A portable oxygen concentration system, the system comprising: a pair of sieve beds (12, 14); a pressure generator configured to generate pressurized gas that is directed through the sieve beds, wherein the sieve beds output enriched gas for delivery to a subject in a pressure swing adsorption process, the PSA process comprising alternating enriched gas production and purge cycles for each of the sieve beds such that when one of the sieve beds is alternating through an enriched gas production cycle, the other sieve bed is alternating through a purge cycle; one or more sensors configured to generate output signals conveying information related to respiration of the subject; valves configured to control gas flow into and out of the pair of sieve beds during the enriched gas production and purge cycles of the PSA process; and one or more processors configured by machine readable instructions to: cause the valves to control the gas flow into and out of the pair of sieve beds during the enriched gas production and purge cycles of the PSA process based on the output signals; determine whether causing the valves to control the gas flow into and out of the pair of sieve beds based on the output signals caused a volume of enriched gas produced by one sieve bed in the pair of sieve beds to be different than a volume of enriched gas produced by the other sieve bed in the pair of sieve beds; and responsive to determining that the volume of enriched gas produced by one sieve bed in the pair of sieve beds is different than the volume of enriched gas produced by the other sieve bed in the pair of sieve beds: determine different purge volumes of gas for the sieve beds based on the different volumes of enriched gas produced by the sieve beds; and cause the valves to control the purge cycles of the PSA process based on the different purge volumes of gas determined for the sieve beds. a pair of sieve beds (12, 14); a pressure generator configured to generate pressurized gas that is directed through the sieve beds, wherein the sieve beds output enriched gas for delivery to a subject in a pressure swing adsorption process, the PSA process comprising alternating enriched gas production and purge cycles for each of the sieve beds such that when one of the sieve beds is alternating through an enriched gas production cycle, the other sieve bed is alternating through a purge cycle; one or more sensors configured to generate output signals conveying information related to respiration of the subject; valves configured to control gas flow into and out of the pair of sieve beds during the enriched gas production and purge cycles of the PSA process; and one or more processors configured by machine readable instructions to: cause the valves to control the gas flow into and out of the pair of sieve beds during the enriched gas production and purge cycles of the PSA process based on the output signals; determine whether causing the valves to control the gas flow into and out of the pair of sieve beds based on the output signals caused a volume of enriched gas produced by one sieve bed in the pair of sieve beds to be different than a volume of enriched gas produced by the other sieve bed in the pair of sieve beds; and responsive to determining that the volume of enriched gas produced by one sieve bed in the pair of sieve beds is different than the volume of enriched gas produced by the other sieve bed in the pair of sieve beds: determine different purge volumes of gas for the sieve beds based on the different volumes of enriched gas produced by the sieve beds; and cause the valves to control the purge cycles of the PSA process based on the different purge volumes of gas determined for the sieve beds. cause the valves to control the gas flow into and out of the pair of sieve beds during the enriched gas production and purge cycles of the PSA process based on the output signals; determine whether causing the valves to control the gas flow into and out of the pair of sieve beds based on the output signals caused a volume of enriched gas produced by one sieve bed in the pair of sieve beds to be different than a volume of enriched gas produced by the other sieve bed in the pair of sieve beds; and responsive to determining that the volume of enriched gas produced by one sieve bed in the pair of sieve beds is different than the volume of enriched gas produced by the other sieve bed in the pair of sieve beds: determine different purge volumes of gas for the sieve beds based on the different volumes of enriched gas produced by the sieve beds; and cause the valves to control the purge cycles of the PSA process based on the different purge volumes of gas determined for the sieve beds. determine different purge volumes of gas for the sieve beds based on the different volumes of enriched gas produced by the sieve beds; and cause the valves to control the purge cycles of the PSA process based on the different purge volumes of gas determined for the sieve beds.