JP 09-24026 A
`
`Japan Patent Office
`Patent Laying-Open Gazette
`
`
`H09-24026
`Patent Laying-Open No.
`January 28, 1997
`Date of Laying-Open:
`A61B 5/022
`International Class(es):
`A61M 1/14 531
`
`A61B 5/02 337Z
`FI:
`A61M 1/14 531
`
`
`
`Examination not requested. No. of Claims: 1
`
`
`(6 pages in all)
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`
`
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`H07-198088
`July 10, 1995
`
`Otsuka Pharmaceutical Factory, Inc.
`115 Azakuguhara, Tateiwa, Muya-cho,
`
`Ken ONISHI
`1-66 Azanibu, Shinkirai, Kitajima-cho,
`
`Eiji SAKASHITA
`42-5 Azamitsuhokaitaku, Mitsuho,
`
`Patent Attorney Yasuhiro Toyosu
`
`
`
`
`
`Patent Appln. No.
`Filing Date:
`
`Applicant(s):
`
`Naruto-shi, Tokushima
`Inventor(s):
`
`Itano-gun, Tokushima
`
`
`Matsusige-cho, Itano-gun, Tokushima
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`Agent(s):
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`JP 09-24026 A
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`English Translation of Patent Laying-Open No. H09-24026
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`(54) [Title of the Invention] Pressure Measuring Device for Blood Circuit
`
`(57) [Abstract]
`[Object] To provide a pressure measuring device for a blood circuit structurally
`simplified and capable of accurately detecting the pressure of blood.
`[Technical Feature] A pressure measuring device has a casing divided by a diaphragm
`1 formed of a flexible sheet into a blood chamber 8 and an air chamber 9 that are both
`enclosed spaces. The pressure of blood passing through the blood chamber 8 is
`transmitted to the air chamber 9 by way of the diaphragm 1, and pressure in the air
`chamber 9 is detected by a pressure sensor to detect pressure in the blood chamber 8.
`The diaphragm 1 is formed into a corrugated shape in cross section, forming an
`irregular surface on both surfaces thereof.
`[Effects] The corrugated diaphragm 1 may be more easily deformable than a planar
`diaphragm, and the blood chamber 8 has an irregularly formed surface. Accordingly,
`blood flowing over the surface of the diaphragm 1 has a turbulent flow, slowing down
`its rate of flow over the surface. This helps to minimize errors in pressure detection.
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`[Scope of Claims for Patent]
`[Claim 1]
`
`A pressure measuring device for a blood circuit, comprising a casing (5)
`divided by a diaphragm (1) formed of a flexible sheet into a blood chamber (8) and an
`air chamber (9) that are both closed spaces, wherein a pressure of blood passing
`through the blood chamber (8) is transmitted to the air chamber (9) by way of the
`diaphragm (1), pressure in the air chamber 9 is detected by a pressure sensor to detect
`pressure of blood in the blood chamber (8), the diaphragm (1) having a corrugated
`shape in cross section, and forming an irregular surface on both surfaces thereof.
`[Detailed Description of the Invention]
`[0001]
`[Technical Field to Which the Invention Belongs]
`
`The invention relates to a device for detecting pressure in a blood circuit.
`[0002]
`[Prior Art]
`
`When blood is extra-corporeally circulated to be subjected to a required
`treatment, it is important to accurately detect pressure of the blood. The treatment of
`blood requires accurate control of the pressure of blood. When, for example, blood
`permeates through a filtration film, the pressure of blood needs to be regulated to a
`predefined pressure. Any deviation in pressure level from the predefined value may
`result in adverse outcomes, such as to be out of optimal filtering condition, ordamage to
`the filtration film.
`[0003]
`Conventionally, a drip chamber 12 illustrated in Fig. 1 has been used to
`
`measure the pressure of blood extracorporeally circulated. The drip chamber 12 is
`air-tightly sealed and used with air 13 being reserved in an upper part thereof. The
`air-tightly sealed drip chamber 12 is capable of detecting the pressure of blood 14 by
`detecting the air pressure. To detect the air pressure, a pressure sensor 15 is coupled
`to the upper section of the drip chamber 12. The drip chamber discharges blood
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`supplied thereto through its bottom section.
`[0004]
`The drip chamber has an advantage in accurate measurement of the pressure of
`
`blood. However, contact of blood with air is unavoidable. Any contact with air can
`accelerate the coagulation of blood. In a drip chamber with a filtration member
`provided inside, therefore, coagulated blood may clog the filtration member and finally
`block the flow of blood. In such a case, interruption of a medical treatment may result.
`Furthermore, contact with air creates a risk of bacterial infection. There is yet a
`further problem: difficulty in large volume reduction of the drip chamber increases a
`priming volume (PV value), which is a burden on a patient’s blood supply. One drip
`chamber has a PV value ranging from 20 to 30 ml. Since three to four drip chambers
`are ordinarily used, it becomes a considerable volume in total.
`[0005]
`With an aim to prevent these adverse outcomes, a diaphragm pressure
`
`measuring device structured to separate blood and air using a diaphragm was invented
`and described in Japanese Patent Laying-Open No. 1986-143069. As illustrated in a
`sectional view of Fig. 2, the pressure measuring device includes a diaphragm 1
`horizontally fixed in a casing 5. A part below the diaphragm 1 is defined as a blood
`chamber 2, and a part above the diaphragm 1 is defined as an air chamber 3. The
`diaphragm 1 is formed of an easy to deform flexible sheet, for example, a silicon rubber.
`[0006]
`[Problems to be Solved by the Invention]
`
`The pressure measuring device illustrated in Fig. 2 may advantageously avoid
`any contact of blood with air, thereby solving the problem of the drip chamber. On
`the other hand, in the pressure measuring device thus structured, there is a drawback in
`that it is difficult to reduce measurement error. This is because it is not possible to
`completely equalize pressure in the blood chamber 2 and the air chamber 3.
`Deformation of the diaphragm 1 necessitates a higher pressure in the blood chamber 2
`than in the air chamber 3. A solution to this problem may be to reduce the diaphragm
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`1 in thickness to be more deformable. Such a thinner diaphragm is, however, attended
`with a higher risk of breakage. Thus, thinning of the diaphragm has a certain limit,
`and thinning the diaphragm more than necessary is not possible.
`[0007]
`The occurrence of measurement error in the diaphragm-embedded pressure
`
`measuring device is induced by poor linearity of pressure in the air chamber relative to
`the pressure in the blood chamber, and hysterisis exhibiting different values when the
`pressure of blood is elevated and when lowered. Fig. 3 is a graphical indication of
`pressure changes in the diaphragm pressure-measuring device. In this graph, a lateral
`axis represents pressures in the blood chamber, and a vertical axis represents pressures
`in the air chamber. The changes in the air chamber when the pressure of blood is
`elevated are plotted with (cid:401), while changes in the air chamber when the pressure is
`lowered are plotted with (cid:184). This graph demonstrates that the air chamber pressure
`does not linearly change relative to the blood chamber pressure, and the air chamber
`pressure further falls when the pressure of blood is elevated than when being lowered,
`namely hysteresis occurs.
`[0008]
`A first object of this invention is to prevent this adverse outcome. The
`
`invention importantly provides a pressure-measuring device for a blood circuit capable
`of accurately detecting the pressure of blood.
`[0009]
`The diaphragm pressure-measuring device may advantageously reduce the PV
`
`value to smaller value as compared to the drip chamber. A drawback of the
`diaphragm pressure-measuring device is larger measurement errors with smaller size of
`the blood chamber for a smaller PV value, because smaller size of the blood chamber
`leads to higher rate of flow of blood passing through the blood chamber. According
`to the pressure measuring device illustrated in Fig. 2, blood flows on the lower surface
`of the diaphragm 1, while there is stagnant air on the upper surface thereof. There is a
`drawback that fluid flowing at a higher flow rate is lowered in pressure. Therefore, a
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`higher flow rate of blood flowing on the surface of the diaphragm 1 adversely lowers
`the pressure on the diaphragm surface. As a result, a detection pressure from the
`pressure measuring device is displayed lower than it should actually read.
`[0010]
`A second object of this invention is to prevent this adverse outcome by
`
`providing a very simplified structure. The invention is directed to providing a
`pressure measuring-device for a blood circuit capable of effectively preventing errors
`that may occur when blood is flowing over the diaphragm surface.
`[0011]
`[Means for Solving the Problems]
`
`To achieve the objects, a pressure measuring-device for a blood circuit
`according to the invention is structurally characterized as described below. The
`pressure-measuring device has a casing divided by a diaphragm 1 formed of flexible
`sheet into a blood chamber 8 and an air chamber 9 that are both enclosed spaces. The
`pressure of blood passing through blood chamber 8 is transmitted to air chamber 9 by
`way of diaphragm 1, and a pressure in air chamber 9 is detected by a pressure sensor to
`detect a pressure in blood chamber 8. In the pressure measuring-device according to
`the invention, the diaphragm 1 has a corrugated shape in cross section, forming an
`concave-convex surface on both surfaces thereof. Corrugated diaphragm 1 may be far
`more easily deformable than a planar diaphragm. Since blood chamber 8 has an
`irregularly formed surface, blood flowing on the surface of diaphragm 1 forms a
`turbulent flow, slowing down its flow rate over the surface.
`[0012]
`[Function]
`
`According to the pressure measuring-device according to the invention,
`diaphragm 1 has a corrugated shape in cross section. Fig. 4 illustrates a pressure
`measuring-device according to a preferred example of the invention. Fig. 5 illustrates
`a perspective view of the diaphragm. Corrugated diaphragm 1 illustrated in these
`drawings may be far more easily deformable than planar diaphragm 1 illustrated in Fig.
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`2. This is because, in contrast to a planar diaphragm that is extended and displaced,
`corrugated diaphragm 1 is displaceable without extension through deformation of its
`bent part. Corrugated diaphragm 1 illustrated in the drawings, because of its bellows-
`like foldable shape, is deformable with a great ease. An ideal diaphragm would be
`deformable without any force applied thereto. A force required to deform corrugated
`diaphragm 1 may be as small as possible. This may minimize a pressure difference
`between blood chamber 8 and air chamber 9, allowing for accurate measurement of the
`pressure of blood.
`[0013]
`Fig. 6 shows a measurement result obtained by the pressure-measuring device
`
`illustrated in Fig. 4. In the pressure measuring-device illustrated in this figure,
`pressure changes linearly in the air chamber on the vertical axis relative to the
`pressures in the blood chamber on the lateral axis. Further advantageously, there may
`be substantially no pressure difference between situations when the pressure of blood is
`elevated and lowered, minimizing the hysterisis phenomenon.
`[0014]
`The graph of Fig. 6 shows a result measured in a system illustrated in Fig. 7
`
`under the following condition. The graph of Fig. 3 was obtained under the same
`measurement condition in a pressure-measuring device using a planar diaphragm unlike
`the drawing of Fig. 7. The pressure acting upon a pressure measuring-device 17 was
`adjusted by a flow regulating valve 19 connected in series to the device with a plasma
`separator 18 interposed therebetween.
`
`1) Flow rate in a blood pump 16: 100 ml/min.
`
`2) Inner diameter of a hose connected to the pressure measuring device: 3.1 mm
`
`3) Semiconductor pressure sensor used as pressure sensor 4
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`4) Water used instead of blood
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`5) Water temperature: 37(cid:113)C
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`6) Film pressure of diaphragm: 380 (cid:80)m
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`7) Outer diameter of diaphragm: 24 mm
`8) Material of diaphragm: soft vinyl chloride sheet
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`[0015]
`In diaphragm 1 with an irregular surface, blood does not flow smoothly along
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`the surface, unlike the planar diaphragm, as illustrated in Figs. 4 and 5. The blood
`flowing on the irregular surface of diaphragm 1 forms a turbulent flow. This may
`reduce measurement errors associated with a smooth blood flow along the diaphragm
`surface.
`[0016]
`[Embodiment]
`
`An embodiment of this invention is hereinafter described based on the
`accompanying drawings. The embodiment describes a non-limiting example of a
`pressure measuring device for a blood circuit to embody the technical idea of the
`invention. The specifics of structural elements of the pressure-measuring device
`according to the invention include but are not limited to materials, shapes, structures,
`and arrangements hereinafter described.
`[0017]
`In this description, a reference character corresponding to the member described
`
`in the embodiment is appended to the member described in “Scope of Claims for
`Patent”, “Function”, and “Means for Solving the Problems” for better understanding of
`the Scope of Claims for Patent. It should be understood that, by no means, is the
`member described in the Scope of Claims for Patent limited to those described in the
`embodiment.
`[0018]
`A pressure-measuring device for a blood circuit illustrated in Figs. 4 and 5 has
`
`an enclosed casing. The casing is divided by a diaphragm 1 into a blood chamber 8
`and an air chamber 9 that are both enclosed. The casing is a cylindrical member
`circumferentially air-tightly sealing an upper case and a lower case. The upper case
`seals an upper section of the casing, and the lower case seals a bottom section of the
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`casing. The upper and lower cases are both plastic molds. The casing is formed
`from a transparent plastic material for positional checking of the diaphragm inside.
`However, not both of the upper and lower cases are necessarily formed from such
`transparent plastic material as far as the diaphragm inside can be positionally checked.
`There can be used even semi-transparent plastic material through which the diaphragm
`inside can be positionally checked. In these drawings, the upper case has an arcuate
`inner surface to allow for undisturbed flow inside the casing.
`[0019]
`Diaphragm 1 is securely interposed between the upper and lower cases. Blood
`
`chamber 8 is disposed in the upper case, and air chamber 9 is disposed in the lower
`case. The lower case defines the volume of air chamber 9. The volume of air
`chamber 9 is designed to have an enough depth to avoid any impact of diaphragm 1
`against the inner surface of the lower case when diaphragm 1 is deformed by the
`pressure of blood flowing into blood chamber 8. The upper case has through holes 10
`formed at opposing positions on sidewalls thereof. One of though holes 10 is an inlet
`for blood. The other one of through holes 10 is an outlet for blood. A hose for blood
`to flow through is connected to each of through holes 10.
`[0020]
`Likewise, the lower case has through holes 11 at opposing positions. A
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`pressure sensor is coupled to one of through holes 11 of the lower case through a hose.
`An injection syringe for injection of air is coupled to the other one of through holes 11
`through a hose similarly to the prior art illustrated in Fig. 2. The pressure-measuring
`device thus having two through holes in the lower case is convenient in that the
`pressure sensor and the injection syringe are separately coupled thereto. Instead, the
`lower case may have one through hole, wherein the pressure sensor and the injection
`syringe are connected to bifurcated ends of a hose connected to the through hole. The
`pressure sensor coupled to air chamber 9 may be selected from any air-pressure
`detectable sensors currently available. An example of the pressure sensor is a
`semiconductor pressure sensor.
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`[0021]
`Diaphragm 1 is cut out in a disc shape from a flexible sheet. The flexible
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`sheet for use in diaphragm 1 may be selected from any flexible sheets unrestrictedly
`deformable and capable of separating air and blood. Examples of the flexible sheet
`are soft vinyl chloride sheet, soft urethane sheet, synthetic rubber sheet made of, for
`example, silicon rubber, and natural rubber sheet. Using a thermoplastic material,
`such as soft vinyl chloride, for diaphragm 1 as well as for the casing, the casing may be
`air-tightly sealed by diaphragm 1 and the casing hot-welded to each other. Optionally,
`the diaphragm and the casing may be adhered to each other with an adhesive.
`[0022]
`Diaphragm 1 has a corrugated shape in cross-section. Diaphragm 1 illustrated
`
`in Figs. 4 and 5 is bent in a triangular corrugation in cross-section. In the pressure
`measuring-device according to the invention, the corrugation of diaphragm is not
`limited to triangular but may have for example a rectangular shape as illustrated in Fig.
`8, a sine-curve shape as illustrated in Fig. 9, or a terraced shape as illustrated in Fig. 10.
`However, diaphragm 1 bent in corrugation is easier to deform with more bent portions.
`Diaphragm 1 illustrated in Fig. 4 is bent so that four mountain-like shapes are located
`concentrically. As illustrated in this drawing, the number of mountain-like shapes in
`diaphragm 1 thus corrugated is preferably two or more for a desired flexibility. Since
`too many mountain-like shapes would require a high molding accuracy, diaphragm 1
`may be preferably designed to have less than or equal to 10 mountain-like shapes at
`most.
`[0023]
`As illustrated in Fig. 5, the pressure-measuring device equipped with the
`
`cylindrical casing is advantageous in that blood flow is not disturbed in blood chamber
`8. However, the casing of the pressure measuring device according to the invention is
`not limited to a cylindrical casing.
`[0024]
`[Effects of the Invention]
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`The pressure-measuring device for a blood circuit according to the invention is
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`structurally simplified and capable of detecting the pressure of blood with a remarkable
`accuracy. These advantageous features of the invention are effectuated by the
`corrugated shape of the diaphragm in cross section. The corrugated diaphragm can be
`displaced in whole by deforming its bent in corrugation portion, and therefore is very
`easily deformable. This allows for minimizing a pressure difference between the
`blood chamber and the air chamber. When the pressure in the air chamber is detected
`by the sensor with such a minimized pressure difference, the pressure in the blood
`chamber may be accurately detected. Another advantage of such an easily deformable
`diaphragm is to minimize hysterisis-associated errors. The measurement result of Fig.
`6 expressly demonstrates that the hysterisis phenomenon-associated errors and
`linearity-associated errors are minimized. As illustrated in this drawing, the pressure-
`measuring device according to the invention minimizes a pressure difference of the
`blood chamber, relative to the air chamber, over a broad range of pressure changes in
`the blood chamber, allowing for accurate detection of the pressure of blood.
`[0025]
`Further, the pressure-measuring device according to the invention, by virtue of
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`the irregular surface of the diaphragm on both surfaces thereof, may also
`advantageously minimize errors associated with the flowability of blood to be detected.
`The irregular surface of the diaphragm on the blood-chamber side turns the blood flow
`into turbulent flow. Unlike the planar diaphragm of the prior art, the turbulent blood
`flow on the diaphragm surface is not allowed to flow fast along the surface. In fact, a
`real flow rate on the diaphragm surface significantly slows down, because the blood
`flow may be temporarily stagnated in each dent on the diaphragm and prevented from
`flowing along the surface. The pressure-measuring device according to the invention
`may effectively minimize error associated with pressure drop on the diaphragm surface
`due to a flow rate of blood flowing on the diaphragm surface.
`[0026]
`
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`As described thus far, the pressure-measuring device according to the invention
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`is advantageous in that the diaphragm is very easily deformable such that a pressure
`difference between the blood and air chambers may be minimized, and hysteresis
`phenomenon-associated error may be nearly absent in total, and blood flowability-
`associated errors may be minimized. Whereby, very accurately measuring the
`pressure of blood in a simplified structure is realized.
`[0027]
`It should also be noted that the pressure-measuring device according to the
`
`invention employing the diaphragm shaped to be easily deformable is apt for
`inexpensive mass production because the diaphragm may be formed from inexpensive
`materials including a soft vinyl chloride sheet. This is also a valuable advantage for
`the pressure-measuring device of this type because the pressure measuring device used
`in this application is, with few exceptions, a disposable device.
`[Brief Description of the Drawings]
`
`Fig. 1 is a sectional view of a drip chamber of a conventional pressure-
`measuring device for a blood circuit.
`
`Fig. 2 is a sectional view of a conventional diaphragm pressure-measuring
`device.
`
`Fig. 3 is a graph showing pressure changes in the conventional
`pressuremeasuring device.
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`Fig. 4 is a sectional view of a pressure measuring device for a blood circuit
`according to an example of the invention.
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`Fig. 5 is a perspective view of a diaphragm illustrated in Fig. 4.
`
`Fig. 6 is a graph showing pressure changes in the pressure-measuring device
`according to the invention.
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`Fig. 7 is a schematic illustration of a measuring method for use with the
`pressure-measuring device.
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`Fig. 8 is a sectional view of a diaphragm in a pressure-measuring device
`according to another example of the invention.
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`Fig. 9 is a sectional view of a diaphragm in a pressure-measuring device
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`according to yet another example of the invention.
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`Fig. 10 is a sectional view of a diaphragm in a pressure-measuring device
`according to yet another example of the invention.
`[Description of the Reference Characters]
`1
`diaphragm
`2
`blood chamber
`3
`air chamber
`4
`pressure sensor
`5
`casing
`6
`upper case
`7
`lower case
`8
`blood chamber
`9
`air chamber
`10
`through hole
`11
`through hole
`12
`drip chamber
`13
`air
`14
`blood
`15
`pressure sensor
`16
`blood pump
`17
`pressure measuring device
`18
`plasma separator
`19
`flow regulating valve
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`Fig. 1
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`Fig. 2
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`Fig. 4
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`CASING
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`BLOOD
`CHAMBER
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`DIAPHRAGM
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`AIR
`CHAMBER
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`Fig. 9
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`Fig. 3
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`PRESSURE
`DROP
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`PRESSURE
`RISE
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`Fig. 6
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`PRESSURE
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`PRESSURE
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`Fig. 5
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`Fig. 7
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`Fig. 8
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`Fig. 10
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`TRANSLATOR’S DECLARATION
`
`I, Tatsuo I-IARA of HARA Patent Translation residing at 11-53-201,
`
`Minoh 2—chome, Minoh~shi, Osaka, Japan, amaadapanese language
`
`translatorwithovertwentyfiveyearsofexperiencetranslating
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`technical,
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`legal, and business documents from Japanese to
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`English and fronlflnglish to Japanese. Being fluent in both the
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`Japanese and English languages,
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`I certify under penalty of
`
`perjury under the laws of the United States that:
`
`1 .To the best of my knowledge and belief, the preceding document
`
`is a true and correct English translation of Japanese Patent
`
`Publication No. H9—24026;
`
`2.All statements made herein of my own knowledge are true and
`
`that all statements made on information and belief are believed
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`to be true; and
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`3.This declaration was made with knowledge that willful false
`
`statements and the like so made are punishable by fine or
`
`imprisonment or both under 18 U.S.C. § 1001.
`
`Date: January 13, 2016
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` Translator Name:
`
`/Z,
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`‘\
`
`Tatsuo HARA
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