A cardiorespiratory monitor (100) that generates bioimpedance sensing signals that produce substantially no interference with bioimpedance signals generated by implanted devices. The monitor detects the bioimpedance signal generated by the implanted device, using a voltage detector (128) or a telemetry circuit (104), for example. The monitor has an impedance sensor control circuit (118) to generate a bioimpedance sensing signal that will not interfere with the sensed signal. For instance, if the monitor produces a pulsed sensing signal, the pulses are delivered in an interval of the detected signal where no pulses are present. Similarly, if the monitor produces a high frequency AC sensing signal, the zero crossings of the AC sensing signal are positioned during the delivery of a pulse by the implanted device.