United States Patent [19J
`Kersten
`
`[54] PRESSURE ISOLATOR
`
`[75]
`
`Inventor:
`
`Jean Kersten, Brussels, Belgium
`
`[73] Assignee: Baxter Travenol Laboratories, Inc.,
`Deerfield, Ill.
`
`[21] Appl. No.: 26,621
`
`[22]
`
`Filed:
`
`Apr. 2, 1979
`
`Int. Cl,3 ................................................ G01L 7/08
`U.S. CI. ........................................ 73/706; 73/715;
`128/214 E; 128/DIG. 13; 210/90
`Field of Search .............. 73/706, 715; 128/214 E,
`128/DIG. 13; 422/48; 210/90
`
`[51]
`[52]
`
`[58]
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`9/1945
`Samiran ................................. 73/706
`Ast! ........................................ 73/715
`8/1960
`3/1978
`Gangemi ...... ...... .. .............. .... 210/90
`
`2,385,382
`2,948,151
`4,077,882
`
`FOREIGN PATENT DOCUMENTS
`580140 7/1959 Canada ...................................... 73/715
`
`[11]
`
`[45]
`
`4,226,124
`Oct. 7, 1980
`
`Attorney, Agent, or Firm-Paul C. Flattery; George H.
`Gerstman
`ABSTRACT
`[57]
`Apparatus for protecting a pressure sensitive transducer
`in an extracorporeal blood system and for providing a
`sterile barrier while the apparatus transmits the blood
`pressure to the pressure sensitive transducer. The appa(cid:173)
`ratus includes a pressure chamber having a lateral inlet
`and a lateral outlet, to enable convenient packaging, and
`having a membrane disposed 'transverse the chamber
`and surrounded by the chamber to segregate an inlet
`side of the chamber from the outlet side of the chamber.
`The membrane has a generally planar, circular center
`portion which lies in a plane between the outer periph(cid:173)
`eral portion of the membrane and the outlet side of the
`chamber. The membrane has an intermediate portion
`contiguous with and between the central portion and
`the outer peripheral portion, with the intermediate por(cid:173)
`tion having a generally U-shaped cross-sectional config(cid:173)
`uration. The central portion has a substantially greater
`thickness than the thickness of the intermediate portion,
`providing a superior displacement of the membrane
`during operation.
`
`Primary Examiner-Donald 0. Woodie!
`
`12 Claims, 5 Drawing Figures
`
`62
`
`72
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`U.S. Patent Oct. 7, 1980
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`Sheet 1 of 2
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`4,226,124
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`TO PATIENT
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`FROM PATIENT
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`FIG. I
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`24
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`18
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`DIALYZER
`
`-28
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`14
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`30
`
`FIG. 5
`
`g
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`h
`
`j
`
`68
`
`~
`~
`0
`I
`
`I
`
`I (72
`!
`k
`1~/~1
`
`t=mt-J
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`U.S. Patent Oct. 7, 1980
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`Sheet 2 of 2
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`4,226,124
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`50
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`40
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`M)
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`46 /
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`0
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`52
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`72
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`FIG. 2
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`·~
`3
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`FIG. 3
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`FIG. 4
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`1
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`PRESSURE ISOLATOR
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`4,226,124
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`2
`verse the chamber and surrounded by the chamber to
`segregate an inlet side of the chamber from an outlet
`side of the chamber. The membrane is fluid imperme(cid:173)
`able and has its outer peripheral portion connected to
`the surrounding housing.
`The improvement comprising the membrane having a
`generally planar, circular central portion lying in a
`plane between the outer peripheral portion and the
`outlet side. The membrane has an intermediate portion
`contiguous with and between the central portion and
`the outer peripheral portion. The intermediate portion
`extends from the outer peripheral portion in the direc(cid:173)
`tion of the inlet side and turns to have a curved portion
`contiguous with the circumference of the circular cen(cid:173)
`tral portion. In this manner, the intermediate portion
`has a generally U-shaped cross-sectional configuration
`with one side of the. U being contiguous with the outer
`peripheral portion, the other side of the U being contig(cid:173)
`uous with the central portion and the bight of the U
`being located in a plane between the outer peripheral
`portion and the inlet side.
`In the illustrative embodiment, the central portion
`has a substantially greater thickness than the thickness
`of the intermediate portion. The inlet includes an inlet
`fittillg which extends generally perpendicular to the
`axis of the pressure chamber and the outlet includes an
`outlet fitting which extends generally perpendicular to
`the axis of the pressure chamber. In the illustrative
`embodiment, the outlet fitting comprises a male luer
`connector.
`A more detailed explanation of the invention is pro(cid:173)
`vided in the following description and claims, and is
`illustrated in the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a diagram of a type of blood system to
`which the present invention is applicable;
`FIG. 2 is a top plan view of isolating apparatus con(cid:173)
`structed in accordance with the principles of the present
`invention;
`FIG. 3 is a cross-sectional view thereof, taken along
`the plane of the line 3-3 of FIG. 2;
`FIG. 4 is an exploded prospective view of an isolating
`apparatus constructed in accordance with the principles
`of the present invention; and
`FIG. 5 is a cross-sectional view of a m~mbrane used
`with the isolating apparatus of FIGS. 2-4.
`
`BACKGROUND OF THE INVENTION
`The present invention concerns an improved appara- 5
`tus for isolating a pressure sensitive device from blood
`flowing in an extracorporeal blood system and for trans(cid:173)
`mitting the blood pressure to the pressure sensing de(cid:173)
`vice.
`In a typical extracorporeal blood system, such as 10
`dialysis or oxygenation for example, blood is pumped
`from a patient through a bubble trap, through the mass
`transfer device (such as the dialyzer or the oxygenator),
`through a bubble trap and back to the patient. The
`blood pressures in the line are typically monitored using 15
`one or more pressure sensitive transducers. The trans(cid:173)
`ducers are isolated from the blood flow line by means of
`a isolating device which may be coupled between the
`blood flow line and the pressure sensitive transducer.
`The isolating device must be operable to protect the 20
`transducer, to provide a sterile barrier and to transmit
`the blood pressure to the transducer.
`One type of isolating and blood pressure transmitting
`device is disclosed in Gangemi, U.S. Pat. No. 4,077,882,
`issued Mar. 7, 1978. I have discovered an isolating de- 25
`vice that is superior in construction and operation with
`respect to the device disclosed in the Gangemi U.S.
`Patent, in that the present invention is more compact in
`construction and thus provides packaging advantages,
`has a construction which leads to a superior membrane 30
`displacement thus resulting in less head pressure losses
`and a more accurate pressure transmission, and has . a
`construction which provides a significantly greater air
`volume displacement for a full membrane displacement.
`Therefore, it is an object of the present invention to 35
`provide an isolating and blood pressure transmitting
`device that is simple in construction and is easy to man(cid:173)
`ufacture.
`Another object of the present invention is to provide
`an isolating and blood transmitting apparatus that is 40
`compact in construction and provides packaging advan(cid:173)
`tages.
`A further object of the present invention is to provide
`an isolating and blood transmitting apparatus that may
`be produced either by injection molding or· thermo- 45
`forming ..
`A still further object of the present invention is to
`provide isolating and blood transmitting apparatus that
`enables a relatively accurate pressure transmission.
`Another object of the present invention is to provide 50
`an isolating and blood transmitting apparatus that has a
`relatively large air volume displaced for the full mem(cid:173)
`brane displacement, enabling the apparatus to be con(cid:173)
`nected to a pressure-monitoring device having a large
`internal volume, or enabling use with a long connecting 55
`tube without sacrificing the precision and the upper
`limit of the applicable pressure.
`Other objects and advantages of the present invention
`will become apparent as the description proceeds.
`
`BRIEF DESCRIPTION OF THE INVENTION
`In accordance with the present invention, an appara(cid:173)
`tus is provided for isolating a pressure sensitive device
`from blood flowing in an extracorporeal blood system
`and for transmitting the blood pressure to the pressure 65
`sensing device. The apparatus includes a pressure cham(cid:173)
`ber having an inlet and an outlet for coupling to the
`pressure sensing device and a membrane disposed trans-
`
`DETAILED DESCRIPTION OF THE
`ILLUSTRATIVE EMBODIMENT
`Referring to FIG. 1, a diagram of an extracorporeal
`blood system is shown therein. This system includes an
`inlet blood line 10 from the patient, through a peristalic
`pump 12 and a bubble trap 14 to the blood inlet 16 of a
`dialyzer 18. A blood outlet 20 is coupled to the dialyzer
`blood outlet 22 and conveys the blood through bubble
`trap 24 and peristalic pump 26 back to the patient. Dial(cid:173)
`ysate fluid is pumped to the dialyzer via line 28 and
`60 from the dialyzer via line 30.
`The blood pressures are measured by a pressure mon(cid:173)
`itor 32 which includes a pressure sensitive transducer
`for each blood line under consideration. The pressure
`sensitive transducers are isolated from the blood lines
`by means of blood pressure isolators 34, each of which
`is coupled between a bubble tube inlet and a pressure
`sensitive transducer. One or more outlets 36 from the
`pressure monitor is utilized to transmit an appropriate
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`signal to control the blood flow in the appropriate
`blood line.
`A blood isolating device 34 constructed in accor(cid:173)
`dance with the principles of the present invention is
`illustrated in FIGS. 2-4. Referring to these figures, 5
`device 34 comprises a plastic pressure chamber 38 in(cid:173)
`cluding an inlet portion 40 and a mating outle~ portion
`42. Inlet portion 40 is generally cup-shaped havmg a top
`wall 44 and downwardly depending side walls 46 and
`defining a recessed inlet 48 which extends generally 10
`perpendicular to the axis a of the inl~t portion. ~t t~e
`bottom of inlet portion 40 there is a ctrcumferent1al ~1m
`50 having a tongue and groove arrangement which
`cooperates with the tongue and groove arrang:ment of
`a circumferential rim 52 carried by outlet portion 42.
`Outlet portion 42 has a bottom wall 54 and upwardly
`extending sidewall portions 56 with a recessed area 58
`having integrally formed adjacent thereto a male luer
`connector 60. Male luer connector 60 forms the outlet
`of the device and extends generally perpendicular to 20
`axis a, so that both the inlet 48 and outlet 60 are laterally
`disposed with respect to the connected inlet and outlet
`portions 40, 42, respectively.
`.
`Flexible palstic tubing 62 is connected to mlet 48 by
`pressure and adhesive bonding and a flexible pl~stic 25
`outlet tube 64 is pressure fitted over outlet 60. The mlet
`and outlet portions 40, 42 are isolated from each ?th~r
`by means of a fluid-impermeable membrane 66, which 1s
`preferably formed of EV A or PVC, with an illustrative
`example of suitable dimensions listed below.
`Membrane 66 has a peripheral portion 68, an interme(cid:173)
`diate portion 70 and a central portion 72. Peripheral
`portion 68 is circular and includes an upward!~ extend(cid:173)
`ing flange 74 which is received within a comphmenta:y
`groove defined by inlet portion 40 (see FIG. 3) while
`the underside 76 of peripheral portion 68 rests on flange
`52. Membrane 66 is formed in an integral, one-piece
`construction either by injection molding or thermo(cid:173)
`forming. Once formed, membrane 66 is sandwiched
`between inner and outer portions 40, 42.
`Intermediate portion 70 extends from the outer pe(cid:173)
`ripheral portion 68 in a direction of top wall 44 and
`turns at 80 to have a curved portion 82 contiguous with
`the circumference 84 of central por~ion ~2. As c.an be
`seen with reference to the cross-sect10nal illustration of
`the membrane 66 in FIGS. 3 and 5, intermediate portion
`70 has a generally U-shaped cross-sectional configura(cid:173)
`tion with one side 86 of the U being contiguous with
`outer peripheral portions 68, the other side 82 of the U
`being contiguous with central portion 72 and the bight
`80 of the U being located in a plane between the outer
`peripheral portion 68 and top wall 44.
`It is preferred that the central portion 72 be at least
`three times thicker than intermediate portion 82 in order
`to provide a superior displacement of the membrane.
`The following dimensions are illustrative only and no
`limitation is intended, but these dimensions have been
`found suitable for providing a satisfactory membrane
`66:
`
`45
`
`50
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`55
`
`60
`
`Reference
`Letter (FIG. 5)
`
`Dimension (In mm.)
`
`a
`b
`c
`d
`e
`f
`
`78.5
`75.5
`71.5
`2.3 radius
`0.3
`2.0 radius
`
`65
`
`15
`
`30
`
`35
`
`40
`
`-continued
`Reference
`Letter (FIG. 5)
`
`Dimension (In mm.)
`
`g
`h
`
`j
`k
`I
`m
`n
`0
`
`8.5
`8.5
`1.5
`3.0 radius
`1.0
`40
`56
`73.5
`2.0
`
`A pressure isolator has been provided which is simple
`in construction and is easy to manufacture. The mem(cid:173)
`brane can be injection molded, blow molded, pressure
`molded, or thermo-formed.
`The pressure isolator of the present inventio~ has a
`relatively flat design providing superior packagmg ca(cid:173)
`pability. As a result of the construction of the me~­
`brane in association with the pressure chamber, there 1s
`a relatively large displacement volume, allowi~g a
`longer line between the unit and the pressure momtor-
`ing device.
`.
`.
`Upwardly extending member 44 forms a sealmg hd
`which permits a large joint area with less risks of leak.
`With solvent soluable materials, an additional safety can
`be obtained by solvent brushing the seal area on both
`sides.
`In operation of the membrane, at the lowest pressure
`(for example 0 to 50 mm. mercury) centr~l portion. 72
`deforms slightly. At higher pressures, th~ mtermed1~te
`portion 70 rolls off while the central portion ~2 remams
`unaffected. This permits achieving approximately 2
`mm. of mercury deviation at 550 mm. of mercury for a
`total membrane displacement of about 17 mm.
`Although an illustrative embodiment of the invention
`has been shown and described, it is to be understood
`that various modifications and substitutions may be
`made by those skilled in the art without d~parti~g from
`the novel spirit and scope of the present mvent10n.
`What is claimed is:
`1. Apparatus for isolating a pressure-sensitive device
`from blood flowing in an extra-corporeal blood system
`and for transmitting the blood pressure from a blood
`flow line coupled to the pressure sensing device
`through the isolating apparatus, including a press~re
`chamber _having an inlet coupled to the blood flow !me
`and an outlet coupled to the pressure sensing device,
`and a membrane disposed transverse said chamber and
`surrounded by the chamber to segregate an inlet side of
`said chamber from an outlet side of said chamber, said
`membrane being fluid-impermeable and having its outer
`peripheral portion connected to the surrounding hous-
`ing, comprising:
`.
`said membrane having a generally planar, ctrcular
`central portion lying in a plane between the outer
`peripheral portion and the outlet side;
`said membrane having an intermediate portion con(cid:173)
`tiguous with and between the central portion and
`the outer peripheral portion, said intermediate por(cid:173)
`tion extending from the outer peripheral portion in
`the direction of said inlet side and turning to have
`a curved portion contiguous with the circumfer(cid:173)
`ence of said circular central portion, whereby said
`intermediate portion has a generally U-shaped
`cross-sectional configuration with one side of the U
`being contiguous with said outer peripheral por-
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`outlet coupled to the pressure sensing device being
`in communication with said outlet side and includ(cid:173)
`ing an outlet fitting which extends generally per(cid:173)
`pendicular to the axis of said pressure chamber;
`said membrane having a generally planar, circular
`central portion lying in a plane between the outer
`peripheral portion and the outlet side;
`said membrane having an intermediate portion con(cid:173)
`tiguous with and between the central portion and
`the outer peripheral portion, said intermediate por(cid:173)
`tion having a generally U-shaped cross-sectional
`configuration with one side of the U being contigu(cid:173)
`ous with said outer peripheral portion, the other
`side of the U being contiguous with the central
`portion and the bight of the U being located in a
`plane between said outer peripheral portion and
`said inlet side; and
`said central portion having a substantially greater
`thickness than the thickness of said intermediate
`portion.
`8. Apparatus as described in claim 7, said central
`portion being at least three times thicker than said inter(cid:173)
`mediate portion.
`9. Apparatus as described in claim 7, said outlet fitting
`comprising a male luer connector.
`10. Apparatus as described in claim 7, said outer pe(cid:173)
`ripheral portion including an annular flange received
`within an annular groove defined by said pressure
`chamber.
`11. Apparatus as described in claim 10, said annular
`flange being spaced inwardly from the outer periphery
`of said outer peripheral portion.
`12. Apparatus as described in claim 7, said chamber
`comprising a pair of generally cylindrical mating por(cid:173)
`tions, with one of said pair defining an annular groove,
`and said outer peripheral portion of said membrane
`including an annular flange received within said
`groove.
`
`* * * * *
`
`5
`tion, the other side of the U being contiguous with
`the central portion and the bight of the U being
`located in a plane between said outer peripheral
`portion and said inlet side;
`said inlet coupled to the blood flow line being in 5
`communication with said inlet side; and
`said outlet coupled to the pressure sensing device
`being in communication with said outlet side.
`2. Apparatus as described in claim 1, said central
`portion having a substantially greater thickness than the 10
`thickness of said intermediate portion.
`3. Apparatus as described in claim 2, said central
`portion being at least three times thicker than said inter(cid:173)
`mediate portion.
`4. Apparatus as described in claim 1, said inlet includ- 15
`ing an inlet fitting which extends generally perpendicu(cid:173)
`lar to the axis of said pressure chamber.
`5. Apparatus as described in claim 1, said outlet in(cid:173)
`cluding an outlet fitting which extends generally per-
`pendicular to the axis of said pressure chamber.
`6. Apparatus as described in claim 5, said outlet fitting
`comprising a male luer connector.
`7. Apparatus for isolating a pressure-sensitive device
`from blood flowing in an extra-corporeal blood system
`and for transmitting the blood pressure from a blood 25
`flow line coupled to the pressure sensing device
`through the isolating apparatus, including a pressure
`chamber having an inlet coupled to the blood flow line
`and an outlet coupled to the pressure sensing device,
`and a membrane disposed transverse said chamber and 30
`surrounded by the chamber to segregate an inlet side of
`said chamber from an outlet side of said chamber, said
`membrane being fluid-impermeable and having its outer
`peripheral portion connected to the surrounding hous-
`ing, comprising:
`said inlet coupled to the blood flow line being in
`communication with said inlet side and including
`an inlet fitting which extends generally perpendic(cid:173)
`ular to the axis of said pressure chamber; and said
`
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