(12) Ulllted States Patent
`Soussan et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,526,357 B1
`Feb. 25, 2003
`
`US006526357B1
`
`(54) ASSOCIATED PARAMETER MEASURING
`AND/OR MONITORING SUCH AS IN THE
`EVALUATION OF PRESSURE DIFFERENCES
`
`(75)
`
`Inventors: Daniel A. Soussan, Lakewood, CO
`(US); Douglas P. Miller, Lakewood,
`co (US)
`
`(73) Assignee: Gambro, Inc., Lakewood, CO (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 105 days.
`
`(21) Appl. N0.: 09/631,204
`
`(22)
`
`Filed:
`
`Aug‘ 1’ 2000
`
`(60)
`
`Related U.S. Application Data
`Provisional application No. 60/147,958, filed on Aug. 9,
`1999.
`
`(51)
`
`Int. Cl.7 .............................................. .. G06F 19/00
`U.S. Cl.
`........................................ ..
`(58) Field Of Search ......................... .. 604/65; 364/509;
`702/45; 73/304; 222/15
`
`(56)
`
`References Clted
`Us. PATENT DOCUMENTS
`2
`9
`’
`4,161,880 A
`4,168,517 A
`4,227,420 A
`4,315,309 A
`4,370,983 A
`4,403,296 A
`4,600,401 A
`4,661,246 A
`4>710>164 A
`4>718>891 A
`4’739’492 A
`4,828,543 A
`4,879,040 A
`4,954,128 A
`
`7/1979 Prosky
`9/1979 Lee
`10/1980 Lamadrid
`2/1982 C011
`2/1983 Lichtenstein
`9/1983 Pmsky
`7/1986 Kamen
`4/1987 Ash
`12/1987 L°Vin 6‘ a1~
`1/1988 Lipps
`4/1988 Cochran
`5/1989 Weiss et al.
`11/1989 Prince et al.
`9/1990 Ford
`
`5,069,792 A
`5,174,894 A
`5200990 A
`5,211,849 A
`
`12/1991 Prince et al.
`12/1992 Ohsawa et a1.
`4/1993 Fwd 6% a1~
`5/1993 Kitaevich et al.
`
`8/1993 Duff
`5234508 A
`(List Continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`EP
`
`EP
`EP
`EP
`
`0967554 A1
`
`12/1999
`
`0990417 A1
`
`4/2000
`
`0993803 A1
`0997102 A1
`0997103 A1
`
`4/2000
`5/2000
`5/2000
`
`Primary Examiner—John S. Hilten
`Assistant Examiner—Xiuqin Sun
`(74) Attorney, Agent, or Firm—Peter H. Scull; Edna M.
`O’Connor; Laura M. Butterfield
`
`ABSTRACT
`(57)
`Closer
`Correction quantities are generated for
`approximations of actual parameters. These are Obtained by
`preliminarily subjecting parametric transducers to pre-
`selected parametric values and recording the measured val-
`ues for each transducer in a data table for later use as or in
`colrrection q1$antitiets)iAn elmbodilment inclufles interpolatifin
`re ative to
`ata ta
`e Va ues c osest
`to t e operationa y
`measured parametric value and using the resulting interpo-
`lated value as a corrected parametric value. Such interpola-
`.
`.
`tions may be performed for two parametric transducers
`relative to two substances. The resulting corrected paramet-
`ric values may then be subtracted to.obtain a parametric
`difference. Afurther embodiment may include using correc-
`tion quantities of a reference parametric transducer in inter-
`polation calculations for the actual parametric transducers.
`Similarly, other data table correction recordations such as
`differences between two measured parameters can be used to
`modify an operationally measured parametric differential.
`Reference transducer corrections can be used here as well
`'
`
`22 Claims, 7 Drawing Sheets
`
`
`
`000001
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`U.S. PATENT DOCUMENTS
`
`5,263,924 A
`53779188 A
`5,326,476 A
`5’344’568 A
`5,370,123 A
`5372709 A
`5,431,811 A
`5,441,636 A
`5,473,537 A
`5,482,049 A
`5,487,827 A
`5,497,665 A
`5,510,716 A
`5,510,717 A
`5,536,237 A
`5,551,440 A
`
`11/1993 Mathewson
`1/1994 5°11“
`7/1994 Grogan et al.
`9/1994 Kitaevich et a1’
`12/1994 Shinzato
`12/1994 H°°d
`7/1995 Tusinietal.
`8/1995 Chevalletetal.
`12/1995 Glazeretal.
`1/1996 Addissetal.
`1/1996 Peterson etal.
`3/1996 Cage etal.
`4/1996 Buffaloe, IV et al.
`4/1996 Buflaloejlv etal.
`7/1996 Prince et 211.
`9/1996 Miyawaki
`
`US 6,526,357 B1
`Page 2
`
`1.
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`‘
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`364 509
`/
`
`4/1997 Rosa et al.
`5,618,441 A
`1
`7/1997 N’ h’
`1
`5,645,642 A
`7/1997 B::g1gZ:r0ef/as
`5650 071 A
`11/1997 Kenley et 211
`5,690,831 A
`.
`’
`’
`Efaflkro oulos et 211
`A
`1/1998 F ldp pt
`1
`5’711’883 A
`3/1998 K0 len eta].
`5,725,776 A
`53745377 A * 41998 P“ 0":
`57499364 A
`41998 siiwerf fig '1~~~~~~~~~~~~~~
`57769091 A
`71998 B“’‘’‘‘’ "te
`57889851 A
`E51998 Kmfgerf
`59109252 A
`6/1999 T°’¥tfyt°1“‘
`63045510 A
`42000 0"“ etai
`9
`9
`/
`.g‘.“ 6 a"
`6,280,408 B1
`8/2001 Slpln ......................... .. 604/65
`
`*
`
`* cited by examiner
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`U.S. Patent
`
`Feb. 25, 2003
`
`Sheet 1 of 7
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`US 6,526,357 B1
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`00
`VB
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`FigureI
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`U.S. Patent
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`Feb. 25, 2003
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`Sheet 2 of 7
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`US 6,526,357 B1
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`Figure 2
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`U.S. Patent
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`Feb. 25, 2003
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`Sheet 3 of 7
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`US 6,526,357 B1
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`Figure 3
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`U.S. Patent
`
`Feb. 25, 2003
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`Sheet 4 of 7
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`US 6,526,357 B1
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`100
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`TRANSDUCER
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`

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`U.S. Patent
`
`Feb. 25, 2003
`
`Sheet 5 of 7
`
`US 6,526,357 B1
`
`J10
`
`PRELIMINARY TO
`A CTUAL USE
`
`
`
`PRESS URIZE APPARA TUS TUBING
`SYSTEM TO ONE OF PLURALITY OF <-j
`PRE-SELECTED PRESSURE VALUES
`
`112
`
`I15
`
`MEASURE AND RECORD IN A
`DATA TABLE CORRESPONDING
`TRANSDUCER PRESSURE VALUES
`
`
`
`J14
`
` PRESS URIZE
`ALL PRE-SELECTED
`
`VALUES .7
` I20
`
`
`
`
`11.7
`
`I22
`
`
`
`PROCEED TO
`ACTUAL USE
`
`
`
`
`
`
`
`
`
`
`
`SELECT FROM DATA TABLE THE
`NEAREST TABLE VALUES FOR
`EACH MEASURED VALUE
`
`
`
`I24
`
`MEASURE OPERA TIONAL
`TRANSDUCER PRESSURE VALUES
`
`
`
`CONVERSION TO
`
`/LCORRECTED PRESSURE VALUES 1
`
`125
`
`
`
`CALCULA TE IMP
`
`
` I30
`
`
`
`126
`
`.728
`
`OPERA TION
`COMPLETE
`
`YES
`
`END
`
`Figure 7
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`
`Feb. 25, 2003
`
`Sheet 6 of 7
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`US 6,526,357 B1
`
`PRELIMINARY TO
`ACTUAL USE
`
`110
`
`
`
`PRESS URIZE APPARA TUS TUBING
`SYSTEM TO ONE OF PLURALITY OF
`PRE—SELECTED PRESSURE VALUES
`
`112
`
`H 7
`
`MEASURE CORRESPONDING
`TRANSDUCER PRESSURE VALUES
`
`
`
`
`RECORD CORRECTIONS IN DA TA TABLE
`
`I I 9
`
`120
`
`
`
` PRESS URIZE
`ALL PRE—SELECTED
`
`VALUES ?
`
`YES
`
`CALCULA TE DIFFERENTIAL
`
`CORRECTION VAL UES
`
`115 118
`
`1“
`
`PROCEED TO
`ACTUAL USE
`
`122
`
`MEASURE OPERA TIONAL
`TRANSDUCER PRESSURE VALUES
`
`SELECT FROM DA TA TABLE THE
`NEAREST TABLE VALUES FOR
`EACH MEASURED VALUE
`
`CALCULA TE TMP
`
`I24
`
`126
`
`J28
`
`
`
`
`
`
`.
`Fzgure 8
`
`OPERA TION
`CoM1;LETE
`
`
`
`
`
`YES
`
`130
`
`END
`
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`U.S. Patent
`
`Feb. 25, 2003
`
`Sheet 7 of 7
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`US 6,526,357 B1
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`534\®
`
`463
`
`//
`
`486
`
`412
`
`'4 /
`/
`/
`F“ / 445
`359 / 397
`/
`309 // 345
`257 // 298
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`203 // 247
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`
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`
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`
`150 200 250 300 350 400 450 500
`APPLIED PRESSURES (Fa) G’ (Wu)
`
`-63
`
`Figure 9
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`US 6,526,357 B1
`
`1
`ASSOCIATED PARAMETER MEASURING
`AND/OR MONITORING SUCH AS IN THE
`EVALUATION OF PRESSURE DIFFERENCES
`
`This patent document claims the benefit of the U.S.
`Provisional Application having the Ser. No. 60/147,958;
`filed on Aug. 9, 1999.
`
`FIELD OF THE INVENTION
`
`invention generally involves means and
`The present
`methods for measuring and/or monitoring parametric differ-
`ences between associated fluid materials and is more par-
`ticularly directed to measuring a pressure difference between
`fluids separated by a semi-permeable membrane. Pressure
`difference monitoring according to this invention presents a
`distinct advantage in extracorporeal blood systems, particu-
`larly in a procedure called therapeutic plasma exchange
`
`BACKGROUND OF THE INVENTION
`
`Many fluid systems require accurate measurements of
`various properties and/or parameters of the fluids flowing
`therethrough. In some of these systems,
`the importance
`derives from the measurements of individual parameters. In
`other cases, it is the change or difference in parameters that
`is important. In either event, the accuracy required for each
`particular fluid system may vary according to the particular
`fluid(s) involved and/or depending on the purpose of that
`system.
`An example of a fluid system having special requirements
`which can be significantly impacted by the accuracy of
`parametric measurements, particularly involving pressure
`determinations, is a blood flow system outside the body, also
`known as an extracorporeal blood system. An extracorporeal
`blood system usually includes a device for processing the
`blood flowing therethrough. There are numerous types of
`such devices. Filtration devices having semi-permeable
`membranes are commonly used in extracorporeal blood
`systems such as those used in dialysis or therapeutic plasma
`exchange
`The primary purpose of a semi-permeable
`membrane is usually to provide for the removal or separa-
`tion of certain elements or components from the blood. Urea
`and other waste products are removed from blood in
`dialysis, and blood plasma is separated from the red blood
`cells in TPE. The processed blood or red blood cells are then
`returned to the patient.
`More specifically,
`in an extracorporeal blood system
`using a semi-permeable membrane device, the process is as
`follows. Blood is removed from the patient, passed along
`and in contact with one side of a semi-permeable membrane.
`Unwanted portions of the blood (urea in dialysis, plasma in
`TPE) diffuse or
`filter
`through the pores of the semi-
`permeable membrane. The blood remaining on the blood
`side of the semi-permeable membrane is then returned to the
`patient with less of the unwanted substance.
`Poor accuracy of pressure measurements in this art can
`create problems for the blood cells flowing through such a
`system. Excessive pressures or pressure differentials may
`cause red blood cells to become stuck in certain components
`of the system such as in the pores of a semi-permeable
`membrane and/or, at worst, these red cells may be pushed
`into or against certain system components until the red cells
`burst, a consequence called hemolysis. Repetitive red cell
`destruction in this fashion would then result in a reduction
`
`in the number of red blood cells available for carrying
`oxygen to the other cells of the body. Asubstantial reduction
`
`5
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`2
`in red blood cells can thereby lead to oxygen deficiency
`injury or death. On the other hand, insufficient pressure
`differences in extracorporeal blood systems will result in
`less effective separation of the blood components from each
`other, as for example, of urea from the blood in a dialysis
`system, or of red blood cells from plasma in apheresis or
`therapeutic plasma exchange (TPE).
`The performance of semi-permeable membrane systems,
`and indeed of the membranes themselves, depends, in part,
`on the pressure difference across the membrane which is
`called the trans-membrane pressure (TMP). Generally, as the
`TMP across the membrane increases, more unwanted sub-
`stances pass through it. If the TMP on the membrane is large
`enough, the membrane will rupture or the blood will be
`damaged as described above. Therefore, there is often a
`desire to make the TMP as high as possible to make the
`treatment proceed faster, but not so high as to damage the
`membrane or the blood. The more accurately the TMP can
`be measured, the closer to the damage point the treatment
`can be performed.
`Pressure difference monitoring across a semi-permeable
`membrane has been conventionally performed using two
`pressure transducers in the fluid system, one on each side of
`the membrane. Pressure readings are then taken and, either
`manually or using a microprocessor, one measured pressure
`is subtracted from the other. The resulting pressure differ-
`ence is the trans-membrane pressure (TMP) referred to
`above. Also, because the fluid pressure varies along the
`length of the membrane, additional pressure transducers
`have also been used on either or both sides of a membrane
`
`to improve the accuracy of the ultimate TMP calculation.
`Average pressures on either or each side of the membrane
`can thus be obtained and these resulting average pressures
`subtracted one from the other to yield a better approximation
`of the actual pressure difference across the membrane.
`More particularly, in conventional extracorporeal blood
`systems using a semi-permeable membrane disposed inside
`a filter device,
`it
`is common to measure the pressures
`outside, yet near the filter device with pressure transducers
`disposed adjacent the inlet and outlet of the filter device on
`the blood side of the membrane and adjacent the outlet of the
`filtrate side of the membrane. This allows calculation of an
`
`average TMP with the formula:
`
`Blood Inlet + Blood Outlet
`
`Average TMP =
`
`2
`
`— Filtrate Outlet
`
`On the other hand, the maximum TMP experienced by the
`membrane needs only two of these transducer readings;
`namely, the pressure measurement at the blood inlet to the
`filter device and the measurement at the filtrate outlet. Thus,
`this maximum TMP maybe expressed as:
`Maximum TMP=Blood Inlet—Filtrate Outlet.
`
`Thus, using three pressure transducers, one each at the blood
`inlet, blood outlet and filtrate outlet, both the average and
`maximum TMP’s can be calculated. Note,
`the semi-
`permeable membrane performance is generally associated
`with the average TMP, whereas failure of the membrane is
`usually related to the highest TMP experienced by the
`membrane.
`
`Nonetheless, both of these (and all other conventional)
`methods also depend for accuracy upon the precision of the
`transducers used. And, most measuring systems have some
`inherent inaccuracy associated with them. Indeed, pressure
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`3
`transducers in this field commonly exhibit 110% error in
`accuracy each relative to the actual pressure at that respec-
`tive point in the fluid system. A linearity error of 11% can
`also be expected. When using two or more of such trans-
`ducers to determine a pressure difference, these error mar-
`gins can then be compounded.
`For example, in a typical pressure transducer system for
`an extracorporeal blood system which has an inaccuracy of
`110% for each transducer measurement, the overall accu-
`racy of the pressure difference when measured with a two
`transducer system may be reduced by as much as a first
`110% from the first measurement. And, it may experience a
`still further accuracy reduction of an additional 110% from
`the second measurement. This invention is intended to
`
`address this compounding of measurement error.
`It is further apparent that there remains a distinct need for
`continued improvements in parametric monitoring particu-
`larly in fluid pressure difference evaluation which provides
`for more accurately determining the difference between the
`pressures occurring on both sides of a semi-permeable
`membrane. Better accuracy in pressure difference measure-
`ments will provide better achievement of target pressure
`differences in practice to substantially eliminate hemolysis
`and improve fluid component separation. It is toward all of
`these ends that the present invention is directed.
`SUMMARY OF THE INVENTION
`
`The present invention is directed to means and methods
`for approximating pressure differentials experienced in a
`fluid system. More particularly,
`the present
`invention
`involves using preliminarily measured and/or calculated
`correction quantities to modify the operationally measured
`pressure values to arrive at a closer approximation of the
`actual pressure differential.
`In general,
`the correction quantities used herein are
`obtained by preliminarily pressurizing the system pressure
`transducers to various pre-selected pressures and recording
`the corresponding preliminarily measured values for each
`transducer in a data table for later use as or in the derivation
`
`of correction quantities. A first use of such correction
`quantities is to interpolate between the two closest data table
`values relative to the operationally measured pressure value
`and use the resulting interpolated value as the corrected
`pressure value. This sort of interpolation may be performed
`for each of two pressure transducers, one on each side of the
`membrane. The resulting corrected pressure values are then
`subtracted from each other to obtain the corrected pressure
`difference or TMP. An alternative of this correction scheme
`
`involves using data table correction quantities of a reference
`pressure transducer in the interpolation calculations of the
`two membrane pressure transducers.
`Similarly, other correction quantities can be recorded in a
`data table during a preliminary pressurization phase as
`describe briefly above. For example, the respective differ-
`ences between the two preliminarily measured pressures of
`each of the trans-membrane pressure transducers may be
`recorded as correction quantities for each preliminarily
`applied pressurization. These correction quantities can then
`be used to mathematically modify the operationally mea-
`sured pressure differential during actual fluid flowing use.
`Also, a reference transducer can be used here as well such
`that the differences between one membrane transducer and
`the reference transducer can be recorded in the data table as
`
`10
`
`15
`
`20
`
`25
`
`30
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`35
`
`40
`
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`
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`
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`
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`one set of correction quantities, and the differences between
`the other membrane transducer and the reference can be
`
`65
`
`recorded as a second set of correction quantities. Both
`correction quantities may then be used in the ultimate
`
`4
`determination of the pressure difference across the
`membrane, the TMP.
`Other fluid parameters such as temperature, volume,
`flowrate and the like can also be better evaluated according
`to the present invention. For the purposes hereof, fluids
`include gases and/or liquids.
`Accordingly, the primary object of the present invention
`is to provide improved accuracy in determining the param-
`eters exhibited in a fluid system, particularly in determining
`pressure differentials in fluid systems having two or more
`fluids separated by a membrane.
`A further object is to improve pressure differential accu-
`racy using only two pressure transducers; one on each side
`of a membrane.
`
`A still further object is to improve pressure differential
`accuracy using two pressure transducers; one on each side of
`a membrane both modified relative to a third pressure
`transducer.
`
`These and other features of the present invention will be
`further illuminated in the following detailed description read
`in conjunction with the accompanying drawings which are
`described briefly below.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic view of an extracorporeal fluid
`system in which the pressure monitoring means and methods
`of the present invention may be used;
`FIG. 2 is an isometric view of an extracorporeal fluid
`apparatus generally incorporating an extracorporeal system
`such as that shown in the schematic of FIG. 1;
`FIG. 3 is a schematic view of a fluid system like that
`shown in FIG. 1 as incorporated on the extracorporeal
`apparatus of FIG. 2;
`FIG. 4 is an isometric view of a disposable pressure
`component which may be used in accordance with the
`present invention;
`FIG. 5 is a cross-sectional view of the disposable pressure
`component of FIG. 4 taken along line 5—5 thereof;
`FIG. 6 is a schematic diagram of a pressure tubing system
`which may be internally incorporated into the apparatus
`shown in FIGS. 2 and 3;
`FIG. 7 is a block diagram showing a method for improved
`parameter monitoring according to the present invention;
`FIG. 8 is a block diagram of an alternative method for
`improved parameter monitoring according to the present
`invention; and
`FIG. 9 is a graphical representation of an example of
`preliminarily applied pressure values and the corresponding
`preliminarily measured pressure values.
`DETAILED DESCRIPTION
`
`The present invention is primarily directed to means and
`methods for measuring pressure differentials, an exemplary
`use of which is shown in the attached drawings. As dis-
`cussed below, this invention can be used in numerous fluid
`systems. Use in one preferred system, generally referred to
`as dialysis, will now be described. The general term dialysis
`as used here includes hemodialysis, hemofiltration, hemo-
`diafiltration and therapeutic plasma exchange, among other
`similar treatment procedures. In dialysis generally, blood is
`taken out of the body and exposed to a treatment device to
`separate substances therefrom and/or to add substances
`thereto, and is then returned to the body.
`An extracorporeal blood treatment system capable of
`performing general dialysis (as defined above,
`including
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`TPE) is shown and identified in the attached drawings by the
`reference numeral 10. In particular and as shown primarily
`in FIG. 1, system 10 generally comprises a blood tubing
`circuit 12 having first and second tubing segments 14 and 16
`which are both connected to the vascular system of a patient
`18 via access and return devices 17 and 19, respectively.
`Devices 17 and 19 are preferably cannulas, catheters,
`winged needles or the like as understood in the art. Tubing
`segments 14 and 16 are also connected to a filtration or
`processing unit 20. In dialysis, filtration unit 20 is a dialyzer,
`which is also often referred to as a filter. In TPE, it may also
`be referred to as a plasma filter. Filtration unit 20 is shown
`schematically divided into a primary chamber 21 separated
`from a secondary chamber 22 by a semi-permeable mem-
`brane 23 (not shown in detail). In this extracorporeal system
`10, primary chamber 21 accepts blood flow from blood
`circuit 12 and, as described below, processing fluid flows in
`and through secondary chamber 22. Aperistaltic pump 24 is
`disposed in operative association with the first tubing seg-
`ment 14 and an air bubble trapping drip chamber 25 is
`shown in the second tubing segment 16. A bubble detector
`26 is often included on or adjacent the bubble trap 25.
`Numerous other component devices of blood circuit 12 are
`preferably also included as, for example, the three pressure
`sensors 27, 28, and 29 as well as the tubing clamps 30 and
`31.
`
`Also shown schematically in FIG. 1 is the processing fluid
`or filtrate side of system 10 which generally comprises a
`processing fluid circuit 40 having first and second process-
`ing fluid tubing segments 41 and 42. As mentioned, each of
`these tubing segments is connected to the secondary cham-
`ber 22 of filtration unit 20. In this schematic, a respective
`fluid pump 44, 46 is operatively associated with each of
`these tubing segments 41 and 42. First tubing segment 41 is
`also connected to a processing fluid source 48 which may
`include electrolytes pre-mixed therein or which may be
`added by an online source 50 (or multiple sources, not
`shown).
`In dialysis,
`the processing fluid is a dialysate
`mixture preferably including sodium bicarbonate, inter alia,
`as is known in the art. A fluid bag 49 (or bags) (see FIGS.
`2 and 3, below) may be used in lieu of sources 48 and 50.
`Dry powder canisters (not shown) may also be used as is
`known in the art. Second tubing segment 42 is connected to
`a waste collection device which, as shown schematically in
`FIG. 1 could be a drain 52. The waste device is also
`
`commonly a waste container such as a bag 53 (not shown in
`FIG. 1, but see description relative to FIGS. 2 and 3, below).
`Apressure sensor 54 is also disposed in second dialysis fluid
`tubing segment 42. At
`times in TPE and certain other
`dialysis procedures, no processing fluid is added or pumped
`into the system. Rather, only filtrate may be removed
`through the membrane 23 and pumped out of the filtration
`device 20 through tubing segment 42.
`FIG. 1 shows and the above description describes a
`system which is common as a basic model for numerous
`dialysis procedures including TPE. Additional fluid lines,
`circuits, and componentry may be added (or deleted) to
`increase treatment options. Shown in more detail in FIGS. 2
`and 3 is an apparatus 60 which may be used to provide the
`basic fluid circuits shown in FIG. 1 as well as some
`
`additional features with which the present invention may be
`used. Though less complex apparatuses may be available for
`use with the present invention, it is preferred to be employed
`with an apparatus such as apparatus 60 as described and
`shown herein. In particular, FIGS. 2 and 3 depict an extra-
`corporeal blood processing or dialysis apparatus 60 which
`provides numerous treatment options which are controlled
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`25
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`30
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`and/or monitored via the control/display screen 61. Touch-
`screen controls may be incorporated herewith and/or other
`conventional knobs or buttons (not shown) may be used.
`Other and more detailed information regarding an example
`apparatus 60 may be found in U.S. Pat. Nos. 5,679,245;
`5,762,805; 5,776,345 and 5,910,252; inter alia.
`A general dialysis treatment procedure as performed, for
`example, with an apparatus 60, will now be described with
`reference to FIGS. 2 and 3. First, blood is removed from the
`patient 18 via access device 17 and flows through access line
`14 to the apparatus 60 and filter 20. Apparatus 60 and filter
`20 process this blood according to a selected one or more of
`a number of extracorporeal blood treatment protocols and
`then return the processed or treated blood to the patient 18
`through return line 16 and return device 19 inserted in or
`otherwise connected to the vascular system of the patient 18.
`The blood flow path to and from the patient 18, which
`includes the access device 17, the access line 14, the filter
`20, as well as the return line 16 and return device 19 back
`to the patient forms the blood flow circuit 12 such as the
`schematic one shown and described relative to FIG. 1 above.
`
`Each of the treatment protocols used by apparatus 60
`preferably involves passing the blood in the blood circuit 12
`through filtration unit 20. The filtration unit 20 uses a
`conventional semi-permeable membrane (not specifically
`shown in FIGS. 2 and 3) which, as described above, divides
`the filter 20 into primary and secondary chambers 21 and 22
`(also not specifically shown in FIGS. 2 and 3). The semi-
`permeable membrane confines the blood in the primary
`circuit 12 to the primary chamber 21. The semi-permeable
`membrane allows matter or molecules from the blood in the
`
`primary chamber 21 to migrate (by diffusion or convection)
`across the semi-permeable membrane into the secondary
`chamber 22, and generally may also allow matter or mol-
`ecules from the secondary chamber to diffuse across the
`semi-permeable membrane from secondary chamber 22 into
`the blood in the primary chamber 21. Each treatment pro-
`tocol here generally involves removing extracorporeally
`undesired matter from the blood and/or adding extracorpo-
`really desirable matter to the blood.
`First pressure sensor 27 is shown in FIGS. 2 and 3 as it
`is connected in the access line 14 (this connection is shown
`better in FIG. 3). The first pressure sensor 27 allows the fluid
`pressure in the access line 14 to be monitored independently
`as well as being used in measuring the trans-membrane
`pressure (TMP) as is described below.
`The first peristaltic pump 24 is also shown as operably
`connected to the access line 14 and controls the rate of blood
`
`flow through the blood circuit 12. Typically, the first pump
`24 is operated when the blood to be treated is withdrawn
`from an artery or vein of the patient 18 through access
`device 17. The first pump 24 creates a pressure downstream
`thereof in the access line 14 which is higher than the blood
`pressure in the patient’s return blood vessel in which the
`return device 19 is inserted. The pressure differential created
`by the first pump 24 draws the blood from the vascular blood
`source through the access device 17, and forces it through
`the blood circuit 12, the filtration unit 20 and back through
`the return line 16 and return device 19 into the lower
`
`pressure environment of the patient’s return blood vessel.
`Second pressure sensor 28 is connected in the blood
`circuit 12 between the first pump 24 and the blood entrance
`into the filter 20. Besides being used for calculation of the
`TMP as described hereinbelow, another general function of
`the second pressure sensor 28 is to detect and monitor the
`pressure of the blood supplied to the entrance to the filter 20.
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`This information may be used to indicate an alarm, for
`example, if the blood pressure at the entrance falls below a
`predetermined value, in which case blood may be leaking.
`A third pressure sensor 29 is connected at or near the
`outlet of the filter 20. Here also, a featured purpose of sensor
`29 is in the determination of the TMP; however, another of
`its functions is to monitor the pressure of the blood in the
`return line 16 at the exit from the filter 20 for comparison
`with the pressure sensed by the sensor 28 such that the
`integrity of the flow path through the filter 20 can be
`monitored and, in particular, clotting of blood inside filter 20
`can be detected. In addition, if the return pressure detected
`by the third pressure sensor 29 is below a pre-selected level,
`disconnection of the return line 16 or the return device 19
`
`may be indicated.
`A bubble detector 26 is shown in FIG. 2 as preferably
`connected in the blood circuit 12 on apparatus 60 down-
`stream of the third pressure sensor 29. The bubble detector
`26 is one of many known in the art and its function is to
`detect the possible presence of bubbles and microbubbles in
`the treated blood being returned to the patient 18 in the
`return line 16. Abubble trap 25 is not shown in FIGS. 2 or
`3. This illustrates a concept known in the art that a bubble
`trap is not required though it had customarily been preferred
`in these procedures as shown in the embodiment of FIG. 1.
`Downstream of bubble detector 26, a return clamp 31 is
`also shown as preferably connected in the blood circuit 12.
`Return clamp 31 selectively allows or terminates the flow of
`blood through the blood circuit 12. Preferably, return clamp
`31 may be activated whenever air is detected in the blood by
`bubble detector 26.
`
`It is desirable when performing any of the various extra-
`corporeal treatments possible using the apparatus 60 that
`anticoagulant be added to the blood in the blood circuit 12.
`The anticoagulant is preferably added to the blood prior to
`its delivery to the filter 20 in order to prevent undesirable
`coagulation of the blood resulting from contact of the blood
`with the semi-permeable membrane and/or other compo-
`nents within the blood circuit 12. To add the anticoagulant,
`a pump 62 (see FIG. 2) on apparatus 60 is connected to an
`anticoagulant container 64 to deliver anticoagulant through
`an anticoagulant line 65 to the blood in tubing segment 14.
`The anticoagulant container 64 is preferably a conventional
`syringe having a barrel and a plunger, and the pump 62 is a
`mechanical drive device to move the plunger into the barrel,
`thereby dispensing the anticoagulant into the blood in the
`blood circuit 12 on either a continuous or periodic basis. The
`anticoagulant container may also be a container connected to
`scales which weigh the content of the anticoagulant in the
`anticoagulant container. In such a case (not shown), pump
`62 would preferably be a peristaltic pump (also not shown)
`which would deliver the anticoagulant from the anticoagu-
`lant container through the anticoagulant line 65.
`It is sometimes desirable when performing certain treat-
`ments using the apparatus 60, such as in TPE procedures, to
`add a replacement fluid to the blood flowing in the blood
`circuit 12. The replacement fluid adds material to the blood
`in order to adjust the pH of the blood, to add nutrients to the
`blood, or to add fluid to the blood (as in TPE), among other
`options known in the art. A second peristaltic pump 66 is
`connectable to the blood circuit 12 either before the entrance
`
`of the blood into the filtration unit 20 (not shown), or as
`shown in FIG. 3, after the exit of the blood from the filter 20.
`The second pump 66 delivers the replacement fluid from a
`replacement fluid container or bag 68 through a replacement
`fluid line 70.
`
`8
`The secondary flow circuit 40 is also shown in FIGS. 2
`and 3 as it interacts with apparatus 60 and filter 20. The
`secondary flow circuit 40 is connected to the secondary
`chamber 22 (see FIG. 1) of filter 20. Matter extracorporeally
`removed from the blood is removed from the secondary
`chamber 22 of filter 20 through the outlet tubing segment 42
`of the secondary flow circuit 40, and matter extracorporeally
`added to the blood is moved into filter 20 through inlet
`tubing segment 41 of the secondary flow circuit 40. The
`secondary flow circuit 40 generally includes a fluid source
`suc