Oxygen/helium breathing mixture

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

A scuba tank is filled with Trimix, a breathing gas mixture for deep scuba diving. The tank contains oxygen with a partial pressure of 20. atm, nitrogen with a partial pressure of 40. atm, and helium with a partial pressure of 140. atm. What is the total pressure of the breathing mixture, in atmospheres ... 

A Hehox breathing mixture of oxygen and hehum is prepared for a scuba diver who is going to descend 200 ft below the ocean surface. At that depth, the diver breathes a gas mixture that has a total pressure of 7.00 atm. If the partial pressure of the oxygen in the tank at that depth is 1140 mmHg, what is the partial pressure, in atmospheres, of the helium in the breathing mixture ... 

A breathing mixture used for dives over 400 ft is trimix, which contains oxygen, helium, and some nitrogen. The addition of some... 

The low breathing resistance of helium—oxygen mixtures is of therapeutic advantage for patients suffering from asthma and other obstmctive respitatory difficulties. The mixtures have also been used for hyperbaric therapy. 

Which difference could account for the fact that a diver is much less likely to suffer from the bends if he breathes a mixture of 80% helium and 20% oxygen than if he breathes air (The bends is a painful, sometimes fatal, disease caused by the formation of gas bubbles in the veins and consequent interruption of blood flow. The bubbles form from gas dissolved in the blood at high pressure.)... 

It is the oxidizer for liquid rocket fuels, and as a gas, oxygen is used in a mixture with helium to support the breathing of astronauts and divers and to aid patients who have dif-flculty breathing. It is use to treat (oxidize) sewage and industrial organic wastes. 

Divers now breathe a mixture of oxygen and helium instead of the oxygen-nitrogen mixture of ordinary air. Nitrogen dissolves in a diver s blood and causes the "bends helium will not dissolve to such an extent. 

Helium (He) is an inert gas whose low density, low solubility, and high thermal conductivity provide the basis for its medical and diagnostic uses the gas is supplied in brown cyhnders. Helium can be mixed with oxygen and administered by mask or tracheal tube. Under hyperbaric conditions, it can be substituted for the bulk of other gases, resulting in a mixture of much lower density that is easier to breathe. 

Divers use a mixture of oxygen and helium in their breathing tanks when diving to depths greater than 150 feet. 

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