Patent ID: 7596411
Filing Date: 2009-09-29
Classification: A61B,A61N

Abstract:
1. An implantable cardiac stimulation and rhythm management device for measuring intra-thoracic fluid impedance comprising: at least one impedance measuring electrode; an impedance measuring circuit coupled to, and in communication with, the at least one impedance measuring electrode, wherein the at least one measuring electrode is operative to measure resistive (R) and reactive (Z) components of impedance; a microcontroller connected to the impedance measuring circuit and configured to calculate ratios (Z/R) that equal the reactive components divided by the resistive components Z/R values has; and a memory connected to the microcontroller and the impedance measuring circuit and operative to store the measured reactive (Z) and resistive (R) components and the ratios; wherein the microcontroller is further configured to directly monitor the calculated ratios over a period of time to establish a baseline intra-thoracic fluid level for the patient and an upper bound relative to the baseline and a lower bound relative to the baseline, wherein the upper bound and the lower bound account for normal variations in intra-thoracic fluid levels over time for the patient, and to continue to directly monitor the calculated ratios relative to the baseline, upper bound and lower bound.