METHOD OF AND APPARATUS FOR DETECTING AN OCCLUSION OF LIQUID TRANSFUSION TUBE

Abstract: There is disclosed an apparatus for detecting an occlusion of a liquid transfusion tube (14) in which a pump section (16) is provided in a liquid transfusion tube for connecting an infusion liquid container (10) with a body infusion element (12), so that an occlusion of the liquid transfusion tube is detected according to an amount of displacement of the liquid transfusion tube displaceable under a pressure of a liquid transfused to the liquid transfusion tube by an operation of the pump section.

Description: The present invention relates to a method of and an apparatus for detecting an occlusion of a flexible liquid transfusion tube, according to the opening portions of claims 1 and 4, particularly in a liquid transfusion pump in accordance with an amount of variation of displacement of the liquid transfusion tube displaced under the pressure of the liquid transfused into the liquid transfusion tube. Such a method and apparatus is known US-A-4 369 780. This medical fluid injection system allows detection of an occlusion. However, it is not possible to operate this system without error when tubes made by different manufacturers are used, such that errors occur, especially when using this system for a longer period. In general, a peristaltic finger pump is used as a liquid transfusion device or an automatic instillation device and is provided between an infusion liquid container such as a pharmaceutical liquid bottle and a body infusion member like an infusion needle as disclosed in the Japanese laid-open patent application No. 58-165 868. The pump of this type is so constructed, that a predetermined quantity of a liquid is transfused by sequeezing an elastic liquid transfusion tube in a liquid transfusing direction by movements of a plurality of the finger members. When a clamper and the like disposed in a liquid transfusion tube system to occlude a pharmaceutical liquid are failed to open for making an occluded state for an extended period and a desired quantity of a liquid is not infused or when a tip of an infusion needle is clogged so that a joint for the liquid transfusion tube is released and when an inner pressure of the liquid transfusion tube is elevated for release of the clogging with an accedential infusion of the pharmacheutical liquid making troubles, a premature baby and a patient in a critical condition are particularly subjected to a great danger. Therefore, it has been required to detect such an occlusion of a liquid transfusion tube quickly for prevention of an occurrence of any trouble. There has been a particular apparatus for detecting an occlusion of the liquid transfusion tube to detect an expansion of the transfusion tube due to a variation of a liquid pressure in the liquid transfusion tube by a strain gauge and the like to give an alarm. However, according to the conventional method of and apparatus for detecting an occlusion of the liquid transfusion tube, the liquid transfusion tube to be detected is requied to have an expansion sufficient for detection by a strain gauge and the like when an inner pressure is elevated by an occlusion and also to have a constant expansion rate for each liquid transfusion unit, notwithstanding there is no substantial expansion from spontaneous state even the clogging occurred and also such the conventional opparatus could not be used for the general purpose liquid transfusion unit having the liquid transfusion tubes of the different hardness according to the manufacturers. The conventional liquid transfusion unit is an instillation liquid transfusion unit manufactured not to intend for use with squeezing by a pump, and since this liquid transfusion unit is free of squeezing portion for the pump, the structure is simple for mass-production in a single species with the reduced cost. According to the present invention, when the liquid transfusion tube to be used for the general-purpose liquid transfusion unit is pressurized into a flat shape, the flat portion is sharply displaced against the variation of the liquid pressure in the liquid transfusion tube. Therefore, an object of the present invention is to provide a method of and an apparatus for detecting an occlusion of a liquid transfusion tube, in which a liquid transfusion tube on the downstream side of a pump is inserted into an insertion portion in a flattened state and the flattened portion of this liquid transfusion tube is pressed elastically by the clamping portion on the pivoting members, a degree of displacement of the flattended portion of the liquid transfusion tube is detected by the detector disposed on the pivoting members, thereby enabling to apply the method and apparatus to a general-purpose liquid transfusion tube. To achieve the foregoing object according to the invention, there is provided an apparatus for detecting an occlusion of a liquid transfusion tube according to claim 1, and a method for detecting an occlusion of a liquid transfusion tube, according to claim 4. In the foregoing apparatus, the detectors to be disposed between the pivoting members may preferably be comprised of a hole sensor unit. Further, pivoting members may preferably be formed of compression springs. Furthermore, against an elastically pressing operation to make a liquid transfusion tube at a clamping portion of a pivoting member in a flattened state, the pivoting member may preferably be operated to enlarge a space between the detecters disposed in a confronting relation. An apparatus for detecting an occlusion of a liquid transfusion tube according to the present invention is described hereinafter in details in connection with a method of operating this apparatus and with reference to the accompanying drawings. Figure 1 is a pictorial view showing an embodiment descriptive of an apparatus for detecting an occlusion of a liquid transfusion tube incorporated into a liquid transfusion equipment according to the present invention; Figure 2 is a partially sectioned front elevation showing an embodiment descriptive of the apparatus for detecting an occlusion of the liquid transfusion tube according to the present invention; Figure 3 is a characteristic diagram showing a sequential variation of an expansion value of the liquid transfusion tube to which a certain internal pressure is applied; Figure 4 is a characteristic diagram showing a sequential variation of the flattening value of the liquid transfusion tube when an external force is applied in the state free of an inner pressure; Figure 5 is a characteristic diagram showing a relation between a magnetic flux density and an output voltage; Figure 6 is a characteristic diagram of a detector showing a relation of a distance between a hole sensor and a magnet with an output voltage; Figure 7 is a waveform diagram showing a relation between an internal pressure of the liquid transfusion tube on account of an experiment of the liquid transfusion tube and the output voltage thereagainst; and Figure 8 is a characteristic diagram showing sequential variations of a voltage difference with an internal pressure applied to the liquid transfusion tube by using the detecting apparatus according to the present invention. In Figure 1, a liquid transfusion equipment in accordance with this embodiment is essentially comprised of a liquid infusion container or a pharmaceutical bottle 10, a body infusion element or an infusion needle 12 and a liquid transfusion tuble 14 connectiong thereof which provides a pump section or a peristaltic finger pump 16. The pump section 16 at its downstream is provided with an occlusion detection means according to the invention to which is connected an amplifier 20 for electrically receiving the detected for amplification. An amplified signal is converted by an A/D converter 22 for transmission into a microcomputer 24 in which an occlusion of the liquid transfusion tube is sequentially monitored by a comparator. When the detection value exceeds over the reference value a warning signal is output through a warning output unit 28 while a pulse motor driving circuit 30 actuating as a driving source of the pump unit 16 is stopped. Further, the reference numeral 32 represents an instillation sleeve. In Figure 2, the reference 14 denotes a liquid transfusion tube for use in the general-purpose liquid transfusion unit, 40 stands for an insertion portion forming a concave portion 42 for receiving a liquid transfusion tube in the flattened state. In the insertion portion 40 is provided a flange member 44 to be secured to a certain fixture. Further, to the insertion portion 40 is integrally secured an arm 48 constituting a pivoting member 46, while to a groove 50 formed alongside of the arm 48 is provided an arm 52 with a pivot pin 54. The pivoting member 46 forming a pair of the arms 48 and 52 provides at its one end clamping portions 56a and 56b to clamp the flattened portion of the liquid transfusion tube 14 for embracement under the pressure. Further, the clamping portions 56a and 56b are extended into the concave portion 52 for embracing the flattened portion for the liquid transfusion tube. Moreover, the fixing arm 48 of the pivoting member 46 at its one end opposite to the clamping partion 56b is provided with a magnet 58a constituting the detector 58 while the pivoting 52 at its one end is provided with a hole sensor 58b in confront to a magnet 58a to actuate the detector 58 and to the hole sensor 58a is connected a lead wire (not shown) for withdrawing an electric signal. In the vicinity of the fixed hole sensor 58b of the pivoting arm 52, a headed pin 62 is buried. Between a washer 66 freely mounted around the headed pin 62 and a head portion of the headed pin 62 is interposed a compression spring 64 so that a washer 66 is made into contact with a fixing arm 48 under energization of the compression spring 64 while a sensing terminal of the pivoting terminal 52 is separated at maximum for the fixing arm 48. The generally used liquid transfusion tubes made by the different manufacturers have been investigated to obtain characteristics thereof as shown in Figures 3 and 4. Namely, Figure 3 is a characteristic diagram showing a sequential variation value under the internal pressure applied for the tube. The diagram shows the sequential variation of the expansion when the tube of each manufacture is inserted respectively into the insertion portion of the occlusion detecting means for applying the internal pressure of 0.8 Kg/cm² to the tube thereby to identify the sequential variation of the expansion rate by means of the detector 58. In the characteristic diagram, an expansion rate of the tube made by the manufacturer A after approximately five minutes is about 0.07 mm while an expansion rate of the manufacturer C is approximately 0.02 mm so that the difference in expansion rate between the A tube and the C tube is 0.05 mm at maximum. In Figure 4, a tube of each manufacturer is inserted respectively into the insertion portion 40 of an occlusion detecting equipment and the pressure under the compressing spring of the detecting means only is applied to the flattened portion of the tube to obtain a flattening rate of the tube as a sequential variation. In the diagram, the flattening rate of the tube made by the manufacturer A about 5 minutes later is about 0.15 mm while the flattening rate of the manufacturer B is 0.08 mm leaving the difference between the A tube and the C tube as 0.07 mm at maximum. Accordingly, it will be appreciated from the characteristic diagram that the flattening rate is sequentially changed with considerably irregular results in the tubes of the different manufacturers. Further, in Figure 5, the characteristic diagram of the flux density with the output voltage showing a hole sensor to be used in the detector has relatively a linear characteristic in the relation of the flux density B (KG) with the output valtage V H (mV). Moreover, as obvious from Figure 6 of the characteristic diagram, a relation of the space between the hole sensor and the magnet with the output voltage has an inversely proportional non-linear charactristic so that a space between the hole sensor 52 and the magnet 58 is determined to obtain a voltage variation substantially equivalent to the output voltage value against the irregular expansions (0.8 Kg F/cm²) of the A tube, B tube and C tube respectively. In Figure 7, an internal pressure of 0.8 Kg F/cm² is applied to the tube as a pulse of the constant time to obtain a sequential variation of the output voltage so that in each tube approximatly 10 hours later the output voltage free of any pressure is decreased to approximately 0.2 V while when an internal pressure of 0.8 Kg F/cm² is applied, the difference in output voltage in each time is 0.4 V, for which reason despite of an elongated use of the occlusion pressure detecting apparatus according to the invention, the detecting signal in relation to the variation of the internal pressure may be obtained in constant. Further, as apparant from characetistic diagram of Figure 8, the tubes of the different manufactures have the values of substantially no sequential vaviation in the voltage difference. As hereinbefore fully described, according to the invention, the safety of the liquid transfusion pump using a general-purpose liquid transfusion unit may be considerably enchanced with the constant detecting effects even in use of various tubes of the different manufactures, thus the liquid transfusion system with an enhanced safty may be realized at the reduced cost using the general-purpose liquid transfusion unit.

Claims: An apparatus for detecting an occlusion of a flexible liquid transfusion tube (14) by detection of an expansion of the tube (14) due to the pressure of the liquid in the tube (14), said tube (14) for connecting a liquid container with a body infusion element (12) and comprising a section to be operated by a pump (16) of the peristaltic type and an insertion portion for inserting the tube in a flattened state into said apparatus downstream of the pump section (16), characterized in that a pair of pivoting members (48, 52) is provided with a clamping portion (56a, 56b) at one end thereof so as to elastically compress the flattened part of said tube (14) in accordance with movements of said pivoting members (48, 52), a detector (58) is disposed between said pivoting members (48, 52) providing a signal corresponding to the displacement of said clamping portion (56a, 56b) due to the expansion of said tube (14), said detected signal corresponding to the expansion of the tube (14) due to the pressure increase inside the tube (14) caused by a single pump stroke, and that means (20, 22, 24, 28) is provided for comparing a value of the detected signal from the detector (28) with a reference value, providing an alarm when a detected signal exceeds said reference value. Apparatus according to claim 1, wherein the detector (58) to be disposed between said pivoting member (48, 52) comprises a hole sensor unit (58b) which is a sensor comprising a hole and is adapted for working together with a magnet (58a). Apparatus according to claim 1, characterized in that said pivoting members (48, 52) are provided with compression spring means (64) for flattening said tube (14). A method for detecting an occlusion of a flexible liquid transfusion tube (14) by detection of an expansion of the tube (14) due to the pressure of the liquid in the tube (14), said tube (14) for connecting a liquid container with a body infusion element (12) and comprising a section to be operated by a pump (16) of the peristaltic type and an insertion portion for inserting the tube in a flattened state downstream of the pump section (16), characterized in that a pair of pivoting members (46, 52) has a clamping portion (56a, 56b) at one end thereof for elastically compressing the flattened part of said tube (14) in accordance with movements of said pivoting members (48, 52), that a detector (58) which is disposed between said pivoting members (48, 52) provides a signal corresponding to the displacement of said clamping portion (56a, 56b) due to the expansion of said tube (14), with said detected signal corresponding to the expansion of the tube (14) due to the pressure increase inside the tube (14) caused by a single pump stroke, and that means (20, 22, 24, 28) compare a value of the detected signal from the detector (28) with a reference value and are for providing an alarm when a detected signal exceeds said reference value. Method according to claim 4, characterized in that said pivoting members (48, 52) are operated to enlarge the distance between members (58b, 58a) of the detector (58) which in operation acts against an elastical pressing operation for bringing a liquid transfusion tube at the clamping portion (56a, 56b) of said pivoting members (46, 52) into a flattened state.

Inventors: AIZAWA, TAKASHI, FUJITANI, AKIRA, MIYAKE, TETSUYA, TANAKA, SHIGERU, YOKOYAMA, KAZUMI
Applicants: NIKKISO CO., LTD.
Application year: 1989
Main classification: A61M5
IPC codes: A61M5, G01L9