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Isobaric Counterdiffusion
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. It has relevance in mixed gas diving and anesthesiology. Background Isobaric counterdiffusion was first described by Graves, Idicula, Lambertsen, and Quinn in 1973 in subjects who breathed one gas mixture (in which the inert component was nitrogen or neon) while being surrounded by another (helium based). Clinical relevance In medicine, ICD is the diffusion of gases in different directions that can increase the pressure inside open air spaces of the body and surrounding equipment. An example of this would be a patient breathing nitrous oxide in an operating room (surrounded by air). Cuffs on the endotrache ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physiology
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical and physical functions in a living system. According to the classes of organisms, the field can be divided into medical physiology, animal physiology, plant physiology, cell physiology, and comparative physiology. Central to physiological functioning are biophysical and biochemical processes, homeostatic control mechanisms, and communication between cells. ''Physiological state'' is the condition of normal function. In contrast, ''pathological state'' refers to abnormal conditions, including human diseases. The Nobel Prize in Physiology or Medicine is awarded by the Royal Swedish Academy of Sciences for exceptional scientific achievements in physiology related to the field of medicine. Foundations Cells Although there are di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underwater Diving
Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well-adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done. In ambient pressure diving, the diver is directly exposed to the pressure of the surrounding water. The ambient pressure diver may dive on breath-hold (freediving) or use breathing apparatus for scuba diving or surface-supplied diving, and the saturation diving technique reduces the risk of decompression sickness (DCS) after long-duration deep di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperbaric Medicine
Hyperbaric medicine is medical treatment in which an ambient pressure greater than sea level atmospheric pressure is a necessary component. The treatment comprises hyperbaric oxygen therapy (HBOT), the medical use of oxygen at an ambient pressure higher than atmospheric pressure, and therapeutic recompression for decompression illness, intended to reduce the injurious effects of systemic gas bubbles by physically reducing their size and providing improved conditions for elimination of bubbles and excess dissolved gas. The equipment required for hyperbaric oxygen treatment consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen. Operation is performed to a predetermined schedule by trained personnel who monitor the patient and may adjust the schedule as required. HBOT found early use in the treatment of decompression sickness, and has also shown great effectiveness in treating conditions such as gas gangrene and carbon mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bühlmann Decompression Algorithm
The Bühlmann decompression algorithm is a mathematical model (algorithm) of the way in which inert gases enter and leave the human body as the ambient pressure changes. Versions are used to create Bühlmann decompression tables and in personal dive computers to compute no-decompression limits and decompression schedules for dives in real-time. These decompression tables allow divers to plan the depth and duration for dives and the required decompression stops. The algorithm was developed by Swiss physician Dr. Albert A. Bühlmann, who did research into decompression theory at the Laboratory of Hyperbaric Physiology at the University Hospital in Zürich, Switzerland. The results of Bühlmann's research that began in 1959 were published in a 1983 German book whose English translation was entitled ''Decompression-Decompression Sickness''. The book was regarded as the most complete public reference on decompression calculations and was used soon after in dive computer algorithms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inner Ear Decompression Sickness
Inner ear decompression sickness, (IEDCS) or audiovestibular decompression sickness is a medical condition of the inner ear caused by the formation of gas bubbles in the tissues or blood vessels of the inner ear. Generally referred to as a form of decompression sickness, it can also occur at constant pressure due to inert gas counterdiffusion effects. Usually only one side is affected, and the most common symptoms are vertigo with nystagmus, loss of balance, and nausea. The symptoms are similar to those caused by some other diving injuries and differential diagnosis can be complicated and uncertain if several possible causes for the symptoms coexist. First aid is breathing the highest practicable concentration of normobaric oxygen. Definitive treatment is recompression with hyperbaric oxygen therapy. Anti-vertigo and anti-nausea drugs are usually effective at suppressing symptoms, but do not reduce the tissue damage. Hyperbaric oxygen may be effective for reducing oedema a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simon Mitchell
Simon Mitchell (born 1958) is a New Zealand physician specialising in occupational medicine, hyperbaric medicine and anesthesiology. Trained in medicine, Mitchell was awarded a PhD for his work on neuroprotection from embolic brain injury. Mitchell has also published more than 45 research and review papers in the medical literature. Mitchell is an author and avid technical diver. He also wrote two chapters of the latest edition of ''Bennett and Elliott's Physiology and Medicine of Diving,'' is the co-author of the diving textbook ''Deeper Into Diving'' with John Lippmann and co-authored the chapter on Diving and Hyperbaric Medicine in Harrison's ''Principles of Internal Medicine'' with Michael Bennett. Background Mitchell received a Bachelor of Human Biology (BHB) in 1988 and later a Bachelor of Medicine and Bachelor of Surgery (MB ChB) in 1990 from the University of Auckland. In 2001, he received a Diploma in Occupational Medicine (DipOccMed) from the South Pacific Und ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decompression Sickness
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. DCS often causes air bubbles to settle in major joints like knees or elbows, causing individuals to bend over in excruciating pain, hence its common name, the bends. Indi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydreliox
Hydreliox is an exotic breathing gas mixture of helium, oxygen and hydrogen. For the Hydra VIII (Hydra 8) mission at 50 atmospheres of ambient pressure, the mixture used was 49% hydrogen, 50.2% helium, and 0.8% oxygen. It is used primarily for research and scientific deep diving, usually below . Below this depth, extended breathing of heliox gas mixtures may cause high pressure nervous syndrome (HPNS). Two gas mixtures exist that attempt to combat this problem: trimix and hydreliox. Like trimix, hydreliox contains helium and oxygen and a third gas to counteract HPNS. The third gas in trimix is nitrogen and the third gas in hydreliox is hydrogen. Because hydrogen is the lightest gas, it is easier to breathe than nitrogen under high pressure. To avoid the risk of explosion, as a rule of thumb hydrogen is only considered for use in breathing mixtures if the proportion of oxygen in the mixture is less than 5%. However, the pressure during the dive must be such that the partial pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saturation Diving
Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used. It is a diving mode that reduces the number of decompressions divers working at great depths must undergo by only decompressing divers once at the end of the diving operation, which may last days to weeks, having them remain under pressure for the whole period. A diver breathing pressurized gas accumulates dissolved inert gas used in the breathing mixture to dilute the oxygen to a non-toxic level in his or her tissues, which can cause decompression sickness ("the bends") if permitted to come out of solution within the body tissues; hence, returning to the surface safely requires lengthy decompression so that the inert gases can be eliminated via the lungs. Once the dissolved gases in a diver's tissues reach the saturation point, however, decompression time does not increase with further exposure, as no more inert g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breathing Gas
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraft, submarines, space suits, spacecraft, medical life support and first aid equipment, and anaesthetic machines. Oxygen is the essential component for any breathing gas, at a partial pressure of between roughly 0.16 and 1.60 bar at the ambient pressure. The oxygen is usually the only metabolically active component unless the gas is an anaesthetic mixture. Some of the oxygen in the breathing gas is consumed by the metabolic processes, and the inert components are unchanged, and serve mainly to dilute the oxygen to an appropriate concentration, and are therefore also known as diluent gases. Most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heliox
Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a patient to breathe in and out of the lungs. It is also used as a breathing gas diluent for deep ambient pressure diving as it is not narcotic at high pressure, and for its low work of breathing. Heliox has been used medically since the 1930s, and although the medical community adopted it initially to alleviate symptoms of upper airway obstruction, its range of medical uses has since expanded greatly, mostly because of the low density of the gas. Heliox is also used in saturation diving and sometimes during the deep phase of technical dives. Medical uses In medicine heliox may refer to a mixture of 21% O2 (the same as air) and 79% He, although other combinations are available (70/30 and 60/40). He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decompression (diving)
The decompression of a diver is the reduction in ambient pressure experienced during ascent from depth. It is also the process of elimination of dissolved inert gases from the diver's body, which occurs during the ascent, largely during pauses in the ascent known as decompression stops, and after surfacing, until the gas concentrations reach equilibrium. Divers breathing gas at ambient pressure need to ascend at a rate determined by their exposure to pressure and the breathing gas in use. A diver who only breathes gas at atmospheric pressure when free-diving or snorkelling will not usually need to decompress, Divers using an atmospheric diving suit do not need to decompress as they are never exposed to high ambient pressure. When a diver descends in the water, the hydrostatic pressure, and therefore the ambient pressure, rises. Because breathing gas is supplied at ambient pressure, some of this gas dissolves into the diver's blood and is transferred by the blood to oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
