DE3234172A1 - Surface-mounted probe for determining pO2 histograms - Google Patents

Abstract

A surface-mounted probe for determining pO2 histograms by means of a plurality of electrodes which are arranged in an insulating body and end in a mounting surface is characterised by the construction of the electrodes as films on insulating fibres, which arrangements are embedded in an insulating manner in a common cast (potted) member. This produces advantages with respect to production as well as, in particular, weight and the large number of electrodes which can be provided. It is preferable for the electrode front faces to be situated at the bottom of a recessed channel whose depth is of the order of magnitude of the thickness of the electrode film. This results in an improved diffusion geometry and in a low sensitivity of the measuring signal to the mounting pressure. The probe can be constructed in a design which is outstandingly capable of sterilisation by using a diaphragm which is directly applied and preferably arranged in the recessed channel, or also as a Clark type probe with an electrolyte chamber below the diaphragm. The latter construction is distinguished by a short run-in period and by long-term stability. The pressure sensitivity specific to this type is greatly reduced by the geometry of the recessed channel.

Description

Attachment probe for the determination of pO2- [iistograms.

The invention relates to a placement probe in the preamble of the claim 1 mentioned Art.

Such attachment probes are in the prior art in one embodiment known, which is described, among other things, in the book "Measurement of the tissue oxygen pressure with patients ", Verlag Gerhard Witzstrock, 1981, on pages 66 (illustration) as well as page 16, right column above (information on construction).

Attachment probes can be used to create pO2 histograms on tissue surfaces determine. The probe is placed with the contact surface on the exposed tissue surface (e.g.

Muscle surface). The measuring points then determine via oxygen diffusion the oxygen pressure (PO2) in the underlying tissue. From the pO2 measured values obtained the histogram is created after statistical calculation, the statements about the Allows oxygen supply to the tissue.

The well-known set-up probe construction has as an elec- to trot Platinum wires that are fused in a glass insulating body. From this it follows a number of significant disadvantages.

First of all, the production of such probes has disadvantages. An extremely skillful glassblower is required to create it. Nevertheless, it is only rarely possible to provide more than eight platinum wires in a probe. In the case of a one-time placement process, only a few measuring locations can therefore be recorded. In addition a pO2 histogram for statistical reasons at least about 100 measurement locations must be made more than ten times to create a complete histogram be put on in different positions.

The known probe construction is relatively light, compressed but, when it is placed on the surface of the organ, the underlying tissue, whereby the oxygen supply would be falsified, if not according to the cited literature Page 46 (illustration) brackets would be provided with which the well-known probe is held relieved of pressure on the surface. When repositioning more than once are consequently considerable changeover times are required. The measurement on the (exposed!) Organ takes time therefore very long.

In the known probe, there is also one surrounding the insulating body Attachment ring provided, which reduces the specific surface load. On moving Organ surfaces, e.g. B. the beating heart, are because of the additional mass forces very large contact surfaces required.

The object of the present invention is therefore to provide a placement probe of the type mentioned to create the determination with simple handling precise histograms within a short period of time.

This object is achieved according to the invention with the features of the marking part of claim 1 solved.

The electrode structure used according to the invention with insulating fibers applied metal film is known from the field of puncture probes, where a Each probe has only one such electrode. According to the invention are such Electrodes cast in an insulating body made of highly insulating potting compound. This results in the possibility of a much higher integration density. It can easily 50 or even 100 electrodes in a relatively narrow area of for example, be placed under a square centimeter. This reduces the weight of the probe is so great that this probe is not affected by compression of the organ can be placed on its surface. Furthermore, with one-off The measured values for a histogram are set up or with only very few set-up processes can be obtained. The sum of these characteristics makes the time to determine one The complete itistogram is considerably shortened compared to the state of the art. There the probe is much lighter, considerably smaller contact surfaces are possible, whereby the required preparation surface is especially available on moving organs can be reduced, for example in the heart from approx. 50 to approx.

2 1 cm. The electrode arrangement that has proven itself in the field of puncture probes also offers the possibility of better measurement stability, which continues to be a overall significantly superior construction results.

With the features of claim 2 there is also one below Use of manufacturing technology that has proven itself in electronics is particularly easy and inexpensive to manufacture, in particular inexpensive contactable construction. The highly flexible multi-conductor film used can, for example, only be 25 μm thick and thus extreme be light. On special holding devices for relief the cable tensile forces can be dispensed with. The rigid arrangement of the conductor tracks on the conductor foil also enables a high level of insensitivity to microphones.

With the features of claim 3 there is also a construction, in which the annular electrode front surface according to the invention of each electrode is arranged in a recess at the bottom of a recess channel opposite the contact surface, which is obtained in a simple manner, for example, by etching away the electrode metal can be.

In this design, the electrode front surface is above the recess channel connected with an essentially one-dimensional diffusion geometry with the contact surface.

This results in advantages with regard to the freedom from stirring effects as well as the speed of response of the probe to changes in p02. From in the present The reduction in pressure sensitivity is of particular interest Measured value display. A major problem with attachment probes is influencing the pressure the contact surface by the contact force. The diffusion geometry changes in the process on the contact surface, for example by compressing or shifting the space under the diffusion membrane. Play with the electrodes in the contact area these geometric changes occur in the immediate vicinity of the electrodes. Above a geometrically determined change in the diffusion distances results Changes in the measured value that falsify it. In the arrangement according to the invention with recess channel the diffusion resistance predominates in this, so that above the contact surface occurring changes in the diffusion geometry are of little influence and the Falsify the measured value only a little.

With the features of claim 4 there is a construction, in which the depth of the recess channel is optimized in terms of its aforementioned properties is.

With the features of claim 5, a construction is specified, in which the membrane only fills the recess channel and is therefore protected against the effects of pressure is. This construction is characterized by its particular pressure independence.

At this point it should be noted that the probe here generic type essentially on the display parallelism of the individual measuring points it is important that these are all the same when PO2 is constant over the contact area Deliver measured value. This task is already carried out with the features of claim 1 the formation of the electrodes as letallfilme advantageously solved, since these in the Production can be brought to the same cross-section in a simple manner. With the features relating to the formation of a recess channel, there is one further significant improvement of the parallelism problem, since during manufacture of the recess, e.g. B. by etching, the surfaces are evened out and substantially can be reduced to the cross-sectional area of the metal film. The recess geometry can be achieved by making the metal films with the same cross-section as well as by Common etching to the same depth for all measuring points with a high degree of correspondence getting produced. According to claim 5, the membrane material is also used at all measuring points applied exactly the same, which means that there are completely identical and measured values overall Result in measuring points. This is especially true if according to the feature of the claim 6 the membrane is only arranged in the recess channels, for example after application on the contact surface and penetration into the recess channels from the Contact surface is removed evenly.

According to claims 7 to 10, the probe according to the invention is advantageous designed as a Clark-type probe.

The Clark probe is principally characterized by the fact that under the Diffusion membrane, so an electrolyte is provided between this and the electrodes is. With this type of probe, the membrane does not have to be permeable to water or electrolyte, but only be permeable to oxygen diffusion. This already results in one greater freedom from drift, as swelling equilibria do not have to be waited for. Furthermore, the provision of an electrolyte supply results in a special long-term constancy. The disadvantages of this construction should not go unmentioned, however. These lie in the fact that the membrane floating on liquid electrolyte is principally pressure-sensitive is. The sterility of the probe, which is important in the present clinical application furthermore leads to disadvantages, since a Clark-type probe is required for sterilization Fully assembled vacuum does not withstand.

With the features of claim 8 there is a construction, in which the pressure sensitivity of the Clark probe is significantly reduced, since the Electrolyte chambers are pressure-protected in the recess channels.

According to the features of claim 9, an almost complete result construction independent of pressure influences.

Finally, with the features of claim 10, there is a construction, in which the electrolyte chambers have a pressure-resistant, electrolyte-permeable support body are filled, the electrolyte chambers with largely any geometric design keeps it free from the effects of pressure. This probe can be sterilized ready for measurement and has nevertheless has the advantages inherent in the Clark type.

In the drawings the invention is exemplary and schematic shown. There are shown: FIG. 1 a perspective view of a device according to the invention Attachment probe in a schematic representation and with an enlarged section of a Measuring point, FIG. 2 shows the partially sectioned representation of a complete embodiment the probe with connecting cable and FIGS. 3a to d enlarged sectional views of different Embodiments of the measuring point.

In Fig. 1 is the basic construction of the probe according to the invention shown schematically. In an insulating body 1 is a number of electrodes, arranged penetrating the body, the in measuring points 2 with their front surfaces in a contact surface 3 are exposed.

One of the measuring points within the circle 4 is in an enlarged section shown partially sectioned with very high magnification.

The measuring points are identical to one another and each consist of an insulating fiber 5, e.g. B. a quartz thread, on its approximately cylindrical surface a metal film 6 is applied. The metal film is made of a suitable material, for example Gold, chosen that is suitable for the polarographic determination of oxygen. The front surface 7 of the film 6 forming the electrode therefore forms a circular ring whose thickness and thus the front surface cross-section are good from a manufacturing point of view are controllable.

For example, thirty-two measuring points are provided in which each the insulating fiber 5 consists of an approximately 20 um thick quartz thread and wherein the metal film 6 is designed as a cold film approximately 1500 Å thick. The diameter with any geometry of the contact surface 3 (e.g. circular or rectangular) Formable insulating body 1 can for example be 8 mm with a thickness of the insulating body 1 perpendicular to the contact surface 3 of, for example, 3 mm.

The electrodes can be individually for example as sections of endless Vaporized quartz fibers are made, bundled and used as an insulating body Casting compound are poured. Highly insulating synthetic resin is suitable as a casting compound, possibly with admixtures that improve the insulation resistance.

The contact surface 3 can after production of the insulating body 1 through the potting compound and the electrode assemblies are ground flat through it.

According to FIG. 1, the front surface 7 of the electrode films is advantageous 6 arranged recessed under the contact surface 3, like the enlarged section Fig. 1 shows. It forms a recess channel 8, which is preferably a Has depth on the order of the film thickness, for example 2.5 times the Film thickness. The latter level has proven to be advantageous.

The recess channel 8 can after completion of the, for example, ground Contact surface 3 can advantageously be obtained by etching the metal film 6. Since the other materials are not etched, a recess channel 8 forms with the width the metal film thickness and the desired depth, which with the etching time for all Measuring points is adjustable evenly. This results under the measuring points constant geometric conditions with regard to the recess channel 8 and the front surface 7.

The recess channel 8 has the advantage of an additional diffusion resistance between its opening in the contact surface 3 and the polarographically active front surface 7 of the electrode film 6. There is essentially one-dimensional diffusion in the channel instead, which is free of external influences on the contact surface 3.

The additional diffusion resistance in the recess channel 8 also reduces the polarographic current and increases the freedom from stirring effects of the measuring points and allows at the same time an optimization of the response speed of the measuring points to p02 changes.

The front surfaces 7 of the electrodes have to be chemically aggressive biological medium at the measurement site covered with a membrane not shown in FIG that can be stretched over the surface, for example, and oxygen and optionally water permeates, but interfering substances such as, for example Protein, keep away.

Fig. 2 shows a specific embodiment of the probe in a slightly enlarged Scale. In the sectional view it can be seen that the electrode films 6 of the measuring points 2 in the contact surface, starting with the insulating body made of potting compound 1 to the opposite surface. This area is a highly flexible one Conductor foil 9 and is attached, for example, by gluing. On her that Insulating body 1 adjacent surface, the conductor foil 9 is provided with conductor tracks 10, which lead to contact points 11 at which the metal films 6 in a suitable Technology are contacted. The conductor tracks 10 run on the z. B. 25 µm thick Conductor foil 9, which also serves as a highly flexible connection cable, to the inputs of a measuring amplifier not shown. Outside the insulating body 1 is the conductor tracks The load-bearing side of the conductor foil 9 is covered with an insulating layer 12.

Via the contact surface of the insulating body (located at the bottom in FIG. 2) 1, a membrane 13 is drawn, which is held at the edge with clamping rings 14. Depending on Embodiment of the probe, the membrane can also, for example, adhesively attached be, for which no edge bracket is necessary.

In the illustrated embodiment of FIG. 2, a probe is from Clark type shown. This probe construction is principally characterized by this from that under the membrane 13, that is, between this and the electrode front surfaces 7 an electrolyte is provided. This cannot be seen on the scale in FIG. It is provided as a film on the contact surface 3 under the membrane 13. On the edge The contact surface is an electrolyte storage space 15 with a pressure relief hole 16 arranged in an anode ring 17. The anode ring 17 is via a conductor track 18 polarized. The clamping ring arrangement is screwed onto the silver ring 17 via a thread 19.

In FIGS. 3a to 3d there are four different embodiments of the measuring points 2 shown, in a greatly enlarged sectional view through the measuring point. The measuring points shown are each in greater number and an identical design according to FIG. 1 or 2 in an insulating body 1.

Common to the illustrated embodiments is the structure of the electrodes forming individual measuring points.

These each consist of a quartz fiber 5 on which an electrode metal film 6 is applied. In a further development of the schematic arrangement according to FIG A chromium film 20 of approximately 800 A, for example, is arranged on the electrode film 6. An insulating film 21 is provided thereover. The chromium film has chemical properties when attacked aggressive, self-healing and self-healing substances during the polarographic process properties that prevent splitting. The additional insulating film 21 improves the insulation of the measuring point with respect to the insulating body 1. The insulating film 21 can for example, consist of tantalum oxide of approx. 10000 A thickness.

What the illustrated embodiments have in common is the one already shown in FIG. 1 explained recess channel 8, at the bottom of which the polarographically active front surface 7 of the electrode film 6 is exposed towards the contact surface 3.

In Fig. 3a a measuring point is shown which is not of the Clark type is. Since the polarographic current on the very small front surfaces 7 of the electrodes 6, due to the small frontal area and the diffusion resistance of the recess channel is very low, Clark-type training is not required. It is enough Covering the electrodes with an oxygen and water permeable membrane, which can for example consist of phenolic or acrylic resins. Preferably is this according to the embodiment of FIG. 3 only in the recess channel as this filling Diaphragm ring 22 is provided. This diaphragm ring is from external influences, in particular Protected against the effects of pressure when the contact surface is placed on the organ surface. The desired diffusion resistance of the membrane is determined by the arrangement in the recess channel enlarged. In another embodiment, not shown, the membrane can both in the Recess channel as well as the contact surface 3 can be formed.

The probe of the embodiment of Fig. 3a is characterized by high Uniformity of the measuring points from one another as well as the fact that they approximate Has solid properties, so largely insensitive to the effects of pressure is. Furthermore, it is also resistant to vacuum and temperature and thus subsides sterilize common sterilization methods. Any assembly operations before Place completely omitted.

In Fig. 3b the measuring point of a Clark-type probe is shown which corresponds for example to the construction of FIG. Under a suitable, for example made of Teflon membrane 23, an electrolyte space 24 is provided, which as a gap under the membrane over the contact surface and into the recess channel extends.

Such a probe has the typical advantages of the Clark probe, viz low drift, as there are no swelling processes in the membrane. The disadvantage is that such a probe can not be exposed to the vacuum and therefore after the Sterilization mounted on site, i.e. provided with electrolyte and with the membrane must be covered. The strong pressure sensitivity observed per se in Clark-type probes is greatly reduced by the inventive provision of the recess channel. Geometric Changes when the membrane 23 is pressed in only have an effect in the area of the contact surface the end. Geometric changes produced there that lead to changes in the diffusion paths lead, have little effect, because the diffusion resistance in the recess channel, the remains constant, predominates.

Fig. 3c shows a further embodiment of the probe that approximately corresponds to the Clark type. A water-permeable membrane 25 is used, which corresponds to the material type according to FIG. 3a, for example made of phenol or Acrylic resin. Below this, however, is an electrolyte-filled, electrolyte-permeable one Support grid 26 is provided, which consists for example of poured pore material. This is firmly connected to the contact surface 3, so that again approximately Solid-state properties in terms of pressure sensitivity and good vacuum sterilizability result. By providing an electrolyte space (electrolyte-filled support grid 26) result in Clark-type properties at the same time. This type of probe represents a excellent compromise with the advantage of a relatively short line time (similar to Clark type), low pressure dependency, relatively wobbly drift and good sterilizability.

In Fig. 3d again a probe according to the Clark type is shown, in which the recess channel is designed as an electrolyte ring chamber 27. Via the contact surface 3, a support grid film 28 is stretched together with a Teflon membrane 29. the Membranes can be kept in stock as double membranes, for example.

So electrolyte fulfills the ring channel and the support grid 28 as well possibly also a small capillary gap between the support grid film 28 and the contact surface 3.

The construction of Fig. 3d also represents a compromise type, however predominantly with Clark-type properties. The benefits of the Clark-type-specific, fast break-in period and long-term stability.

However, sterile assembly on site is required. lich. By providing the support grid film 28, however, it is completely insensitive to pressure in practice given.

The following applies to the probe structure shown in FIG. 2 noted: The conductor foil 9 can be extremely thin, e.g. B.

25 pm. The insulating layer 12 can also be made correspondingly thin be. The cable connection to the probe head is therefore extremely light and highly flexible. Interfering forces originating from the cable are completely eliminated by this training. Holding devices that hold the cable or keep the probe head free of cable tension influences are dispensable.

Compared to known arrangements there is also the advantage that due to the fixed position of the conductor tracks 10 on the film 9 sensitivity to microphonism is completely eliminated.

To shield against interfering radiation, the entire system shown in Fig. 2 arrangement shown (of course excluding the membrane 13) with be provided external shielding, for example from an externally applied Conductor film.

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Claims (10)

CLAIMS: Attachment probe for the determination of pO2 histograms on surfaces living organs, with several distributed over the contact surface, to measuring amplifier connected polarographic measuring points, in each of which the front surfaces a common insulating body penetrating electrodes from a diffusion-permeable Membrane are arranged covered, characterized in that the electrodes as metal films (6) arranged on each insulating fiber (5) are formed, which to the membrane (22, 23, 25, 29) with an annular surface (7) expose that the insulating body (1) consists of highly insulating potting compound and that the electrodes are connected to the amplifier arrangement via flexible cables (9). 2. Probe according to claim 1, characterized in that the in one the contact surface (3) of the Isolierkör pers (1) facing away from the surface ending in metal films (6) there with conductor tracks (10, 11) of a circuit board adjacent to the insulating body (9) are contacted, the circuit board being designed as a highly flexible film is, which serves as a multi-conductor connection cable (9, 12). 3. Probe according to one of the preceding claims, characterized in that that the front surfaces (7) of the electrode films (6) opposite the contact surface (3) recessed at the bottom of a recess channel (8). 4. Probe according to claim 3, characterized in that the recess depth is on the order of the film thickness and is preferably about 2.5 times its thickness. 5. Probe according to one of claims 3 or 4, characterized in that that the membrane (22) fills the recess channel (8). 6. Probe according to claim 5, characterized in that the membrane (22) is arranged only in the recess channel (8). 7. Clark probe according to one of claims 1 to 4, characterized in that that between membrane (23, 25, 29) and electrode front surface (7) an electrolyte space (24, 26, 27, 28) is arranged. 8. Probe according to claim 7, characterized in that the recess channel is designed as an electrolyte space (26, 27). 9. Probe according to claim 8, characterized in that only the recess channel is designed as an electrolyte space (27), the membrane (28, 29) of the contact surface (3) of the insulating body (1) is in direct contact. 10. Probe according to one of claims 7 to 9, characterized in that that the electrolyte chambers with an electrolyte-permeable, pressure-resistant support body (26, 28) are filled.