1. Richard W. Montgomery, Ph.D. and Leslie D. Montgomery, Ph.D.
Electrical Impedance Spectroscopic (EIS) Three Compartment Fluid Volume Monitoring by
Richard W. Montgomery, Ph.D.
and Leslie D. Montgomery, Ph.D.
LDM Associates
San Jose, CA
June 15, 2008
NIH SBIR Phase II Grant No. 2 R44 HL A2

2. Segmental Compartment VolumesVb Vc Vb Vc Vi Vi

3. Dialysis Patient Populations
Source:
New York
George Washington
Patients
Walk-in, healthy, except for excess fluids.
Hospitalized, with a variety of symptoms.
Repeatability
Routine repeated sessions for several patients.
Significant health changes between sessions.
Interventions
Nearly constant ultra-filtration rates; minor interventions (e.g., saline infusions).
Frequent UF-rate changes; significant patient management interventions.

4. UF Rate and Amount of Fluid Removed vs. Elapsed Time
NY08B

5. Hematocrit Response to Dialysis Ultra-filtration Rate vs. Elapsed Time

6. Typical Fixed Frequency Measure of Segmental Resistance
Elapsed time - MIN
NY08B
Elapsed time - MIN
NY11B

7. Typical Multi-Frequency Measures of Segmental Resistance
Elapsed time - MIN
Elapsed time - MIN

8. Basic EIS Volume Data (NY08B)
100 C 50 20 40 60 80
100
120
140
160
180
200
Fluid volume (ML)
-50 I
-100 B
-150
Total
-200
-250
Elapsed time (MIN)

9. Data Smoothing: Total Calf Volume50
Elapsed time (min) 20 40 60 80
100
120
140
160
180
200
-50
Fluid volume (ML)
-100
Data
-150
Smoothed
-200
NY08b
-250

10. Calf Compartment Fluid Volumes, Smoothed
Elapsed Time - MIN

11. Inter-compartment Flow Rates Derived from EIS Volumes vs. Elapsed Time
NY08B
Elapsed Time - MIN
NY11B
Flow rates estimated from changes in volume
Positive values indicate flows into compartment.
Negative values indicate outflows

12. Hematocrit and Its Rate of Change
vs. Elapsed Time
NY08B
Elapsed Time - MIN
NY11B
Elapsed Time - MIN

13. Derivation of %Extravascular Fluid Removed in Calf Outflow

14. Relation of dHCT/dT and Percentage Extravascular Fluid in Calf Outflow
Elapsed Time - MIN
Elapsed Time - MIN

15. Actual vs. Predicted Rate of Change of Hematocrit

16. Actual HCT vs Integrated Prediction of Rate of Change of HCT
NY08B
R2=0.998
NY11B
R2=0.932

17. Possible Insights from EIS Results
Fluids shift between compartments (and between body segments) in a very discontinuous manner: They "slurp" back and forth.
Hematocrit, a widely used monitoring method, is related to the percentage of interstitial fluid being removed as well as to the ultrafiltration rate.
Calf (and perhaps body) fluid removal often slows to near zero well before the end of the dialysis session.
Cells usually absorb fluids during dialysis, often considerably so.

18. Summary
We can obtain time-fluid volume profiles for each of three fluid compartments for the calf: the vascular, interstitial, and intra-cellular compartments.
We can use that data to derive the minute-by-minute fluid exchanges between these compartments, and between the calf and surrounding body segments.
We can compute the percentage of extravascular fluid (interstitial fluid) flowing out of the calf vascular compartment along with blood.
We can show that this percentage influences the rate of change the independently-measured hematocrit ratio (the small changes in the slope of its time-profile).