The least expensive and least portable device for oxygen therapy is an oxygen concentrator, which concentrates atmospheric oxygen and provides this as supplemental oxygen to the patient. This design makes the concentrator suitable only for patients who are confined to home. In addition to their low cost, concentrators have the advantage of requiring the lowest number of maintenance visits. A monthly visit to check the operation of the concentrator is typical. Portable systems, which dispense oxygen from cylinders, are of two basic types based on whether the oxygen is stored as a liquid or gas.
Gas cylinders are readily available and of moderate cost.
Although more portable than a concentrator, the patient's mobility is still somewhat restricted by the bulkiness of these cylinders. These systems are feasible for patients who require a low oxygen flow. Because they rely on smaller cylinders that are readily refilled at home from a reservoir, liquid oxygen systems provide the greatest degree of portability and versatility. Liquid oxygen systems are the most costly option, and are not available to all patients, particularly those who live in rural areas. Liquid oxygen is usually available in most large towns, and within a 50-60 mile radius of most cities.