FR2508175A1 - METHOD FOR DETERMINING AND CONTROLLING THE GAS CONTENT OF BLOOD AND APPARATUS FOR IMPLEMENTING SAID METHOD - Google Patents

Abstract

A.PROCESS FOR THE MEASUREMENT AND CONTROL OF THE PARTIAL GAS PRESSURE, IN PARTICULAR CARBON ANHYDRIDE AND OR OXYGEN, DISSOLVED IN THE BLOOD OF A PATIENT, IN A SIMPLE, CONTINUOUS AND RELIABLE MANNER AND APPARATUS FOR ITS IMPLEMENTATION. B. THE APPLIANCE INCLUDES AN OPERATIONAL DEVICE 1 INCLUDING A FIRST SPACE 2 SUPPLIED WITH A GASEOUS MEDIUM SERVING AS CARRIER GAS, AND A SECOND SPACE 3 CONNECTED TO THE ARTERIAL OR VEIN CIRCULATION OF A PATIENT TO ENSURE A CONTINUOUS CURRENT OF BLOOD IN THE SECOND SPACE 3. THE OPERATIONAL DEVICE 1 INCLUDES A GAS PERMEABLE MEMBRANE 4 THAT SEPARATES THE TWO SPACES 2, 3. THE SPACES 2, 3 AND THE MEMBRANE 4 ARE DIMENSIONED AND SELECTED TO OPTIMIZE THE DIFFUSION OF GAS DISSOLVED IN THE BLOOD A THROUGH MEMBRANE 4 TO ENTER THE GASEOUS MEDIUM SERVING AS CARRIER GAS IN ORDER TO OBTAIN IN THE FIRST SPACE 2 A SAMPLE WHICH REPRESENTS THE GAS CONTENTS OF A PATIENT'S BLOOD. THE APPARATUS ALSO INCLUDES MEANS 9 ALLOWING TO DETERMINE THE RESEARCHED LEVELS OF GAS PASSING BY DIFFUSION OF THE BLOOD OF A PATIENT THROUGH A MEMBRANE 4 TO ENTER THE CARRIER GAS IN THE FIRST SPACE 2 AND TO OBSERVE THE VARIATIONS OF THESE CONTENTS. C. APPLICATIONS: TO OXYGENATORS AND HEMODIALYSIS EQUIPMENT, FOR EXAMPLE.

Description

The present invention relates to a method for

  to measure and control the partial pressure of gas, in particular

  carbon dioxide and / or oxygen, dissolved in the

blood of a patient.

  Several methods are known that make it possible to measure the partial pressure of gases dissolved in the blood of a patient. Conventionally, blood samples are taken from a patient using a catheter and these samples are transferred.

  in a laboratory for their analysis. If the analysis

  same can be done in 2 to 3 minutes, thanks to modern equipment highly automated, to have a complete analysis

  gases contained in the blood, the overall process since the pre-

  until the results of the analysis are obtained is often inevitably too long and does not represent the

  At the moment of sampling, these analyzers

  are sophisticated and expensive devices.

  One way of analyzing a blood sample is the so-called bubble method, in which blood drawn from a patient is brought into contact with one or more gas bubbles, so that the bubble provides a sample representing the levels of blood levels, these levels being determined from the sample by infra-red spectrometry.

  Because of the lack of precision, this process is complicated and slow.

  Since the concentrations of gas, especially C 02 gases, dissolved in the blood constitute, for the ch 4, emergency, intensive care or other treatment of a patient, an important and useful indicator of the metabolism as well as

  that the efficiency of the blood circulation and the respiratory

  an indicator, which responds rapidly to variations, it is necessary to develop simple and rapid processes and equipment for determining gas contents.

some blood.

  A device for determining the blood Co 2 content is described in US Pat. No. 3,987,303. The determination is made directly through the skin by ensuring that the gases contained in the blood in

  cutaneous capillaries cross, by diffusion, a membrane

  The result is that the CO 2 content of the blood is the same on each side of the membrane, which makes it possible to determine the CO 2 content from the sample present in the sample. The determination is not continuous but is based on separate samples taken by scraping the upper layer of the skin to remove some of it. It is obvious that a determination made by the dermal route is sensitive to various factors leading to inaccuracies, such as skin impurities It may also be difficult to apply the device tightly to the skin

in a determined position.

  A practical approach used in the operating rooms

  in the intensive care wards is to determine the CO 2 content of the blood from the gases expelled by an oxygenator connected to a patient's bloodstream. Because the gas-permeable membrane serves, in an oxygenator, to separate, from one another, spaces in which, on the one hand, is introduced a portion of the blood flow of a patient and, on the other hand, CO 2 gas or a gas mixture 02 / C 02, can

  to achieve a continuous determination of the CO 2 content

  of the fact that the role of an oxygenator is, on the one hand, to oxygenate the blood of a patient and, on the other hand, to eliminate

  excess CO 2 'blood it is necessary to provide the circula-

  blood ulation of important quantities of the spare gases

  This is the reason why the chambers of oxygen

  substantially equal size Because the blood CO levels of a patient must be maintained

2 2

  within fairly narrow limits, diffusion through the membrane must be precisely controlled,

  which results in tight requirements for the mem-

  The surface of such a membrane is typically of the order of 1 m 2 under these conditions, and furthermore seen that there could be significant local gradients as regards the gas contents of the membrane. blood passing through an oxygenator, determination of blood gas levels from expelled gases

  by an oxygenator give results quite imprecise.

  An object of the invention is to eliminate the disadvantages

  Prior art and provide a method which reliably and simply allows the use of gas diffusion through a membrane to measure and control gases dissolved in the blood of a patient. to achieve a continuous operation apparatus providing reliable results for the implementation of this method and to analyze the blood gas content of a patient, this device being economical in terms of its manufacture and operation Another goal of the The object of the invention is to provide an apparatus, the best possible, which makes it possible in particular to determine the contents of CO 2 or 2 'which makes it possible to determine the gas contents of the blood and to detect as rapidly as possible variations of these contents. of the invention and to provide a method and apparatus for the analysis of blood gas contents which can preferably be used in combination with oxygenators or h emodialysis as an organ of a system

  to be connected to a patient's bloodstream.

  To do this, the present invention provides a method for measuring and controlling the partial pressure of gas, especially carbon dioxide and / or oxygen, dissolved

  in the blood of a patient, characterized in that the measurement is effected

  kills with the help of an operational measuring device

  this end and comprising a first space, in which is introduced

  a gaseous medium serving as a carrier gas, and a second space separated from the first by a membrane permeable to gas and having a volume greater than that of the first space, the second space

  being connected to the arterial or venous circulation of a pat-

  or a system connected thereto to produce a continuous blood stream in the second space without any appreciable influence on the composition or blood gas contents in that space, in that the gases dissolved in the blood are diffused through the membrane for entering the carrier gas gaseous medium to generate a sample representing the gas gas contents of the patient in the first space and in that the desired gas contents obtained by diffusion in the first space from the first space; patient's blood are determined and

  the variations of these contents are controlled.

  In addition to these main provisions, the following provisions can be envisaged: the gases taken off pass into a separate analysis device and the carrier gas passes into the first space in order to determine the desired gas contents so that, thanks to the diffusion effect, gases are taken continuously in the first space, the desired gas contents are determined from the gases taken in the first space or in an analysis chamber connected thereto to be in direct communication with him,

  the contents of certain gases, for example oxygen

  are determined in an analysis chamber separate from the first space, this chamber being filled with a carrier gas but

  being separated from the carrier gas circulation system.

  The subject of the invention is also an apparatus for

  the implementation of this method for measuring and

  controlling the partial pressure of gas, especially carbon dioxide

  and / or oxygen, dissolved in the blood of a patient,

  erised in that it comprises an operational device made for this purpose and comprising a first space powered in a medium

  gaseous carrier gas, and a second volume space sensib-

  more important than that of the first space and connected to the arterial or venous circulation of a patient to generate a

  continuous flow of blood in the second space without significant influence

  on the composition or blood gas contents in said space, in that the operative device comprises a gas permeable membrane arranged to separate said spaces from one another, in that the spaces and the membrane are sized and selected to optimize the diffusion of gases dissolved in the blood so that they pass through the membrane and enter the gaseous carrier gas medium to obtain a sample representing the blood gas contents of a patient in the blood. first space, and in that the apparatus comprises means for determining blood levels of gas passing by diffusion of the patient's blood into the carrier gas of the first space and controlling

  variations in these gas contents.

  In addition to these main provisions, the following provisions may be envisaged: in order to determine the desired gas contents, the gases taken by diffusion in the carrier gas in the first space are introduced into a separate analysis device and the carrier gas passes into the first space so that, thanks to the diffusion effect, gases are continuously withdrawn and introduced into the analysis device, the carrier gas stream and the gas stream taken from it form a system of In the case of closed continuous flow, the collected gases pass into the pulse analysis device when the determined gas contents have reached a sufficient equilibrium on both sides of the membrane, the passage of the gases taken from the analysis device. is carried out continuously, the flow rate being chosen so that the determined gas contents reach a sufficient equilibrium on both sides of the membrane, the flow rate of Said gas is 4,200 ml / min, the operational device constitutes a replaceable sterilized element and, preferably disposable, releasably connected to the rest of the apparatus, for the purpose of determining the desired gas contents from the gases sampled. on the carrier gas in the first space by diffusion, the operational device comprises an analysis space which is preferably part of the first space, for the purpose of determining the desired gas contents from the gases taken by diffusion on the carrier gas , the first space is divided into two parts, one of which

  separated from the carrier gas circulation system to

  stituer an independent analysis chamber, the operative device is divided into two elements hermetically fixed to one another, one of the elements delimiting the first space while the other delimits the second space, and the elements of the operating device can be

  separated from each other and united by means of the permeable membrane

  each of the spaces comprises a system of channels, the channel systems having dimensions such that the distance traveled by the carrier gas and the gases taken from it is substantially longer than the distance traveled by the blood and

  the channel system provided for the carrier gas has a volume considered

  less than that of the channel system connected to the blood circulation, the amount of carrier gas being optimized to obtain a sufficient amount of gas removed,

  the channels of the first space are arranged sensib-

  transversely to the channels of the second space, and intermediate ribs are provided between the channels to carry the membrane, the surface of the membrane is 250 cm 2, the volume of the first space is $ 5 cm 3, the carrier gas is air,

  the operational device and the means

  determining the gas contents are part of an oxygenator or hemodialysis system connected to a patient's bloodstream to control the oxygenation or hemodialysis process using the information on the contents in

  gases obtained and determined from the blood.

  An embodiment of the present invention is hereinafter described by way of example with reference to the accompanying drawings in which: FIG. 1 is a basic view of an apparatus according to the invention; FIG. embodiment of an operational device forming part of the apparatus according to the invention; Figure 3 is a basic view of another embodiment of the apparatus according to the invention; and FIG. 4 shows schematically the application of an apparatus according to the invention to a treatment system

  of blood connected to a patient's bloodstream.

  In the drawings, the reference numeral 1 denotes an operating device containing a space 2 into which a carrier gas is introduced, for example air, another space

  3 being connected to the bloodstream of a patient.

  Intake and discharge ducts connected to these spaces are designated by numerals 5, 6, 7 and 8 and the flow directions are represented in the drawing by arrows. The operational device 1 further comprises a membrane permeable to gas 4, made of silicone rubber, separating the spaces 2 and 3 from each other The apparatus further comprises a device for analyzing the contents of gas, C 02 and / or O 2, or other gases dissolved in the

  As an example, the following description speaks only of

  gas CO 2 and 2 According to the invention, the gases dissolved in the blood of a patient can pass-by diffusion of space 3 through a membrane 4 to come into the carrier gas contained in space 2,

  the CO 2 and 2 contents being the same on each side of the

  brane 4 The sample of gas obtained in this way represents the C 02 and 2 contents of the blood and follows the variations of these contents, which makes it possible to determine the contents of these gases using conventional means and processes, by example using an analyzer

  infrared gas and oxygen detectors.

  In the embodiment shown in the figure

  1, a sample of gas is entrained by the carrier gas and transmits

  in a separate analysis device 9 This transfer of

  the gas sample can be carried out continuously or

  Continuous with the aid of a suction pump of the 6 huitillon (not shown in the figures) forming part of the analysis device 9 For example, the transfer can be done once every 15 minutes providing a flow, preferably, 50 ml / min, for ten seconds. For a continuous transfer of the gas sample, the preferred flow rates are 4,200 ml / min.

  the gas sample returns to the space of the operating device

  The advantage of this solution is that, thanks to these repeated cycles, the carrier gas represents a new sample of gas to be generated, which tends to eliminate the defects of the gas sample with respect to a provision that new carrier gas is sucked or continuously introduced into the space 2 Therefore, because the mixture of the carrier gas and the new gas sample in the space 2 is not, in the embodiment of FIG. 1, very critical with regard to the gas contents, the operational device can be of a simpler design. On the other hand, an open system needs only a single connecting line between the operational device 1 and the analysis device 9 and the

  disadvantages mentioned above can be compensated by providing for a

  longer course of the carrier gas in the operational device 1.

  FIG. 2 represents an embodiment of the operational device 1 that can advantageously be used both in a closed system for circulating the carrier gas and in an open carrier gas supply system. As shown in FIG. 2, the operational device comprises a device 10 which delimits a space 2 in the form of a plurality of channels or ducts, and a member 11 which defines a space 3 in the form of channel system 13 The members 10 and 11 are hermetically sealed The sealing may preferably be provided by means of a diaphragm 4 Intermediate ribs 14 and 15 channel systems provide a preferred bearing surface of the

membrane 4.

  The time required to obtain a sample of gases representative of the contents of CO and dissolved in the

2 2

  blood can be influenced by the design, length, volume and diffusion area of the channel system 12 If there is a

  risk that the new carrier gas introduced into the area 2 pro-

  excessive effect on the sample of gas to be analyzed, a more complicated and / or longer channel system 12 must be provided. On the other hand, the volume of the channel system 12 and the volume of the channel system 12

  of the entire carrier gas system and the sample

  gas is low, and the larger the area of diffusion is

  ante, the shorter the time required to obtain a gas sample and the faster the system responds to variations

  occurring in blood gas levels.

  In addition, it can be provided, always according to

  the invention, in the immediate vicinity of space 2, a space for

  lysis of gas samples, that is to say a chamber forming part of a gas content analysis system, the analysis means constituting, preferably, a separate unit which can be connected in operation to the analysis chamber When using infrared gas analysis means, it is sufficient to provide appropriate windows in the analysis chamber. If necessary, it is also possible to provide an oxygen detector associated with the chamber.

analysis.

  Another advantageous solution consists in associating the aforementioned variants so that, firstly, for measuring the C 02 content, a sample passes into a separate analyzer and, on the other hand, measuring the O 2 content. is carried out in space 2 or in a space preferably separated therefrom. A principle view of this embodiment is shown in FIG. 3 according to which space 2 is divided into two parts 2a and 2b. Part 2b is filled with a carrier gas but is separated from the circulation system constituted by the elements 2a, 8, 9, 7 so as to provide an independent analysis chamber, into which the gases dissolved in the blood from space 3 and in which they, especially 02, can be determined using one or more detectors 27 According to this embodiment, the Co 2 content can be determined using

  of the carrier gas circulation system and Part 2a of J'es-

  Pace 2 may include a channel system, as shown in Fig. 2. Measuring the O 2 content, on the other hand, is very advantageous because, in general, the O 2 sensors are rather slow because the analysis chamber 26 includes

  carrier gas, the accuracy of the measured values of the

  It is independent of the properties of the membrane 4 and, for example, the speed of blood flow. The analysis chamber 26 may, of course, also be used for ditermination.

gas dissolved in the blood.

  Thus, in all the cases described above, the operational device 1 can be produced in the form of a disposable product, eccnomic and simple, of simple design, which can be connected to the separate system for each patient, thereby ensuring a greater applicability of the entire system The volume of space; The space of the gas chamber is preferably 45 cm 3 in order to obtain a simple and effective resonance. The space S has a substantially greater density than that of space 2, for example Usqu'Ato ten. more importantly, this allows a sampling

  They are fast enough and there are short intervals between them.

  For the same purpose, the area of a I = -cabrane 4 is preferably

of <250 cm 2.

  Figure 4 shows schematically how the dis-

  According to the invention, the positive system according to the invention can advantageously be used for a blood treatment system connected to the blood circulation of a patient 16, this treatment system comprising, for example, an oxygenator or an apparatus for The apparatus 17 comprises those chambers 21 and 22 which, in practice, may be in the form of complicated channel systems. The chambers are separated from one another by a membrane. 23 which, in an oxygenator, is generally permeable to gases and, in a hemodialysis apparatus, permeable to certain liquids and to certain materials. The chamber 21 is connected to the blood circulation 1, using a duct

  18 and a chamber 22 is associated with a flow system 20.

  The apparatus 17 further comprises a circulation pump as well as an element, said bubble trap through the blood introduced into a patient (trap not shown in Figure 4) The blood, after being treated in the apparatus 17 dela desired way, crosses

  a conduit 24 to enter an operational device,

  As a practical precaution, the system further comprises a bubble trap, disposed downstream of the operating device 1, trap not shown in FIG. a blood analysis provided to the patient 16, analysis performed according to the invention, it is possible to ensure that the blood has correct levels of Co 2 and 2 If these levels are not correct, the information obtained by the device 9 may be used to control diffusion through the membrane 23 and, if necessary, to cut blood supplying the blood system of the patient 16 with the aid of a closure valve 26 and / or a bypass (the control shown symbolically by the arrows 24 and 25) It is furthermore possible to reverse the connection order of the operational device 1 and the device 17, so that information is received.

  concerning the patient's blood gas levels prior to treatment.

  blood, thus making it possible to determine the metabolism of the patient, the operating efficiency of the heart, the blood circulation and the respiratory organs, etc. The invention can advantageously be applied to fluid flow systems relating to body organs,

  for example the kidneys, separated from a patient, the circulating liquid

  can be a nutrient solution instead of blood.

  It goes without saying that many modifications can be made to the device described and represented without

depart from the scope of the invention.

1 1

Claims (17)

  A method for measuring and controlling the partial pressure of gas, especially carbon dioxide and / or oxygen, dissolved in the blood of a patient, characterized in that   measurement is carried out using an operational measuring device   nel (1) produced for this purpose and comprising a first space (2), into which a gaseous medium serving as a carrier gas is introduced,   and a second space (3) separated from the first space (2) by a member   gas-permeable brane (4) and of a substantially larger volume   ant that of the first space (2), the second space (3) being connected to the arterial or venous circulation of a patient (16) or to a system connected thereto in order to achieve a continuous blood flow in the second space (3) without any appreciable influence on the composition or the blood gas contents in said space, in that the gases dissolved in the blood flow through the membrane (4) to penetrate into the gaseous medium serving as a carrier gas in order to generating a sample representing the blood gas contents of the patient in the first space (2) and in that the desired gas contents obtained by diffusion in the first space from the patient's blood are determined and the   variations of these contents are controlled.   Process according to Claim 1, characterized in that the withdrawn gases pass into a separate analysis device and in that the carrier gas passes into the first space (2) in order to determine the desired gas contents so that thanks to the diffusion effect, gases are collected in such a way   continue in the first space (2).   3 Process according to claim 1 or 2, characterized in that the desired gas contents are determined from the gases taken from the first space (2) or from an analysis chamber (9) connected thereto to be in communication direct with him.   4 Process according to claim 1 or 2, characterized in that the content of certain gases, for example oxygen, is determined in an analysis chamber (9) separated from the first space (2), this analysis chamber being filled a carrier gas but   being separated from the carrier gas circulation system.   Apparatus for carrying out the method according to   any one of the preceding claims permitting   measuring and controlling the partial pressure of gas, in particular carbon dioxide and / or oxygen, dissolved in the blood of a patient, characterized in that it comprises an operational device (1) designed for this purpose and comprising a first space (2) supplied with a gaseous medium serving as a carrier gas, and a first space (3) with a volume substantially larger than that of the first space (2) and connected to the arterial or venous circulation of a patient to generate a continuous stream of blood in the second space (3) without appreciable influence on the composition or blood gas contents in said space (3), in that the operative device (1) comprises a gas-permeable membrane (4) arranged in such a way as to separate the spaces (2, 3) from one another, in that the spaces (2, 3) and the membrane (4) are sized and selected so as to optimize the diffusion of the dissolved gases in the blood so that they cross the membrane ( 4) and enter the gaseous medium serving as a carrier gas to obtain a sample representing the gas contents of the blood of a patient in the first   space (2), and in that the apparatus comprises means (9) permitting   making it possible to determine the contents of the blood in gas passing through the diffusion of the patient's blood into the carrier gas of the first space   (2) and to control the variations of these gas contents.   6. Apparatus according to claim 5, characterized in that, to determine the desired gas contents, the gas sample obtained by diffusion in the carrier gas in the first space (2) is introduced into a separate analysis device (9). ) and in that the carrier gas passes into the first space (2) so that, thanks to the diffusion effect, gas is taken from the   continuously and introduced into the analysis device (9).   Apparatus according to claim 6, characterized in that the carrier gas stream and the gas stream withdrawn therefrom constitute a closed continuous flow system (2,7,8,9).   Apparatus according to claim 6 or 7, characterized   in that the sample gas passes into the analysis device (9) in pulses when the gas contents to be determined have   reaches a sufficient equilibrium on both sides of the membrane (4).   9 Apparatus according to claim 6 or 7, characterized in that the passage of the gas sampled in the analysis device (9) is effected continuously, the flow rate being chosen so that the gas contents to be determined reach a sufficient equilibrium   on both sides of the membrane (4) -   Apparatus according to claim 9, characterized   in that the flow rate of said gas is <200 ml per minute.   System according to any one of the claims   10, characterized in that the operating device (1)   a sterilized, replaceable and, preferably, jet-   able connected removably to the rest of the device.   Apparatus according to claim 5 or 6, characterized   in that, in order to determine the desired gas contents from the sample gas obtained from the carrier gas in the first space (2) by diffusion, the operative device (1) comprises an analysis space which is preferably part of of the first space (2).   Apparatus according to claim 5 or 6, characterized   in that, in order to determine the desired gas contents from the gases obtained obtained, by diffusion, of the carrier gas, the first space (2) is divided into two parts (2 a, 2 b), one of which (2 b ) is separated from the carrier gas circulation system for   constitute an independent analytical chamber.   Apparatus according to any of the claims   5 to 13, characterized in that the operative device (1) is divided into two elements (10, 11> hermetically fixed to one another, one of the elements (10) delimiting the first space (2) while the other (11) delimits the second space (3), and in that the elements (10, 11) of the operating device (1) can be separated from one another and joined together by means of the membrane permeable with gases (4).   Apparatus according to any of the claims   5 to 14, characterized in that each of the spaces (2, 3)   renders a channel system (12, 13), in that the channel systems have dimensions such that the distance traveled by the carrier gas and the collected gases obtained therefrom is substantially longer than the distance traveled by blood, and in that the channel system (12) of the carrier gas has a volume considerably less than that of the channel system (13) connected to the blood circulation, the amount of carrier gas being optimized to allow obtaining a sufficient amount of collected gas.   Apparatus according to claim 15, characterized in that the channels of the first space (2) are arranged substantially transversely to the channels of the second space (3), and in that intermediate ribs (14, 15) are arranged   between the channels to carry the membrane (4).   Apparatus according to any of the claims   ions 5 to 16, characterized in that the surface of the membrane is 4,250 cm   Apparatus according to any of the claims   ions 5 to 17, characterized in that the volume of the first space (2) is <5 cm 3.   Apparatus according to any of the claims   ions 5 to 18, characterized in that the carrier gas is air.   Apparatus according to any of the claims   5 to 19, characterized in that the operating device (1) and the averages (7, 8, 9) for determining the gas contents are part of an oxygenator or a hemodialysis system (17, 18). , 19, 20) connected to the bloodstream of a patient to control the process of oxygenation or hemodialysis using the information relating to the levels of ga-z obtained and determined from the blood.