Systems and methods involve use of a medical device comprising sensing circuitry. One or more respiratory parameters are detected using the device. Patient baseline weight is provided, and an output signal indicative of a patient's congestive heart failure status is generated based on a change in the one or more respiratory parameters and a change in the patient's measured weight or predicted weight relative to the patient baseline weight. The respiratory parameters may include one or more of respiration rate, relative tidal volume, an index indicative of rapid shallow breathing by the patient, an index derived by computing a respiration rate and a tidal volume for each patient breath, and an index indicative of dyspnea, for example.