Calibrating volume measurements made using the dual-field conductance catheter
- 1
- 2
- 3
- 4
Abstract
The conductance catheter technique allows real- time measurements of ventricular volume based on changes in the electrical conductance of blood within the ventricular cavity. Conductance volume measurements are corrected with a calibration coefficient, α, in order to improve accuracy. However, conductance volume measurements are also affected by parallel conductance, which may confound cali-bration coefficient estimation. This study was un-dertaken to examine the variation in α using a physical model of the left ventricle without parallel conductance. Calibration coefficients were calculated as the conductance-volume quotient (αV(t)) or the stroke conductance-stroke volume quotient (αSV). Both calibration coefficients varied as a non-linear function of the ventricular volume. Conductance volume measurements calibrated with αV(t) estimated ventricular volume to within 2.0 ± 6.9%. By contrast, calibration with αSV substantially over-estimated the ventricular volume in a volume-dependent manner, increasing from 26 ± 20% at 100ml to 106 ± 36% at 500ml. The accuracy of conductance volume measurements is affected by the choice of calibration coefficient. Using a fixed or constant calibration coeffi-cient will result in volume measurement errors. The conductance-stroke volume quotient is associated with particularly significant and volume-dependent measurement errors. For this reason, conductance volume measurements should ideally be calibrated with an alternative measurement of ventricular vol-ume.
- Baan, J., Aouw Jong, T. T., Kerkhof, P. L., Moene, R. J., van Dijk, A. D., van der Velde, E. T., and Koops, J., (1981) Con-tinuous stroke volume and cardiac output from in-tra-ventricular dimensions obtained with an impedance catheter. Cardiovascular Research, 15, 328–334.
- Mur, G. and Baan, J., (1984) Computation of the input imped-ances of a catheter for cardiac volumetry, IEEE Transactions on Biomedical Engineering, 31, 448–453.
- Baan, J., van der Velde, E. T., de Bruin, H. G., Smeenk, G. J., Koops, J., van Dijk, A. D., Temmerman, D., Senden, J. and Buis, B., (1984) Continuous measurement of left ventricular volume in animals and humans by conductance catheter, Cir-culation, 70, 812–823.
- Wu, C. C., Skalak, T. C., Schwenk, T. R., Mahler, C. M., Anne, A., Finnerty, P. W., Haber, H. L., Weikle II, R. M. and Feldman, M. D., (1997) Accuracy of the conductance catheter for meas-urement of ventricular volumes seen clinically: Effects of elec-tric field homogeneity and parallel conductance, IEEE Trans-actions on Biomedical Engineering, 44, 266–277.
- Salo, R. W., (1992) Improvements in intracardiac impedance volumes by field extrapolation, European Heart Journal, 13(Suppl E), 35–39.
- Wei, C. L., Valvano, J. W., Feldman, M. D. and Pearce, J. A., (2005) Nonlinear conductance-volume relationship for murine conductance catheter measurement system. IEEE Transactions on Biomedical Engineering, 52, 654– 661.
- Cassidy, S. C. and Teitel, D. F., (1992) The conductance vol-ume catheter technique for measurement of left ventricular volume in young piglets, Pediatric Research, 31, 85–90.
- Boltwood, C. M., Appleyard, R. F., and Glantz, S. A. (1989) Left ventricular volume measurement by conductance catheter in intact dogs: parallel conductance volume depends on left ventricular size, Circulation, 80, 1360–1377.
- Applegate, R. J., Cheng, C. P. and Little, W. C., (1990) Simul-taneous conductance catheter and dimension assessment of left ventricular volume in the intact animal, Circulation, 81, 638–648.
- Szwarc, R. S., Laurent, D., Allegrini, P. R., and Ball, H. A., (1995) Conductance catheter measurement of left ventricular volume; evidence for nonlinearity within cardiac cycle, American Journal of Physiology-Heart and Circulatory Physi-ology, 268, H1490–H1498.
- Danton, M.H., Greil, G.F., Byrne, J.G., Hsin, M. Cohn, L. and Maier, S.E. (2003) Right ventricular volume measurement by conductance catheter. American Journal of Physiology-Heart and Circulatory Physiology, 285, H1774–H1785.