A gas valve is arranged for controlling the flow of medical gas for oxygen therapy in case of spontaneous breathing. An embodiment of the gas valve contains a connection component to connect the gas valve to an external supply such as for example an external supply network for medical gases at a pressure lower than 50 bars. The gas valve may contain a regulating system configured to select and supply a pulsating or continuous flow of medical gas in which the regulating system contains a flow rate regulator to controllable set the flow rate of the continuous flow.