A body fluid analysis system and a method for flushing and single-point calibration

Abstract: The present invention relates to e.g. a body fluid analysis system (10) for extracorporeal body fluid analysis with a sensor means (20). The system (10) additionally comprises a container (12), holding at least one flushing liquid, and a first tube (14), connected to the container (12) at a first point (16) and a second point (18) to form a closed system. The sensor means (20) is connected to the first tube (14) and to a second tube (22) for connection to a patient. The body fluid analysis system (10) additionally comprises a pump means (24) connected to the first tube (14) between the container (12) and the sensor means (20).

Description: A body fluid analysis system and a method for flushing and single-point calibration The present invention relates to a body fluid analysis system for extracorporeal body fluid analysis with a sensor means. The present invention also relates to a method for flushing and single-point calibration of a sensor means in a closed, body fluid analysis system. In e.g. extracorporeal analysis of blood with known systems for continuous or semi-continuous blood analyses via a venous or arterial catheter, the heart or an external pump pumps the blood to a sensor outside the body. US-A-5 165 406 describes a body fluid analysis system, wherein after the blood analysis, performed by the sensor, the blood is returned to the body when a flushing liquid is pumped in the opposite direction. After a large part of the blood has been pumped back to the patient, the sensor is flushed with additional flushing liquid to remove any residual blood. This flushing liquid can either be infused into the patient or collected in a special bag. When flushing has been concluded, the flushing liquid, which is then in contact with the sensor, is sometimes used for calibration. Instability and a short operating life are the main disadvantages of these known systems for blood analysis. The plurality of pumps and plurality of bags/containers employed by these known systems are additional disadvantages. The objective of the present invention is to solve the aforementioned problems. This is achieved with a body fluid analysis system for extracorporeal body fluid analysis using a sensor means according to claim 1. The body fluid analysis system according to the present invention comprises a container, holding at least one flushing liquid, and a first tube connected to the container at a first point and a second point to form a closed system. The sensor means is connected to a second tube for connection to a patient. The body fluid analysis system also comprises a pump means connected to the first tube between the first point and the sensor means. One advantage of the body fluid analysis system according to the present invention is that it can be realised at low cost. The system is also easy to operate. An additional advantage is that the system only needs one pump and one container. Moreover, the body fluid analysis system according to the present invention is stable and has a long operating life. In conjunction herewith, it would be advantageous if the body fluid analysis system also comprised a valve means, connected to the first tube between the second point and the sensor means, the pump means and valve means being connected to the first tube on either side of the sensor means. In conjunction herewith, it would be advantageous if the body fluid analysis system operated with counter-pressure in the container. In conjunction herewith, an advantageous embodiment of the body fluid analysis system is achieved when the valve means is arranged by the sensor means and is also connected to the second tube. An additional advantage is achieved in conjunction herewith when flow resistance in the two tubes is optimised by the choice of appropriate tube diameters and/or chokes using the valve means. In conjunction herewith, it would be advantageous if a filter means for filtering out bacteria were connected to the first tube between the pump means and sensor means. An additional advantage in conjunction herewith is achieved when the body fluid analysis system comprises analysis means, connected to the container, for determining contamination of the flushing liquid(s). In conjunction herewith, an advantageous embodiment of the body fluid analysis system is achieved when the analysis means consists of a spectral analysis means or an absorption analysis means. In conjunction herewith, it would be advantageous if the body fluid analysis system additionally contained an indication means, connected to the analysis means, for indicating when contamination of the flushing liquid(s) exceeds a redetermined level. The method, according to the present invention, for flushing and single-point calibration of a sensor means in a closed, body fluid analysis system comprises the following steps: pumping body fluid to the sensor means; analysing the body fluid; pumping flushing liquid from a container through the sensor means in order to flush same; and collecting flushing liquid in the container after the sensor means is flushed. In conjunction herewith, it would be advantageous if the method additionally comprised the following steps: closing a valve means at the same time as the pump means pumps towards the container in order to pump body fluid to the sensor means; keeping the valve means closed, and the pump means inactive while the sensor means analyses body fluids; keeping the valve means closed at the same time as the pump means pumps towards the sensor means in order to return body fluid to the body fluid source; and opening the valve means at the same time as the pump means pumps towards the sensor means in order to pump flushing liquid through the sensor means. An additional advantage is achieved in conjunction herewith when the method additionally comprises the following step: a filter means filters out bacteria in the body fluid or flushing liquid respectively. In conjunction herewith, it would be advantageous if the method additionally comprised the following step: after the flushing stage, flushing liquid is used for single-point calibration of the sensor means. The invention will now be explained in greater detail, referring to attached drawings, in the following description of preferred embodiments of same. FIG. 1 shows a body fluid analysis system according to the present invention; FIG. 2 is a schematic view of an alternative embodiment of the valve means in the body fluid analysis system shown in FIG. 1; and FIG. 3 is a flow chart depicting a method, according to the invention, for flushing and single-point calibration of a sensor means in a closed, body fluid analysis system. FIG. 1 shows a body fluid analysis system 10, according to the present invention, for extracorporeal body fluid analysis. This body fluid analysis system 10 is preferably used for blood analyses and will henceforth be referred to as a blood analysis system, even if other body fluids can also be analysed with this system. The blood analysis system 10 comprises a container 12 holding at least one flushing liquid. The blood analysis system also comprises a first tube 14, connected to the container 12 at two different points, i.e. a first point 16 and a second point 18. The first tube's 14 connection points 16, 18 are arranged so recirculation develops in the system. These points 16, 18 are therefore separated at a specific distance from each other to keep them from opening onto the same point in the container 12. The container 12 and the first tube 14 accordingly form a closed system. The blood analysis system 10 also comprises a sensor means 20, connected to the first tube 14 and to a second tube 22. The second tube 22 connects the system 10 to a patient's blood circulation via a venous or arterial catheter (not shown). The blood analysis system 10 also comprises a pump means 24, connected to the first tube 14 between the container 12 and the sensor means 20, and a valve means 26, connected to the first tube 14 between the container and the sensor means 20. As FIG. 1 shows, the pump means 24 and the valve means 26 are connected to the first tube 14 on either side of the sensor means 20. The pump means 24 is a double-action pump, i.e. it is able to pump in both directions. The valve means 26 can be any kind of ON/OFF valve or the equivalent. The blood analysis system 10 also comprises a filter means 28, connected to the first tube 14 between the pump means 24 and the sensor means 20, for filtering out bacteria in blood or flushing liquid(s) respectively. The blood analysis system 10 shown in FIG. 1 operates with counter-pressure in the container 12. FIG. 1 schematically depicts an analysis means 30, connected to the container 12, for analysing the level of contamination in the flushing liquid(s). This analysis means 30 can consist of e.g. a spectral analysis means or an absorption analysis means. An indication means 32 is, in turn, connected to the analysis means 30 in order to indicate when contamination of the flushing liquid(s) exceeds a predetermined level. The indication can consist of e.g. an acoustic or optical signal or a combination thereof. When the indication means 32 indicates that contamination of the flushing liquid(s) exceeds the predetermined level, the entire container 12 is replaced with a new container, or the flushing liquid(s) in the container 12 is/are replaced. As regards contamination, it should be noted that only traces of residual blood can be carried to the container 12, so the same flushing liquid can be used for a long time. In one version of the body fluid analysis system 10 shown in FIG. 1, the valve means 26 is excluded, and the system's container 12 does not utilise counter-pressure. If the pump means 24 stops or the pump means 24 starts pumping in reverse (towards the point 16), arterial pressure will force blood up into the sensor means 20 for a predetermined period of time. The pump means 24 will then pump hard in the opposite direction (towards the point 18), the pressure then generated exceeding arterial pressure, whereupon blood and flushing liquid are carried both to the patient and through 18 to the container 12. A version with an ON/OFF valve means on the catheter is also possible. When the valve means is open and the pump means operates, some of the flushing liquid flows through the catheter. The sensor means is flushed when the valve means is closed and the pump means operates. When the valve means is open and the pump means is inactive, the heart pumps blood through the sensor means. This naturally assumes that there is no positive pressure in the container. The container 12 can either be flexible and empty of gas or hold just enough air to allow the volume of liquid to increase somewhat without any ill effects. A gas-tight container 12 is needed for blood gas analysis, of course, so the volume of gas (CO 2 in particular) remains constant. FIG. 2 is a schematic view of an alternative embodiment of and location for the valve means in the blood analysis system 10 shown in FIG. 1. This figure only shows the sensor means 20, the first tube 14 and the second tube 22 in the blood analysis system 10, in addition to the valve means 26'. As FIG. 2 shows, the valve means 26' is arranged by the sensor means 20 and is connected to and acts on both the first tube 14 and the second tube 22. As FIG. 2 schematically depicts, the valve means 26' is able to close off either of the tubes 14, 22, leaving the unclosed tube open. FIG. 3 is a flowchart showing a method, according to the invention, for flushing and single-point calibration of a sensor body in a closed, body fluid analysis system, e.g. devised according to FIG. 1. The method will be described below for blood, according to the description in FIG. 1, but any other body fluid can be substituted for blood. The method starts at block 30. A pump means at block 32 pumps blood to the sensor means. The sensor means performs a blood analysis at block 34. The pump means then pumps the blood at block 36 back to the blood source, i.e. the patient. At block 38, the pump means pumps flushing liquid from a container through the sensor means in order to flush same. After the sensor means has been flushed at block 40, flushing liquid is collected in the container. The method then concludes at block 42. Since the flow of flushing liquid is to and from the same container, the flushing liquid, which is initially sterile, becomes increasingly contaminated. But cleaning is still sufficient if the volume of the container is large enough. The method according to the invention also comprises the following steps: A valve means is closed at the same time the pump means pumps towards the container in order to pump blood to the sensor means. The valve means is then closed and the pump means is inactive while the sensor means performs the blood analysis. The valve means is then closed at the same time as the pump means pumps towards the sensor means in order to return blood to the blood source. The valve means is then open at the same time as the pump means pumps towards the sensor means in order to pump flushing liquid through the sensor means. In addition, a filter means filters bacteria out of the blood and flushing liquid respectively. After the flushing step, the flushing liquid is used for single-point calibration of the sensor means. The above description of the method according to the present invention is also a description of the function of the blood analysis system shown in FIG. 1. The invention is not limited to the depicted embodiments. A plurality of variations are possible within the framework of the attached claims.

Claims: A body fluid analysis system (10) for extracorporeal body fluid analysis with a sensor means (20), characterised in that the system comprises a container (12), holding at least one flushing liquid, and a first tube (14), connected to the container (12) at a first point (16) and a second point (18) to form a closed system, the sensor means (20) is connected to the first tube (14), and to a second tube (22), for connection to a patient, and the body fluid analysis system (10) additionally comprises a pump means (24) connected to the first tube (14) between the first point (16) and the sensor means (20). The body fluid analysis system according to claim 1, characterised in that the body fluid analysis system (10) additionally comprises a valve means (26), connected to the first tube (14) between the second point (18) and the sensor means (20), the pump means (24) and the valve means (26) being connected to the first tube (14) on either side of the sensor means (20). The body fluid analysis system (10) according to claim 2, characterised in that a counter-pressure is present in the container (12). The body fluid analysis system (10) according to any of claims 1-3, characterised in that the valve means (26') is arranged by the sensor means (20) and is also connected to the second tube (22). The body fluid analysis system (10) according to any of claims 1-4, characterised in that flow resistance in both tubes (14, 22) are optimised by the appropriate choice of tube diameter and/or chokes with the valve means (26, 26'). The body fluid analysis system (10) according to any of claims 1-5, characterised in that a filter means (28) is connected to the first tube (14) between the pump means (24) and the sensor means (20) to filter out bacteria. The body fluid analysis system (10) according to any of claims 1-6, characterised in that the system additionally comprises an analysis means (30), connected to the container (12), for analysing contamination of the flushing liquid(s). The body fluid analysis system (10) according to claim 7, characterised in that the analysis means (30) consists of a spectral analysis means (30) or an absorption analysis means (30). The body fluid analysis system (10) according to any of claims 7-8, characterised in that the system additionally comprises an indication means (32), connected to the analysis means (30), for indicating when contamination of the flushing liquid(s) exceeds a predetermined level. The method for flushing and single-point calibration of a sensor means (20) in a closed, body fluid analysis system (10) according to any of claims 1-9, said method being characterised by the following steps: Body fluid is pumped to the sensor means (20); The sensor means (20) analyses the body fluid; A pump means (24) pumps the body fluid back to the body fluid source; The pump means (24) pumps flushing liquid from a container (12) through the sensor means (20) in order to flush same; and The flushing liquid is collected in the container (12) after the sensor means (20) has been flushed. A method for flushing and single-point calibration according to claim 10, characterised in that the method additionally comprises the following steps: The pump means (24) pumps body fluid to the sensor means (20); A valve means (26; 26') is closed at the same time as the pump means (24) pumps towards the container (12) in order to pump body fluid to the sensor means (20); The valve means (26; 26') is closed, and the pump means (24) is inactive while the sensor means (20) performs a body fluid analysis; The valve means (26; 26') is closed at the same time as the pump means (24) pumps towards the sensor means (20) in order to pump body fluid back to the body fluid source; and The valve means 26; 26') is open at the same time as the pump means (24) pumps towards the sensor means (20) in order to pump flushing liquid through the sensor means (20). The method for flushing and single-point calibration according to claim 10 or 11, said method additionally characterised by the following step: A filter means (28) filters bacteria out of the body fluid and flushing liquid respectively. The method for flushing and single-point calibration according to any of claims 10-12, characterised in that the method additionally comprises the following step: Flushing liquid is used after the flushing step for single-point calibration of the sensor means (29).

Inventors: VON BAHR PONTUS, VON BAHR, PONTUS
Applicants: SIEMENS ELEMA AB, SIEMENS-ELEMA AB
Application year: 1998
Main classification: G01N33
IPC codes: A61B5, G01N33