M.K. Delano and Tom 0’Dwyer A PORTABLE BIOIMPEDANCE SPECTROSCOPY MEASUREMENT SYSTEM FOR CONGESTIVE HEART FAILURE (CHF) MANAGEMENT An estimated five million people are currently diagnosed with congestive heart failure (CHF) in the United States, with over 400,000 new diagnoses annually. Almost one in two patients will be readmitted to the hospital within four to six months of discharge. Up to 50% of these early readmissions may be prevented if symptoms are recognized early enough. Bioimpedance measurements have been shown to be predictive of heart failure decompensation up to 14 days before an event occurs. We have developed a portable bioimpedance system that can measure body impedance from 1 kHz to 1 MHz. The system uses the magnitude ratio and phase difference detection method to calculate the magnitude and phase of the measured impedance (see Figure 1). The system is enclosed in an aluminum box (see Figure 2) and can be used with four coaxial cables to reduce the impact of stray capacitances. The device has been characterized with RC networks and is being tested with healthy volunteers. ISine ZBody IA1 VBody VBody Gain Phase Detector R1 IA2 VRef VRef Figure 1: A schematic overview of the magnitude ratio and phase difference detection method. A fixed sinusoidal current is driven through the body and a sense resistance. The voltage is amplified and measured by a gain phase detector chip (AD8302). Visit analog.com Figure 2: The portable bioimpedance spectroscopy measurement system inside the enclosure. Analog Devices, Inc. Worldwide Headquarters Analog Devices, Inc. Europe Headquarters Analog Devices, Inc. Japan Headquarters Analog Devices, Inc. Asia Pacific Headquarters Analog Devices, Inc. One Technology Way P.O. Box 9106 Norwood, MA 02062-9106 U.S.A. Tel: 781.329.4700 (800.262.5643, U.S.A. only) Fax: 781.461.3113 Analog Devices, Inc. Wilhelm-Wagenfeld-Str. 6 80807 Munich Germany Tel: 49.89.76903.0 Fax: 49.89.76903.157 Analog Devices, KK New Pier Takeshiba South Tower Building 1-16-1 Kaigan, Minato-ku, Tokyo, 105-6891 Japan Tel: 813.5402.8200 Fax: 813.5402.1064 Analog Devices 5F, Sandhill Plaza 2290 Zuchongzhi Road Zhangjiang Hi-Tech Park Pudong New District Shanghai, China 201203 Tel: 86.21.2320.8000 Fax: 86.21.2320.8222 ©2015 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. Ahead of What’s Possible is a trademark of Analog Devices. BR13432-0-7/15(A) analog.com