Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
  • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons

Definitions

• the invention relates to medicine, namely to non-invasive 5 methods for determining the volume of fluid in the patient’s body in which an alternating electric current is used as a probing signal, as well as to devices implementing this method.
• HD Hemodialysis
• ESR end-stage renal failure
• AH arterial hypertension
• BCC circulating blood
• UV ultrafiltration
• This reaction during UV exposure affects 20–30% of patients who experience clinical manifestations in the form of convulsions of 5 calf muscles, nausea, vomiting, and loss of consciousness.
• a marked decrease in blood pressure during UV can cause the occurrence of fatal arrhythmias, impaired coronary and cerebral circulation, leading to sudden death of the patient.
• hypotension occurs as a result of excess UV.
• the patient’s weight, measured before the HD procedure is planned to be reduced due to the amount of UV to the so-called “dry weight” value.
• dry weight is interpreted as the smallest weight obtained by removing fluid by UV, in which the normotension corresponds to the normotension between and during the patient’s blood pressure procedures and after the patient has undergone HD, the patient is in 15 states of normovolemia.
• a non-invasive method based on measuring the electrical impedance of parts of the body is used to control fluid volumes in the HD process [2].
• the use of impedance only for a single part of the body: the leg or thoracic region did not allow to obtain an integral picture of the dynamics of 20 volumes of fluid, allowing us to formulate practically significant clinical conclusions [3,4].
• Intravascular fluid is delimited by the endothelial 15 lining of blood vessels.
• an increase in extracellular fluid volumes is achieved through a proportional increase in plasma and interstitial fluid volumes.
• an increase in the volume of extracellular fluid is ensured only by changing the interstitial space.
• T.O. interstitial space 20 serves as a kind of compensating reservoir for intravascular space.
• an increase in interstitial fluid volume is manifested by tissue edema.
• tissue edema for clinicians, an important point is the determination of preclinical hyperhydration, i.e. accumulation of fluid in the interstitial space in excess of stress - 25 normal.
• Diagnostic methods in which an alternating electric current is used as a probe signal, is the most sparing. This is achieved through the use of a probe signal of lower intensity, compared with other influences. For example, a study of the liquid-fat composition of the body is carried out by means of an alternating probing current with a force of tenths of a milliampere. Sounding an organism alternating current allows monitoring the dynamic state of the circulatory system and respiratory system [6].
• An alternating current containing two or more harmonic components spaced in the frequency range allows obtaining information on the quality state of 5 tissues and organs, for example, on the water balance and fat mass of the body and its parts, on the state of tissues, grafts and their suitability for implantation [7].
• a known method for determining the volume of body fluid during hemodialysis carried out by measuring the impedance of the legs at low and high frequencies and determine the volume of extracellular, cellular, and total body fluid based on the relationship of impedance with the volume of the electrically conductive fluid in the measured part of the body [3].
• the disadvantage of this method is the low accuracy due to the fact that the fluid volumes of the whole organism are estimated indirectly, additionally using the parameters of the change in blood parameters
• a known method for determining the volume of liquid sectors of the body carried out by measuring the growth (geometric size of the body) and the impedance of the body when sensing it with a current of low and high frequency, which is passed from hand to foot [8].
• the disadvantage of this method is low
• a known method of bioimpedance determination of fluid volumes in parts of the body which consists in measuring growth (geometric size of the body), applying potential and current electrodes to the distal parts of the limbs, measuring the impedance of the arms, trunk and legs when probing tissues with a low frequency current and determining, based on the measured extracellular fluid volume parameters [9].
• the disadvantage of this method is the low accuracy of determining the volume of body fluid and the volumes in the upper (thoracic) and lower (abdominal) parts, which is due to the high uneven distribution of the probe current in the body.
• Measurement of the impedance of the body in this method is carried out at the passage of the probe current between the right (left) hand and the left (right) foot and measuring the voltage drop across the body between the left (right) and right (left) foot.
• the probe current changes its direction almost to the opposite, as a result of which its distribution in the 5th volume of the upper body is uneven and leads to a decrease in the accuracy of measuring the impedance of the entire body.
• the uneven distribution of the current density arises due to the fact that the tissues of the thoracic and abdominal regions differ significantly both in the anatomical structure and in the amount of fluid contained in them, for example, the thoracic region is largely filled with the air volume of the trachea and lungs.
• the closest analogue of the proposed method is a method for determining violations of the water balance of the extracellular fluid of the body, which consists in measuring the geometric size of the body: L and electric
• the body fluid volume is determined by probing it with a low and high frequency current, while the equipotential surfaces for low and high frequency currents in the shoulder area do not coincide due to the significant heterogeneity of the tissue structure: muscle and pulmonary, which leads to significant errors in the measurement of capacitive ( high-frequency) component of the impedance, and, consequently, a decrease in the accuracy of determining the volume of the cellular fluid of the body.
• a device for determining the volumetric content of 35 extracellular and intracellular fluid in the tissues of a biological object containing four pairs of potential-current electrodes, a current generator, a controlled switch, a detector, an analog-to-digital converter and a processing and indication unit that allows you to measure the impedance of body parts: arms, trunk and legs and using its values obtained from measurements at low and 5 high frequencies determine the volume of liquid [9].
• the body impedance in the device is measured using electrodes located on the arms and legs. This arrangement of the electrodes does not interfere with procedural manipulations in the body area. But when measuring the impedance of the body, a probing current is passed between the right (left) hand and the left (right) foot and the voltage drop across the body between the left (right) and right (left) legs is measured.
• the probing current changes its direction almost to the opposite, as a result of which in the upper part of the body, its distribution is uneven and the accuracy of measurement of the impedance of the body is reduced.
• the body contains at least half of the total fluid volume
• the error in measuring the body impedance significantly reduces the accuracy of determining fluid volumes not only in the body, but for the whole organism. Uneven distribution of the probe current in the shoulder area reduces the accuracy of measuring the impedance of the hands, because to calculate it, the value of the impedance of the body is used.
• the closest analogue of the proposed device is a device for measuring electrical impedance in body parts, containing four pairs of electrodes, each of which contains a current and potential electrode, designed to be fixed on the limbs, a fifth current electrode, designed to be fixed on the neck, and a fifth potential
• the probe signal generator 25 is an electrode, a probe signal generator, the opposite outputs of which through the first and second switches are connected to pairs of electrodes, and the potential outputs of the switches are connected to the inputs of the detector, the output of which through an analog-to-digital converter is connected to the signal input of the control and registration unit, the control outputs of which are connected with control inputs of the switches and the probe signal generator [5].
• the disadvantage of this device is that the impedance of the body is measured using current electrodes located on the neck and leg and potential electrodes located on the arm and leg. In this device, the tissues of the hands are used as an electrical conductor
• the body fluid volume is determined by probing it with a low and high frequency current, while the equipotential surfaces for low and high frequency currents in the shoulder area do not coincide due to a significant 5 heterogeneity of the tissue structure: muscle and pulmonary, which leads to significant errors in the measurement of capacitive ( high-frequency) component of the impedance, and, consequently, a decrease in the accuracy of determining the volume of the cellular fluid of the body.
• the technical result of the invention is to increase the accuracy of determining the volume of cellular fluid of the body of its thoracic and abdominal regions, as well as to increase the accuracy of determining extracellular and cellular volumes of body fluid when measuring the impedance of the body using electrodes not located on the body, as well as
• ZTH 1 / [(Kp) 2 / Zp + ( ⁇ ) 2 / ⁇ + (K H T) 2 / ZAT + (K H ) 2 / Z H ], measure the impedance of body parts at high frequency, determine its capacitive component and find the capacitive integral component of the body impedance
• the measured volume of the body’s cell fluid is determined as the product of the statistical norm of the QOL volume of the body and the square root of the ratio of the statistical norm of the capacitive component of the body impedance to the measured value of the capacitive component of the body impedance:
• QWht WLt ⁇ (ZHTC / ZTC ) % , while:
• weight (P) determine the normal values of the volumes of extracellular and cellular fluids of the patient: VZhn and QOL, as a product of the coefficient
• Zo SV P - LVJ + LKZH / (KZhn / Vzhn).
• the patient is also determined the normal value of the volume of extracellular fluid in the thoracic part of the body, as the product of the coefficient of the statistical norm of the volume of the VL of the thoracic part of the body Kvzhtt per square product of the geometric size of the body
• VZhntt Kvzhtt ⁇ ( ⁇ ⁇ L) 2 , determine the measured volume of extracellular fluid of the thoracic part of the body as the product of the statistical norm of the VL volume of the thoracic part of the body by the square root of the ratio of the statistical norm to the measured impedance of the thoracic part of the body 5 measured at a low frequency:
• VZhdt VZHNAT - ( ⁇ / ⁇ ) / 2 , the degree of violation of the extracellular hydration of the abdominal part of the body is estimated by the value:
• the capacitive integral component of the impedance of the limbs of the patient ZKC is also determined, as:
• the technical result in the part of the device is achieved due to the design of the device for measuring electrical impedance in parts of the body containing four pairs of electrodes, each of which contains a current and potential electrode, intended for fixation on the extremities, a fifth current electrode, intended for fixation on the neck, and the fifth potential electrode, a probe signal generator, the opposite outputs of which through the first and second switches are connected to pairs of electrodes, moreover
• the pairs of electrodes are connected via the first and second electric buses to the outputs of the switches, the first electric bus contains taps for two pairs of electrodes in a sequence starting from the switch, for: legs and hands, and the second busbar contains taps for three pairs of electrodes in
• a calibration chain is connected containing a resistor in series and a controlled key, the input of which is connected to the fourth output of the control and registration unit.
• the fifth current electrode and the fifth potential electrode can be connected to the bus via a detachable connection.
• the device may comprise a radio channel unit connected to the fifth output of the control and registration unit.
• FIG. 1 - reference designation of the impedance of body parts.
• FIG. 2 is a diagram of the application of electrodes for measuring
• FIG. 3 is a flow chart for calculating the total impedance of a patient’s body.
• FIG. 4 conditional boundaries of the probing current in the leads: arm-arm and neck-leg.
• FIG. 5 equivalent components of the body impedance for the vascular and interstitial spaces.
• FIG. 6 is an equivalent circuit showing the transition resistance of the electrode-tissue and functional blocks for its measurement.
• FIG. 7 is a structural diagram of a device for measuring impedance in parts of the body.
• FIG. 8 conditional display of a logical sequence
• FIG. 9 conditional display of the logical sequence of measurements in the " ⁇ -cycles" of the device.
• FIG. 10 is a functional diagram for transmitting measured
• a device for measuring the electrical impedance of body parts contains: a probe signal generator 1 whose outputs are connected to the inputs of the first switch 2 and the second switch 3, a control unit 4 and
• the first electric bus 7 connected to the electrode output of the switch 2 and containing a pair of electrodes 9 for the legs and a pair of electrodes 10 for the hands in series
• the second electric bus 8 connected to the electrode output of the switch 3 and containing a pair of electrodes 11 for legs, a pair of electrodes 12 for the hands and a pair of electrodes for the neck in series 13 and
• a pair of electrodes for the neck 13 and 14 can be connected to the bus 8 by means of a detachable connection 17.
• the tetrapolar method is used, in which pairs of electrodes containing the current and potential electrodes are applied to the distal parts of the forearms, lower legs and neck, and the current electrode is superimposed on the right side of the neck, and the potential one on the left.
• the impedance in the selected leads is measured by means of a probing current of low and high frequencies, the switching of which between current electrodes is carried out by means of the first and second commutators.
• potential signals are used to measure
• ⁇ is the impedance of the right side of the body, which was measured during the passage of current between the right hand and the right foot by measuring the lead voltage between the right side of the body;
• Zl is the impedance of the left side of the body, which was measured during the passage of current between the left hand and left foot by measuring the lead voltage between the left side of the body;
• ZH is the impedance of the legs, which is measured by the passage of current between the legs by measuring the voltage between them;
• Znmp - the impedance of the right hand and the right side of the neck which is measured by the passage of current between the right side of the neck and the right hand by measuring the voltage between the right hand and the left side of the neck;
• ZB is the impedance of the upper body, which is measured with the passage of current between the right hand and the left hand by measuring the lead voltage between the upper body;
• Z fl is the diagonal impedance of the body, which is measured by the passage of current between the right hand and the left foot by measuring the voltage between the right hand and the left foot;
• Zmn H is the body impedance, which is measured by the passage of current between the right side of the neck and the right foot by measuring the voltage between the left side of the neck and the right foot;
• the impedance of the right hand ⁇ is determined from the results of the following measurements:
• the impedance of the left hand Z p is determined from the following measurements:
• the impedance of the thoracic part of the body ⁇ is determined from the results of measurements of the impedance ⁇ ⁇ and the impedance ⁇ ⁇ ⁇ and Znp.
• the lower body impedance ⁇ ⁇ ⁇ is determined according to the expression:
• the volume of the electrically conductive physiological fluid located in the investigated volume of the human body is determined based on the theory of electricity.
• An alternating probing current of constant magnitude is passed through the studied part of the body and the voltage drop arising on it is measured.
• the value of the measured voltage is proportional to the impedance
• p is the resistivity of the physiological fluid
• / is the distance between the potential electrodes
• Z is the electrical impedance of the investigated area.
• An alternating probing current of constant magnitude (1h) is passed through current electrodes of the body, for example, a “hand”, using current electrodes, and 35 the voltage drop arising on it (Up) between potential electrodes (Fig.Z).
• the value of the measured voltage is proportional to the impedance (Z P ) of the investigated area. If the cross-sectional areas of the investigated area along the path of the probing current are approximately the same value, then its volume of the electrically conductive 5 fluid is found from the following expression:
• p is the resistivity of physiological fluid
• Lp is the distance between potential electrodes
• Zp is the electrical impedance of the investigated area
• the distance between the conditionally located potential electrodes of the hand can be expressed as: 20 "k l_" and the volume of liquids of these parts of the body will be calculated by the formulas:
• Vp p (Lp) z / Z P ;
• V T p (k L P ) VZ T ,
• formula (2) is used as follows:
• formula (2) is used as follows:
• Tissue impedance measured at a low frequency (5 kHz) is due to the passage of current through a space filled with extracellular fluid.
• Tissue impedance measured at a high frequency (500 kHz) is additionally characterized by the presence of a capacitive component due to the capacitive properties of cell membranes, which in an equivalent circuit can be represented by resistance (Zc), connected in parallel with resistance (Z w ).
• Zc resistance
• Z w resistance
• the values of Zc are used to calculate the volumes of intracellular fluid of body parts [10].
• ZTC 1 / [(KP) 2 / ZPC + (KTT) 2 / ZTTC + (K A T) 2 / Z A TC + (K H ) 2 / Z HC ] (6)
• pk is the coefficient conditionally equivalent to the specific conductivity of the intracellular body fluid when used to estimate the value of the capacitive component of the integral impedance of the body
• VZh VZh N t - (2nt / g T n) , / 2 (11)
• QOL KZhnt - (GNS / g-gs) 1/2 (12) where: (ZTH, ZJC) - current measured values: impedance of the body at a low frequency and the corresponding value of the capacitive component, degree “14” is introduced as compensation in the case of significant deviations of the current values of fluid volumes from statistical values of the statistical norm of the patient's fluid volume.
• SV dry weight
• the SV parameter is defined as: the patient’s weight measured in (kg) with the state of his blood pressure in normotension and in the absence of symptoms characterizing hyperhydration (obvious edema, ...) or dehydration (convulsions, hoarseness, ).
• Assessment of the degree of hydration of the patient is carried out on the basis of abnormalities of AFL and AFL.
• the amount of UV is taken from the volume of the body fluids, which can be considered the primary factor.
• the amount of QOL in the body will decrease due to a decrease in the volume of VL, which can be considered a secondary factor.
• it is advisable to calculate the assessment of CB based on the values of AFL and take into account the change in QOL volume in recalculating its dynamics into VL volumes based on the physiological ratio of QL and VL volumes.
• P is the patient's weight (kg) measured after the HD procedure and before bioimpedance determination of body fluid volumes; LVZhs - the calculated value of the excess VL volume (l) of the patient, taking into account the correction of the deviation of the QOL volume from the statistical norm
• LVZhs VZhn + (DKZh / k) (14) where: k - statistical coefficient of interrelation of volumes of QOL and VZh in "norm" (to "2)
• Table 2 presents the dynamics of the hydration parameters of patient A. 52 years for 15 months. from the beginning of a permanent DG.
• Intensive infusion therapy for patients in the intensive care unit when the patient is in a supine position for a long time, is associated with a high degree of risk of hydrothorax, accumulation of excess extracellular fluid in the pleural cavity.
• Assessment of the degree of excess of VL in the thoracic region of the body is made according to the deviation of the volume of VZh in this part of the body from the individually calculated value of the statistical norm:
• VZhntt vzhtt - (Ktt - L) 2 - individually calculated value of the statistical norm
• VZhtt VZhntt ⁇ ( ⁇ ⁇ ) - the value of the current measured volume of VZh in the thoracic region.
• the 5 upper and lower parts of the trunk showed that the ratio of QOL to VL in the upper part of the body, the studied volume of which is mainly made up of the heart, lungs, thoracic aorta and superior vena cava, differs significantly from the same parameter for the lower body, the investigated volume of which is mainly composed of organs and tissues of the abdominal region.
• the value characterizing the “norm” of the QoL ratio of VF for the upper body is equal to 1, 61, and for the lower 1, 73, i.e. the relative content of VL in the upper part of the body is much greater than in the lower.
• the volumes of VL obtained by the bioimpedance study of the upper and lower parts of the body differ from each other in that in the volume of VL of the upper part of the body relative to the volume of VL of its lower part, the volume of vascular fluid is more reflected
• the torso impedance obtained by passing the probing current in the arm-arm direction to a greater extent reflects the parameters of the tissues of the upper torso.
• the torso impedance obtained by passing the probe current in the neck-leg direction reflects the parameters characterizing all body tissues (Fig. 4). Based on this when passing
• the 25 probing currents in the arm-arm and neck-leg directions of the ratio of the volumes of vascular and interstial fluids will be different. So, in the torso impedance obtained by measuring the arm-arm, the vascular component of the measured volume of the body fat is reflected to a greater extent.
• the quantitative ratios of the vascular and interstitial components in the volume of the body trunk are obtained as a result of the analysis of the body impedance measured at a low frequency (5 kHz) during the passage of the probe current in the arm-arm and neck-leg directions.
• the conditional display of the measured impedance of the body, necessary for calculating the volume of vascular and interstitial fluids is presented in figure 5.
• the total value of the torso impedance during the passage of arm-to-arm current ZB is presented as a parallel connection of the impedance of the vascular space ZCTT and the impedance of the interstitial space ⁇ , and the total value of the torso impedance during the passage of current is the right arm-right leg ⁇ is represented as a parallel connection of the vascular space impedance ZCAT interstitial space impedance
• ZAT (ZCAT 'ZMAT) / (ZCAT + ZMAT);
• ZTT (ZCTT ⁇ ZHTT) / (ZCTT + ZMTT);
• VL of the body can be represented in the following form (taking into account the fact that the volume of fluid is proportional to 1 / ⁇ ):
• the value of the coefficient K 2 taking into account the statistical values of ⁇ ⁇ ⁇ and ⁇ obtained when determining the statistical norm using multisegment bioimpedansometry for men and women, are: 2.1 and 1, 9, respectively. Substituting these values of K 2 into formula (16) and additionally taking into account the ratio of the length of the thoracic and abdominal parts of the trunk, we obtain formulas for calculating the ratio of the volumes of VL in the interstitial and vascular spaces.
• Table 3 shows the dynamics of changes in the water sectors of the body, taking into account the distribution of extracellular fluid in the vascular and interstitial spaces of patient B. 54 years old with poisoning by psychopharmacological drugs of moderate severity during infusion therapy. Upon admission to the hospital in this patient, deviations from the proper volumes of QOL and VZh were within the stress norm. Moreover, a slight fluid deficiency was revealed in the vascular bed, while its volume in the interstitium showed a tendency to increase. Against the background of the introduction of 3.0 l of infusion media, a further accumulation of fluid was recorded in all the studied water sectors one day after the start of treatment. With a subsequent reduction in the volume of water load to 1.5 liters per day by 3 days, the volumes of QOL, VL, including vessels and interstitial space, did not practically differ from the proper values
• Table 4 reflects changes in the water sectors of the patient B.'s body, 35 years old, with poisoning by psychopharmacological drugs against the background of forced diuresis. It follows from the table that after intravenous administration of 2.0 L of plasma-replacing solutions, an increase in QL and VL volumes occurred, the latter being more due to the accumulation of fluid in the interstitial space. The introduction of diuretics contributed to a decrease in fluid, both in the vascular and in the interstitial spaces.
• VL (l) 11.3 12.6 11.5 12.0 6.2
• Evaluation of the quality of contact of the current electrodes with the patient’s body is carried out by measuring the value of the transition resistance "Ra” at a frequency of 5 kHz of the probing current (I) (Fig. 7).
• the shunt resistor “RUJ” is connected to the output of the current generator using a controlled key “kl” and the voltage drop across the measured section of the body “ish” is measured using potential electrodes and a voltage meter “V”, after which without connecting a resistor Rm measure the information voltage "II", which is used to calculate the impedance of the investigated area of the body "RT”.
• the calculation of the value of Ra is carried out according to the following mathematical transformations:
• Ra (g e + g e );
• R R 3 + R T ;
• Ur is the voltage at the output of the generator 5 kHz
• R3 ⁇ RLIJ - [(U / UUJ) -1] ⁇ - RT
• the impedance measurement: Zn, Zl, Z H , Znujp, ZB, Zfl, ZmnH is made by connecting, through the switches 2 and 3, the outputs of the generator 1 5 of a sinusoidal signal with a frequency of 5 and 500 kHz and a stabilized current value, for example 0.3 mA to current electrodes as well as by connecting potential electrodes through the switches 2 and 3 to the inputs of the detector 5.
• a stable value of the probing current is connected via switches 2 and 3 to the current electrodes of pairs 9 and 10, and with potential electrodes these also couples through switches 2 and 3 are connected to the inputs of the detector 5, the output of which is formed by the voltage proportional to the amount of the investigated body part impedance whose value after digitization converter 6 is fed to the data input unit 4.
• pairs of electrodes 9 and 10 are used, and for measuring the impedance of the legs ZH, pairs of electrodes 7 and 8 are used.
• pairs of electrodes 10 and (13,14) are used.
• the operation of the generator 1 is controlled by block 4 in such a way that to measure the impedance in one lead on the current electrodes of the selected pairs of electrodes from the generator 1
• a sinusoidal signal with a frequency of 5 and 500 kHz is supplied in the time sequence shown in FIG.
• block 4 controls the operation of the key 16, switching it into a closed or open state.
• a resistor 15 is connected in parallel with the output of the generator 1.
• the sequence of probing signals in the form of voltages recorded by potential electrodes is shown in Fig. 8.
• the current electrodes are supplied with intervals of 80 ms in the stable value of the probing current in the first and second intervals with a frequency of 5 kHz and in the third interval with a frequency of 500 kg c.
• key 16 is closed.
• the signal amplitudes recorded by potential electrodes have the following relationships: the amplitude in the first interval is less than in the second, because resistor 15 is connected and part of the current flows through it, the amplitude in the third interval is less than in the second, because tissue impedance has a capacitive component. Amplitude ratio in
• the amplitude of the signal in the second interval is proportional to the active component of the tissues ( ⁇ , ⁇ , ⁇ , ⁇ ⁇ ), and its ratio with the amplitude in the third third interval allows us to calculate the capacitive component of the tissue impedance (Zpc, ZTTC, Z A TC, Z H C) -
• Signals from potential electrodes through switches 2 and 3 are fed to the inputs of detector 5, which amplifies them, detects the effective value, and through converter 6 in digital form, values proportional to the signals for each interval of the probing current are fed to the input of block 4.
• Block 4 is sequential schreib generates control signals providing voltage measurement shown in Fig. 8 for all leads that are selected for impedance measurement: ⁇ , ⁇ , ⁇ , Znujp, ZB, ⁇ , ZmnH - Measured voltages (Fig. 8) for all selected leads (Z n > Z H , Znmp, ZB, Z fl , ZmnH) are stored in
• Block 4 controls for sequential measurement and storage of the measured voltages for the " ⁇ -cycles" of Fig.9. After measuring the stresses in the "p-cycles", the measurement mode in the operation of block 4 is considered to be completed and all measured values become available for display on the indicator of block 4 or
• the detachable connection 17 allows you to disconnect the electrodes 13 and 14 from the device.
• unit 4 measures R 3 as equal to “oo” and then goes into the zo mode without measuring the impedance: Znujp and ZujnH-
• the measurement and subsequent calculations will be made according to one of the known 4 electrode circuits.
• Ra 35 magnitude of the transition resistance between the current electrode and the body (R 3 ).
• the control of Ra allows eliminating unpredictable errors when measuring the impedance of the body, to a large extent this is significant when examining older people whose skin is drier. If the device detects that the threshold value is exceeded by the measured Ra value, additional wetting of the surface of the current electrodes is performed.
• connection of the electrodes to the device via buses 7 and 8 allows to reduce the value of the capacitance Ce, due to the fact that the wires from the opposite outputs of the generator 1, through the switches 2 and 3 pass to versatile electrodes relative to the patient’s body: (9, 10) and ( 1 1, 12, 13, 14).
• the connection of the electrodes by means of buses 7 and 8 significantly normalizes the residual value of the capacitance Ce and allows you to make a correction to the value of the measured impedance at a frequency of 500 kHz.
• Patent RU Ns2242165 class A61 B 5/053. 2003.
• Rodin I.N Instrumental definition of "dry weight” and the optimal amount of ultrafiltration in a patient under treatment with programmed hemodialysis. Nephrology and dialysis. T.4, Ns1, 2002, S.41 - 44.
• Patent SU Ns 1 826 864 class A61 B 5/05. 1990.

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