Method and apparatus for detecting change in intrathoracic electrical impedance

A method for detecting changes in impedance in a medical device, comprising:

• generating measured impedances;
• calculating period average impedances corresponding to a plurality of the measured impedances generated during a first time period;
• generating an adaptive baseline trend of the calculated period average impedances;
• generating a short term trend of the measured impedances corresponding to a second time period different from the first time period;
• determining changes in relative position of the short term trend and the baseline trend, the determined changes in relative position corresponding to determining intersecting of the baseline trend by the short term trend;
• determining differences between the baseline trend and calculated period average impedances;
• and
• accumulating, in response to the determined changes in relative position of the baseline trend and the short term trend, the determined differences between the baseline trend and the calculated period average impedances.

A a non-transitory computer readable medium having computer executable instructions for performing a method, the method comprising:

• generating measured impedances;
• calculating period average impedances corresponding to a plurality of the measured impedances generated during a first time period;
• generating an adaptive baseline trend of the calculated period average impedances;
• generating a short term trend of the measured impedances corresponding to a second time period different from the first time period;
• determining changes in relative position of the short term trend and the baseline trend, the determined changes in relative position corresponding to determining intersecting of the baseline trend by the short term trend;
• determining differences between the baseline trend and calculated period average impedances;
• and
• accumulating, in response to the determined changes in relative position of the baseline trend and the short term trend, the determined differences between the baseline trend and the calculated period average impedances.