Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Patent
1995-03-23
1998-07-21
Bahr, Jennifer
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
600584, A61B 500
Patent
active
057827540
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for non-invasively monitoring the concentration of a substance in a fluid produced by a human or an animal, in which method a pickup unit is held against the skin and the amount of substance received in the pickup unit is measured.
Such a method is disclosed in Japanese patent application 61-25541. This known method is intended for measuring the glucose concentration in the blood, in particular in patients with diabetes.
It is observed that hereinafter the term "patient" is understood to mean a human or an animal in general, whether healthy or ill.
According to this known method, a glucose oxidase enzyme is immobilized directly behind a cellulose membrane which has a good permeability to water and substances dissolved therein. Behind that, a limiting membrane is provided, which arrests reduced substances but allows water, hydrogen peroxide and salts to pass therethrough. Behind this membrane, hydrogen peroxide is detected with a platinum electrode.
The glucose oxidase enzyme produces hydrogen peroxide and an acid, depending on the amount of glucose which has passed through the cellulose membrane. The acid is arrested by the limiting membrane, but the hydrogen peroxide is allowed to pass. Through the electrode flows an electrical current which is dependent on the amount of hydrogen peroxide which has entered the fluid. Thus, on the basis of the current intensity, the amount of glucose which has passed through the cellulose membrane can be determined. The amount of glucose which has passed through the cellulose membrane, in turn, is dependent on the glucose concentration in the blood. Thus, this concentration can be monitored continuously and without
A drawback of this known method is that it is only suitable for monitoring the glucose concentration.
In other known methods where, on the basis of the substance penetrating through the skin, the extent to which that substance is present in the body is measured transcutaneously, that substance is accumulated over a given period. An interruption of the accumulation or an unreliable period within the time period of the accumulation is then disastrous for the reliability of the results obtained after that interruption or unreliable period.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method which is also suitable for non-invasively monitoring the concentration of other low-molecular, water-soluble substances.
According to the present invention, this object is realized in that, in a method of the type described in the opening paragraph hereof, liquid is passed through the pickup unit continuously and the concentration of the substance is measured in the liquid stream, downstream of the pickup unit.
In the method according to the invention any accumulation of the substances received in the liquid is avoided in that the liquid is continuously refreshed. As a result, regardless of the duration of the monitoring, as long as the concentration of the substance in question, for instance in the blood, remains within a given range, the concentration in the liquid of the substance whose concentration in the blood is to be monitored will remain within a corresponding, relatively limited range. This range can moreover be influenced by appropriately choosing the replacement rate of the liquid in the cavity. Thus, the concentration of the substance in question in the liquid can be caused to remain within a range within which it can be properly measured.
Further, the concentration of the substance in question in the liquid is to a high degree directly proportional to the concentration of that substance in the blood. Thus, the course of the concentration of the substance in the liquid provides in a simple manner an indication of the course of the concentration of that substance in the blood. Interruption of the measurements or periods within the time duration of the monitoring which are considered unreliable have no or hardly any adverse influence on the reliability of the results obtained aft
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patent: 4311789 (1982-01-01), Nylen et al.
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patent: 4756314 (1988-07-01), Eckenhoff et al.
patent: 5050604 (1991-09-01), Reshef et al.
Lo et al., "Transepidermal Potassium Ion, Chloride Ion, and Water Fluxacross Delipidized and Cellophane Tape-Stripped Skin," Dermatologica, 1990, v. 180, pp. 66-68.
Websters II New Riverside University Dictionary, The Riverside Publishing Company, 1994, p. 550.
de Boer Jaep
Korf Jakob
Bahr Jennifer
Yarnell Bryan K.
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