JPS6157768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved structure of a sensor for a device for percutaneously measuring oxygen concentration or partial pressure in arterial blood.
Knowing the oxygen concentration or partial pressure in blood, particularly in arterial blood, is extremely important in performing treatments such as respiratory management for newborns and critically ill patients who require artificial respiration. Unlike the conventional method of measuring oxygen concentration or partial pressure in arterial blood, which involves drawing blood from the arterial blood vessel and directly measuring it, this method captures oxygen diffused from the blood through the subcutaneous tissue on the skin surface. A transcutaneous oxygen measurement method that allows continuous measurement over time without causing pain to the patient is already known.

The mechanism of the conventional sensor used in this method, as shown in FIG.
A cylindrical silver anode 3 is disposed substantially concentrically with the cathode 1 via a cylindrical silver anode 3, an electrode holder 4 holds both electrodes 1 and 3 in an assembled state, and a cylindrical silver anode 3 is provided so as to cover the tips of the electrodes 1 and 3. The arranged electrode membrane 5, a cylindrical electrode membrane holder 6 that firmly supports the outer circumference of the electrode membrane 5, and an annular packing 7 provided between the electrode membrane holder 6 and the electrode holder 4, The electrode film 5 is composed of a thin electrolyte layer 8 formed between the electrode film 5 and the tip of the electrode, and a heating section main body 10 made of aluminum or the like with good heat conductivity and including a heater 9. The electrode film 5 is hydrophobic. The electrolytic solution is made of a synthetic resin material that is permeable to oxygen gas, and the electrolytic solution is composed of an electrolytic solution containing KCl as a main component, and when this is applied to the skin surface of the subject, the subcutaneous tissue near the contact area of the heating section main body 10 is heated. The oxygen in the subcutaneous tissue is heated by heat transfer from the heater 9 and becomes locally arterialized, and the oxygen in the subcutaneous tissue diffuses from the skin surface, passes through the electrode membrane 5, and further diffuses through the electrolyte layer 8 to reach the cathode 1. At this time, if a voltage necessary for reducing oxygen is applied between the two electrodes, the reduction reaction of oxygen occurs at the cathode 1, and the oxidation reaction of silver occurs at the anode 3. As a result, a voltage between the two electrodes occurs. An electrolytic current flows, and by measuring the current, the oxygen concentration or partial pressure in the subcutaneous tissue and therefore in the arterial blood can be approximately measured.

To assemble such a sensor, first drop an electrolytic solution onto the tip of the electrode, and then cover the electrode film 5 in advance.
After fitting the electrode membrane holder 6 with the electrolytic solution stretched onto the electrode with the electrolyte dripped onto the tip thereof and fitting the heating section main body 10 thereto, the heating section main body 10 and the electrode holder 4 are screwed together. This is done by tightening and fixing with, etc.

In the conventional sensor, tension is applied to the electrode membrane 5 between the upper inner surface of the bottom surface 11 of the heating section main body 10 and the tip of the electrode section, and an electrode chamber is formed between the inner surface of the membrane and the tip of the electrode section. Although the electrolytic solution 8 is held, since the electrode holder 4 is retracted, the capacity of the electrode chamber increases. Therefore, it is necessary to use a large amount of electrolyte so that no air remains in the electrode chamber.

On the other hand, in principle, in the measurement state of this sensor, dissolved oxygen in the electrolytic solution 8 near the cathode 1 is close to zero.

Further, the electrode film 5 needs to be replaced every 4 to 10 days, and each time the sensor must be assembled as described above. There is enough oxygen dissolved in the newly dropped electrolyte to maintain equilibrium with the oxygen partial pressure in the air, and when a voltage is applied between cathode 1 and anode 4 of the sensor, oxygen is reduced at cathode 1. Oxygen decreases as it is consumed, and finally reaches a stable state where the amount of oxygen consumed at the cathode 1 and the amount of oxygen supplied from the outside after passing through the electrode membrane 5 are balanced. Only then can it be measured. Now, since the gap between the electrode film 5 and the electrode tip is very small and the thickness of the electrolyte 8 is very thin, the oxygen concentration in the electrolyte 8 near the cathode should normally decrease quickly and reach a stable state. As mentioned above, in conventional sensors, which have a large space between the electrode holder 4 and the electrode membrane 5 and require a large amount of electrolyte, there is a large amount of dissolved oxygen in the surrounding area. You will have a supply source. Therefore, oxygen is supplied from the periphery in the circumferential direction toward the cathode 1 by diffusion over a long period of time, and it takes a very long time to reach a stable state. Furthermore, because the space is so large, the thickness and amount of the electrolytic solution 8 layer tend to vary for each sensor or for each assembly of the same sensor, making it difficult to obtain consistent sensor performance.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned conventional drawbacks and provide a sensor for measuring transcutaneous blood oxygen concentration that has a shorter stabilization time and has better reproducibility. Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 shows one of the specific examples of the present invention, in which 1 is a cylindrical cathode made of a noble metal such as gold or platinum;
2 is an insulator such as glass or synthetic resin; 3 is a silver anode arranged concentrically with the cathode 1 through the insulator 2; 4 is both electrodes; an electrode holder that holds 1 and 3 in an assembled state; An electrode membrane is stretched to cover the tips of the electrodes 1 and 3; 6 is an electrode membrane holder that firmly supports the outer periphery of the electrode membrane 5; 7 is a seal between the electrode membrane holder 6 and the electrode holder 4; 8 is an electrolytic solution layer held between the tips of the electrodes 1 and 3 and the insulator 2 and the electrode film 6; 10 is the heating unit main body in which the heater 9 is embedded; A bottom surface 11 surrounding the electrodes 1 and 3, the electrode holder 4, and the electrode membrane holder 6.
A hole 12 exposing a part of the electrode film 5 at the center of the hole 12
has.

In the above configuration, the feature of the present invention is the shape of the electrode film holder 6. As shown in Figure 1, the conventional electrode membrane holder has a vertical cross section of “1”.
Although it is cylindrical to form a mold, the one according to the present invention is
As shown in FIG. 2, it has a structure in which the bottom part protrudes toward the center of the circle so that its longitudinal section forms an "L" shape. The thickness of the bottom part is about 0.1 mm thicker than the gap between the lower end surface of the electrode holder 4 and the upper inner surface of the bottom surface 11 of the heating section main body 10, and when assembling the sensor,
When the electrode holder 4 is fastened and fixed to the heating section main body 10 with screws or the like, it is preferable that the lower end surface of the electrode holder 4 and the upper inner surface of the bottom surface 11 of the heating section main body 10 are strongly pressed together. Further, it is preferable that the inner diameter of the bottom surface of the electrode film holder 6 be almost in contact with the outer diameter of the silver anode 3.
The lower end of the silver anode 3 is preferably positioned approximately horizontally with the upper inner surface of the bottom surface 11 of the heating section main body 10. This is so that when the sensor is assembled, the space between the sensor and the electrode membrane 5 does not become too large, and unreasonable tension is not applied to the membrane.

The tip of the electrode part is located on the bottom surface 11 of the heating part main body 10.
It is best to make it almost flush with the bottom of the , but don't worry about this. In the above configuration, when the sensor is assembled, the lower end surface of the electrode holder 4 is in close contact with the electrode membrane holder 6, so that no space is left, and only a small amount of electrolyte needs to be used. The time required for stabilization is therefore greatly reduced, compared to 2 to 4 hours with conventional sensors, to 10 to 30 minutes with the sensor configuration according to the invention. Furthermore, since variations in the spatial portion are reduced, reproducibility from sensor to sensor or from assembly to assembly of the same sensor is also improved.

FIG. 3 shows another embodiment embodying the present invention. In this embodiment, the bottom surface 1 of the heating section main body 10
The upper inner surface of 1 and the lower end surface of silver anode 3 are almost in contact with each other,
Moreover, the inner diameter of the bottom surface 11 is configured so as to be in almost contact with the outer periphery of the insulator 2. In this figure, the lower surface of the bottom surface 11 of the heating section main body 10 is sloped so that the thickness becomes thinner toward the center, so that the skin surface and the surface of the electrode film 5 can easily come into close contact. However, this is not a necessary condition. In this example, the electrode chamber space can be made smaller than in the example shown in FIG. 2, but the stabilization time remains almost the same.

Further, in these embodiments, the circulation of outside air is cut off by the annular gasket 7, but in the present invention, the bottom surface of the electrode membrane holder 6 is connected to the lower end surface of the electrode holder 4 and the upper inner surface of the bottom surface 11 of the heating section main body 10. Since it is compressed by

Although the cathode 1 has a cylindrical shape in all of the above embodiments, the cathode used in the sensor of the present invention is not limited to this, and a cylindrical cathode or a plurality of needle-like cathodes may also be used. It has exactly the same effect.

As described above, by using the configuration according to the present invention, it is possible to eliminate the extra space generated in the electrolyte layer, and it is possible to obtain a sensor with good reproducibility and a short stabilization time.

In addition, in FIGS. 1 to 3, there is close contact between the electrode holder 4 and the heating section main body 10, and between the lower end surface of the electrode membrane holder 6 and the upper inner surface of the bottom surface section 11 of the heating section main body 10 in FIG. Although it is depicted as if there is a gap, this is just to make it easier to see, and they are actually in close contact.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional sensor, and FIGS. 2 and 3 are sectional views of a transcutaneous blood oxygen concentration sensor according to the present invention. In the figure, 1... cathode, 2... cylindrical insulator,
3... Anode, 4... Cylindrical part of the electrode holder,
5... Electrode membrane, 6... Membrane holder, 7... O-ring packing, 8... Electrolyte, 9... Heater,
10... heating portion, 11... plate-like protrusion, 12...
…Skin.

Claims (1)

[Scope of Claims] 1. A cylindrical insulator in which a noble metal negative electrode is buried and its end exposed, an anode arranged concentrically with the cylindrical insulator, and a cylindrical insulator fitted into the anode. An electrode holder consisting of a cylindrical part that fixedly holds an object and an anode, and a base part that continues to one end of the cylindrical part. A gap is provided on the outer periphery of the electrode holder, and a plate-shaped protrusion is provided at one end of the heating unit body made of a good thermal conductor arranged concentrically with the anode, and the plate-shaped protrusion exposes the cylindrical insulator. The other end of the heating part main body is removably fixed to the electrode holder base, and the heating part main body has an opening between the cylindrical part of the electrode holder and the heating part main body. A cylindrical membrane holder fitted in the cavity is arranged, and an electrode membrane is attached to the end face of the membrane holder facing the protrusion of the heating section, and the electrode membrane is filled with an electrolytic solution that moistens the cathode and anode end surfaces. In a sensor for measuring transcutaneous blood oxygen concentration, the end of the membrane holder on the side where the membrane is attached expands toward the center, and the surface on which the electrode membrane is attached to the cylindrical membrane holder. A sensor for transcutaneous blood oxygen concentration measurement characterized by an enlarged view of the sensor. 2. In the sensor for transcutaneous blood oxygen concentration measurement according to item 1, the tip of the expanded portion at the lower end of the membrane holder is expanded until it comes into contact with the anode, and the thickness of the expanded portion is equal to that of the cylindrical lower end of the electrode holder and the heated portion. A sensor for transcutaneous blood oxygen concentration measurement, characterized in that the thickness of the membrane holder is approximately equal to the thickness of the gap between the membrane holder and the protruding part, and the expanded part of the membrane holder is clamped and pressed into these gaps.