology: The Essentials. Williams & Wilkins, 22.  
  2. ^ a b Kenneth Baillie and Alistair Simpson. Altitude oxygen calculator. Apex (Altitude Physiology Expeditions). Retrieved on 2006-08-10. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 612 BC - Killing of Sinsharishkun, King of Assyrian Empire - Online interactive oxygen delivery calculator
  3. ^ Kenneth Baillie and Alistair Simpson. Oxygen content calculator. Apex (Altitude Physiology Expeditions). Retrieved on 2006-08-10. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 612 BC - Killing of Sinsharishkun, King of Assyrian Empire - A demonstration of the effect of anaemia on oxygen content
  4. ^ Hobler, K. E. ; L. C. Carey (1973). "Effect of acute progressive hypoxemia on cardiac output and plasma excess lactate" (scanned copy). Ann Surg 177 (2): 199–202. doi:10.1097/00000658-197302000-00013. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 4572785.  
  5. ^ West, John B. (2004). "The Physiologic Basis of High-Altitude Diseases". Annals of Internal Medicine 141: 791.  
  6. ^ West, John B. (1995). "Oxygen Enrichment of Room Air to Relieve the Hypoxia of High Altitude". Respiration Physiology 99: 230. doi:10.1016/0034-5687(94)00094-G. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  7. ^ West, John B. (2004). "The Physiologic Basis of High-Altitude Diseases". Annals of Internal Medicine 141: 793.  

Bibliography

Airbus SAS (ˈɛərbʌs in English, Airbus2ogg|/ɛʁbys/]] in French, and /ˈɛːɐbʊs/ in German) is an aircraft manufacturing
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