A system and method of controlling the application of energy to tissue using measurementsof impedance are described. The impedance, correlated to the temperature, maybe set at a desired level, such as a percentage of initial impedance. The set impedancemay be a function of the initial impedance, the size and spacing of the electrodes,the size of a targeted passageway, and so on. The set impedance may then be enteredinto a PID algorithm or other control loop algorithm in order to extract a powerto be applied to a treatment device.
