A gas analyzer for analyzing and delivering a therapeutic blend of nitric oxide gas to a patient is disclosed. The analyzer includes a nitric oxide metering circuit to meter a flow of nitric oxide into a blended gas mix, a gas sampling circuit to sample the blended gas mix, a user interface to allow a user to input a lower threshold concentration and an upper threshold concentration of nitric oxide in the blended gas mix, and a controller. In some cases, the controller is configured to operate the nitric oxide metering circuit to meter a flow of the nitric oxide into the blended gas mix to maintain the concentration of nitric oxide in the blended gas mix between the lower threshold concentration and the upper threshold concentration. Other implementations are described.
