Multi-sensor device

Abstract

In a multi-sensor device for a medical apparatus at least one first sensor unit and at least one second sensor unit are arranged at a fluid-guiding line connection along which the sensor units detect at least one variable from a flowing fluid in predetermined proximity to each other in such manner that predetermined signal portions occur and are detectable practically simultaneously in outputs of each of the first and second sensor units. In a method for defining a proximity in said multi-sensor device, positions of the individual sensors are varied in the multi-sensor device and the occurrence of predetermined signal portions is detected in at least two signals detected by the individual sensors, and those positions at which the predetermined signal portions occur practically simultaneously are defined as positions of the proximity.

Claims

1. A multi-sensor device for a medical apparatus, comprising: a first sensor unit; and at least one other sensor unit, the first sensor unit and the at least one other sensor unit arranged at a fluid-guiding line connection along which the first and the at least one other sensor units detect at least one variable from a flowing fluid in predetermined proximity to each sensor unit; wherein a maximum distance between the first sensor unit and the at least one other sensor unit is determined by a predetermined maximum time delay between the detection of a first signal change of a first signal of the first sensor unit and the detection of another signal change of another signal of the at least one other sensor unit, the other signal change corresponding to the first signal change at a predetermined flow rate through the fluid-guiding line connection; and wherein proximity of the first sensor unit and of the at least one other sensor unit is predetermined in such manner that, at the predetermined flow rate, in the first signal of the first sensor unit and in the other signal of the at least one other sensor unit corresponding signal changes occur without time shift when both signals are simultaneously detected in parallel within the predetermined maximum time delay.

2. The multi-sensor device according to claim 1, wherein the medical apparatus is a machine for extracorporeal blood treatment; the first sensor unit is a non-optical sensor unit; the at least one other sensor unit is an optical sensor unit; and the fluid-guiding line connection is a drain line for used dialysis fluid of the machine for extracorporeal blood treatment.

3. The multi-sensor device according to claim 2, further comprising: a housing unit arranged at the drain line for used dialysis fluid to accommodate the at least one non-optical sensor unit and the at least one other optical sensor unit in the predetermined proximity to each other; wherein the non-optical sensor unit is arranged to detect and to output the other signal from the used dialysis fluid flowing in the drain line for used dialysis fluid; and wherein the proximity of the first sensor unit and of the at least one other sensor unit along the drain line for used dialysis fluid is predetermined such that in the first signal of the first sensor unit and in the other signal of the at least one other sensor unit the corresponding signal portions occur without time shift when both signals are simultaneously detected in parallel.

4. The multi-sensor device according to claim 1, wherein: the first sensor unit includes a conductivity cell for determining conductivity of used dialysis fluid and a temperature probe for measuring a temperature of used dialysis fluid and for temperature compensation of the conductivity cell; and the at least one other sensor unit includes at least one optical sensor in the form of at least one photodiode for determining an absorption characteristic of the used dialysis fluid.

5. The multi-sensor device according to claim 4, wherein the conductivity cell and the temperature probe are combined and installed in a joint unit within the multi-sensor device.

6. The multi-sensor device according to claim 4, wherein a direct vicinity of the temperature probe to the optical sensor is predetermined such that a temperature detected by the temperature probe can be used to correct temperature-dependent effects within the optical sensor.

7. The multi-sensor device according to claim 1, wherein the predetermined proximity is defined such that within the multi-sensor device the respective sensor units are arranged and accommodated among each other free from tube connections.

8. The multi-sensor device according to claim 4, wherein the optical sensor is arranged directly upstream of the conductivity cell or directly downstream of the temperature probe.

9. The multi-sensor device according to claim 4, wherein the optical sensor is arranged to be combined with a blood leakage detector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings are the following figures:

(2) FIG. 1 shows a schematic view of a multi-sensor device according to an example embodiment; and

(3) FIG. 2 shows a schematic view which, on the left side, shows a time curve of two signals of a first sensor and of a second sensor whose spatial arrangement results in time shift between extremums of the individual sensor signals, and on the right side shows a time curve of two signals of the first and second sensors in proximity of the sensors such that extremums of the individual sensor signals will appear simultaneously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) In conformity with FIG. 1 and as shown in simplified form in the same, within the scope of extracorporeal blood treatment blood is withdrawn from a patient 1 via an arterial tubing system 2 with a delivery unit 3 and is delivered to a dialyzer 4. In the dialyzer 4 the blood of the patient is freed from substances usually to be eliminated with the urine and from excess water. Subsequently, the purified blood is returned to the patient via a venous tubing system 5. Withdrawal and return of the blood via a joint cannula is equally imaginable.

(5) It is noted that in FIG. 1 components and parts known per se of a machine for extracorporeal blood treatment used for a detailed description in this example embodiment, such as units for proportioning the dialysis fluid or for balancing or other components which take over basic functions of a common machine for extracorporeal blood treatment, are not illustrated and will not be described herein.

(6) In the dialyzer 4 hollow fiber capillaries (not shown) including a semi-permeable membrane (not shown) are provided. The so-called dialysis fluid which, on the one hand, absorbs substances usually to be eliminated with the urine and excess water from the blood and, on the other hand, gives off especially hydrogen carbonate for treating an acidosis of the patient 1 flows around the capillaries.

(7) The dialysis fluid flows through a feed line 6 into the dialyzer 4. An outlet for used dialysis fluid 4a of the dialyzer 4 opens into a drain line 7 in the further course of which at least one non-optical sensor 8, 9 and at least one optical sensor 10 are arranged.

(8) In the present example embodiment, the at least one non-optical sensor 8, 9 comprises for example a conductivity cell 8 for determining the conductivity of used dialysis fluid and a temperature probe 9 for measuring the temperature of used dialysis fluid and for temperature compensation of the conductivity cell 8.

(9) The at least one optical sensor 10 in the present example embodiment comprises for example at least one photodiode and preferably two photodetectors and is used to determine an absorption characteristic of the used dialysis fluid.

(10) Of preference, this is the absorbance or extinction which can be measured when the used dialysis fluid includes substances which are absorbing light. The photodiode of the optical sensor 10 for this purpose emits narrow-band light in the UV range having wavelengths preferably between 200 and 350 nm. Further preferred, light having a peak wavelength of from 275 to 295 nm is emitted. The invention is not limited to said concrete numbers of sensors and wavelengths of light used. The invention also comprises the emission and detection of plural wavelengths.

(11) As an alternative, the optical sensor 10 may be arranged to emit light for exciting optically active substances and to subsequently measure fluorescent emissions. Further alternatively, the optical sensor 10 may be based on a laser-induced plasma spectroscopy.

(12) As is shown in greater detail in FIG. 1, in the present example embodiment of the multi-sensor device the afore-mentioned sensors 8, 9 and 10 are accommodated in a common housing or a housing unit 11 and are arranged so that they are in direct vicinity to each other and preferably form a compact unit. Within the multi-sensor device specifically the conductivity cell 8 and the temperature probe 9 may further be combined and installed to form a joint unit.

(13) In the present example embodiment, an inner diameter of the drain line 7 may be, for example, 5 mm and used dialysis fluid may flow through said drain line 7 at a flow of e.g. 500 ml/min. It is noted that the afore-mentioned values are practical values from a field realized and/or adjustable in a known dialysis machine. For example, at a known dialysis machine flows of fresh and, respectively, used dialysis fluid between 300 ml/min or less and 800 ml/min can be adjusted. A flow of 500 ml/min in this respect constitutes a mean value in the setting range of the known dialysis machine.

(14) In the present embodiment, moreover a maximum time delay of e.g. 1 second concerning or between the signals is to be tolerable at a first sensor (for example sensor 8) and at a second sensor (for example sensor 10). Assuming an average flow of 500 ml/min in the drain line 7, a maximum distance between the first and second sensors is calculated to be 424 mm. It is noted that the maximum distance increases with an increasing flow rate through the drain line 7 and at a flow of 800 ml/min is about 679 mm.

(15) Consequently, the direct vicinity according to the invention is given by the time delay maximally to be tolerated (e.g. 1 second) between signals of two sensors (a first sensor and a second sensor) to be considered. In other words, two sensors are provided in direct vicinity to each other when the time delay between the signals thereof does not amount to more than approx. 1 second.

(16) In this example embodiment, therefore preferably a maximum distance between a first sensor (e.g. sensor 8) and a n-th sensor (e.g. sensor 10) of 680 mm (corresponding to the highest adjustable flow rate of 800 ml/min in this case) is defined. Between the first sensor and the n-th sensor then (n-2) further sensors (e.g. sensor 9) may be arranged, alternatively for example especially also similar and thus multiply arranged sensors which in this case for lower flow rates ensure the condition of direct vicinity while observing the time criterion, as described before. Advantageously, said n sensors are arranged so closely to each other that long tube connections are omitted.

(17) It is understood that the invention is not limited to the numerical values and/or setting ranges afore-stated by way of example, but that appropriate ratios, relations and orders of magnitude will result also for other diameters of the drain line 7 and/or adjustable flows and/or distances and, respectively, time conditions.

(18) The multi-sensor device according to the present example embodiment including the individual sensors 8, 9 and 10 in direct vicinity to each other enables reliable compensation of an effect of temperature and, respectively, impact of temperature on the conductivity measurement without having to take temperature losses or time-shifted signals into account.

(19) Due to the direct and immediate vicinity of the temperature probe 9 to the optical sensor 10, moreover advantageously the (detected) temperature can be used to correct possible temperature-dependent effects in the optical sensor 10.

(20) The arrangement of the sensors 8, 9 and 10 in proximity to each other moreover advantageously minimizes effects occurring especially due to flow-dependent time-shifted signals or signal changes. In this way, signals or signal changes can be detected, within the scope according to the invention, quasi simultaneously by the respective sensors 8, 9 and 10, and the flow of used dialysis fluid flowing through the drain line 7 may remain irrelevant, i.e. it plays no further role as regards the signals to be detected and to be processed. This is of interest especially when methods for determining relevant parameters are based on approaches of sensor merger and approaches of sensor combination.

(21) For qualitative illustration of these facts, in the following FIG. 2 will be referred to. On the left and on the right in FIG. 2 a time curve of two signals is shown. A first signal 1 originates from a first sensor (for example the non-optical sensor 8, 9 in the present example embodiment) and a second signal 2 originates from a second sensor (for example the optical sensor 10 in the present example embodiment). Accordingly, it is understood that the first signal 1 may also originate from the optical sensor 10 and the second signal 2 may also originate from the non-optical sensor 8, 9.

(22) As is shown on the left side in FIG. 2 and as comparative example of a known arrangement, after detection time of e.g. about 30 s a signal change of the first signal 1 is detected by the first sensor. By way of example, a maximum or extremum of the first signal 1 occurring after about 33 s is to be of interest. A minimum or extremum in the second signal 2 of the second sensor occurs, related to the maximum of the first signal 1, only 4 s later, i.e. the two extremums of the first signal 1 and of the second signal 2 are detected shifted in time. When the flow rate and the volume between the first and second sensors are known, the time shift can be calculated therefrom. Both extremums then can be merged and unified or combined.

(23) On the right side in FIG. 2, in conformity with the multi-sensor device according to the present embodiment equally two signal curves are shown. In this case, too, for example after a detection time of approx. 30 s a signal change of the first signal 1 is detected by the first sensor, and by way of example a maximum or extremum of the first signal 1 occurring after about 33 s is to be of interest. Directly evident, according to the example embodiment a minimum or extremum occurs in the second signal 2 of the second sensor related to the maximum of the first signal 1 practically simultaneously with the maximum of the first signal 1, i.e. the two extremums of the first signal 1 and the second signal 2 are detected practically simultaneously. The knowledge of flow rates and volumes is not required, as both extremums appear simultaneously and thus calculation of a time shift between the signals and merger of the extremums of the signals may be dropped.

(24) Consequently, it is possible for example in a development phase of the multi-sensor device to detect, by way of a criterion such as drop of shift calculation with sufficiently simultaneous occurrence of sensor signal extremums by variation of sensor positions of the individual sensors in the multi-sensor device, the occurrence of extremums in at least two signals detected by sensors of the multi-sensor device and then to define those sensor positions at which the extremums occur practically or, respectively, sufficiently simultaneously as being spatially close to each other according to the invention.

(25) Another advantage of the arrangement spatially close according to the invention consists in the fact that the arrangement of the sensors in direct vicinity to each other enables to dispense with tube connections among each other. Tube connections usually require tube olives having appropriate length at the individual components so as to be able to safely arrange the tubes there. Such connections also bear the risk of dead spaces being formed, however, which are difficult to disinfect.

(26) For three sensors according to the present example embodiment (conductivity cell 8, temperature sensor 9 and optical sensor 10) six options of arranging the same in the flow direction within the drain line 7 are resulting. However, it may be advantageous not to separate the conductivity cell 8 and the temperature probe 9 from each other so that they are located directly next to each other in any case and to dispose the optical sensor 10 either directly upstream of the conductivity cell 8 or directly downstream of the temperature probe 9. Of preference, the optical sensor 10 is disposed next to the temperature probe 9, as sensors the data of which are to be merged should advantageously be positioned in direct vicinity to each other.

(27) As described in the foregoing in conformity with the present example embodiment, the individual sensors 8, 9 and 10 accommodated in the housing unit 11 may form an optical sensor for determining extinction and a temperature-compensating or temperature-compensated conductivity cell. However, the invention is not limited to that, but moreover even further sensors may be accommodated.

(28) Dialysis machines, for example, usually have an optical sensor for detecting a possible blood leakage in the drain line 7. Therefore, preferably such blood leakage detector and the optical sensor 10 may be combined with each other, as both sensors also include already related component parts (e.g. light sources, photodetectors and the like).

(29) As described in the foregoing, in a multi-sensor device for a medical apparatus at least one first sensor unit 8, 9 and at least one second sensor unit 10 are disposed on a fluid-guiding line connection 7 along which the sensor units 8, 9, 10 detect at least one variable from a flowing fluid in predetermined proximity to each other in such manner that predetermined signal portions occur and are detectable practically simultaneously in outputs of each of the first and second sensor units. In a method for defining a proximity in such multi-sensor device, positions of the individual sensors 8, 9, 10 are varied in the multi-sensor device and the occurrence of predetermined signal portions is detected in at least two signals detected by the individual sensors 8, 9, 10, and those positions at which the predetermined signal portions occur practically simultaneously are defined as positions of proximity.

(30) It is understood that the invention is not limited to the afore-described example embodiment, but that changes, modifications and equivalent arrangements within the scope of protection as defined according to the claims are equally comprised by the invention.