A weak electrical current enhances intracellular delivery of therapeutic substances.

Cell membranes have electrical properties which can be measured and modified. Administering a weak electrical signal across a tissue is a technique which can be used to determine the quantity of water in the intracellular and extracellular compartments. Using this real-time method of bioelectrical impedance, it was found that a variety of stimuli (including an electrical current) can enhance the passage of water and other substances into the cell. We propose an inexpensive and safe technique which could be utilized to enhance delivery of a wide variety of therapeutic agents into cells for the enhanced delivery of antibiotics, chemotherapy or other therapeutic agents.

[Whole body and thoracic impedance changes induced by cardiopulmonary bypass]. / Modifications de l'impédance corporelle totale et thoracique induites par la circulation extracorporelle.

Impedance is defined as resistance to alternating electrical current. It is inversely proportional to the volume of tissues traversed by the current. Cardiopulmonary bypass, as used in cardiac surgery, results in extravascular fluid overload manifested by a decrease in whole body and thoracic impedance. This non-invasive method has been used in 18 adult patients before, and in the days immediately following cardiopulmonary bypass for non-mitral cardiac surgery. Right and left thoracic impedances were reduced by 32 and 37 percent respectively during the first postoperative hour and returned to preoperative values after the second postoperative day. Whole body impedance was reduced by 14 percent in the first post-operative day, and this was accompanied by 17 percent and 16 percent decreases in the PaO2/PAO2 and PaO2/FIO2 ratios respectively. There was no correlation between impedance and these ratios which reflect pulmonary gases exchanges. Impedance appears to be a simple method to evaluate whole body and thoracic water contents, thereby providing guidance in post-cardiac surgery management.

Fat-free mass estimation by the two-electrode impedance method.

In 202 healthy subjects (81 men, 121 women) aged 12-71 y, impedance (Z) was measured with a two-electrode analyzer. Fat-free mass was assessed by hydrodensitometry (FFMd). This population was randomized into two groups for cross-validation. In group 1 the relationship between ht2/Z at 1 MHz and FFMd was highly significant (r = 0.85, P less than 0.001). The equation for predicting FFMd from impedance, height2, weight, and age obtained in group 1 (r = 0.97) was applied to group 2 (r = 0.96) without reduction in r value. The accuracy of this equation was not different between men and women or between active and sedentary people. These data indicate that the two-electrode impedance method is a reliable and valid approach not only for the determination of extracellular water (as previously shown) but also for that of FFM.

[Edema in pregnancy. Calculation of the contents of maternal cells]. / Contribution à l'étude des oedèmes gravidiques. Estimation chiffrée du contenu cellulaire maternel.

In 1963 F.D. Moore and his colleagues described "the body cell mass", but up till now there has not been a practical method to isolate other components of the body. Electrical body impedance measurement makes it possible in pregnant women not only to separate the values relating to maternal tissues from those relating to fetal tissues but it is also possible to make out in the Lean Mass of the mother those parts that are due to extra-cellular fluid in the supporting tissues and particularly those that come from the cytoplasmic mass (water, proteins, electrolytes and dissolved substances). The method, which is founded on a well-known scientific basis, is simple and almost a-traumatic. It consists in measuring the electrical resistance given to the passage of a weak alternating current that is passed through two electrodes, one of which is placed on one hand and the other on the foot of the other side. This method gives a result in units of electricity (ohms) of the value of the active cellular component of the mother. As we know that the normal values are closely linked to the morphological features of the woman which are fixed, it is easy to determine them and compare the measurement obtained by impedance at the time the measurements are being taken. We therefore obtain an index N which is normally equal to 1 +/- 0.10 which gives evidence of an excess of cellular content when Nis greater than 1.10 or a decrease if N is less than 0.90.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

[The components of body weight in pregnant women determined by electrical impedance measurements of the whole body (author's transl)]. / Les composantes du poids corporel chez la femme enceinte estimées par la mesure de l'impédance électrique globale.

For a long time estimating body weight has not been the sole parameter of knowledge of the body constituents and the method of measuring "skin folds" only was of value in differentiating between the "thin mass" and the "fat mass". The authors used Thomasset's method of determination of body fluid compartments by electrical impedance measurements to measure objectively the extra-cellular water content and the total water content, which means the thin mass and the fat mass of the body. It is possible in pregnancy to work out how much of the increase in weight comes from the maternal structures and how much from the utero-fetal mass. The authors point out that the impedance method makes it possible to determine independently the maternal body constituents and those of the fetus carried by the mother. In this way it is easy to work out in cases of pathological weight gain whether this has arisen because of oedema or because of becoming fat. Furthermore the authors point out that what they call "eutrophy of pregnancy", which is the normal weight gain brought about by pregnancy, is similar to the state of affairs brought about by women taking oral contraceptives, which they call "oestroprogestative eutrophy".

[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.