Patent ID: 8515535

Claim:
An implantable cardiac device, comprising: a housing configured for implantation in a patient; an implantable sensor configured to sense transthoracic impedance; an implantable activity sensor configured to make an activity measurement indicative of patient activity; a memory provided in the housing and configured to store at least a pulmonary function index versus activity level profile comprising a plurality of index values associated with different ranges of patient activity levels; a controller provided in the housing and coupled to the respective sensors and the memory, the controller configured to: compute an index indicative of patient pulmonary function using the sensed transthoracic impedance by computing a ratio of multiple respiration parameters; and detect an episode of dyspnea based on a parameter of the computed patient pulmonary function index exceeding an index value of the profile stored in the memory, the index value associated with an activity range of the profile which the patient activity level is calculated to be within; and communication circuitry provided in the housing and configured to facilitate communication of information between the implantable cardiac device and a device external of the housing.