A therapeutic gas delivery system, comprising: at least one gas supply subsystem ((112(a); 112(b)) comprising, a gas source coupling (115(a); 115(b)) configured to receive a therapeutic gas source (116(a); 116(b)) and form a fluid flow connection with the therapeutic gas source (116(a); 116(b)); a gas source valve (117(a); 117(b)) adjacent to and in fluid communication with the gas source coupling (115(a); 115(b)), wherein the gas source valve (117(a); 117(b)) is configured to have at least an open state and a closed state; a gas pressure sensor (120(a); 120(b)) adjacent to and in fluid communication with the gas source valve (117(a); 117(b)), wherein the gas source valve (117(a); 117(b)) provides a gas flow path from the gas source coupling (115(a); 115(b)) to the gas pressure sensor (120(a); 120(b)), and the gas pressure sensor (120(a); 120(b)) is configured to measure a gas pressure at the gas source coupling (115(a); 115(b)) at least when the gas source valve (117(a); 117(b)) is in an open state, to be in communication over a communication path with a therapeutic gas delivery system controller comprising a CPU, and to communicate a pressure value over the communication path to the therapeutic gas delivery system controller (144; 164); and a therapeutic gas pressure regulator (122(a); 122(b)) down stream from the gas pressure sensor (120(a); 120(b)), gas source valve (117(a); 117(b)), and gas source coupling (115(a); 115(b)), and in fluid communication with the gas source coupling (115(a); 115(b)), gas source valve (117(a); 117(b)), and gas pressure sensor (120(a); 120(b)); one or more display(s) (102; 112(a); 112(b)) configured to be in communication over a communication path with the therapeutic gas delivery system controller (144; 164), wherein the CPU of the therapeutic gas delivery system controller (144; 164) is configured to calculate a value for a run-time-to-empty from a gas volume value, a pressure value communicated from the gas pressure sensor (120(a); 120(b)), and an average therapeutic gas consumption rate calculated by the CPU from the gas flow rate value communicated from a therapeutic gas flow controller, and wherein the system display (102; 112(a); 112(b)) is configured to display the calculated run-time-to-empty value. at least one gas supply subsystem ((112(a); 112(b)) comprising, a gas source coupling (115(a); 115(b)) configured to receive a therapeutic gas source (116(a); 116(b)) and form a fluid flow connection with the therapeutic gas source (116(a); 116(b)); a gas source valve (117(a); 117(b)) adjacent to and in fluid communication with the gas source coupling (115(a); 115(b)), wherein the gas source valve (117(a); 117(b)) is configured to have at least an open state and a closed state; a gas pressure sensor (120(a); 120(b)) adjacent to and in fluid communication with the gas source valve (117(a); 117(b)), wherein the gas source valve (117(a); 117(b)) provides a gas flow path from the gas source coupling (115(a); 115(b)) to the gas pressure sensor (120(a); 120(b)), and the gas pressure sensor (120(a); 120(b)) is configured to measure a gas pressure at the gas source coupling (115(a); 115(b)) at least when the gas source valve (117(a); 117(b)) is in an open state, to be in communication over a communication path with a therapeutic gas delivery system controller comprising a CPU, and to communicate a pressure value over the communication path to the therapeutic gas delivery system controller (144; 164); and a therapeutic gas pressure regulator (122(a); 122(b)) down stream from the gas pressure sensor (120(a); 120(b)), gas source valve (117(a); 117(b)), and gas source coupling (115(a); 115(b)), and in fluid communication with the gas source coupling (115(a); 115(b)), gas source valve (117(a); 117(b)), and gas pressure sensor (120(a); 120(b)); one or more display(s) (102; 112(a); 112(b)) configured to be in communication over a communication path with the therapeutic gas delivery system controller (144; 164), wherein the CPU of the therapeutic gas delivery system controller (144; 164) is configured to calculate a value for a run-time-to-empty from a gas volume value, a pressure value communicated from the gas pressure sensor (120(a); 120(b)), and an average therapeutic gas consumption rate calculated by the CPU from the gas flow rate value communicated from a therapeutic gas flow controller, and wherein the system display (102; 112(a); 112(b)) is configured to display the calculated run-time-to-empty value.