Oxygen concentrator
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 industrial processes.
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[edit] How oxygen concentrators work
An oxygen concentrator has two cylinders filled with zeolite materials that selectively adsorbs the nitrogen in the air. In each cycle, air flows through one cylinder at a pressure of around 20 pounds per square inch (absolute), where this is the gauge pressure of 1.36 atmospheres (138 kilopascal) at which the nitrogen molecules are captured by the zeolite, while the contents of the other cylinder are vented away at atmospheric pressure to dissipate the captured nitrogen.
The following applies to stationary oxygen concentrators and not to the newer portable devices. The older oxygen concentrators cycled with a period of about 20 seconds, and they provided a continuous supply of oxygen at a flow rate of about five liters or less per minute at oxygen concentrations selectable from about 25 percent to 95 percent. This process is called pressure swing adsorption (PSA). Since about 1999, oxygen concentrators providing up to 10 liters per minute have been available for patients requiring higher flows of oxygen. These devices come in sizes that are not much larger or heavier than the devices that yield five liters per minute.
[edit] Portable oxygen concentrators
Since the year 2000, a number of companies have produced portable oxygen concentrators. Typically, these devices produce less than one liter 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 three liters per minute of oxygen continuously. 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. [1]
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 Adminstration (FAA) of the United States has approved the use of portable oxygen concentrators on commercial airlines. However, users of these devices should check in advance as to whether a particular brand or model is permitted on a particular airline.
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.
[edit] Military uses
Military aircraft sometimes use molecular sieve oxygen concentrators (MSOC) to supply the aircrewmen with oxygen at high altitudes. Otherwise, supplies of liquid oxygen are used.
Oxygen concentrators have also been used by the Armed Forces of the United States in the conflicts in Iraq and Afghanistan as part of the equipment used by medical and surgical units in the field.
[edit] Safety
In both clinical and emergency-care situations, oxygen concentrators have the advantage of not being as dangerous as oxygen cylinders, which can, if ruptured or leaking, greatly increase the combustion rate of a fire. As such, oxygen concentrators are particularly advantageous in military or disaster situations, where oxygen tanks may be dangerous or infeasible.
Oxygen concentrators are considered sufficiently foolproof to be leased to individual patients as a prescription item for use in their homes. Typically they are used as an adjunct to CPAP treatment of severe sleep apnea. There also are other medical uses for oxygen concentrators, including emphysema and other respiratory diseases.
Used and refurbished units should be purchased through a reputable dealer. Temperamental units are worthless to the medical community since an individual's health frequently relies on the constant extended operation of the unit. However, such units are valuable to metal and glasswork hobbyists. Because oxygen is a "permanent gas" (cannot be liquefied at any pressure at room temperature), it is expensive to obtain in bottled form. Medical oxygen concentrators or specialized industrial oxygen concentrators can be made to operate small oxyacetylene cutting and welding torches.[2]
[edit] Industrial oxygen concentrators
Industrial processes may use much higher pressures and flows than medical units. To meet that need, another process, called vacuum swing adsorption (VSA), has been developed by the Air Products company. This process uses a single low pressure blower and a valve that reverses the flow through the blower so that the regeneration phase occurs under a vacuum. Generators using this process are being marketed to the aquaculture industry.[3] Industrial oxygen concentrators are often available in a much wider range of capacities than medical concentrators.
Industrial oxygen concentrators are sometimes referred to as oxygen generators within the oxygen and ozone industries to distinguish them from medical oxygen concentrators. The distinction is used in an attempt to clarify that industrial oxygen concentrators are not approved medical devices by the Food and Drug Administration (FDA) and they are not suitable for use as bedside medical concentrators. However, applying the oxygen generator nomenclature can lead to confusion. The term, oxygen generator, is a misnomer in that the oxygen is not generated as it is with a chemical oxygen generator, but rather it is concentrated from the air.
The use of the oxygen generator terminology can also be a problem in shipping in the wake of the crash of ValuJet Flight 592. Non-medical oxygen concentrators can be used as a feed gas to a medical oxygen system, such as a the oxygen system in a hospital, though governmental approval is required, such as by the FDA, and additional filtering is generally required.
[edit] See also
- Portable oxygen concentrator
- The section on Storage and Sources of Oxygen in the Oxygen therapy article.
- Nitrogen separation membrane
[edit] Notes
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