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Recreational scuba divers commonly breathe nitrox containing up to 40% oxygen, while technical divers use pure oxygen or nitrox containing up to 80% oxygen to accelerate decompression. Divers who breathe oxygen fractions greater than of air (21%) need to be educated on the dangers of oxygen toxicity and how to manage the risk. [76]
The formula simply divides the absolute partial pressure of oxygen which can be tolerated (expressed in atm or bar) by the fraction of oxygen in the breathing gas, to calculate the absolute pressure at which the mix can be breathed. (for example, 50% nitrox can be breathed at twice the pressure of 100% oxygen, so divide by 0.5, etc.).
To date, no comparable series of studies has been performed. In one seminal experiment, Donald exposed 36 healthy divers to 3.7 bars (370 kPa; 54 psi) of oxygen in a chamber, equivalent to breathing pure oxygen at a depth of 27 metres (90 ft), and recorded the time of onset of various signs and symptoms.
Although pure oxygen pre-breathing is an effective method to protect against altitude DCS, it is logistically complicated and expensive for the protection of civil aviation flyers, either commercial or private. Therefore, it is currently used only by military flight crews and astronauts for protection during high-altitude and space operations.
If the casualty can breathe pure oxygen further improvements will occur because the increase in the proportion of oxygen in the blood may keep previously oxygen-starved tissues alive and the oxygen window will accelerate the removal of inert gases from the bubbles making the bubbles smaller. The unacceptable risks of oxygen toxicity convulsions ...
The subject in the centre is breathing 100% oxygen from a mask. The result of breathing increased partial pressures of oxygen is hyperoxia, an excess of oxygen in body tissues. The body is affected in different ways depending on the type of exposure.
Static apnea is defined by the International Association for Development of Apnea (AIDA International) and is distinguished from the Guinness World Record for breath holding underwater, which allows the use of oxygen in preparation. It requires that the respiratory tract be immersed, with the body either in the water or at the surface, and may ...
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. 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 ...