NASA Technical Reports Server (NTRS) 20000038205: A Review of Electrical Impedance Spectrometry Methods for Parametric Estimation of Physiologic Fluid Volumes

38 Pages·1.4 MB·English

by  NASA Technical Reports Server (NTRS)

NASA/TM--2000-210200
A Review of Electrical Impedance
Spectrometry Methods for Parametric
Estimation of Physiologic Fluid Volumes
(MSFC Center Director's Discretionary Fund Final Report,
Project No. 96-03)
B. Dewberry
Marshall Space Flight Center, Marshall Space Flight Center, Alabama
January 2000
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NAS A/TM--2000-210200
A Review of Electrical Impedance
Spectrometry Methods for Parametric
Estimation of Physiologic Fluid Volumes
(MSFC Center Director's Discretionary Fund Final Report,
Project No. 96-03)
B. Dewberry
Marshall Space Flight Center, Marshall Space Flight Center, Alabama
National Aeronautics and
Space Administration
Marshall Space Flight Center • MSFC, Alabama 35812
January 2000
=
Available from:
NASA Center forAeroSpace Info_alion National Technical Information Service ,_
7121 Standard Drive 5285 Port Royal Road
Hanover, MD 21076-1320 Springfield, VA 22161
[phone] [phone]
ii
TABLE OF CONTENTS
I. INTRODUCTION ..................................................................................................................... 1
2. BACKGROUND ...................................................................................................................... 3
2.1 Fluid Shifts During Space Flight and Bed Rest Studies .................................................. 3
2.2 Standard Countermeasures to Fluid Shifts ....................................................................... 3
2.3 Computer Modeling ......................................................................................................... 4
2.4 Simple Volume Conductor Theory of Electrical Impedance Measurement ..................... 5
2.5 Clinical Measurement of Total Body Water Using Electrical Impedance ....................... 6
2.6 Intracellular and Extracellular Fluid Impedances ............................................................ 7
2.7 The Advantages of Multiple Frequency (Spectroscopy) Measurement ........................... 10
2.8 Parameter Identification for Total Body Water Volume Estimation ................................ 12
2.9 Intracellular and Extracellular Volume Measurement in a Single Body Segment ........... 13
3. INSTRUMENTATION DESIGN CONSIDERATIONS .......................................................... 17
3.1 Rationale for a Tetrapolar System .................................................................................... 17
3.2 Swept Sine Protoype High-Level Diagram and Description ........................................... 18
4. PATIENT SAFETY CONSIDERATIONS ................................................................................ 21
5. SOCIETAL IMPLICATIONS ................................................................................................... 23
APPENDIX --PRELIMINARY DESIGN OF A PROGRAMMABLE-WAVE
ELECTRICAL IMPEDANCE SPECTROMETER ......................................................................... 24
REFERENCES .............................................................................................................................. 25
iii
LIST OF FIGURES
0 Simplified volume conductor model of segmental impedance ........................................ 5
2a. Simplified body segment illustrating high-frequency and low-frequency
current paths ..................................................................................................................... 7
2b. Equivalent electrical circuit model of electrical conductive path
through a body segment ................................................................................................... 8
Complex plot of equivalent circuit ................................................................................... 9
,
4. Equivalent circuit model and complex impedance locus for a sys!em with tWO -
time Constan[s (a)_and_(c);:and a:sys(em-w_ a distn_ui_onofn:time constralntS :
(b) and (d). A distribution of time constants causes a "depressed" impedance locus ...... 10
o Distribution of relaxation times F(s), where s=loge(r/r0) and r/r ois the
normalized relaxation time .............................................................................................. 12
° Cole-Cole model parameters overtime ..................... . : : 14
7. A tetrapolar impedance measuring system with electrode impedances included
(adapted from Avhandling (1985)) ................................................................................... 18
8. A high-level diagram of a swept sine electrical impedance spectrometer ....................... 19
, Preliminary design of a programmable-wave electrical impedance spectrometer .......... 24
iv
LIST OF ACRONYMS
AC alternating current
ADC analog-to-digital convener
BIA bioimpedance analysis
BIS bioimpedance spectrometry
BPM beats per minute
DAC digital-to-analog converter
DC direct current
DSP digital signal processor
ECG electrocardiogram
ECW extracellular water
EIS electrical impedance spectrometry
EMI electrical interference
FFM fat-free mass
HDT head-down tilt
ICW intracellular water
MFBIA multiple-frequency bioimpedance analysis
PROM programmable read-only rnemory
rms root mean square
SNR signal-to-noise ratio
SRAM static random access memory
TBW total body water
V
NOMENCLATURE
A cross-sectional area
o: a variable to incorporate the distribution of time constants
Cm membrane capacitance
J 4-1
L segment length
mean
P specific resistivity
(y standard deviation
R lumped resistance
r correlation coefficient
Rc resistance at the characteristic frequency
extracellular resistance
R e
resistance of extracellular water
ReCW
intracellular resistance
R i
Ricw resistance of intracellular water
Roo resistance at infinite frequency
Ro resistance at a frequency of zero (DC)
relaxation time constant of dielectric suspension
"C system time constant
mean time constant of the time-constant distribution
'_0
vi
NOMENCLATURE (continued)
characteristic frequency
Y function of admittance
Z* complex impedance loci
z0 impedance at zero frequency (DC)
Zoo impedance at infinite frequency
zL load impedance
vii