A DETECTOR SYSTEM FOR THE CHECKING OF A FLUID TUBE CONNECTABLE TO A MONITOR

Abstract: A detector system for the checking of a fluid tube (1) which is connectable to a monitor (12), by means of which it is intended to control the flow within the tube (1), comprising a transmitter (15) and a receiver (16) respectively for a signal or beam of preferably infrared light, and means (17) for the conducting of this beam through the tube (1) when the same is assembled on the monitor. The system in accordance with the invention is character­ ized principally in that it is adapted so as to be able to sense on the one hand whether the tube (1) is assembled in the correct position, on the other hand whether it is filled or not. The system in accordance with the invention is intended in particular to be applied to a system for the extracorporeal treatment of blood, whereby the said tube may be filled with either blood or priming fluid. Special advantages can be gained through the invention, particularly during the so-called priming phase, when especially certain false alarms can be avoided.

Description: TECHNICAL FIELD The present invention relates to a detector system for the checking of a fluid tube which is connectable to a monitor by means of which it is intended to control the flow within the tube, comprising a transmitter and receiver for a light beam of preferably infrared light and means for the conducting of this beam through the tube, when the same is assembled on the monitor, applied to a system for the extracorporeal treatment of blood, whereby the said tube may be filled with either blood or a priming fluid and the receiver is joined to an arrangement for comparing the values received with at least one reference value. The detector system in accordance with the invention is intended in particular to be applied to a system for the extracorporeal treatment of blood, e g dialysis, the said tube being filled either with blood or a so-called priming fluid, that is to say a physiologically acceptable salt solution. BACKGROUND ART A number of systems are known for the checking of fluid tubes assembled on guiding monitors. In dialysis monitors, for example, air detectors are known for checking whether any air is allowed to accompany the blood back to the patient. Furthermore, so-called blood-leakage monitors are known in dialysis monitors which sound an alarm if blood leaks over from the blood side to the dialysate. It is a disadvantage of these known systems that they are directly adapted to the actual treatment. As a result in certain cases they may cause more trouble than good, for example, during the running in or the so-called priming of a dialysis system. It has happened, for example, that during this running in blood leakage monitors gave false alarms because of air bubbles during the priming phase. Thus, an alarm was raised even though during this phase there clearly can be no kind of blood leakage. Furthermore, the afore-mentioned air-flow monitor naturally can sound an alarm during priming, if no special measures are adapted for by-passing the same. It is the object of the present invention, therefore, to provide a special detector system of the above mentioned type and adapted especially to facilitate this priming phase. The invention may also be said to be an improvement of the system disclosed in US-A-3 812 482. DISCLOSURE OF INVENTION To achieve the above mentioned object a detector system of the above mentioned type has been produced, which is characterized in that the said arrangement is programmed to establish: a) whether the signal received exceeds a first higher reference value, corresponding to the absence of a tube, b) whether the signal received exceeds a second lower reference value, corresponding to the assembled tube, which is empty or filled with a substantially colourless fluid, c) whether the signal received falls short of the lower reference value, corresponding to the assembled tube being filled with blood. Monitors of the type discussed here normally comprise one or more alarm functions intended to sound an alarm, if critical limit values are exceeded or fail to be attained in the extracorporeal treatment of blood. It is an advantage of the invention that certain of these alarm functions can be wholly disengaged or reduced in state a) and/or b), but are brought into full operation as soon as state c) occurs. If the present invention is applied in connection with a monitor which comprises a clamp for the compression of the tube in connection with at least certain alarms, the further advantage is obtained that the said means for the conducting of the light beam through the tube can be assembled connected directly to the clamp in such a manner that the tube has to be installed in the claimp, when it is connected up in a state which can be sensed by the detector system. If the invention is applied in connection with a monitor which comprises a blood pump intended to act on a pump segment incorporated in the tube, the further advantage is gained that the pump can be adapted so that it cannot be actuated in state a), whereas, on the other hand, it can be actuated a limited number of turns or during a limited time in state b) and without any hindrance in state c). Monitors with transmitters and receivers of the above mentioned type normally have these and associated electrical components installed in the monitor itself or directly on its front. If this is the case, the above mentioned means for conducting the light beam advantageously can be included in a tube holder assembled on the monitor front through which the light is adapted to be conducted first substantially straight outwards from the front, subsequently, after it has passed the tube, to be refracted in the opposite direction towards the front. In this way the risk of the effects of external light interference is reduced, at the same time as this holder can be given a very simple technical design. It may be formed, for example, in one piece by die casting provided with a circular passage or guide for the tube, into which the latter can be inserted via a securing device which may be in the form of a slot which is narrower than the tube. Preferably the signal sent out from the transmitter is given a defined form, e g the form of a pulse train of a defined frequency. Through this it becomes possible to compare the signal received by the receiver with that sent out in order to discover any interferences. In a preferred embodiment of the system in accordance with the invention it comprises a main computer adapted so as to send out the said signals or beams via the transmitter and receiver to two comparators for comparison with a higher and lower reference signal respectively, which may also be issued from the computer or from a so-called safety computer. Appropriately a second computer, a so-called safety computer is provided for the checking and comparing of all the data read against given preset values, based e g on information fed into the main computer. BRIEF DESCRIPTION OF DRAWINGS The invention is described in more detail in the following with reference to the attached drawings, wherein Fig 1 shows schematically the most important outer components of a system in accordance with the invention, Fig 2 a detector incorporated in the system, and Fig 3 a schematic circuit diagram for the same. BEST MODE OF CARRYING OUT THE INVENTION Although the invention is intended first and foremost to be used for the control of dialysis and will be described, therefore, in the following with reference to such an application, it will be obvious to those versed in the art, that the invention can be applied also, for example, to another extracorporeal blood treatment or to the control in general of different flows through a tube which can be connected to a monitor. In Fig 1 is thus shown such a tube or tube system which as a whole is referred to by numeral 1 and whose one end 2 is intended for the withdrawal of blood from a patient. The tube or the tube system is normally connected to the front of a control monitor. For the sake of simplicity only certain components, taken from this front, are shown in Fig 1, namely an arterial clamp 3, with the help of which the flow of blood can be stopped, e g in connection with alarms, an arterial pressure controller 4 of conventional type, a pump 5, a combined air detector and holder 6 for a drip chamber 7 and a conventional venous clamp 8. In the Figure is shown schematically, moreover, dialyzer 9 and a detector 10 essential for the invention. The latter is arranged directly connected to the venous clamp 8 in such a manner that the tube can be assembled in this detector only when it is also assembled in the venous clamp 8. Numeral 11 designates the other end of the tube or tube set 1 which is intended to be connected to the patient for return of the blood after the dialysis. Finally 7a in Fig 1 designates a venous pressure gauge connected to the drip chamber 7. The arterial pressure controller 4 and the venous pressure gauge 7a appropriately are connected to different pressure gauges and to a computer included in the monitor in such a manner that an alarm is released when certain pressure limits are exceeded or fail to be reached. In Fig 2 is shown the detector 10 fitted on a monitor front 12. The actual tube holder is formed by a circular passage or guide 13 into which the tube can be inserted via a securing device 14 in the form of a slot which is narrower than the tube. In the monitor front is a transmitter 15 for preferably infrared light assembled together with a receiver 16 for the same light. This light is made to pass via a light conductor 17 through the circular passage 13 and thereby the tube 1, if the same is in assembled position. The light is then refracted with the help of angled surfaces 18 and 19, so that, passing through a wavelength filter 20, it is directed towards the receiver 16. Reference 21 finally designates how transmitter and receiver can be connected to the rest of the electronics inside the monitor. This electronics pack is described in more detail in Fig 3. The electronics pack included may, of course, be designed in many different ways. In Fig 3 is shown, however, a preferred realization, wherein a main computer 22 is adapted to put out a signal via a driver stage, e g a transistor 23, to an infrared light-emitting diode 24 which via a resistor 25 is connected to a positive pole. From the light-emitting diode 24 is emitted a light beam 26 which is received by a phototransistor 27, which on one side is connected to a positive pole and on the other side via a resistor 28 to earth 29. The signal obtained is passed to two comparators 30 and 31, each of which obtains a reference signal from a so-called safety computer 34 via two converters 32 and 33. The latter convert a digital signal from the safety computer 34 to an analogue signal which can be compared with the analogue signal from the phototransistor 27. The upper converter 32 transmits a higher reference signal corresponding to a wholly disconnected tube, whereas the lower converter 33 sends out a lower signal corresponding to an assembled empty tube or an assembled tube filled with a substantially transparent fluid. By means of the comparators 30 and 31 it is thus possible to establish whether at all a tube is installed in the holder 10 and whether this tube is filled with blood or not. If blood is present in the tube the signal 26 is practically wholly extinguished, so that the value obtained from the phototransistor 27 will be located clearly below the reference signal from the converter 33. Values obtained from the comparators 30 and 31 are transmitted evidently not only to the main computer 22 but also to the above mentioned auxiliary or safety computer 34. SUPPLEMENTARY INFORMATION The plastics from which tubes of the above mentioned type normally are manufactured have essentially no absorption peaks within the range 850 nm to 1000 nm. Hence the wavelength of the infrared light is chosen appropriately within this range. It has been found particularly suitable to use a wavelength of 940 nm where these plastics have practically no absorption at all. The refractive index of these plastics is normally within the range 1.4-1.6 depending on the material and the wavelength of the light. This may be made use of for detecting an empty tube or a tube filled with a substantially transparent fluid. Owing to the tube being round it acts as a lens and refracts the light. This causes the intensity to diminish on the receiver side. In order to obtain the same measured value every time under the same conditions, the tube must not be deformed in the holder but should be "loose", whilst it must still be maintained in a certain place. It is suitable for the detector to be calibrated before any tube is inserted. This is in order to compensate for any ripples within the light transmission system. If a tube is incorporated already in the holder 10 when the system is put into operation, the computer 22 may be adapted so that it starts out instead from the last calibration result. The smallest opening within the light conductor 17 on the transmitter side ought to be selected according to the smallest tube dimension used. In practice it has been found appropriate to use a circular opening of a diameter of approx. 1.5 mm, a square opening of 1.5 mm side length or a gap of dimensions 1.5 mm × 5 mm. The corresponding smallest opening on the receiver side ought to be a little larger. It may, for example, have a corresponding diameter or side of 2 mm. In this manner good reliability is obtained with different tube diameters down to at least 1.5 mm. Such fine-calibre tubes, however, ought to be fixed in some manner in the light beam path. Naturally the invention is not limited simply to the embodiment described above, but can be varied within the scope of the following claims. the components shown schematically, for example, may be designed in a different manner.

Claims: A detector system for the checking of a fluid tube (1) which is connectable to a monitor (12), by means of which it is intended to control the flow within the tube, comprising a transmitter (15) and a receiver (16) respectively for a light beam of preferably infrared light, and means (17) for the con­ ducting of this beam through the tube when the same is assembled on the monitor, applied to a system for the extracorporeal treatment of blood, whereby the said tube (1) may be filled with either blood or a priming fluid and the receiver (16) is joined to an arrangement (30 or 31) for comparing the values received with at least one reference value, characterized in that the said arrangment is programmed to establish: a) whether the signal received exceeds a first higher reference value, corresponding to the absence of a tube, b) whether the signal received exceeds a second lower reference value, corresponding to the assembled tube, which is empty or filled with a substantially colourless fluid, c) whether the signal received falls short of the lower reference value, corresponding to the assembled tube being filled with blood. A detector system in accordance with claim 1, the monitor (12) comprising one or more alarm functions intended to sound an alarm if certain critical limit values are exceeded or fail to be attained in the extracorporeal treatment of blood, characterized in that certain of these alarm functions are wholly disengaged or reduced in state a) and/or b), but are brought into full operation as soon as state c) occurs. A detector system in accordance with anyone of the preceding claims, applied in connection with a monitor (12) which comprises a clamp (8) for compression of the tube (1) in connection with at least certain alarms, characterized in that the said means (17) for the conducting of the light beam through the tube (1) is assembled directly connected to the clamp (8) in such a manner that the tube (1) has to be installed in the clamp (8) when it is connected up in a state which can be sensed by the detector system. A detector system in accordance with anyone of the preceding claims, the monitor (12) comprising a blood pump (5) intended to act on a pump segment incorporated in the tube, characterized in that the pump (5) is arranged so that it cannot be actuated in state a) whilst it can be actuated a limited number of turns or during a limited time in state b), and with­ out any hindrance in state c). A detector system in accordance with anyone of the preceding claims, the said transmitter (15) and receiver (16) and associated electrical components (e g 24,27) being installed in the monitor (12) or directly on its front, characterized in that the said means (17) for conducting the light beam is in­ cluded in a tube holder (10) assembled on the monitor front, through which the light is intended to be condcuted first sub­ stantially straight outwards from the front, subsequently, after it has passed the tube, to be refracted in the opposite direc­ tion towards the front. A detector system in accordance with claim 5, charac ­ terized in that the tube holder (10) comprises a preferably circular passage and guide (13) for the tube (1), into which the latter can be inserted via a securing device, for example, in the form of a slot (14) which is narrower than the tube. A detector system in accordance with anyone of the preceding claims, characterized in that the signal sent out from the transmitter (15) is of a defined form, e g the form of a pulse train of a defined frequency, and that the signal received by the receiver (16) is compared with that sent out in order to discover any interferences. A detector system in accordance with anyone of the preceding claims, characterized in that a main computer (22) is adapted to send out signals or beams via the transmitter (15) and the receiver (16) to two comparators (30,31), for comparison with a higher or a lower reference signal respectively likewise issued from the computer (22) or from a so-called safety compu­ ter.

Inventors: ERICSON, BJOERN INGE, GUMMESSON, BENGT-AKE GOERAN, OERNDAL, CARL-HENRY, Ericson, Björn Inge, Gummesson, Bengt-Ake Göran, Örndal, Carl-Henry
Applicants: GAMBRO AB
Application year: 1987
Main classification: A61M1
IPC codes: A61M5, A61M1