17-09-2012, 03:15 PM
Oxygen concentrator
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An oxygen concentrator is a device providing oxygen therapy to a patient at minimally to substantially higher concentrations than available in ambient air. They are used as a safer, less expensive, and more convenient alternative to tanks of compressed oxygen. Common models retail at around $800. Leasing arrangements may be available through various medical-supply companies and/or insurance agencies.
Oxygen concentrators are also used to provide an economical source of oxygen in How oxygen concentrators work
Oxygen concentrators operate on the principle of pressure swing adsorption of atmospheric nitrogen onto zeolite materials. At high pressure, nitrogen sticks to the surface of the zeolite. Because the zeolite is extremely porous, it has a very large surface area and can adsorb large volumes of gas. At low pressure the nitrogen is released.
An oxygen concentrator has two cylinders filled with zeolite pellets. Air is compressed to a few times normal atmospheric pressure (typically 20 psi/138 kPa gauge, or 2.36 atmospheres absolute) and passed through the zeolite bed. The bed adsorbs the nitrogen, leaving nearly-pure oxygen (plus small amounts of argon, CO₂, water vapor and other minor atmospheric components) in the output.
The zeolite becomes saturated within a few seconds, at which point the compressed air is fed to the second cylinder while the first is vented to ambient pressure, and the nitrogen escapes. When the second cylinder is saturated, the compressor switches back to the now-available first, and the cycle repeats.
Older units cycled with a period of about 20 seconds, and supplied up to 5 liters per minute of 90+% oxygen. Since about 1999, units capable of supplying up to 10 lpm have been available.
Portable oxygen concentrators
Since the year 2000, a number of companies have produced portable oxygen concentrators. Typically, these devices produce one to five liters per minute of oxygen, and they use some version of pulse flow or "demand flow" to deliver oxygen only when the patient is inhaling. However, there are a few portable oxygen concentrators that produce up to three liters per minute of oxygen continuously such as the Invacare Solo2[1] or SeQual Eclipse. Also, they can provide pulses of oxygen either to provide higher intermittant flows or to reduce the power consumption.
These portable concentrators typically plug into an electrical outlet like the larger, heavier stationary oxygen concentrators. [2]
Portable oxygen concentrators usually can also be plugged into the DC outlet of a vehicle, and most of these devices have the ability to run from electric batteries, also, for ambulatory use. Concerning for airline travel, The Federal Aviation Administration (FAA) of the United States has approved the use of portable oxygen concentrators on commercial airlines.[3] However, users of these devices should check in advance as to whether a particular brand or model is permitted on a particular airline. Unlike in commercial airlines, users of aircrafts without cabin pressurization need oxygen concentrators wich are able to deliver enough flowrate even at high altitudes, such as OXYFLY[4].
Usually, "demand" or pulse-flow oxygen concentrators are not used by patients while they sleep. There have been problems with the oxygen concentrators not being able to detect when the sleeping patient is inhaling. Some larger portable oxygen concentrators are designed to operate in continuous-flow mode in addition to pulse-flow mode. Continuous-flow mode is considered safe for night use when coupled with a CPAP