Microprocessor-based system for measurement of electrical impedances during haemodialysis and in postoperative care
- 51 Downloads
The paper describes an instrument designed for accurate measurement of the mean specific electrical impedance of tissue. Two basic measurements are possible. One implementation called tetrapolar impedance plethysmography is employed for investigation with respect to transcellular fluid shifts during haemodialysis. The other measuring configuration called differential tetrapolar impedance plethysmography, deals with measurement of intrathoracic fluid content, which is important in monitoring treatment and prevention of lung oedema. An alternating current of 1 mA is passed through the tissue at different frequencies. Two measuring channels are available for differential tetrapolar measurement. Only one channel is required for straightforward tetrapolar measurement. Recovery of the impedance signals is achieved by synchronous demodulation. The impedance signal is passed through an analogue-to-digital convertor for digital processing to estimate the specific impedance in case of a differential tetrapolar measurement. Output display is possible via an xy recorder. The design of the instrument is discussed and some results shown.
KeywordsElectrical impedance plethysmography Fluid shift Microprocessor Specific impedance Thoracic impedance
Unable to display preview. Download preview PDF.
- De Vries, P. M. J. M., Meijer, J. H., Oe, P. L., van Bronswijk, H., Bossink, A. W. J., Schneider, H. andDonker, A. J. M. (1986) Electrical impedances as a measure for transcellular fluid shifts during hemodialysis.Life Support Systems,4, Suppl. 2, 243–245.Google Scholar
- Goovaerts, H. G., van Veen, C. andMeekes, M. A. A. M. (1984) A general purpose microprocessor system for medical instrumentation and electrical stimulation.J. Biomed. Eng. 6, 90–96.Google Scholar
- Kanai, H., Haeno, M. andSakomoto, K. (1982) Electrical measurement of fluid distribution in legs and arms: estimation of extra-cellular and intra-cellular fluid. IEEE Conf. Frontiers of Eng. in Health Care, 1982, 273–276.Google Scholar
- Khan, M. R., Tandon, S., Guha, S. K. andRoy, S. B. (1977) Quantitative electrical-impedance plethysmography for pulmonary oedema.Med. & Biol. Eng. & Comput.,15, 627–633.Google Scholar
- Korsten, H. H. M., Meijer, J. H., Hengeveld, S. J., Delmarre, J. B. V. M., Leusink, J. A., Schurink, G. A. andSchneider, H. (1983) Continuous monitoring of intrathoracic fluid. InComputing in anaesthesia and intensive care.Prakash, O. (Ed.), Martinus Nijhoff, Boston and The Hague.Google Scholar
- Korsten, H. H. M. (1984) Intrathoracale vloeistofvolume-veranderingen tijdens en na open-hart chirurgie. Thesis, University of Leiden.Google Scholar
- Korsten, H. H. M., Leusink, J. A. andMeijer, J. H. (1984) Monitoring changes in intrathoracic fluid after open heart surgery. Int. Symp. Pulmonary Circulation in Acute Respiratory Failure, Barcelona, Spain.Google Scholar
- Kubicek, W. G., Karnegis, J. N., Patterson, R. P., Witsoe, D. A. andMattson, R. M. (1966) Development and evaluation of an impedance cardiac output system.Aerospace Med.,37, 1208–1212.Google Scholar
- Meijer, J. H., Reulen, J. P. H., Oe, P. L., Allon, W., Thijs, L. G. andSchneider, H. (1982) Differential impedance plethysmography for measuring thoracic impedances.Med. & Biol. Eng. & Comput.,20, 187–194.Google Scholar
- Meijer, J. H. andOe, P. L. (1982) Osmotic aspects in artificial kidney dialysis. InExogeneous and endogeneous influences on metabolic and neural control. Adding, A. D. F. andSpronk, N. (Eds.), Vol. I, invited lectures, 351–362.Google Scholar
- Meijer, J. H., Korsten, H. H. M., Glaudemans, P. W., Leusink, J. A., Schurink, G. A. andSchneider, H. (1983) Differential impedance plethysmography for monitoring chest fluid.Medica Jadertina,15s, 291–294.Google Scholar