Continuous measurements by impedance of haematocrit and plasma volume variations during dialysis

• Published in: Medical & biological engineering & computing Vol. 35; no. 3; pp. 167 - 171
• Main Authors: MAASRANI, M, JAFFRIN, M. Y, BOUDAILLIEZ, B
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.05.1997; Springer Nature B.V
• Subjects: Adolescent; Aged; Aged, 80 and over; Biological and medical sciences; Biothermics. Biomagnetism. Bioelectricity; Child; Electric Impedance; Fundamental and applied biological sciences. Psychology; Hematocrit; Humans; Plasma; Plasma Volume; Renal Dialysis; Tissues, organs and organisms biophysics; Human; Plasma; Electrical properties; Experimental study; In vitro; Modeling; Artery; Concentration measurement; In vivo; Volume measurement; Hematocrite; Dialysis; Continuous measurement; Circulatory system; Technique; Comparative study; Electrical impedance
• ISSN: 0140-0118; 1741-0444
• DOI: 10.1007/BF02530032

A technique for continuous measurements of haematocrit and plasma volume in the arterial line of dialysed patients has been tested in vitro and in vivo. This method uses impedance measurements at 5 kHz and requires a single haematocrit measurement. It relies on two assumptions: that plasma resistivity does not change during dialysis and that blood resistivity obeys Hanai's model. Both assumptions are verified during in vitro tests. Haematocrits measured in vivo by this method are found to be in good agreement with direct measurements from blood samples. The haematocrit variation is then used to monitor changes in plasma volume, assuming conservation of erythrocyte volume. In addition, it is possible to obtain the variation in interstitial volume by combining these data with body impedance measurements.