A pressure swing adsorption (PSA) system and methods for controlling each PSA cycle performed by the PSA system to produce oxygen enriched gas during productive portions of a user breathing cycle, and to cease production of oxygen enriched gas during non-productive portions of the user breathing cycle, is provided. The PSA system synchronizes PSA cycle phases including adsorption and desorption phases with a user's individual inhalation and exhalation phases, on a breath by breath basis, such that each PSA cycle can be dynamically varied from a succeeding PSA cycle, in real time in response to variations in the user's breathing cycle. An oxygen delivery device including a breathing cycle sensor provides breathing cycle inputs to a controller for use with at least one algorithm to detect breathing flow phases during each user breath, and to synchronize each PSA cycle to the user's breathing flow phases, on a breath-by-breath basis.