Surgery – Truss – Pad
Patent
1983-12-21
1988-12-27
Coven, Edward M.
Surgery
Truss
Pad
128748, A61B 505
Patent
active
047933623
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of monitoring the fluid balance of the body and to an apparatus for carrying out the method.
At many illnesses and their treatment it is of vital importance to be able to determine changes in the patient's fluid balance. For making this determination, conventionally the patient has been weighed repeatedly, and in combination therewith the liquid and foodstuff intake and the amounts of urine and of evacuation of the bowls were accurately recorded. This method is very complicated and uncomfortable both for the patient and the medical staff. The method, moreover, yields unsafe results, due to many sources of error, of which the human factor is not the least one.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention proceeds on an entirely different and more direct way and eliminates the aforesaid shortcomings, in that two constant high-frequency partial alternating currents of a size innocious for the body, for example 100 .mu.A, but with frequencies of entirely different magnitudes, for example 1.5 and, respectively, 150 kHz, are caused to pass through the body between two peripherally remote places thereof, for example a wrist and a diametrically opposed ankle, that the voltage drop between two other places each located near one of the two firstmentioned places is measured, that the voltage drop is separated into its two components of different frequency, each of which scalary represents the impedance of the body at the frequency in question, that the measuring process is repeated after a desired period, and the ratio between the differences in impedance at the two measuring occasions is evaluated so as to indicate the change in the fluid balance between the first and the second measuring occasion.
The invention proceeds from the fact that the body fluid contains substantially constant concentrations of electrolytes and, therefore, the body impedance is a measure of the fluid amount. The application of two significantly different frequencies is based on the observation, that the tissue resistance varies with the frequency, due to the fact that the current flows on different paths at different frequencies. At low frequencies, for example, the current flows substantially on paths between the cells while at high frequencies it also passes through the cells. This is explained in that the cell membranes act as capacitors and at sufficiently high frequencies behave as high-pass filters. It was found that the frequency combination 1.5 and 150 kHz yields a conception of optimum correctness of the fluid amount.
On the basis of a great number of test series, the following general relation was established empirically for the change in the fluid balance. ##EQU2## where .DELTA.V=change in fluid weight and, respectively, higher frequency (for example 150 kHz) at the second measuring occasion measuring occasion (initial values)
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention is described in the following, with reference to the accompanying drawing, in which
FIG. 1 is a basic diagram for the total arrangement,
FIG. 2 is a block diagram for the current supply part, and
FIG. 3 is a block diagram for the detecting part.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to FIG. 1, tape electrodes E1 and, respectively, E2 are applied low-resistant about the left-hand wrist and the right-hand ankle of the patient P. The electrodes are connected via flexible lines L1 and, respectively, L2 to a constant current source. At the embodiment described, the current source is capable to feed the electrodes with alternating current of 100 .mu.A of two differently high frequencies, viz. 1.5 and 150 kHz. The measuring, of course, also can be carried out between a right-hand wrist and a left-hand ankle or even between hand and foot on the same side of the body. It is also possible to carry out local measurements, for example over only one leg or one arm in order to study the changes in fluid in the body part in question.
At a sho
REFERENCES:
patent: 3851641 (1974-12-01), Toole et al.
patent: 4008712 (1977-02-01), Nyober
Hoffer et al. "Corrgelation & Whole-Body Impedance w/TBWV", J Appl Phys 27:4 1969.
Dverot et al., "Determination du Volume des Liquides . . . Totale" La Presse Medicale 1970.
Taumasset, "Proprietes Bio-Eleltriques des Tissus" Trwavx Originavx 1963.
Coven Edward M.
Karolinska Institutet
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