Faculty Collaboration Database

Effects of physical parameters on the cylindrical model for volume measurement by conductance. Ann Biomed Eng 1997;25(1):126-34

Date

01/01/1997

Pubmed ID

9124727

DOI

10.1007/BF02738544

Scopus ID

2-s2.0-0031029416 (requires institutional sign-in at Scopus site)   14 Citations

Abstract

Despite its undisputed utility for determining changes in ventricular pressure-volume relationships, the conductance catheter technique has not been proven reliable for measuring absolute volume. This limitation is due to violations of the assumptions inherent in the cylindrical model on which the method is based (i.e., homogeneous electric field and no leakage current). The purpose of this investigation was to relate cylindrical model correction factors to the physical environment of the catheter and to the cylindrical equation. Physical measurements of saline-filled, nonconductive cylinders using a four-electrode conductance catheter were compared with a three-dimensional finite element model of the physical apparatus. These measurements were incorporated into a parallel conductance model to relate physical parameters to corrections in the cylindrical equation for volume measurement. Excellent agreement between measured and modeled data was found. Results demonstrated a nonlinear relationship between the field nonhomogeneity correction factor (alpha) and cylinder diameter. The relationship between alpha and diameter was consistent with a theoretical extrapolation of cylinder diameter toward infinity. An inverse relationship between alpha and the parallel conductance volume (Vp) was also clarified. The parallel conductance model was able to demonstrate opposite effects of the physical presence of the catheter body and electrodes, which tended to cancel out any net effect on measured conductance. Results of this investigation and the developed finite element model clarify the nature of the correction terms in the cylindrical model and may lead to greater application of the conductance technique.

Author List

Hettrick DA, Battocletti JH, Ackmann JJ, Linehan JH, Warltier DC

Author

David C. Warltier PhD Emeritus Professor in the Anesthesiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Cardiac Volume
Catheterization
Electric Conductivity
Electrophysiology
Models, Theoretical
Ventricular Pressure