Patent ID: 8055335

Claim:
A method of monitoring fluid levels by an implantable device, comprising: the device taking a series of intra-thoracic impedance measurements from a patient; the device modifying a short-term impedance value based on the series of intra-thoracic impedance measurements; the device modifying a baseline impedance value based on the series of intra-thoracic impedance; the device adding a difference of the baseline impedance value minus the short-term impedance value to a cumulative index in response to the short-term impedance value being less than the baseline impedance value minus a predetermined positive hysteresis value; the device resetting the cumulative index in response to the short-term impedance value being greater than the baseline impedance value minus the hysteresis value; and the device notifying the patient of possible fluid accumulation in response to the cumulative index exceeding a predetermined threshold value.