JPS6157770B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrode device for percutaneously measuring the concentration (or partial pressure) of carbon dioxide in tissue or blood. Knowing the carbon dioxide concentration in the blood is extremely important in clinical tests for determining the quality of the respiratory and metabolic functions of a living body and the approximate value of the PH concentration in the blood. Conventionally, the main method used to measure the concentration (or partial pressure) of carbon dioxide in blood is to draw blood, especially blood from the arteries, and directly measure it, but this method requires continuous measurement over time. The problem was that it was impossible and caused pain to the patient. Particularly in the case of premature infants and newborns, blood sampling is highly invasive, making implementation extremely difficult. Unlike the above-mentioned direct method, the transcutaneous electrode method captures carbon dioxide gas diffused from blood through tissues on the skin surface, and can continuously measure it over time without causing pain to the patient. The present invention relates to the improvement of a transcutaneous blood carbon dioxide sensor, and particularly to the structure of a glass electrode for detecting PH changes. Figures 1a to d show the basic structure of a transcutaneous blood carbon dioxide sensor, showing the interior of a glass container 2 with an H ⁺ ion-sensitive (PH-responsive) glass thin film 1 welded to the bottom. , a glass electrode 5 in which an internal electrolyte 3 mainly composed of an aqueous solution such as KCl or NaCl, an internal reference electrode 4, etc. are enclosed, and an upper lid part 7 in which an external reference electrode 6 such as silver/silver chloride is built-in; A membrane holder 9 to which a polymer membrane 8 is attached in advance, a heating part 12 in which a heating element 10 and a heat sensitive element 11 are embedded
It consists of three independent parts, and has a structure in which the membrane holder part can be easily installed between the upper lid part and the heating part. Note that between the electrode film and the glass thin film there is NaHCO ₃ ,
Electrolyte 1 consisting of a mixed aqueous solution of Nacl or Kcl, etc.
3, and a spacer 14 made of paper, nylon cloth, etc. is interposed as necessary. However, the sensor with the above basic structure
The structure is such that the internal electrolyte is sealed inside a PH-responsive glass container, so if the sensor is overturned or inverted due to patient movement, the internal electrolyte on the PH-responsive glass thin film surface will move. As the liquid runs out, it loses its function as a sensor. When stored or transported in cold regions, the internal electrolyte may freeze, causing problems such as glass breakage. When the sensor is heated during transdermal measurement, a portion of the internal electrolyte evaporates and condenses due to the temperature distribution within the glass container, resulting in abnormal sensor response. Internal electrolyte leaks easily, resulting in poor insulation. Glass thin film part is easily damaged. There are other problems. The present invention eliminates the various problems that occur when using the glass electrode filled with an internal electrolyte, and provides a transdermal blood carbon dioxide sensor that is stable, robust, and has good workability. FIGS. 2a to 2d show the structure of a sensor according to the present invention, and the structure of the glass electrode is completely different from that of conventional products. In the figure, 21 is a glass thin film sensitive to H ⁺ ions, 2
2 is a highly insulating glass tube, and at the end of the glass tube
A glass container is constructed by bonding a glass thin film sensitive to H ⁺ ions with welding or adhesive. The conductive film 23 is a thin film made of metal such as Ag, Pt, Au, etc. formed on the entire surface of the glass thin film 21 and a part or the entire surface of the glass tube 22, and is formed by vacuum evaporation, ion plating, electroless plating, etc. It is formed. 24 is a lead wire of the glass electrode, which is connected to the metal thin film surface by solder or conductive adhesive. Reference numeral 26 is a hardening liquid rubber or thermosetting resin such as silicone rubber and epoxy resin, which is filled inside the glass electrode for the purpose of reinforcing the lead wire attachment portion and reinforcing the glass thin film. 27 is an external reference electrode made of silver/silver chloride, etc.
It is provided on the outer periphery of the glass electrode according to the present invention.
The glass electrode and the external electrode are fixed to an upper lid part 28 made of an insulating material. FIG. 2C shows a membrane holder 35 with a carbon dioxide permeable polymer membrane 34 made of a hydrophobic film attached to the end, and FIG. 2D shows a skin heating device equipped with a heating mechanism 36 and a temperature detection mechanism 37. The same conventional sensor as shown in Figure 1d is used in the body. Next, the features and effects of the present invention will be explained. Changes in H ⁺ ion concentration (PH changes) can be measured without using an internal electrolyte; (a) The sensor function will not be impaired even if the sensor is turned over or inverted due to the patient's posture. (b) There is no problem of the internal electrolyte freezing and damaging the glass electrode in cold regions. (c) When the sensor is heated, there is no abnormal behavior in potential caused by part of the internal electrolyte evaporating and condensing in the space of the glass electrode. D. There is no risk of problems such as insulation deterioration due to internal electrolyte leaking from the glass electrode. (e) Since the inside of the glass electrode is filled with metal or a solid such as silicone or epoxy resin, the mechanical strength of the H ⁺ ion-sensitive glass thin film increases and it becomes less likely to break. Next, one specific example of the present invention will be explained. In FIG. 2, the H ⁺ ion-sensitive glass thin film 21 had a composition of 25% by weight of Na ₂ O, 6% by weight of CaO, and 72% by weight of SiO ₂ and was welded to a highly insulating lead glass tube 22 . This glass container was previously dried at 200° C. for 2 hours, and then 600 Å of silver was sputtered onto the bottom of its inner surface by ion sputtering, and then 50 μm of silver was further deposited thereon by vacuum evaporation. To remove the lead wire 24 from the conductive film 23 formed by vapor deposition, we use a silver-containing epoxy adhesive 25.
Connected. Room temperature curing silicone rubber (KE67RTV manufactured by Shin-Etsu Chemical Co., Ltd.) is used for the 26 part in Figure 2 a and b.
filled with. Other parts in FIG. 2, such as the silver/silver chloride external electrode 27, were assembled using the same materials and methods as conventional ones. Table 1 shows a comparison of the performance of the sensor according to the present invention and the sensor according to the conventional method. The experiments in Table 1 are 0.005 for electrolytes 13 and 33.
mol NaHCO ₃ Using an aqueous solution containing 0.02 mol NaCl and saturated with AgCl, as the polymer membranes 14 and 34,
Using a 25 μm thick polytetrafluoroethylene film

[Table] As shown in Table 1, the sensor according to the present invention not only has performance that is not significantly different from that of the conventional sensor, but also has the above-mentioned features. It is clear that this method is superior to conventional methods as a skin blood carbon dioxide detector. Although the above specific example is an example of a conductive film for potential reading made of a vapor-deposited film, the conductive film for potential reading can also be formed by wet electroless plating using a silver mirror reaction or the like. Also, conductive adhesives (e.g. Dotite D-
723S) can also form a conductive film for potential reading.

[Brief explanation of the drawing]

FIGS. 1a, b, c, and d are explanatory views of a conventional transcutaneous blood carbon dioxide sensor, and FIGS. 2a, b, c, and d are explanatory views of a sensor according to the present invention. 1,21...H ⁺ ion sensitive glass thin film, 3
...Internal electrolyte, 4...Internal reference electrode, 23...
Conductive film, 24... Lead wire, 6, 27... External reference electrode, 13, 33... Electrolyte, 14, 34...
...Polymer membrane.

Claims (1)

[Claims] 1. A carbon dioxide permeable polymer membrane is placed on the patient's skin, and an electrolyte solution is held on the side of the polymer membrane facing the skin, and carbon dioxide gas passes through the polymer membrane from the skin and diffuses into the electrolyte solution. However, the PH of the electrolyte solution changes according to changes in blood carbon dioxide partial pressure,
In a transcutaneous blood carbon dioxide sensor that detects this PH change as a potential difference between a glass electrode and an external reference electrode, a conductive film is formed on the inner bottom surface of a glass container that has an H ⁺ ion-sensitive glass thin film on the bottom. A transcutaneous blood carbon dioxide sensor that detects as a potential difference between a glass electrode and an external reference electrode.