An apparatus is described that includes a medical device including an output device, a memory, and a processor, electrodes configured to provide an electrical impedance signal to the processor, wherein the impedance signal corresponds to an impedance measured at a patient's chest, and sensors configured to provide a motion signal to the processor, wherein the motion signal is indicative of chest compressions performed during a cardiopulmonary resuscitation (CPR) treatment of the patient, wherein the processor is configured to receive the impedance signal and the motion signal and to execute instructions to determine threshold values of a signal processing algorithm for the impedance signal, adaptively modify the threshold values in response to motion signal changes, apply the modified threshold values to the impedance signal to identify airflow activities represented in the signal, calculate characteristics of the airflow activities, and provide an output indicative of the characteristics of the airflow activities.
