Monitoring lung fluid status using the cardiac component of a thoracic impedance-indicating signal

摘要

This patent document describes, among other things, systems and methods for monitoring lung fluid status, such as monitoring the presence or absence of pulmonary edema, in a subject using information about the cardiac impedance-indicating component of a measured impedance-indicating signal. In various examples, an amplitude or contribution change over multiple cardiac cycles of the cardiac impedance-indicating component is used to compute and provide a lung status indication. In various examples, a decreasing amplitude or contribution trend of the cardiac impedance-indicating component signifies an increasing amount of fluid in the subject's lungs, as a greater portion of an injected thoracic impedance measurement current formerly traversing the heart is rerouted through the lung due to the less resistance path created by the fluid accumulation therein. In another example, measurements of the impedance-indicating signal, and thus the cardiac impedance-indicating component, are taken at one or a combination of end-inspiration or end-expiration.