Oxygen concentrator
The supply of therapeutic oxygen to patients in homes and other residential settings is an important and growing market in the health care industry. Supplemental oxygen is necessary for patients suffering from lung disorders; for example, pulmonary fibrosis, sarcoidosis, or occupational lung disease. For such patients, oxygen therapy is an increasingly beneficial, life-giving development. While not a cure for lung disease, supplemental oxygen increases blood oxygenation, which reverses hypoxemia. This therapy prevents long-term effects of oxygen deficiency on organ systems such as the heart, brain and kidneys. Oxygen treatment is also prescribed for chronic obstructive pulmonary disease (COPD), and for other ailments that weaken the respiratory system, such as heart disease and AIDS. Supplemental oxygen therapy is also prescribed for asthma and emphysema. There are currently three modalities for supplemental medical oxygen: high pressure gas cylinders, cryogenic liquid in vacuum insulated containers or thermos bottles commonly called "dewars," and oxygen concentrators. Oxygen concentrators have been available for many years as a source of oxygen enriched air for patients requiring supplemental oxygen. Oxygen concentrators are used in medical applications for increasing the oxygen concentration of air, typically atmospheric air, and processing it into a relatively pure source of oxygen. Atmospheric air typically contains about 21% oxygen and 78% nitrogen, with remaining trace gases including carbon dioxide, hydrocarbons and helium. Oxygen concentrators are devices that generate relatively pure oxygen by utilizing an air compressor, typically operating at between 40 and 60 psig, with filters such as a molecular sieve bed, which purify the atmospheric air into concentrated oxygen. The oxygen content can be typically increased to the range of about 90-95% after concentration. Typically, an oxygen concentrator includes an air compressor which delivers a flow of pressurized, filtered air to a molecular sieve bed which passes oxygen while blocking the flow of nitrogen. The oxygen enriched air at an output from the molecular sieve bed is typically about 90% to 95% pure oxygen, with the remainder being primarily argon. In operation, a compressor applies filtered pressurized air through a flow control valve to an inlet port on one of the molecular sieve beds and about 95% pure oxygen flows under pressure from an outlet port on such bed. The oxygen may flow to an accumulator and then pass through a pressure regulator, an optional flow meter and a final filter to a patient. As oxygen flows through the sieve bed, the separated nitrogen is retained in the sieve bed. After a short time, one or more valves are changed to apply the pressurized air to the inlet port of a second sieve bed and to vent the inlet port of the first sieve bed. A small portion of the pressurized oxygen output from the second sieve bed is delivered to the outlet port of the first sieve bed to purge nitrogen and any other trapped gases from the first sieve bed. The valves are periodically reversed to alternate the sieve beds between the gas separating cycle and the trapped gas purging cycle. The optional accumulator holds a volume of concentrated oxygen under pressure to provide a continuous oxygen flow when the valves are cycled. Most oxygen concentrators operate on the principle of pressure swing adsorption, which uses cycled pressure shifts across adsorbent beds to increase or decrease the content of a particular constituent gas in a gas mixture. The cycling of the pressure in the beds allows for more efficient concentrator operation, and multiplebed systems are in use which further increase concentrator efficiencies while increasing the available desired gas follow-through.
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