US20120316447A1

US20120316447A1 - System and method for diverting flow to facilitate measurement of system parameters

Info

Publication number: US20120316447A1
Application number: US13/593,833
Authority: US
Inventors: Naveen Thuramalla; Nikolai Krivitski; Mark Alsberge
Original assignee: Transonic Systems Inc
Current assignee: Transonic Systems Inc
Priority date: 2007-04-11
Filing date: 2012-08-24
Publication date: 2012-12-13
Also published as: WO2008127703A3; WO2008127703A2; US8273048B2; US20080275354A1

Abstract

A method facilitating the measurement of hemodynamic parameters by injection of an indicator in an indicator dilution technique using an extracorporeal circuit connected to a patient, includes reducing a pressure spike associated with the introduction of the indicator into the extracorporeal circuit. The method diverts blood flow during an indicator introduction and then returns the diverted blood back into the extracorporeal circuit after the introduction is completed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of pending U.S. Ser. No. 12/082,692 filed on Apr. 11, 2008 hereby incorporated by reference, which claims priority under 35 USC §119(e) from U.S. provisional application Ser. No. 60/922,863 filed on Apr. 11, 2007 entitled System and Method for Redirecting Flow to Facilitate Measurement of System Parameters and United States hereby incorporated by reference, and provisional application Ser. No. 60/962,554 filed Jul. 30, 2007 titled System and Method for Redirecting Flow to Facilitate Measurement of System Parameters, each of which are hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A “SEQUENCE LISTING”

None.

FIELD OF THE INVENTION

The present invention relates to a system and method for facilitating the determination of the physical parameters of a dynamic fluid system. More particularly it relates to a method for diverting flow during an indicator dilution procedure in an extracorporeal circulatory system to facilitate determination of various hemodynamic parameters.

BACKGROUND OF THE INVENTION

Indicator dilution techniques have been used for well over a hundred years to determine various hemodynamic parameter, in particular blood flow volume etc. Indicator dilution involves the injection of some type of indicator into the circulatory system of the patient as part of the process of using the technique. For example two common types of indicators that can be injected into a circulatory system are saline solutions and dye solutions. Flow is determined by the concentration of the indicator after the indicator has flown through the system being studied. It should be noted that those skilled in the art are familiar with many other types of indicators including thermal dilution and many different techniques and sensors for implementing indicator dilution measurements.
Quite often indicator dilution is used with an extracorporeal circulating line which is attached to a patient to determine blood flow, cardiac output, blood water content or other hemodynamic parameters of the patient. An example of an extracorporeal line established in a patient for determination of cardiac output and other hemodynamic parameters is disclosed in pending U.S. patent application Ser. No. 11/370,721 filed Mar. 7, 2006 and titled System and Method for Determining Cardiac Blood Flow, which application is incorporated herein by reference as if set forth herein at length. Briefly, this patent application discloses an extracorporeal circuit that connects to the ends of a standard patient arterial catheter and venous catheter to allow the circulation of blood from the patient through the extracorporeal circuit and back into the patient. The purpose as described in detail in that patent application is to measure cardiac output and other blood parameters with indicator dilution techniques.
The use of indicator dilution techniques with extracorporeal circuits, in particular the bolus or sudden injection method of indicator dilution, can provide highly accurate readings of blood flow volume, cardiac output, etc. However, the sudden injection of the bolus of indicator creates problems and in fact can cause havoc to the flow of blood in the extracorporeal circuit. The sudden injection into an extracorporeal blood circuit of a bolus of indicator, such as a saline solution, tends to disrupt the ordinary flow of blood in the extracorporeal blood circuit in that portion of the circuit upstream from the site of injection. Typically, the indicator is being injected into an extracorporeal blood line that is already carrying its full capacity of blood flow. The sudden injection thus causes a spike in the pressure in the extracorporeal blood circuit at the point of injection as it is being forced into the line.
This sudden spike in pressure and interruption in flow of blood in the extracorporeal circuit typically results in a stoppage the flow of blood in the extracorporeal circuit upstream from the site of injection and quite often can cause a reversal of the flow of blood. This sudden stoppage or reversal of flow, even though it is only for the period of injection, creates problems with the final readings obtained by the indicator dilution technique. These problems can arise in passive systems where there is no pump or other device to regulate flow. These problems are also significant problems in systems where the blood flow in the extracorporeal circuit has been induced by and is being regulated by a pump. The stoppage of flow and/or its reversal upstream from the site of injection causes a corresponding slowing down or stopping of a pump located upstream from the injection site. The slowing or stopping of the pump introduces inaccuracies into the readings ultimately obtained with the indicator dilution injection.
Thus what is needed is a system and method that allows for the injection of a bolus into an extracorporeal circuit that prevents the sudden spike in pressure in the extracorporeal circuit from disrupting the flow of blood in the extracorporeal circuit. A system and method that eliminates the possibility that blood flow in the extracorporeal circuit above the site of injection will stop or reverse. A system and method that thus prevents conditions from developing in the extracorporeal circuit that interfere with a pump regulating flow of blood in the extracorporeal circuit.

SUMMARY

Thus, it is an objective of the present invention to provide a system and method for injecting a bolus of indicator that prevents the spike in pressure caused by the injection from disrupting the flow of blood in the extracorporeal circuit. It is a further objective to provide a system and method that maintains continuous blood flow in an extracorporeal circuit and avoids stoppage or reversal of blood flow during injection of a bolus in the extracorporeal circuit. It is an additional objective of the present invention to provide a system and method that prevents a pump regulating flow in the extracorporeal circuit from being slowed or stopped during injection of a bolus of indicator.
To achieve these and other objectives the invention provides a method for facilitating the injection of a bolus into an extracorporeal circuit that has the steps of: a.) diverting a blood flow in an extracorporeal circuit above an injection site of a bolus during the injection of the bolus into the extracorporeal circuit; and b) reintroducing the blood flow into the extracorporeal circuit that had been diverted during the injection of the bolus after the injection of the bolus has stopped. In this method the steps of diverting blood and then reintroducing it can be accomplished by providing a second blood line for redirecting flow of diverted blood from a point upstream in the extracorporeal circuit from the injection site in the extracorporeal circuit around the injection site to a point downstream from the injection site in the extracorporeal circuit. In another aspect of this method the step of diverting blood and then reintroducing it can be accomplished by diverting the blood upstream from the injection site into a volume accumulating reservoir connected to the extracorporeal circuit, which reservoir is located upstream from the injection site in the extracorporeal circuit and then reintroducing the blood from the volume accumulating reservoir into the extracorporeal circuit after the injection ceases. In a further aspect of the method of the invention it includes the step of blocking flow between the injection site and diverting site during the injecting step.
In a further aspect of the invention it provides a flow diversion apparatus in fluid communication with an extracorporeal circuit at a point upstream from an injection site in the extracorporeal circuit, the flow diversion apparatus diverting blood flow upstream in the extracorporeal circuit when a bolus is injected and reintroduces the diverted blood flow into the extracorporeal circuit after diversion of the blood stops. The flow diversion apparatus for diverting blood during injection and returning the diverted blood after injection can be selected from one of the following devices: a flow volume accommodating case, an automatic flow pressure relief system, a diverting lumen providing an alternate route to a venous catheter, or a syringe connected to the extracorporeal circuit for manually diverting blood and then returning the diverted blood to the extracorporeal circuit. In a further aspect of this variation of the invention it includes a check valve positioned between the flow diversion apparatus and the injection site to prevent flow downstream from the check valve during injection of an indicator.
In another aspect of the invention it provides a device for relieving excess pressure in an extracorporeal circuit during and injection process the device having a) a case connectable to an extracorporeal circuit; b) a conduit through the case for unimpeded flow of blood through the conduit and thus through the case, the conduit forming part of the extracorporeal circuit; c) the conduit has an expansion portion responsive to pressure increases in blood flowing in the conduit such that the expansion portion accommodates a build up of blood caused by a constriction or interruption of flow downstream from the case in the extracorporeal circuit; and d) wherein the expansion chamber accommodates the build up of blood by expansion of the expansion portion into a volume accumulation reservoir chamber within the case without loss of blood and upon the ending of the constriction or interruption of flow the expansion portion contracts back to its original shape returning the accumulated blood back to the flow of blood in the extracorporeal circuit. In one variation the expansion portion of the device responsive to pressure is rubber like material forming the conduit. In another variation of the invention the expansion portion is a lid forming a portion of the conduit wall adjacent to the expansion chamber which lid is spring loaded to thereby allow it to retract into the expansion chamber in response to restrictions or interruptions of blood flow. Another aspect of the invention includes a one way or check valve positioned in the extracorporeal circuit between the site of injection and the case with expansion chamber to prevent both back flow from the site of the injection and stop flow upstream from the one way valve to thereby accumulate blood in the expansion chamber during injection of an indicator.
In another aspect of the invention it provides an apparatus for relieving excess pressure in an extracorporeal circuit during and injection process which apparatus consists of: a) a fluid line connected at a first end to an extracorporeal circuit at a point upstream from an injection site in the extracorporeal circuit; b) a bubble trap connected at a first end of the bubble trap to a second end of the fluid line; c) a saline bag in fluid communication with the bubble trap through a tube that runs from the saline bag to a second end of the bubble trap; d) the saline bag being positioned at a point above the bubble trap and the bubble trap being positioned above the extracorporeal circuit such that fluid will run from the saline bag to the bubble trap to the extracorporeal circuit; e) a clamping mechanism that can be secured on the tube connecting the saline bag and the bubble trap after fluid from the saline bag has filled the fluid line and partially fills the bubble trap to thereby stop flow of fluid from the saline bag and seal off the bubble trap and the fluid line; and f) wherein fluid filling the fluid line and half filing the bubble trap is in a dynamic pressure balance with blood flowing in the extracorporeal circuit at standard pressure and wherein when a restriction or blockage of blood flow occurs in the extracorporeal circuit downstream from the connection of the fluid line blood from the extracorporeal circuit flows into the fluid line and when the restriction or blockage of flow ends the blood in the fluid line flows back into the extracorporeal circuit.
In another aspect of the present invention, the invention achieves these and other objectives by providing: a method for facilitating the determination of hemodynamic parameters which has the steps of: a) establishing a regulated blood flow in an extracorporeal circuit between an arterial connection and a venous connection in a patient; b) diverting blood flow from the extracorporeal circuit; c) injecting an indicator into the extracorporeal circuit; d) accumulating the diverted blood; e) ending injection of the indictor; f) ending diverting of blood from the extracorporeal circuit; g) returning the diverted blood to the extracorporeal circuit; h) measuring the changes caused by the injecting of the indictor; and i) calculating a hemodynamic parameter from the measured change caused by the indicator. In further aspect of this method the step of diverting blood flow consists of diverting blood flow into a second conduit upstream from the indicator injection location, which second conduit diverts flow of the blood around the injection location into a venous connection to the patient. In another aspect of the present invention the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood from the extracorporeal circuit and returning the diverted blood to the extracorporeal circuit are accomplished by using a pressure activated expansion reservoir.
In another variation of the method of the present invention the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood from the extracorporeal circuit and returning the diverted blood to the extracorporeal circuit are accomplished by using a pressure activated side fluid line connected to the extracorporeal circuit at a position upstream from the injection site, which side fluid line accepts diverted blood flow from the extracorporeal circuit during the injection step and return diverted blood to the extracorporeal circuit when the injection ends.
In another variation of the present invention it provides a system for facilitating the determination of hemodynamic parameters, which system has: a) an extracorporeal fluid conducting circuit with a first end that connects to an arterial catheter of a patient and a second end connecting to a venous catheter of a patient; b) a fluid propelling apparatus to move fluid through the extracorporeal circuit from the first end to the second end; c) at least one injection port on the extracorporeal circuit for access to the at least one conduit of the extracorporeal circuit; and d) an expandable reservoir in fluid communication with the extracorporeal fluid circuit at a position upstream on the extracorporeal circuit from the injection site for receiving accumulating fluid resulting from a constriction or interruption of flow downstream by an injection of an indicator and then releasing the accumulated fluid to flow down the extracorporeal circuit when the constriction or interruption of flow caused by the injection ceases.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will he better understood by an examination of the following description, together with the accompanying drawings, in which:

FIG. 1 provides a schematic diagram of one embodiment connected to a patient;

FIG. 2 is a view of a standard arterial catheter;

FIG. 3 is a view of a two lumen venous catheter with which an embodiment could be practiced;

FIG. 4 is a flow chart of one variation of a method of an embodiment;

FIG. 5 provides a schematic diagram of another embodiment;

FIG. 6. is a view of a three lumen venous catheter with which another embodiment might be practiced;

FIG. 7 is a flow chart of another variation of the method;

FIG. 8 provides schematic diagrams of another embodiment of the system attached to a patient that uses a volume accumulating case that expands as blood flow is interrupted during injection then releases the accumulated blood as flow is reestablished;

FIG. 9 provides a view of the volume accumulating case, of the embodiment depicted in FIG. 8, that expands to accumulate blood when flow is interrupted and then releases the accumulated blood after flow is restored in the system at the end of the injection of indicator;

FIG. 10A provides a schematic diagram of yet another embodiment that uses and expanding chamber in the system of FIG. 8 to accommodate accumulating blood when flow of blood is interrupted during the injection process by a shut off valve, the view in FIG. 10A being of the chamber before pressure of the accumulating blood forces the chamber to open to accumulate blood;

FIG. 10B provides a view of the expansion chamber of 10B when the accumulating blood forces the chamber to open and accumulate blood and then contract releasing the accumulated blood when flow is restored; and

FIG. 11 is a detailed schematic view of another system that automatically diverts blood during and injection to a bubble trap line and then returns it to the system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As noted above the present disclosure provides a method and system designed to facilitate the use of and indicator dilution technique for the determination of hemodynamic parameters in a circulatory system. Specifically, the disclosure facilities the injection of indicator. One example of a system and method where the present invention can be used is disclosed in pending U.S. patent application Ser. No. 11/370,721 filed Mar. 7, 2006 and titled System and Method for Determining Cardiac Blood Flow, which application is incorporated herein by reference as if set forth herein at length.
It should be noted that in this specification diverting will be utilized in its ordinary sense and to cover several possibilities to be discussed at length below, such as: 1) redirecting the flow to another location in the extracorporeal circuit or catheter to which the extracorporeal circuit attaches, or 2) accumulating the blood at a particular spot or location upstream from the site of injection where it can then be released to flow down stream. Examples which are set out below of flow redirecting are the second lumen or conduit that directs at least a portion of the blood flowing in the extracorporeal circuit around the site of injection. Examples set out below of accumulating blood being the volume accumulating case or expansion reservoir, and the flow diversion bubble line trap line.
A first embodiment of the apparatus is depicted in FIG. 1, which provides a schematic diagram of the major components of the system connected to a patient 20. The external blood circulating line or tubing 21 connects at an upstream end 23 to an arterial catheter 25 in patient 20. The down stream end 27 of the circulating line 21 connects to a venous catheter 29 in the patient. Line 21 is standard catheter tubing that creates a fluid connection between the arterial catheter 25 and the venous catheter 29. An arterial catheter 25 is typically placed in a patient in intensive care to periodically monitor the patient's blood pressure. The venous catheter 29 is placed in the patient to provide access for measuring central venous pressure (CVP) and as an intravenous (IV) connection through which prescribed drugs and other medications can be introduced into the patient's blood circulatory system.
Flow of blood in the line 21 is in the direction of arrow 31 from the arterial catheter 25 to the venous catheter 29. Line 21 also includes standard three way stopcocks 33, 35 and 37 to control flow in the line 21 as well as allow for access to line 21 so that samples or portions of blood can be withdrawn or indicators or medication can be introduced.
Access ports are provided by connectors 38 and 39 and offer additional means for obtaining fluid access to line 21. T type fluid conduit connectors 38 and 39 provide access port that are open at each end 40, 41 and 42. The conduits inside connectors 38 and 39, not shown, that run from each end and share an open interior space. Line 21 makes an unobstructed sealed fluid connection through connectors 38 and 39 where line 21 connects at end 40 and 42 of each connector respectively. Flexible tubes 43 and 44 forms sealed fluid connections to ends 41 respectively of connectors 38 and 39. Tubes 43 and 44 in turn form sealed fluid connections with flush syringe 79 and injection syringe 83 respectively. Clamps 45 and 46 close off tubes 43 and 44 respectively when access to line 21 is not needed.
Sensors 47 and 49 connect by communication lines 91 and 93 to a computer/meter 97. The sensors 47 and 49 are any standard sensor used for indicator dilution measurements. The sensors can be ultrasound sensors, laser sensors, electromagnetic, etc. all of which are well known in the art. Each sensor is controlled through signals sent from computer/meter 97 along the lines 91 and 93. Signals of reading from the sensors 47 and 49 are sent along the lines 91 and 93 to the computer meter 97 for evaluation. Appropriately programmed software, such as HDO2 software, running on a standard personal computer with a flow meter alternatively or an HDO3 meter, both of which are made by Transonic Systems, Inc. of Ithaca, N.Y. can be used to control the function of sensors 47 and 49 as well as analyze and display the results of reading taken. The apparatus depicted in FIG. 1 shown a stand Transonic Systems HDO2 setup. This specification discusses only two embodiments of transit time ultrasound sensors systems used to measure flow with indicator dilution techniques. Transit time ultrasound sensing for indicator dilution is now well known in the art. However, there are a number of sensor systems or apparatuses that can be used for measurements to determine blood flow which are familiar to those skilled and can be used without departing from the concepts and teachings of the present disclosure, among them are electromagnetic sensors, laser sensors, or any number of similar types of sensors.
FIG. 2 provides a view of the standard arterial catheter 25, well known in the art, attached to a standard stopcock 33. The arterial catheter 25 has a catheter body 24 that ends in a hub 28 which can be releasably attached to a variety of fluid access control devices, which in FIG. 2 is stopcock 33. Typically, the arterial catheter has only one lumen. A lumen being a fluid conduit passing through the body of the catheter to allow the passage of a liquid. In the catheter 25 depicted in FIG. 2, the lumen, which is not shown since it is an interior space in the catheter runs from an exterior end 32 to an interior end 30. The catheter body 24 is made of a very flexible and pliable material. Depending on the situation or needs of the patient, the arterial catheter 25 can be placed in a central artery or peripheral artery. However, the arterial catheter 25 typically is placed in the radial or femoral artery of the patient. Typically, the end 30 of catheter 25 does not intrude too far into the artery when placed, only far enough to allow the taking of blood pressure.
Referring to FIG. 1, a stopcock 33 controls access between the blood circulating line 21 and the arterial catheter 25. The stopcock 33 is as noted above attached to the arterial catheter 25 as a standard procedure to control access to the arterial catheter for obtaining pressure measurements. Referring back to FIG. 2, the stopcock 33 is a standard four way stopcock well known in the art. The stopcock 33 has three openings, one 33A that connects to the arterial catheter 25, one 33B through which access can be obtained for making pressure readings and the third opening 33C to which the blood line 21 can be attached. Typically, a standard stopcock has four settings as follows: 1) all three openings 33A, 33B and 33C are open to each other, 2) access is opened only between opening 33A, and opening 33B, 3) access is only opened between opening 33A and opening 33C and 4) access is only opened between opening 33B and opening 33C. Control lever 36 controls the selection of the four different settings described above. Further discussion regarding the function of this access control device is not necessary since it is well known in the art.
The standard venous catheter 29 of FIG. 1 differs in a number of significant aspects from standard arterial catheters. Typically, the venous catheter 29 has two lumens or sometimes three lumens. The two lumen catheter will be discussed here and the three lumen catheter will be discussed below. A catheter with at least two lumens is used in the venous catheter set up so that one of the lumens can be dedicated as an intravenous feed (IV) for introducing prescribed medications into the patient etc. The second lumen provides a general access for obtaining central venous pressure (CVP) etc. The venous catheter 29 can be inserted into a central or peripheral vein depending on the circumstances of the patient. However, typically it is inserted into the sub clavicle vein or femoral vein of the patient.
FIG. 3 is a schematic diagram of a two lumen catheter 53. The basic parts of the catheter 53 are: 1) the tip 51, 2) distal body 54, 3) catheter body 56, 4) hub 58 and 5) proximal connectors 60. The proximal connectors 60 cooperate with proximal lumen 57 and distal lumen 59. The proximal lumen 57 and distal lumen 59 join into one body at hub 58. The conduit, not shown, formed by the proximal lumen 57 then empties at the port 65 at the end of catheter body 56. The conduit formed by the distal lumen 59 then continues on and empties at the port 67 at the tip 51. Typically, the proximal lumen 57 is the one through which medication and other substances are fed directly to the patient's circulatory system. The distal lumen 59 allows for access to the patients venous system so the central venous pressure of the patient can be taken. The sections 51, 54 and 56 of catheter 53 are the portions of the catheter inserted into the veins of the patient. Although the catheter body 56 is depicted as relatively short in FIG. 3, the body can be much longer depending on the application.
Connected to the end 69 of the lumen 57 is a standard one way valve also known as a check valve 71. In a standard procedure to administer medication intravenously into the patient a syringe could be connected to the valve 71 and the medication injected. Alternately, the lumen 57 could be connected to a continuous intravenous feed with or without the valve 71 being present and flow then would be controlled in a standard fashion by a side clamp 70.
An end 68 of the lumen 59 has connected to it a standard four way stopcock 37 an example of which was described above in detail. The stopcock 37 has three openings 74, 75 and 76. Access between the openings is controlled by a valve lever 77. This stopcock functions in the same manner as stopcock 33 described above. Three different catheter control devices have been discussed herein 1) stopcocks, 2) one way valves and 3) slide clamp clips. There are other variations of these devices as well as other catheter access control devices all of which are well known in the art and can be used to practice the present invention.
Referring to FIG. 1, flow of blood through line 21 from the arterial catheter 25 to the venous catheter 29 is induced and controlled by a pump 103. In the preferred embodiment, the pump 103 used is a standard peristaltic pump. A peristaltic pump is used because such pump does not need to come in contact with the blood in line 21.
One method of the present disclosure includes the following steps: Line 21 such as all of its component parts is assembled but not connected to the arterial catheter 25 or the venous catheter 29. The stopcock 35 is opened to allow flow along the line 21. The line 21 is then filled with a saline solution and then the line is connected to the arterial catheter 25 and the venous catheter 29 as depicted in FIG. 1. Then the stopcocks 33 and 37 are opened and the pump 103 is turned on to start a flow from the end 23 to the end 27 of the line 21. Once blood flow completely fills the line 21 and the original saline in line 21 has dissipated or mixed with the patient's blood, the stopcock 35 is set to a position where the syringe 81 has fluid access to the line 21 and flow downstream in the line 21 beyond the stopcock is stopped. At the same time, the slide clamp clip 46 is moved to open up the line 44 and thereby allow downstream fluid access for the syringe 83 to the line 21, upstream flow from the line 21 as noted above being blocked.
The syringe 81, which is partially filled with a heparinized saline solution, is set so that it will fill with blood from the line 21 to thereby maintain blood flow in the line 21 from the upstream end 23 to the stopcock 35. Simultaneously, the syringe 83 which has been filled with an indicator is activated to commence injection of the indicator into the line 21 where the introduced indicator then flows downstream into the patient through the lumen 59. Operation of the syringes 81 and 83 is coordinated so that the syringe 81 accepts blood flowing in the line 21 upstream from the stopcock 35 while the indicator is injected by the syringe 83. Once the syringe 83 has completed injection of the indictor, the slide clamp clip 46 is reset closing off of access of the syringe 83 to the line 21. At the same time the stopcock 35 is reset to allow the free flow in the line 21 from the upstream direction to the downstream direction with the syringe 81, now partially filled with blood, also in fluid communication with the line 21. Then the blood in the syringe 81 is slowly reintroduced into the blood flow in the line 21. When all of the blood from the syringe 81 has been reintroduced into the line 21, the stopcock 35 is reset again to close off the syringe 81 from the line 21 but allow the continued flow of blood through the line 21 from the upstream end 23 to the downstream end 27. Readings are taken with one or both the sensors 47 and 49 at the appropriate time to determine the concentration of indicator in the blood circulating through the line 21.
Thus, as depicted in the flow chart of FIG. 4 the method encompasses setting up a controllable fluid connection, such as the extracorporeal blood circuit depicted in FIG. 1, between an arterial catheter and venous catheter in a patient 201; establishing a blood flow in the extracorporeal circuit from the arterial catheter to the venous catheter 203; diverting temporarily blood flow in the extracorporeal line to a holding area before the flow reaches the venous catheter 205; simultaneously, with or shortly after commencing the temporary diverting of blood, injecting an indicator into the extracorporeal line down stream from the point where the blood is being diverted so that it passes through the venous catheter into the circulatory system of the patient 207; once the indicator has been fully injected stopping the diversion of blood 209; reestablishing the flow of blood in the extracorporeal circuit through the venous catheter 211; slowly reintroducing the diverted blood into the extracorporeal circuit 213; measuring the concentration of indicator in the extracorporeal line caused by the injection of the indicator 21 5; and calculating the hemodynamic parameters from the measured change 217.
FIG. 5 provides a schematic diagram of another embodiment of and its connection to a patient 20. In FIG. 5, a blood line 321 at an upstream end 323 connects to an arterial catheter 325 through a stopcock 333. The external blood line 321 connects at a downstream end 327 to one of the lumens 329D of a triple lumen catheter 329 though a stopcock 337. The line 321 includes standard liquid conduit T connectors 338 on the arterial side and 339 on the venous side to allow access for a flush syringe 334 and an injection syringe 381 respectively.
An injection syringe 381 connects to the liquid conduit T connector 339 though a tubing 344. A slide clamp clip 346 controls the opening of the tube 344 to allow the passage of a liquid between the line 321 and the injection syringe 381. Likewise, a slide clamp clip 345 controls the opening of a tube 343 to allow the passage of liquid between a flush syringe 334 and the line 321. The tube 343 connects to both the T connector 338 and the flush syringe 334.
In this variation a stopcock 349 in line 321 provides an operable fluid connection to a tube 350, which tubing in turn is connected to the 2nd or medial lumen 329M of the three lumen catheter 329. The third lumen 329P, the proximal lumen of the three lumen catheter 329 is used to administer medication by an intravenous feed that is not shown.
In this embodiment, the sensors 47 and 49 connect respectively by lines 91 and 93 to a Transonic HDO3 Flowmeter. The HDO3 being an upgrade of the Transonic Systems, Inc of Ithaca N.Y. HDO2 system previously mentioned. As previous noted this is one of the embodiments of the present invention, but there are many other sensor arrays known by those skilled in the art that can be used to take the readings and analyze the data and not depart from the concepts and spirit of the present invention. The ultimate objective of the sensors and flow meter being the determination of indicator concentration in the blood after the indicator circulates through the circulatory system of the patient. From this information cardiac output and other hemodynamic parameters are determined.
FIG. 6 provides a perspective view of one variation of the three lumen catheter 329 that might be used with the present disclosure. The three lumen catheter 329 has a tip 360, a distal end 361, a catheter body 362, a hub 363 and proximal connectors 364. The proximal connectors 364 include a proximal lumen 329P, a medial lumen 329M and a distal lumen 329D. Each lumen forms a separate conduit. All three lumens 329P, 329M and 329D are joined together at hub 363. The conduits formed by each lumen then pass through catheter body 362. The conduit formed by proximal lumen 329P ends at interior proximal port 330 at the beginning the distal end 361. The conduit formed by medial lumen 329M passes into distal end 361 and has an opening at interior medial port 331. The conduit formed by distal lumen 329D passes through distal end 361 and has an opening interior distal port 332 at tip 360.
As is well known in the art each of the conduits formed by each lumen is separate from the other. Since the conduits are inside the structure of the catheter they are not shown. The conduit formed by a proximal lumen 329P has an exterior opening, not shown at the end of fastener 365, which forms the end of proximal lumen 329P. The conduit formed by proximal lumen 329P runs from interior proximal port 330 to the exterior opening in the fastener 365, and thus allows fluid communication between the interior proximal port and the exterior opening. Likewise, the conduit formed by the medial lumen 329M has an exterior opening not shown on fastener 366, which fastener forms the end of the medial lumen 329M. This conduit then runs from the exterior opening at the end of fastener 360 to interior medial port 331 to allow fluid communication between the exterior opening and interior medial port. Finally, the conduit formed by the distal lumen 329D runs from the exterior opening formed by a fastener 367, which fastener forms the end of distal lumen 329D, to the interior distal port 332 to allow for fluid communication between these points.
The hub 363 and the fasteners 365, 366 and 367 are generally made of a hard plastic type of material. On the other hand, the lumens 329P, 329M and 329D as well as the catheter body 362, the distal end 361 and the tip 360 are all made of a very flexible and pliable material. The catheter body 362, the distal 361 and the tip 360 are the portion of the catheter that is inserted into the veins of the patient.
There are various ways to control access and flow in each lumen of the catheter 329. Some of these ways to control access and flow were discussed above in some detail and will be mentioned again. One way valves 381 and 383 are each detachably connected to the fasteners 365 and 366 respectively. The ones shown have screw on attachments not shown. A stopcock 385 is attached to the fastener 367 by a twist mechanism not shown. Additionally, each lumen has a slide clamp clip 371, 372 and 373 to provide an additional means for controlling access and flow.
A somewhat detailed discussion with descriptions have been provided regarding arterial catheters, two lumen venous catheter and a three lumen venous catheter. This has been included to provide a basis for discussing the embodiments of the present disclosure. All of the information concerning catheters, their structure and function is well known in the art. Thus, what has been detailed is by way of example and not meant to limit in any way the invention. There are other types of catheters and similar devices well known in the art which could just as easily be used without departing from teaching of the present invention.
The method of this embodiment of the present invention includes assembling line 321 as depicted in FIG. 5 connecting the line to the stopcocks 337 and 333. When the line 321 is connected to the stopcocks 333 and 337 the stopcocks are in the closed position so there is no fluid communication between the arterial catheter 325, the venous catheter 329 and the line 321. The flush syringe 334 has been filled with a heparinized saline solution. The clamp 345 is released and the saline solution in the syringe 334 is injected into the line 321 to fill the line. The flow is then started in the line 321 by opening the stopcocks 333 and 337 and starting the pump 357. Once blood completely fills the line 321, the stopcock 349 is also opened to allow blood flow in the line 350 to lumen 329M and then back into the patient circulatory system. It should be noted at all times the tube 350 and lumens 329M and 329D are all pre-primed with saline solution to avoid the introduction of air into the patient circulatory system.
Next, the clamp 346 is released to open fluid communication between the injection syringe 381 and the line 321. The indicator injection syringe 381 then injects the indicator into the line 321. Since part of the blood flow in the line 321 is being diverted above by connector 329 back into the patient by way of the line 350 and the medial lumen 329M, flow volume is decreased in the line 321 at the stopcock 349 through the distal lumen 329D to the patient. This decreased flow volume allows the easy injection of the indicator from the syringe 381 into the patient without an excessive spike in pressure or the reversal of flow in the line 321.
Thus, referring to FIG. 7, the steps of this embodiment include: setting up a controllable fluid flow connection in an extracorporeal circuit between an arterial catheter and a venous catheter in a patient 401; establishing a blood flow in the extracorporeal circuit from the arterial catheter to the venous catheter 403; diverting a portion of the flow of blood in the extracorporeal circuit at a point above an injection point in the extracorporeal circuit into an alternate line for return to the patients circulatory system 405; injecting at the injection point an indicator into the extracorporeal circuit 407; measuring the concentration of injection the extracorporeal circuit after the indicator has passed at least once through the patient's circulatory system 409; and calculating the hemodynamic parameters from the measured change 411.
The two embodiments described above require operator intervention to first commence the accumulation of diverted blood from the extracorporeal circuit while the indicator is being injected and then reintroducing the diverted blood in the case of the first embodiment or shutting off of the diversion route in the case of the second example. Two additional embodiments will now be described that provide an automatic set up that accumulates or diverts that flow of blood during the injection process and then automatically reverses the process once the injection of the indicator ceases. Both of the methods or systems described below use a one way or check value to prevent reverse flow and eliminate the need to use stop cocks.
FIG. 8 is a schematic diagram of a set up of a system that would use another embodiment of the present invention that provides for the automatic release of blood that has accumulated during injection of the indicator. During the injection of indicator by an injection syringe 505, the pressure of forcing the indicator into a circulatory line 521 causes the blood circulating in the line 521 to back up and accumulate in flow accommodating case 527 which, as described in detail below, expands to accommodate the blood displaced during injection of the indicator. In most other respects the set up depicted in FIG. 8 is the same or similar to those in FIGS. 1 and 5. In FIG. 8 the circulating line 521 connects to an arterial catheter 529 at a stopcock 531 and a venous catheter 536 at a stopcock 539. Blood flow in circulating line 521 flows in the direction of arrow 541. Computer/flow meter 543 connects through a line 545 to a sensor 549 and a line 547 to a sensor 551. A flush syringe 553 connects to the circulating line 521 through a T connector 555. An injection syringe 505 connects to the circulating line 521 through a connector 559. A peristaltic pump 560 controls flow as described above.
A one way valve or check valve 563 on the line 521 prevents injected indicator from the injection syringe 505 or blood that has flowed past the check valve 563 from being forced back upstream in the circulating line 521. However, when injection syringe is injecting indicator into the line 521 check valve 563 can be forced closed, blocking during the injection process, the flow of blood in the line 521 above or upstream of the valve 563. When flow is thus blocked this does not interrupt flow in the rest of circulating line 521 since flow accommodating case 527 expands to accommodate the blood that is blocked from flowing past check valve 563, thus the case 527 acts as an expanding reservoir or volume accumulating chamber. Once the injection of indicator by the injection syringe 505 has ended the check valve 563 reopens and the flow in the line 521 is reestablished from the check valve 563 to the venous catheter 536 and the excess blood accumulated in the flow accommodating case 527 flows out. Thus, when the injection of indicator starts in this embodiment flow is stopped and accumulates and once the injection is completed flow recommences and the accumulated blood automatically flows through the system to venous catheter 536.
FIG. 9 provides a schematic diagram of one variation of flow accommodating case 527. The accommodating case 527 includes a rigid outer shell 571 with an expandable conduit 573 which before an injection forms a flow channel 575 through the shell with a diameter approximately equal to the diameter of the circulating line 521. Blood flows through the channel 575 from an entrance 577 to an exit 579. However, when flow is interrupted by an injection, the conduit 573 expands from a position 573A to 573B to accommodate the build up of blood caused by the interruption of flow. Once the injection stops and flow is no longer interrupted, the conduit 573 contracts from its expanded position at 573B back to its position during normal flow 573B. The conduit 573 can be made of any suitable flexible rubber like material.
The size that the interior space 557 of an expansion chamber defined by the shell 527 into which expanding the conduit 573 will need to expand can be easily determined by calculating the amount of blood that would accumulate during injection of the indicator. In making the calculation one would start with the pump rate at which the pump will continue to pump blood. For example if the pump rate is 12 ml/min (0.2 ml/sec) and the injection typically lasts for 6 seconds then the volume that would be accumulated by the flexible membrane of conduit 573 is 0.2 ml×6=1.2 ml. As noted above, after the injection is finished the one-way or check valve 563 will reopened and the extra volume of blood accumulated in the flexible membrane of the conduit 573 will be released into the system. Naturally, it is important that the membrane has sufficient flexibility to accommodate the estimated volume of blood that will accumulate.
FIGS. 10A and 10B provide a schematic view of another variation of a volume accommodating chamber or expansion reservoir 601 for accumulating blood during an injection with the syringe 505 (FIG. 8). Referring to FIG. 10A when the check valve 563 is open normal unobstructed flow along the line 521 occurs as indicated with blood flow as indicated by arrows 605 and 607. The expansion chamber 601 has a lid 609 and a compression or bias element 611 behind it. The lid 609 naturally has a tight seal with the sides of expansion chamber 601. The compression element 611 can be a spring or similar type of device that responds to pressure by compressing but returns to an expanded position when the excess pressure is removed. Referring to FIG. 8 when an injection with the syringe 505 begins the injectate displaces the blood flowing in the line 521, this causes blood upstream from the injections site to back up and force the check valve 563 closed. Referring to FIG. 10B once the check valve 563 closes as a result of the injection, blood begins to accumulate upstream from the check valve 563 causing pressure to build up to the point where the accumulating blood forces the lid 609 to compress the spring or compression element 611. The movement of the lid 609 into the expansion chamber 601 creates an expanding reservoir in which the blood flowing upstream from the check valve 563 accumulates. Once the injection ceases and check valve 563 reopens the pressure causing the compression element 61 to collapse, the force of the accumulating blood, is withdrawn, the compression element 611 will then force the lid 609 back to its first position in FIG. 10A. This naturally reintroduces the diverted blood back into the line 521.
Thus, as is readily apparent both the preferred embodiments shown in FIGS. 8, 9, 10A and 10B are in effect automatic systems which by means of mechanical methods provide systems to automatically accumulate blood when the flow of blood needs to be diverted during an injection and then automatically reintroduce the accumulated blood back into the system without further human intervention. One way or check valves 563 are well known in the art. The description of the flow accommodating case 527 and the flexible conduit 573 or the movable lid case 601 or its component parts the above description should be sufficient for those of ordinary skill in the art to make and use them.
FIG. 11 is a schematic diagram of another system and method for automatically diverting blood flow during and injection. The automatic flow diversion system depicted in FIG. 11 is the same in all respects as that in FIG. 8, with one exception that the flow accommodating case 527 is not used and is replaced with an automatic flow pressure relief system 701. Otherwise all of the other features of the system depicted in FIG. 11 are the same as those depicted in FIG. 8 and have the same identifying numbers.
The automatic flow pressure relief system 701 includes a T connector 703, a fluid line 705, a bubble trap 707, a fluid tubing 709, a saline bag 711, a stand 713 and a tubing clamp 715. In system 701, the T connector 703 puts a first end of fluid tubing line 705 in fluid contact with the blood circulating line 521 at a position upstream from the check valve 563 and downstream from the pump 560. At a second end, the fluid tubing line 705 is in fluid communication with the bubble trap 707 and the bubble trap 707 is in fluid communication with the saline filled bag 711 through the fluid line 709. The saline bag 711 is connected to the stand 713 at a point above the plane of the patient 20 so that when saline fluid is released from the bag 711 by removal of the clamp 715 the saline flows down into the bubble chamber 707 which is below the saline bag 711 and on into the tubing 705 which is below the bubble trap 707.
In typical setup when automatic flow pressure system is first assembled, before the introduction of saline fluid, and the first end of the fluid tubing line 705 is connected to the T 703, the clamp 715 is removed and enough saline liquid is allowed to flow into the bubble trap 707 and the line 705 to completely fill the line 705 and half fill the bubble trap 707. Once the bubble trap 707 is half full flow of fluid from the saline bag 711 is stopped by reconnecting the clamp 715 to the line 709. As is typical with this type of set up when blood is flowing in the line 521 under pressure created by the action of the pump 560 a fluid pressure balance is reached between blood flowing in the line 521 and the saline solution line 705 of the system 701 so that saline fluid is not forced and does not flow into the line 521. However, when the injection syringe 505 injects an indicator into the line 521, the one way valve 563 closes, then pressure builds up above the valve 563 as the result of accumulating blood. This build up of pressure causes blood to be diverted into the line 705 and the fluid in the line 705 then backs up into the bubble trap 707.
Once the injection is finished and the valve 563 reopens, the build up of pressure is relieved and the blood that flowed into the line 705 begins to flow back into the line 521 until all the blood has flowed back out of the line 705. At this point, the pressure balance between the automatic flow pressure relief system 701 and the blood line 521 is back to the original pressure balance and more blood does not flow into the line 521. It should be noted that this system works by compressing the air in the bubble chamber 707 and against the force of gravity when the blood is forced into the line 705 during injection of the indicator. Another variation or embodiment could dispense with the saline bag and have a sealed partially filled chamber in fluid communication with the line 705.
Although the present invention has been described in terms of preferred embodiments, it will be understood that variations and modifications may be made without departing from the true spirit and scope thereof.

Claims

1. A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:

(a) introducing, at a first site in an extracorporeal circuit, an indicator into the extracorporeal circuit, the extracorporeal circuit extending between an arterial connection with a patient and a venous connection with the patient;

(b) diverting, at a second site in the extracorporeal circuit, blood flow from the extracorporeal circuit;

(c) accumulating the diverted blood flow;

(d) ending introduction of the indictor;

(e) ending diverting blood flow from the extracorporeal circuit;

(f) returning the diverted blood flow into the extracorporeal circuit;

(g) measuring a change caused by introducing the indictor into the extracorporeal circuit; and

(h) calculating a hemodynamic parameter from the measured change.

2. The method of claim 1, wherein the steps of introducing an indicator into the extracorporeal circuit and diverting blood flow from the extracorporeal circuit are concurrent.

3. The method of claim 1, wherein the step of introducing an indicator into the extracorporeal circuit starts before the step of diverting blood flow from the extracorporeal circuit.

4. The method of claim 1, wherein the step of diverting blood flow from the extracorporeal circuit starts before the step of introducing an indicator into the extracorporeal circuit.

5. The method of claim 1, wherein the calculated hemodynamic parameter is one of cardiac output, central blood volume and lung water.

6. The method of claim 1, wherein the second site is upstream of the first site.

7. The method of claim 6, further comprising, after ending diverting blood flow from the extracorporeal circuit, the step of returning diverted blood flow back into the extracorporeal circuit at the second site.

8. The method of claim 1, wherein the step of diverting blood flow includes redirecting at least a portion of the blood flow from the second site into a second conduit bypassing the first site.

9. The method of claim 8, wherein the step of redirecting at least a portion of the blood flow includes one of (i) redirecting the blood flow to the venous connection and (ii) redirecting the blood flow to a third site in the extracorporeal circuit downstream of the first site.

10. The method of claim 1, further comprising establishing a regulated blood flow in an extracorporeal circuit between the arterial connection and the venous connection.

11. The method of claim 10, wherein the step of establishing a regulated blood flow comprises starting a pump attached to the extracorporeal circuit.

12. The method of claim 1, wherein the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood flow from the extracorporeal circuit and releasing the diverted blood to the extracorporeal circuit are accomplished by using a pressure responsive side fluid line connected to the extracorporeal circuit upstream of the first site, the side fluid line accepts diverted blood flow from the extracorporeal circuit during the introducing step and releases diverted blood flow to the extracorporeal circuit when the introducing step ends.

13. The method of claim 1, wherein the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood flow from the extracorporeal circuit and returning the diverted blood to the extracorporeal circuit are accomplished by using a pressure activated expansion reservoir.

14. A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:

(a) diverting, at a diverting site, a flow of blood from an extracorporeal circuit fluidly connecting an arterial connection with a patient and a venous connection with the patient during introduction of an indicator into the extracorporeal circuit at an indicator introduction site located downstream of the diverting site; and

(b) returning the diverted blood into the extracorporeal circuit after the introduction of the indicator has stopped.

15. The method of claim 14, wherein the steps of diverting the flow of blood and returning the diverted blood includes providing the diverting site upstream of the indicator introduction site and a third site for returning the diverted blood downstream from the indicator introduction site.

16. The method of claim 14, wherein the steps of diverting a flow of blood and returning the diverted blood includes diverting the blood flow into a fluid volume accumulating reservoir connected to the extracorporeal circuit upstream from the indicator introduction site during the introduction and returning the blood from the reservoir into the extracorporeal circuit after the introduction of the indicator ceases.

17. The method of claim 14, further comprising the step of blocking flow in the extracorporeal circuit between the indicator introduction site and the diverting site during the introduction of the indicator.

18. A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:

(a) introducing an indicator into an extracorporeal circuit fluidly connecting an arterial connection with a patient and a venous connection with the patient; and

(b) reducing a pressure spike in the extracorporeal circuit associated with introducing the indicator into the extracorporeal circuit.

19. The method of claim 18, wherein reducing the pressure spike includes diverting a flow of blood from the extracorporeal circuit during introduction of the indicator and returning the diverted blood into the extracorporeal circuit after the introduction of the indicator has stopped.