The physiological surveillance of hemodialysis sessions by the continuous measurement of L.F. impedance of the circulating blood (Thomasset's method).

Everybody grants as a fact that hemodialysis disturbances are produced by volemia variations. During H-D the vascular sector is the necessary transit medium to withdraw excessive interstitial water. If this withdrawing is greater than the coming back of the interstitial water into the vascular sector, the plasmatic volume will be decreasing. Thus, to measure the variations of the plasmatic volume in circulating blood it is sufficient to effect a continuous measurement of these ones in a transducer having a definite volume. So, by the mean of an impedancemeter, 5 kHz impedance is continuously measured between the two electrodes of the transducer, because it is known (Thomasset's method) that at 5 kHz current uses only the plasma in order to pass from one electrode to another.

Determination of body fluid compartments by impedance measurements: differences in the repartition of water between Duchenne muscular dystrophy and some neurological diseases.

Body fluid volumes were determined by impedance measurements in several groups of patients. Boys with Duchenne muscular dystrophy had decreased intracellular and extracellular fluid volumes. Patients with severe sequelae of poliomyelitis and with other severely disabling neurological diseases did not exhibit such profound alterations of their body fluid compartments.

Some observations on the dielectric properties of hemoglobin's suspending medium inside human erythrocytes.

Dielectric permittivity and conductivity data for human erythrocytes exhibit two consecutive dispersions with frequency in the range from 0.1 to 250 MHz. The dispersion observed above 50 MHz yields a circle in the complex impedance plane with its center on the real axis, suggesting a Debye relaxation, for the erythrocyte interior medium, centered in the microwave frequency range as for bulk water. Moreover, the Maxwell mixture equation, indicates that this "free" water forms most of the suspending medium of hemoglobin macromolecules. These results extend to lower frequencies (earlier results obtained by Schwan) with biological tissues such as muscles, skin, or liver at microwaves frequencies.

[Survival of tumor fragments as a function of temperature: correlation with electric impedance]. / Vitalité de fragments tumoraux en fonction de la température. Corrélation avec l'impédance électrique.

The ability of small pieces of Rat Walker's tumour carcinome 256 to develop a subcutaneous tumour on another Rat is dependent on the value and the duration of heat treatment.

[Determination of the lean body mass in adult using the impedance method]. / Détermination de la masse maigre chez l'adulte par la méthode de l'impédance.

It deals with a new formula which gives the estimation of lean body mass (LBM) by the electric impedance measure at 1 MHz. According to the authors the weight of LBM is set up in two parts: the total water (TBW) conductive of electricity and an inert part (ILBM) which is a bad conductive one: the weight is an individual constant at the grown up. ILBM is calculated from simple morphological datums (H = height and C = wrist circonference). From which one concludes the formula: LBM = TBW + ILBM.

[Evaluation of sectorial fluid movement by measurement of the global impedance of the body. Study during hemodialysis and during treatment with major diuretics]. / Appréciation des mouvements liquidiens sectoriels par mesure de l'impédance globale du corps. Etude faite au cours d'hémodialyses et de traitements par diurétiques majeurs

During courses of haemodialysis or treatment with powerful diuretics, the clinician at the present time bases his actions on blood pressure levels which reflects blood volume and on weight variation which is dependent on water loss. The authors show, in studying variations in total body impedance at 5kHz and 1kHz and their ratio R, that there exists another method of observation which complements the basic notions provided by blood pressure levels and baseline weight. They were thus able to detect the possible formation of cellular oedema due to excessively rapid osmotic depletion. The method makes possible the evaluation of these sectorial fluid transfers when they occur, even though they are not evident clinically. This easy to use method is perhaps less rapid than the usual means of observation but is nevertheless more rational and provides information on electrolyte balance.

Determination of body fluid compartments by electrical impedance measurements.

?The ratio of the LF and HF impedances appears to be an excellent and simple tool for investigation of liquid specimens, either of the total human body, taking into consideration global impedances, or of a particular organ, taking into consideration local impedances. We have sketched out in this communication a study of the global impedance ratio variations with age, but a large number of studies still remain to be undertaken in those cases of severe denutrition, as in all cases of metabolic illnesses. We can state that, in most cases, not only does the ratio decrease but that there is extreme difficulty in reestablishing normal values. Whatever action is undertaken, it seems that the intracellular liquid compartment remains insufficient with respect to that of the extracellular liquid compartment. It is as if the water will not enter in the cells or as if it were no longer retained within the cells. Finally, with this concept of impedance ratios of Zlf/Zhf a promising experimental method has been found which will, perhaps, enable better infestigations in a field which has often been left to one side.

Investigation of electrical impedance variations of dog brain tissue during experimental metabolic disturbances.

Experiments were carried out on dogs using bielectrode probes having as adequate impedancemeter. The probe is introduced via a cranial opening into the grey matter. This gives the following: a low frequency reading which is related to the extra cellular fluid component; a high frequency reading which is related to the total overall liquids; and a proportionality ratio of these liquids in the explored volume. The impedance variations are functions of the nature and intessity of vascular disturbance. Variation of the low frequency impedance (5 kHz) is the most significant. The experimental prodedure consists of: 1) Abrupt and permanent circulatory arrest; 2) Circulatory reduction by haemorrhage followed by recovery (if necessary by means of blood transfusion); 3) Anoxia by CO inhalation, recovery affected by means of O2 inhalation; and 4) Hypoglycemic coma induced by intravenous injection of insulin. The changes in the biochemical state of the cerebral tissue give very large variations of the low frequency impedance. It is these variations which are to constitute the object of this communication.