Patent ID: 8483817

Claim:
A method for assessing a degree of pulmonary edema of a patient using an implantable medical device, comprising the steps of: detecting first, second and third different body positions of said patient, the first body position being an upright position and the second body position and the third body position being a respective one of lying on the back, on the stomach, or on a side, wherein the step of detecting first, second, and third different body positions comprises the steps of: sensing an activity level signal of said patient; using said sensed activity level signal to detect said body positions of said patient; determining whether said sensed activity level signal is below a predetermined activity level signal limit; and detecting that the patient is lying down when said sensed activity level signal has been below said signal limit during a predetermined period of time; sensing first trans-thoracic impedance signals when said patient is in the first position, sensing second thoracic impedance signals when said patient is in the second position, and sensing third trans-thoracic impedance signals when said patient is in the third position; obtaining first, second, and third impedance values respectively from said first, second, and third impedance signals; determining a relation among the respective first, second, and third impedance values; storing said relation; and using said relation as a metric of pulmonary edema to assess the degree of pulmonary edema; wherein the step of detecting that the patient is lying down when said sensed activity level signal has been below said signal limit during a predetermined period of time comprises the steps of: obtaining AC impedance values from said impedance signals; creating an AC impedance morphology using said AC impedance values; and detecting whether the patient is lying on the back, on the stomach, or on a side using an AC impedance morphology.