Oxygen Concentrators

An oxygen concentrator is a device used to provide oxygen therapy to people at substantially higher concentrations than available in regular air. They are used as a safer, less expensive, and more convenient alternative to oxygen tanks, which have compressed oxygen. Common concentrator models retail starting at around US$700. Oxygen concentrators provide a continuous supply of oxygen. They have two cylinders, each filled with a zeolite material which selectively adsorbs the nitrogen in the air. In each cycle, air flows through one cylinder at a pressure of around 20 psig, where psig indicates the gauge pressure (138 kPa, or 1.36 atmospheres) where the nitrogen molecules are captured by the zeolite, while the other cylinder is vented off to ambient atmospheric pressure allowing the captured nitrogen to dissipate.

Typical units have cycles of around 20 seconds, and allow for a continuous supply of oxygen at a flow rate of up to approximately five liters per minute (LPM) at concentrations anywhere from 50 to 95 %. This process is called pressure swing adsorption (PSA). Since 1999, concentrators providing up to 10 LPM have been available for high flow patients, in sizes not much larger or heavier than 5 LPM concentrators.

Since 2000, a number of manufacturers have introduced portable oxygen concentrators. Typically, these produce less than one liter per minute (LPM) of oxygen and use some version of pulse flow or demand flow to deliver oxygen only when the user is inhaling. However, there are few portable oxygen concentrators that produce 3 LPM of continuous-flow oxygen. Also providing pulse flow available to either provide higher flows or reduce power consumption. These portable concentrators typically plug into a wall outlet like the larger, heavier stationary concentrators.

Portable oxygen concentrators usually can also be plugged into a vehicle DC adapter, and most have the ability to run from battery power as well, either for ambulatory use or for use away from power or for airplane travel. The FAA has approved portable oxygen concentrators for use on commercial airlines, although it is necessary to check in advance whether a particular brand or model is permitted on a particular airline.

Historically, demand or pulse flow concentrators have not been used for nocturnal use—sleeping. If the nasal cannula moves such that the concentrator is not able to detect when the patient is inhaling, it is unable to deliver the pulse while the patient is inhaling.