Fraction of inspired oxygen (FIO2), corrected denoted with a capital "I",[1] is the molar or volumetric fraction of oxygen in the inhaled gas. Medical patients experiencing difficulty breathing are provided with oxygen-enriched air, which means a higher-than-atmospheric FIO2. Natural air includes 21% oxygen, which is equivalent to FIO2 of 0.21. Oxygen-enriched air has a higher FIO2than 0.21; up to 1.00 which means 100% oxygen. FIO2 is typically maintained below 0.5 even with mechanical ventilation, to avoid oxygen toxicity,[2] but there are applications when up to 100% is routinely used.
Often used in medicine, the FIO2 is used to represent the percentage of oxygen participating in gas-exchange. If the barometric pressure changes, the FIO2 may remain constant while the partial pressure of oxygen changes with the change in barometric pressure.
https://en.wikipedia.org/wiki/Fraction_of_inspired_oxygen
Cold shock response is a series of cardio-respiratory responses caused by sudden immersion in cold water.
In cold water immersions, cold shock response is perhaps the most common cause of death,[1] such as by falling through thin ice. The immediate shock of the cold causes involuntary inhalation, which, if underwater, can result in drowning. The cold water can also cause heart attack due to vasoconstriction;[2] the heart has to work harder to pump the same volume of blood throughout the body. For people with existing cardiovascular disease, the additional workload can result in cardiac arrest. Inhalation of water (and thus drowning) may result from hyperventilation. Some people are much better able to survive swimming in very cold water due to body or mental conditioning.[1]
https://en.wikipedia.org/wiki/Cold_shock_response
The science of underwater diving includes those concepts which are useful for understanding the underwater environment in which diving takes place, and its influence on the diver. It includes aspects of physics, physiology and oceanography. The practice of scientific work while diving is known as Scientific diving. These topics are covered to a greater or lesser extent in diver trainingprograms, on the principle that understanding the concepts may allow the diver to avoid problems and deal with them more effectively when they cannot be avoided.
A basic understanding of the physics of the underwater environment is foundational to the understanding of the short and long term physiological effects on the diver, and the associated hazards of the diving environment and their consequences which are inherent to diving.
https://en.wikipedia.org/wiki/Science_of_underwater_diving
In physiology, isobaric counterdiffusion (ICD) is the diffusion of different gases into and out of tissues while under a constant ambient pressure, after a change of gas composition, and the physiological effects of this phenomenon. The term inert gas counterdiffusion is sometimes used as a synonym, but can also be applied to situations where the ambient pressure changes.[1][2] It has relevance in mixed gas diving and anesthesiology.
https://en.wikipedia.org/wiki/Isobaric_counterdiffusion
Diving medicine
Diving
disorders
List of signs and symptoms of diving disorders Cramp Motion sickness Surfer's ear
Pressure
related
Alternobaric vertigo Barostriction Barotrauma Air embolism Aerosinusitis Barodontalgia Dental barotrauma Pulmonary barotrauma Compression arthralgia Decompression illness Dysbarism
Oxygen
Freediving blackout Hyperoxia Hypoxia Oxygen toxicity
Inert gases
Avascular necrosis Decompression sickness Isobaric counterdiffusion Taravana Dysbaric osteonecrosis High-pressure nervous syndrome Hydrogen narcosis Nitrogen narcosis
Carbon dioxide
Hypercapnia Hypocapnia
Breathing gas
contaminants
Carbon monoxide poisoning
Immersion
related
Asphyxia Drowning Hypothermia Immersion diuresis Instinctive drowning response Laryngospasm Salt water aspiration syndrome Swimming-induced pulmonary edema
Treatment
Demand valve oxygen therapy First aid Hyperbaric medicine Hyperbaric treatment schedules In-water recompression Oxygen therapy Therapeutic recompression
Personnel
Diving Medical Examiner Diving Medical Practitioner Diving Medical Technician Hyperbaric nursing
Screening
Atrial septal defect Effects of drugs on fitness to dive Fitness to dive Psychological fitness to dive
Research
Researchers in
diving physiology
and medicine
Arthur J. Bachrach Albert R. Behnke Paul Bert George F. Bond Robert Boyle Albert A. Bühlmann John R. Clarke Guybon Chesney Castell Damant Kenneth William Donald William Paul Fife John Scott Haldane Robert William Hamilton Jr. Leonard Erskine Hill Brian Andrew Hills Felix Hoppe-Seyler Christian J. Lambertsen Simon Mitchell Charles Momsen John Rawlins R.N. Charles Wesley Shilling Edward D. Thalmann Jacques Triger
Diving medical
research
organisations
Aerospace Medical Association Divers Alert Network (DAN) Diving Diseases Research Centre (DDRC) Diving Medical Advisory Council (DMAC) European Diving Technology Committee (EDTC) European Underwater and Baromedical Society (EUBS) National Board of Diving and Hyperbaric Medical Technology Naval Submarine Medical Research Laboratory Royal Australian Navy School of Underwater Medicine Rubicon Foundation South Pacific Underwater Medicine Society (SPUMS) Southern African Underwater and Hyperbaric Medical Association (SAUHMA) Undersea and Hyperbaric Medical Society (UHMS) United States Navy Experimental Diving Unit (NEDU)
https://en.wikipedia.org/wiki/Fraction_of_inspired_oxygen
Salt water aspiration syndrome is a rare diving disorder suffered by scuba divers who inhale a mist of seawater from a faulty demand valve causing irritation of the lungs. It is not the same thing as aspiration of salt water as a bulk liquid, i.e. drowning.[1][2] It can be treated by rest for several hours. If severe, medical assessment is required.
https://en.wikipedia.org/wiki/Salt_water_aspiration_syndrome
High-pressure nervous syndrome (HPNS – also known as high-pressure neurological syndrome) is a neurological and physiological diving disorder which can result when a diver descends below about 500 feet (150 m) using a breathing gas containing helium. The effects experienced, and the severity of those effects, depend on the rate of descent, the depth and the percentage of helium.[1]
"Helium tremors" were first widely described in 1965 by Royal Navy physiologist Peter B. Bennett, who also founded the Divers Alert Network.[1][2] Russian scientist G. L. Zal'tsman also reported on helium tremors in his experiments from 1961. However, these reports were not available in the West until 1967.[3]
The term high-pressure nervous syndrome was first used by Brauer in 1968 to describe the combined symptoms of tremor, electroencephalography (EEG) changes, and somnolence that appeared during a 1,189-foot (362 m) chamber dive in Marseille.[4]
HPNS has two components, one resulting from the speed of compression and the other from the absolute pressure.
Those suggest that helium might cause substantial lipid membrane distortion. The high hydrostatic pressure itself has a less damaging influence on the membrane, reducing molecular volumes, but leaving the molecular boundary intact.[6]
https://en.wikipedia.org/wiki/High-pressure_nervous_syndrome
Hydrogen narcosis (also known as the hydrogen effect) is the psychotropic state induced by breathing hydrogen at high pressures. Hydrogen narcosis produces symptoms such as hallucinations, disorientation, and confusion, which are similar to hallucinogenic drugs. It can be experienced by deep-sea divers who dive to 300 m (1,000 ft) below sea level breathing hydrogen mixtures.[1] However, hydrogen has far less narcotic effect than nitrogen (which causes the better known nitrogen narcosis) and is very rarely used in diving. In tests of the effect of hydrogen narcosis, where divers dived to 500 m (1,600 ft) with a hydrogen–helium–oxygen (Hydreliox) mixture containing 49% hydrogen, it was found that while the narcotic effect of hydrogen was detectable, the neurological symptoms of high-pressure nervous syndrome were only moderate.[2][3]
https://en.wikipedia.org/wiki/Hydrogen_narcosis
Narcosis while diving (also known as nitrogen narcosis, inert gas narcosis, raptures of the deep, Martini effect) is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high pressure. The Greek word νάρκωσις (narkōsis), "the act of making numb", is derived from νάρκη (narkē), "numbness, torpor", a term used by Homer and Hippocrates.[1] Narcosis produces a state similar to drunkenness (alcohol intoxication), or nitrous oxide inhalation. It can occur during shallow dives, but does not usually become noticeable at depths less than 30 meters (100 ft).
Except for helium and probably neon, all gases that can be breathed have a narcotic effect, although widely varying in degree.[2][3] The effect is consistently greater for gases with a higher lipid solubility, and although the mechanism of this phenomenon is still not fully clear, there is good evidence that the two properties are mechanistically related.[2] As depth increases, the mental impairment may become hazardous. Divers can learn to cope with some of the effects of narcosis, but it is impossible to develop a tolerance. Narcosis affects all divers, although susceptibility varies widely among individuals and from dive to dive.
Narcosis may be completely reversed in a few minutes by ascending to a shallower depth, with no long-term effects. Thus narcosis while diving in open water rarely develops into a serious problem as long as the divers are aware of its symptoms, and are able to ascend to manage it. Diving much beyond 40 m (130 ft) is generally considered outside the scope of recreational diving. In order to dive at greater depths, as narcosis and oxygen toxicity become critical risk factors, specialist training is required in the use of various helium-containing gas mixtures such as trimix or heliox. These mixtures prevent narcosis by replacing some or all of the inert fraction of the breathing gas with non-narcotic helium.
Narcosis results from breathing gases under elevated pressure, and may be classified by the principal gas involved. The noble gases, except helium and probably neon,[2] as well as nitrogen, oxygen and hydrogen cause a decrement in mental function, but their effect on psychomotor function (processes affecting the coordination of sensory or cognitive processes and motor activity) varies widely. The effect of carbon dioxide is a consistent diminution of mental and psychomotor function.[4] The noble gases argon, krypton, and xenon are more narcotic than nitrogen at a given pressure, and xenon has so much anesthetic activity that it is a usable anesthetic at 80% concentration and normal atmospheric pressure. Xenon has historically been too expensive to be used very much in practice, but it has been successfully used for surgical operations, and xenon anesthesia systems are still being proposed and designed.[5]
Some components of breathing gases and their relative narcotic potencies:[2][FN 1][3]
Gas Relative narcotic potency
He 0.045
Ne 0.3
H2 0.6
N2 1.0
O2 1.7
Ar 2.3
Kr 7.1
CO2 20.0
Xe 25.6
Modern theories have suggested that inert gases dissolving in the lipid bilayer of cell membranes cause narcosis.[16]
Rapid compression potentiates narcosis owing to carbon dioxide retention.[19][20]
An early theory, the Meyer-Overton hypothesis, suggested that narcosis happens when the gas penetrates the lipids of the brain's nerve cells, causing direct mechanical interference with the transmission of signals from one nerve cell to another.[15][16][20]
The symptoms of narcosis may be caused by other factors during a dive: ear problems causing disorientation or nausea;[36] early signs of oxygen toxicity causing visual disturbances;[37] or hypothermia causing rapid breathing and shivering.[38]
For example, hydrogen at a given pressure has a narcotic effect equivalent to nitrogen at 0.55 times that pressure, so in principle it should be usable at more than twice the depth. Argon, however, has 2.33 times the narcotic effect of nitrogen, and is a poor choice as a breathing gas for diving (it is used as a drysuit inflation gas, owing to its low thermal conductivity).
https://en.wikipedia.org/wiki/Nitrogen_narcosis
Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply.[1] Early on, there may be no symptoms.[1] Gradually joint pain may develop which may limit the ability to move.[1] Complications may include collapse of the bone or nearby joint surface.[1]
Risk factors include bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids.[1] The condition may also occur without any clear reason.[1] The most commonly affected bone is the femur.[1] Other relatively common sites include the upper arm bone, knee, shoulder, and ankle.[1]Diagnosis is typically by medical imaging such as X-ray, CT scan, or MRI.[1]Rarely biopsy may be used.[1]
Treatments may include medication, not walking on the affected leg, stretching, and surgery.[1] Most of the time surgery is eventually required and may include core decompression, osteotomy, bone grafts, or joint replacement.[1] About 15,000 cases occur per year in the United States.[4]People 30 to 50 years old are most commonly affected.[3] Males are more commonly affected than females.[4]
https://en.wikipedia.org/wiki/Avascular_necrosis
Decompression sickness (abbreviated DCS; also called divers' disease, the bends, aerobullosis, and caisson disease) is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a caisson, decompression from saturation, flying in an unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and arterial gas embolism are collectively referred to as decompression illness.
Since bubbles can form in or migrate to any part of the body, DCS can produce many symptoms, and its effects may vary from joint pain and rashes to paralysis and death. Individual susceptibility can vary from day to day, and different individuals under the same conditions may be affected differently or not at all. The classification of types of DCS by its symptoms has evolved since its original description over a hundred years ago. The severity of symptoms varies from barely noticeable to rapidly fatal.
Risk of DCS caused by diving can be managed through proper decompression procedures and contracting it is now uncommon. Its potential severity has driven much research to prevent it and divers almost universally use dive tables or dive computers to limit their exposure and to monitor their ascent speed. If DCS is suspected, it is treated by hyperbaric oxygen therapy in a recompression chamber. Diagnosis is confirmed by a positive response to the treatment. If treated early, there is a significantly higher chance of successful recovery.
In 1960, Golding et al. introduced a simpler classification using the term "Type I ('simple')" for symptoms involving only the skin, musculoskeletal system, or lymphatic system, and "Type II ('serious')" for symptoms where other organs (such as the central nervous system) are involved.[1]
The term dysbarism encompasses decompression sickness, arterial gas embolism, and barotrauma, whereas decompression sickness and arterial gas embolism are commonly classified together as decompression illness when a precise diagnosis cannot be made.[6] DCS and arterial gas embolism are treated very similarly because they are both the result of gas bubbles in the body.[5]The U.S. Navy prescribes identical treatment for Type II DCS and arterial gas embolism.[7] Their spectra of symptoms also overlap, although the symptoms from arterial gas embolism are generally more severe because they often arise from an infarction(blockage of blood supply and tissue death).
While bubbles can form anywhere in the body, DCS is most frequently observed in the shoulders, elbows, knees, and ankles.
https://en.wikipedia.org/wiki/Decompression_sickness
Dysbaric osteonecrosis or DON is a form of avascular necrosis where there is death of a portion of the bone that is thought to be caused by nitrogen embolism(blockage of the blood vessels by a bubble of nitrogen coming out of solution) in divers.[1] Although the definitive pathologic process is poorly understood, there are several hypotheses:
Intra- or extravascular nitrogen in bones, "nitrogen embolism".[citation needed]
Osmotic gas effects due to intramedullary pressure effects.[citation needed]
fat embolism[citation needed]
hemoconcentration and increased coagulability.[citation needed]
https://en.wikipedia.org/wiki/Dysbaric_osteonecrosis
Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the release of a gas that was dissolved, trapped, frozen, or absorbed in some material.[1] Outgassing can include sublimation and evaporation (which are phase transitions of a substance into a gas), as well as desorption, seepage from cracks or internal volumes, and gaseous products of slow chemical reactions. Boiling is generally thought of as a separate phenomenon from outgassing because it consists of a phase transition of a liquid into a vapor of the same substance.
https://en.wikipedia.org/wiki/Outgassing
Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion.
Ventilation is the process by which air moves in and out of the lungs.
Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the alveoli and the capillaries in the lungs.
Perfusion is the process by which the cardiovascular system pumps blood throughout the lungs.
https://www.merckmanuals.com/home/lung-and-airway-disorders/biology-of-the-lungs-and-airways/exchanging-oxygen-and-carbon-dioxide
https://wiki.oroboros.at/index.php/Oxygen_flux
DIW, Distance Inc W, Oxygen Triangles, Cascades, etc..
Arterial hypoxaemia in fibrotic lung disease is related more to ventilation-perfusion mismatching than to thickening of the alveolar wall.
Diffusion
Pulmonary oedema
Acute respiratory distress syndrome (particularly with fibrosis in later stages)
Ventilation-perfusion mismatch
Alveolar collapse
Acute respiratory distress syndrome
Pneumothorax
Obstructive airways disease
Drugs—pulmonary vasodilators
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114207/
https://link.springer.com/chapter/10.1007/978-3-642-40717-8_2
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