Enhancements to the detection of pulmonary edema when using transthoracic impedance

Abstract

This patent document discusses, among other things, systems, devices, and methods for enhancing detection of pulmonary edema using, in addition to thoracic impedance, one or a combination of: physiologic information about a subject, at least one statistical parameter, a user-programmable detection level, at least one parameter associated with a previous pulmonary edema event, and patient symptom information about the subject. In one example, a (base) thoracic impedance threshold is modified to an adjusted thoracic impedance threshold. The adjusted thoracic impedance threshold provides an increased sensitivity of pulmonary edema detection as compared to the base thoracic impedance threshold. In another example, an alert is provided to a subject, a caregiver, or other user based on a pulmonary edema indication determined by the present systems, devices, and methods. In a further example, a therapy (provided to the subject) is adjusted or initiated in response to the pulmonary edema indication.

What is claimed is: 
     
         1 . A system comprising:
 an implantable thoracic impedance measurement circuit, adapted to sense a thoracic impedance signal from a subject;   a parameter collection device, adapted to sense or receive physiologic information about the subject, the physiologic information selected from a physiologic information group consisting essentially of: at least one heart sound, at least one lung sound, a respiratory pattern, a weight, a neurohormone level, a creatinine level, and a heart wall motion; and   a processor, coupled with the thoracic impedance measurement circuit to accept the thoracic impedance signal, and coupled with the parameter collection device to accept the physiologic information,   wherein the processor is adapted to determine a pulmonary edema indication using the thoracic impedance signal and the physiologic information.