• bubbles
  • Rebreathers extend the time spent underwater compared to open circuit for the same gas consumption, they produce fewer bubbles and less noise than scuba which makes them attractive to covert military divers to avoid detection, scientific divers to avoid disturbing marine animals, and media divers to avoid bubble interference. (wikipedia.org)
  • arterial bubble model Decompression model in which the filtering capacity of the lung is assumed to have a threshold radius of the size of a red blood cell and sufficiently small decompression bubbles can pass to the arterial side, especially during the initial phase of ascent. (wikipedia.org)
  • diver
  • Open circuit scuba systems discharge the breathing gas into the environment as it is exhaled, and consist of one or more diving cylinders containing breathing gas at high pressure which is supplied to the diver through a regulator. (wikipedia.org)
  • An important step for the development of open circuit scuba technology was the invention of the demand regulator, a mechanism that conserves air supply by providing air flow only when the outlet pressure is reduced when the diver inhales. (wikipedia.org)
  • This would be the first diving suit that could supply air to the diver on demand by adjusting the flow of air from the tank to meet the diver's breathing and pressure requirements. (wikipedia.org)
  • Under stress it is likely that a diver will increase breathing rate and decrease swimming speed. (wikipedia.org)
  • In an effort to reduce the decompression problems resulting from the high partial pressures of nitrogen the diver is exposed to when breathing air at depth, oxygen may be added as a substitute for some of the nitrogen. (wikipedia.org)
  • Reducing decompression time can be important to reduce time spent at shallow depths in open water (avoiding dangers such as water currents and boat traffic), and to reduce the physical stress imposed on the diver. (wikipedia.org)
  • In other words, the larger oxygen window due to a higher oxygen partial pressure can allow the diver to decompress faster at a shallower stop at the same risk, or at the same rate at the same depth at a lower risk, or at an intermediate rate at an intermediate depth at an intermediate risk. (wikipedia.org)
  • The top plate of the bellows is ballasted, so that the lifting force of the air inside is balanced by the weights: when the diver is trimmed horizontally, face down, the weights create a slight positive pressure relative to ambient. (wikipedia.org)
  • When the diver is upright the effect of the weights is cancelled as the weight is carried by the hinge, and when the diver is horizontal, face up, the weight causes a slight negative pressure in the bellows, which compensates for the increased hydrostatic pressure on the counterlung compared with the lungs. (wikipedia.org)
  • This approach is based on the assumption that the volumetric breathing rate of a diver is directly proportional to metabolic oxygen consumption, which experimental evidence indicates is close enough to work. (wikipedia.org)
  • In the context of surface supplied diving, the place of safety for a diver with a decompression obligation is often the diving bell. (wikipedia.org)
  • alternative air source A secondary supply of air or other breathing gas used by the diver in an emergency alternobaric vertigo Dizziness caused by a difference of pressure between the middle ears. (wikipedia.org)
  • An ascent may be interrupted by stops (q.v.), when the diver maintains a functionally constant depth for the purpose of decompression, and pulls (q.v.), during which periods there is consistently upwards movement (minor variations in the scale of a few seconds are generally ignored). (wikipedia.org)
  • underwater
  • In 1864, the French engineers Auguste Denayrouze and BenoĆ®t Rouquayrol designed and patented their "Rouquayrol-Denayrouze diving suit" after adapting a pressure regulator and developing it for underwater use. (wikipedia.org)
  • It optimizes respiration by preferentially distributing oxygen stores to the heart and brain which allows staying underwater for extended periods of time. (wikipedia.org)
  • DCS most commonly refers to problems arising from underwater diving decompression (i.e., during ascent), but may be experienced in other depressurisation events such as emerging from a caisson, flying in an unpressurised aircraft at altitude, and extravehicular activity from spacecraft. (wikipedia.org)
  • apparatus
  • open-circuit surface supplied equipment where the diver's exhaled gas is vented directly into the water, and closed-circuit breathing apparatus where the diver's carbon dioxide is filtered from unused oxygen, which is then recirculated. (wikipedia.org)
  • cylinders
  • They may include additional cylinders for decompression gas or emergency breathing gas. (wikipedia.org)
  • By the mid twentieth century, high pressure cylinders were available and two systems for scuba had emerged: open-circuit scuba where the diver's exhaled breath is vented directly into the water, and closed-circuit scuba where the carbon dioxide is removed from the diver's exhaled breath which has oxygen added and is recirculated. (wikipedia.org)
  • Cylinders used for scuba typically have an internal volume (known as water capacity) of between 3 and 18 litres (0.11 and 0.64 cu ft) and a maximum working pressure rating from 184 to 300 bars (2,670 to 4,350 psi). (wikipedia.org)
  • however, this is a misnomer since these cylinders typically contain (compressed atmospheric) breathing air, or an oxygen-enriched air mix. (wikipedia.org)
  • cylinder
  • The system still had to use surface supply, as the pressure cylinder provided was only a low capacity accumulator. (wikipedia.org)
  • Each cylinder volume and working pressure must be sufficient to contain the required quantity of gas. (wikipedia.org)
  • When pressurised, a cylinder carries an equivalent volume of free gas greater than its water capacity, because the gas is compressed up to several hundred times atmospheric pressure. (wikipedia.org)
  • The pressure vessel is a seamless cylinder normally made of cold-extruded aluminium or forged steel. (wikipedia.org)
  • An especially common cylinder provided at tropical dive resorts is the "aluminium-S80" which is an aluminium cylinder design with an internal volume of 0.39 cubic feet (11.0 l) rated to hold a nominal volume of 80 cubic feet (2,300 l) of atmospheric pressure gas at its rated working pressure of 3,000 pounds per square inch (207 bar). (wikipedia.org)
  • scuba
  • Closed circuit equipment was more easily adapted to scuba in the absence of reliable, portable, and economical high pressure gas storage vessels. (wikipedia.org)
  • valve
  • Exhalation will increase of bellows angle and will increase loading on the control spring, pushing the dosage inlet valve open and allowing gas to flow into the dosage chamber until the increased pressure lifts the diaphragm and closes the valve again. (wikipedia.org)
  • blood
  • There appears to be a connection between pulmonary edema and increased pulmonary blood flow and pressure which results in capillary engorgement. (wikipedia.org)
  • profile
  • However mathematical models have been proposed which approximate the real situation to a greater or lesser extent, and these models are used to predict whether symptomatic bubble formation is likely to occur for a given pressure exposure profile. (wikipedia.org)
  • less
  • Pulmonary DCS ("the chokes") is very rare in divers and has been observed much less frequently in aviators since the introduction of oxygen pre-breathing protocols. (wikipedia.org)
  • supply
  • The volume of the dosage chamber is matched to a specific supply gas mixture, and is changed when the gas is changed. (wikipedia.org)
  • level
  • citation needed] Nevertheless, much is still unknown about how long this extension should be and the level of decompression efficiency gained. (wikipedia.org)