Abstract: Systems and methods are provided that employ both a liquid oxygen source and a gaseous oxygen source. In this way, a seamless switch between these sources is possible and oxygen can be continuously provided during replacement of a depleted oxygen source. To this end, an oxygen delivery system includes a connection box and dispenser along with the liquid oxygen source and the gaseous oxygen source. The connection box has a common conduit and first, second, and third ports fluidly coupled to the common conduit. The liquid oxygen source is fluidly coupled to the common conduit through the first port and the gaseous oxygen source is fluidly coupled to the common conduit through the second port. The dispenser is fluidly coupled to the common conduit through the third port. Such systems and methods provide uninterrupted oxygen to injured persons and can improve the time and/or effectiveness of recovery.