Systems and methods for generating a signal that indicates a respiration rate of a patient are provided. Differential sinusoidal current signals having a modulation frequency are generated. The differential current signals are passed between electrodes in contact with a patients chest. A voltage signal is received based on the passing of the differential current signals between the electrodes. The voltage signal includes a sinusoidal voltage at the modulation frequency with an amplitude that varies based on the patients respiration. An output signal including a low-frequency component and a high-frequency component is generated by multiplying the voltage signal by a sinusoidal signal. The sinusoidal signal has the modulation frequency. The output signal is filtered to remove the high-frequency component, and the filtered output signal includes a waveform with characteristics indicative of a respiration rate of the patient. Related apparatus, systems, techniques and articles are also described.
