Patent ID: 8070686

Claim:
A system comprising: an implantable medical device including an electrical impedance measurement circuit configured for injecting electrical energy between two or more electrodes and for concurrently measuring a potential difference created thereby in a thoracic region of a subject between the same or different two or more electrodes; and an implantable or external processor circuit including an input to receive the information about the injected electrical energy and the measured potential difference, the processor circuit configured to compute an impedance-indicating signal using the information about the electrical energy and the potential difference, the processor circuit further configured to extract an alternating current (AC) cardiac impedance-indicating component of the impedance-indicating signal including attenuating a respiration-indicating component of the impedance-indicating signal, then to extract AC amplitude information from the extracted AC cardiac impedance-indicating component, and to determine, using the extracted AC amplitude information, an AC amplitude change over time of the extracted AC cardiac impedance-indicating component of the impedance-indicating signal to provide a lung fluid status indication.