Liquid leakage detection system

A liquid leakage detection system requiring no power supply from an outer source and configured to be relatively simple and moderate in price. A liquid leakage detection system (10) including an infusion tube (11), a syringe needle (12) coupled to the infusion tube (11), an absorbent element (16) adapted to be placed in the vicinity of a point (12a) of the syringe needle (12) to be pricked through a patient skin and a sensor unit (14) located on an upper side or within the absorbent element (16).

TECHNICAL FIELD

The present invention relates to liquid leakage detection systems and more particularly to liquid leakage detection systems for the medical purpose of detecting leakage of various kinds of liquid possibly occurring during drip infusion, blood collection, returning of blood from dialysis machine back to patient bodies, collection of various kinds of bodily fluids, for example, cerebrospinal fluid, ascitic fluid or pleural effusion or returning of such bodily fluids back to patient bodies.

BACKGROUND

Conventionally, a system used to detect leakage of liquid from a syringe needle having been pricked into a human body is well known. For example, JP 2006-55588 A (PTL 1) discloses a liquid leakage detection system including a circuit component formed on a copper-clad laminate, circuit terminals located on the circuit component and a sensor main body.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

In the detection system disclosed in PTL 1, when the liquid such as blood flows between the circuit terminals of the circuit component which is in unelectrified open-circuit condition, the open circuit is changed to an electrified closed circuit whereupon the sensor main body is actuated to send out an alarm, thereby informing the persons in charge of a leakage from the needle is occurring.

However, in such detection system, it is required to include a power supply part since the circuit component must be always kept to be energized with weak voltage and, in addition, it is required to put the copper-clad laminate in contact with a patient body. Consequently, the patient might feel uncomfortable during use of the detection system.

An object of the present invention is to improve the liquid leakage detection system of prior art, thereby providing a liquid leakage detection system requiring no power supply from an outer source and having an arrangement which is more moderate in price and more simple than the system of prior art.

Solution to Problem

According to the present invention, there is provided a liquid leakage detection system including an infusion tube, a syringe needle coupled to the infusion tube, an absorbent element adapted to be placed in a vicinity of a point of the syringe needle to be pricked through a patient skin and a sensor unit located on an upper side or within the absorbent element.

According to one embodiment of the present invention, the sensor unit is composed of a liquid battery adapted to generate electricity in the presence of the leaked liquid.

According to another embodiment of the present invention, the sensor unit is composed of the liquid battery and a sender coupled to the liquid battery.

According to even another embodiment of the present invention, the sensor unit is provided to the absorbent element by means of a pressure-sensitive adhesive fixing tape.

According to still another embodiment of the present invention, the liquid battery includes a positive electrode plate, a negative electrode plate, positive-electrode active material directly or indirectly in contact with both the positive electrode plate and the negative electrode plate, and an external capsule sheet adapted to capsule them and wherein an electrical insulator layer is interposed between the positive electrode plate and the negative electrode plate.

According to yet another embodiment of the present invention, the absorbent element is interposed between the inner surface of the external capsule sheet and the liquid battery so that the positive electrode plate and the negative electrode plate may be wrapped with the absorbent element within the external capsule sheet.

Advantageous Effects of Invention

With the liquid leakage detection system according to the present invention, the liquid leakage can be detected by the relatively compact sensor unit adapted to generate electricity in response to leakage of the liquid without power supply from an outside source. In this way, the liquid leakage can be quickly detected with use of the arrangement which is more moderate in price and more simple than conventional liquid leakage detection devices and systems using the electronic circuits and the semiconductor elements.

DESCRIPTION OF EMBODIMENTS

Referring toFIGS. 1 and 2, a liquid leakage detection system10includes an infusion tube11coupled to a bag for drip infusion or a bag for blood collection, a butterfly needle (syringe needle)12coupled to the tube11and to be pricked into blood vessel on top H of a patient hand, a sensor unit14fixed to the patient hand by a pressure-sensitive adhesive fixing tape13, and a receiver15to receive electrical waves emitted from the sensor unit14. Between the pressure-sensitive adhesive fixing tape13and the vicinity of a point12aof the butterfly needle12pricked into the blood vessel, an absorbent element16, for example, folded gauze for blood stanching is interposed. As used herein, the term “liquid” means various kinds of liquids used for transfusion in a medical front, for example, blood, drip infusion liquid, cerebrospinal fluid, ascitic fluid or pleural effusion.

Referring now toFIGS. 3 and 4, the sensor unit14is composed of a relatively compact liquid battery20externally capsuled by a liquid permeable fibrous nonwoven fabric sheet and a relatively compact sender22coupled to the liquid battery20by the intermediary of lead wires21a,21bextending out from the liquid battery20. The sensor unit14is interposed and clamped between the inner surface of the pressure-sensitive adhesive fixing tape13and the absorbent element16under the effect of an adhesive region of the pressure-sensitive adhesive fixing tape13. The pressure-sensitive adhesive fixing tape13is fixed to the top H of the patient hand so as to cover almost the entire absorbent element16in a transverse direction of the absorbent element16and therefore there is no possibility that the sensor unit14should not be displaced during treatment. To fix the sensor unit14between the pressure-sensitive adhesive fixing tape13and the absorbent element16more stably and more reliably, the surface of the absorbent element16facing the sensor unit may be coated with an adhesive at certain interval sensuring the sensor unit14to be supplied with the liquid.

Referring toFIG. 3, the sensor unit14is placed so as to face the point12aof the butterfly needle12through the intermediary of the absorbent element16(upper part ofFIG. 3). When the liquid26, for example, blood or infusion leaks from the blood vessel region slightly protruding due to insertion of the point12aof the butterfly needle12and permeates the entire absorbent element16or a relatively wide range thereof around the blood vessel region, the leaked liquid26permeates the fibrous nonwoven fabric sheet externally capsuling the liquid battery20. The liquid26permeating the fibrous nonwoven fabric sheet functions as a catalyzer causing an electrochemical reaction to develop an electromotive force within the liquid battery20. The electromotive force generated in this manner causes electrical current to be carried via the lead wires21a,21bto the sender22which, in response to the electric current, emits electrical waves. In this way, when the liquid leakage occurs from the blood vessel region25in which the top12aof the butterfly needle12has been pricked into the blood vessel, the sensor unit14located so as to face this blood vessel region25can quickly detect such liquid leakage and inform the persons working outside of this liquid leakage.

The electrical waves emitted from the sender22can be transmitted to locations remote from the leakage detection system10to the receivers15placed, for example, in a central control room such as a nurse center. Thus, for example, the receiver15may be directly coupled with annunciation means located in the central control room or/and a hospital to inform a plurality of persons working in the hospital of the fact that the liquid leakage has occurred, thereby preventing medical accidents due to such liquid leakage.

The liquid leakage detection system10according to the present invention uses, in addition to the medical components which are necessary for blood collection and drip infusion, for example, the infusion tube11coupled to the bag for drip infusion or blood collection, the butterfly needle12and the blood stanching element composed of the pressure-sensitive adhesive fixing tape13and the absorbent element16, the sensor unit14composed of the compact liquid battery20and the compact sender22to ensure the liquid leakage to be quickly detected. Considering such aspect, it will be reasonable to evaluate the detection system according to the present invention to be more easy-to-use and more moderate in price than the conventional automatic liquid leakage detection device as well as the conventional automatic liquid leakage detection system including precision measuring equipment using semiconductor devices and integrated circuits. The side of the receiver also requires neither large scale device nor large scale system and therefore the liquid leakage detection system10according to the present invention can be used not only in the medical facilities such as hospitals but also in the care facilities and even for home use.

Generally, the liquid battery20constituting a part of the sensor unit14includes the electrode plate and the sender22is formed of a metallic element as will be described later in details. With such an arrangement, if the sensor unit comes in direct contact with the patient's skin, the patient might feel uncomfortable. However, according to the present embodiment, the sensor unit14is put in indirect contact with the patient skin by the intermediary of the absorbent element16folded in two or more layers without creating an uncomfortable feeling against the patient. Additionally, the absorbent element16having a required thickness is interposed between the sensor unit14and the patient skin and, therefore, a slight amount of liquid is retained in the absorbent element16before the liquid can reach the sensor unit14. Specifically, a slight amount of blood or infusion which sometimes flows out at the moment of the needle insertion should not generate electricity and the sensor unit should not lead to a malfunctioning of the system. Furthermore, the thickness of the absorbent element and/or the number of layers of the folded absorbent element may be selected to adjust a reaction velocity from leakage of the liquid from the blood vessel to generation of electricity by the liquid battery20appropriately.

Referring toFIG. 5illustrating another embodiment of the present invention, at least the liquid battery20constituting the sensor unit14may be placed so as to be interposed between upper and lower layers of the doubled up absorbent element16. With this arrangement, the liquid battery20is tightly held between two layers of the doubled up absorbent element16and the liquid battery20should not be displaced during a medical treatment. In addition, the liquid battery20is entirely wrapped with the absorbent element16and consequently the liquid26absorbed by the absorbent element16and diffused therein is supplied to an entirety of the liquid battery20. In this way, electricity generating efficiency is further improved.

So long as the liquid leakage can be detected, the liquid battery20may be located on the upper side of the absorbent element16or within the absorbent element16and it is not essential for the sensor unit14to include the sender22. Specifically, the lead wires21a,21bextending from the liquid battery20may be directly coupled to the external annunciation means to inform the persons working in the locations remote from the detection system of the liquid leakage. Though not illustrated, it is also possible to couple the liquid battery20directly to the sender22by, for example, caulking them together without use of the lead wires21a,21b.

In order that such effect can be produced in the present invention, the liquid battery20constituting a part of the sensor unit14should be relatively compact and arranged so as to generate electricity as soon as the liquid battery20is soaked with water. Details of the arrangement of the liquid battery20used in the present invention to achieve the above-mentioned effect will be described hereunder.

FIG. 6is a perspective view of the liquid battery20, FIG.7is an exploded plan view of the liquid battery20,FIG. 8is a perspective view illustrating an assembling process for the liquid battery20andFIG. 9is a sectional view taken along line IX-IX inFIG. 8.

The liquid battery20has a substantially rectangular shape defined by a longitudinal direction P, a transverse direction Q, first and second side edges20c,20dextending in the longitudinal direction P in parallel to each other, an open end20aand an closed end20bclosed by adhesion or sealing and spaced apart from and opposed to the open end20ain the longitudinal direction P. This substantially rectangular liquid battery20includes an external capsule sheet30, a positive electrode plate31, a negative electrode plate32both capsuled by the external capsule sheet30, and positive-electrode active material33put in contact with the positive electrode plate31within the external capsule sheet30. The positive electrode plate31, the negative electrode plate32and the positive-electrode active material33are stacked on one another and capsuled by the external capsule sheet30. The lead wires21a,21battached to the positive electrode plate31and the negative electrode plate32, respectively, extend outward through the open end20a. In this regard, it is possible to close the open end20awith an adhesive or by a heat sealing technique in a fashion similar to the closed end20b.

The external capsule sheet30is made of electrically insulative and liquid-permeable sheet material, for example, a water-permeable fibrous nonwoven fabric or a porous plastic film.

As illustrated inFIG. 7, the external capsule sheet30has, as viewed in the developed state, a substantially square shape defined by first and second surfaces35A,35B, first and second side edges37,38spaced apart from and opposed to each other in the transverse direction Q and extending in the longitudinal direction P, and first and second ends39,40spaced apart from and opposed to each other in the longitudinal direction P and extending in the transverse direction Q wherein first-third fold lines41,42,43respectively extending in the longitudinal direction P are formed between the first and second side edges37.38. A width dimension of the external capsule sheet30in the transverse direction Q is almost evenly divided into four regions by the first and second side edges37,38and the first-third fold lines41,42,43. Specifically, the width dimension is divided into a first region45defined between the first side edge37and the first fold line41, a second region46defined between the first fold line41and the second fold line42, a third region43defined between the second fold line42and the third fold line43and a fourth region48defined between the third fold line43and the second side edge38. In this regard, a joining region50extending in the longitudinal direction P is formed between the fourth region48and the second side edge38of the external capsule sheet30. The joining region50is preferably coated with an adhesive at certain intervals to ensure that the external capsule sheet30may absorb water through the second surface35B thereof and the water absorbed in this manner may function as catalyst for the oxidation reaction of the positive-electrode active material33placed within the external capsule sheet30. So long as permeation of water into the liquid battery is ensured, the joining region50may be joined with use of a heat sealing technique instead of an adhesive. The lead wires21a,21bare coupled to the positive electrode plate31and the negative electrode plate32with use of soldering51a,51b, respectively.

The positive electrode plate31is a substantially rectangular thin plate placed in the second region46of the external capsule sheet30and made of material which has relatively superior electrical conductivity, indistinctive ionization tendency and relatively high electrochemical stability, for example, metals such as nickel, copper or silver, or the alloy containing such metals as principal alloy elements.

The negative electrode plate32is a thin plate which is substantially the same as the positive electrode plate31in shape as well as in size and placed in the third region47of the external capsule sheet30and made of electrode active material having relatively high ionization and/or oxidation tendencies, for example, metallic magnesium, aluminum or zinc or alloy containing at least two or more of these metals.

The positive-electrode active material33is powdery material bonded to the first region45of the external capsule sheet30by the intermediary of an adhesive sprayed to the first region45and made of oxidizing material having relatively high oxidizing power, for example, a commixture containing but not limited to activated carbon, manganese dioxide, iron oxide and crystalline silver oxide wherein kinds of the commixture and the mixing ratio for the respective commixtures are appropriately selected depending on the desired oxidizing power. In order that the liquid battery20as a whole can be shaped to be relatively thin and the desired electromotive force can be generated with use of a relatively small amount of the positive-electrode active material, two or more kinds of the active materials may be used or such active materials subjected to appropriate processing treatments may be used. While the positive-electrode active material33is powdery according to the present invention, it is also possible to form the powder of the various active materials such as the activated carbon into a sheet and to affix this sheet to the first region45with an adhesive. In this regard, the adhesive with which the positive-electrode active material33is bonded to the first region45is preferably applied to the sheet of the positive-electrode active material at certain intervals so that the liquid may smoothly permeate the sheet.

To transfigure the liquid battery20from the developed state as illustrated inFIG. 7to the assembled state as illustrated inFIG. 6, first, as illustrated inFIG. 8, the first region45of the external capsule sheet30is folded inwardly so that the first region45and the second region46may face each other, more specifically, the positive-electrode active material33bonded to the first region45and the positive electrode plate31located in the second region46may be overlapped and put in contact with each other. Then, the regions in which the positive electrode plate31and the positive-electrode active material33are capsuled, respectively, are folded inwardly along the second fold line42so that the second surface35B of the first region45to which the positive-electrode active material33is bonded and the negative electrode plate32located in the third region47may be overlapped and put in contact with each other. Finally, the fourth region48is folded along the third fold line43toward the second surface35B of the second region46and the fourth region48is joined to the second surface35B of the second region46by the intermediary of the joining region50. In this way, the liquid battery20can be assembled.

Referring now toFIG. 9, within the liquid battery20, the positive electrode plate31and the positive-electrode active material33are kept in contact with each other and the positive-electrode active material33is kept in contact with the negative electrode plate32by the intermediary of the external capsule sheet30to which the positive-electrode active material33is bonded. In the liquid battery20with such arrangement, when the liquid permeates the liquid battery20through the second surface35B of the external capsule sheet30and/or the open end20a, water is diffused in the positive-electrode active material33through the region defining the first region45of the external capsule sheet30. The water diffused in this manner functions as catalyst for oxidation reaction and, as a result, ionization reaction develops between the both electrodes so as to generate an electromotive force.

The liquid battery20according to the present invention includes the respective constituent materials stacked on one another and capsuled by the external capsule sheet30and is, in consequence, much more thin and lightweight than the conventional cylindrical liquid battery. In addition, even when only a drop of the liquid (various kinds of liquids such as urine, water or blood) is supplied, it is possible to supply the positive-electrode active material55with the liquid through the external capsule sheet interposed between the respective constituent materials and to diffuse the liquid so that a required electromotive force can be quickly developed.

As for specific dimensions of the liquid battery20, a length dimension in the longitudinal direction P of the first and second side edges20c,20dis in a range of about 5.0 to about 10.0 mm, a length dimension in the transverse direction Q of the open end20aand the closed end20bis in a range of about 2.0 to about 5.0 mm, and a thickness dimension thereof is in a range of about 0.1 to about 0.3 mm. A surface area of the positive electrode plate31and the negative electrode plate32is in a range of about 20 to about 50 mm2. A mass of the positive-electrode active material33composed of various active materials such as activated carbon at a predetermined mixing ratio is in a range of 0.01 to 0.05 g. The liquid battery20dimensioned as indicated above is able to supply the sender22with electric current having a magnitude in a range of about 2.5 to 10.0 mA for several seconds-several minutes. In this regard, these values are exemplified for convenience of description of this embodiment and the respective dimensions of the liquid battery20as well as the magnitude of electrical current may be varied as the occasion demands.

Though not illustrated, it is also possible to form the liquid battery20including the absorbent element16by affixing the absorbent element16to a part of the external capsule sheet30or wedging the absorbent element16between parts of the external capsule sheet30, then folding the absorbent element16together with the parts of the external capsule sheet30and fastening them with use of fastening means such as a string or a cylindrical plastic film.

FIG. 10is a perspective view of the liquid battery20according to another embodiment andFIG. 11is a sectional view taken along line XI-XI inFIG. 10. The basic arrangement of the liquid battery20according to the present embodiment is substantially the same as that of the liquid battery20illustrated inFIG. 1-FIG.9and therefore only the dissimilarities to the first embodiment will be described hereunder.

The liquid battery20according to the present embodiment has a substantially rectangular pad-like shape contoured by a first convex surface60, a rather flat second surface61defined on a side opposite to the first convex surface60, and an outer peripheral edge62along which the first and second surfaces60,61are joined to each other by adhesion or heat sealing. The external capsule sheet30is formed from two substantially rectangular nonwoven fabric sheets and two absorbent elements16are arranged so as to be wedged between inner surfaces of the respective external capsule sheets30. The absorbent element16placed on the side of the convex first surface60is thicker than the absorbent element16placed on the side of the second surface61. A separating sheet (electrical insulator layer)64formed of insulative material which is the same as or different from the material of the external capsule sheet30is interposed between the two external capsule sheets30and joined to the respective external capsule sheets30along an outer peripheral edge62common to these three sheets. The lead wires21a,21bare secured together with these sheet members and extend outward from the liquid battery20. While the liquid battery20is coupled through the lead wires21a,21bto the sender22located outside the liquid battery20according to the present embodiment, it is also possible to locate the sender22within the external capsule sheet30so as to form the sensor unit14integrally composed of the liquid battery20and the sender22.

Within the external capsule sheet30, the positive electrode plate31located on the side of the second surface61and the negative electrode plate32located on the side of the first surface60are covered with the respective absorbent elements16and put in indirect contact with each other by the intermediary of the separating sheet64. Within the external capsule sheet30, the positive-electrode active material33bonded to the inner surface of the absorbent element16by means of adhesive sprayed on the inner surface of the absorbent element16or formed into a sheet is kept in contact with the positive electrode plate31.

The liquid battery20according to the present embodiment includes therein the absorbent element16and whereby it is unnecessary to interpose the absorbent element for blood stanching between the liquid battery20and the patient's skin. The liquid battery20may be positioned directly on the blood vessel region or the affected site where the point of the syringe needle is pricked to ensure blood stanching so long as an amount of bleeding is less than a predetermined amount. If leakage of liquid (e.g., blood or infusion) exceeds the predetermined amount, an electrochemical reaction will generate electromotive force within the liquid battery20and electric current will be carried to the sender22coupled to the liquid battery20, making it possible to inform the persons working outside the system of occurrence of the liquid leakage. The second surface61has a rather flat shape and makes it possible to use this second surface61as a contact surface adapted to be stably placed on the patient's skin. The liquid battery20has a pad-like shape and can be put in direct contact with the patient's skin without creating an uncomfortable feeling against the patient. Such pad-like shaped liquid battery20is preferable also from the viewpoint of design.

REFERENCE SIGNS LIST