Long-term oxygen therapy (LTOT) revisited: in defense of non-delivery LTOT technology.

The term ‘‘non-delivery LTOT’’ is used to describe installations of newer home oxygen therapy systems where oxygen concentrator technology is used to provide both stationary and ambulatory oxygen.1 The use of non-delivery LTOT equipment obviates the need for oxygen supply companies to make repeat (and costly) home deliveries to replenish depleted gaseous or liquid oxygen contents, the majority of which is most often used during ambulation away from the stationary system. The evidence base for LTOT supports the use of both stationary and ambulatory oxygen systems to maintain adequate oxygenation at all times and under all conditions of use.1,2 Non-delivery LTOT systems therefore offer hypoxemic COPD patients requiring continuous, uninterrupted supplemental oxygenation, and meaningful, real-time options. With a properly functioning non-delivery system, LTOT users now have the option of spontaneously going where they want to go, when they want to go, and how they want to go, as opposed to constantly waiting (and hoping) that a much needed re-supply delivery will take place as scheduled. There are three options presently available to provide non-delivery LTOT.1 One method is to use a standard stationary oxygen concentrator, in tandem with a pressure booster, to re-fill small portable cylinders. A second option is the use of a portable oxygen concentrator (POC). The third option, still under development, is a standard oxygen concentrator, used in tandem with a cryogenic liquefier, to re-fill a small canister with liquid oxygen. All three options employ the use of concentrated oxygen (≈93%) as opposed to medical grade oxygen (99.9%). All of the aforementioned non-delivery systems incorporate the pulse dose delivery of oxygen. With pulse dose delivery, a preset volume (or bolus) of oxygen is administered at some point during the inspiratory phase of a