Apparatus and method for continuous monitoring of tissue carbon dioxide and pH using capnometric recirculating gas tonometry

• US 5,743,259 A
• Filed: 02/16/1995
• Issued: 04/28/1998
• Est. Priority Date: 02/16/1995
• Status: Expired due to Fees

• Current Assignee: Wayne State University
• Original Assignee: Wayne State University
• Inventors: Guzman, Jorge Alberto, Kruse, James Alexander
• Primary Examiner(s): Lacyk, John P.
• Application Number:
  US08/390,406
• Time in Patent Office: 1,167 Days
• Field of Search: 128/632-635, 128/637, 128/664-665
• US Class Current: 600/309
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/6853 with a balloon

Abstract

A tonometry catheter apparatus comprising an elongate flexible tube having a proximal extracorporeal end and a distal interacorporeal end. The distal end of the tube has a distensible, gas-permeable tonometry vessel, the vessel and the distal end defining therebetween a space which may be filled with a gas. An in-flow orifice lies in communication with the space, through which gas may enter the vessel. An in-flow lumen with a distal end and a proximal end is also provided, the distal end being in communication with the in-flow orifice. An out-flow orifice lies in communication with the space, through which the gas may exit the vessel. An out-flow lumen is disposed with a distal end and a proximal end, the distal end being in communication with the out-flow orifice. The proximal end of the tube has a pump for propelling gas into the vessel. A capnometer and a sensor quantify the level of carbon dioxide (CO₂) gas exiting the vessel. A hollow connecting member defines with the vessel, the in-flow lumen and the out-flow lumen a closed path through which the gas may continuously recirculate.

Claims

1. A tonometry catheter apparatus comprising:

an elongate flexible tube having a proximal extracorporeal end and a distal intracorporeal end;

the distal end of the tube having

a distensible, inflatable, gas-permeable tonometry vessel, the vessel and the distal end defining therebetween a space which is filled with a gas,

an in-flow orifice in communication with the space, through which gas may enter the vessel,

an in-flow lumen with a distal end and a proximal end, the distal end being in communication with the in-flow orifice,

an out-flow orifice in communication with the space, through which the gas may exit the vessel, and

an out-flow lumen with a distal end and a proximal end, the distal end being in communication with the out-flow orifice,

the proximal end of the tube having

means for propelling gas into the vessel, the propelling means being selected from a group consisting of a peristaltic pump, a roller pump, an impeller pump, a blower, a propeller, a fan, a circulator, and their equivalents, and

means for continuously quantifying the level of carbon dioxide (CO₂) gas exiting the vessel, and

a hollow connecting member linking the propelling and quantifying means to define with the vessel, the in-flow lumen and the out-flow lumen a closed path through which the gas may continuously recirculate under a relatively constant pressure, thereby resulting in a substantially error-free, stable reading.

2. The tonometry catheter apparatus of claim 1, wherein the in-flow orifice is spaced apart from and upstream of the out-flow orifice, thus forcing gas flow through the length of the vessel, thereby enhancing gas mixing and gas diffusion through the vessel wall.

3. The tonometry catheter apparatus of claim 1, wherein the out-flow orifice is spaced apart from and upstream of the in-flow orifice, thus forcing gas flow through the length of the vessel, thereby enhancing gas mixing and gas diffusion through the vessel wall.

4. The tonometry catheter apparatus of claim 1, wherein the means for quantifying the level of CO₂ gas is selected from the group consisting of a CO₂ sensor, capnometer, or capnograph.

5. The tonometry catheter apparatus of claim 4, further comprising:

a capnometry means connected to the CO₂ sensor, the capnometry means providing an image of pCO₂.

6. The tonometry catheter apparatus of claim 5, wherein the means for quantifying provides real time trending information of the gas level in a tissue or organ of interest.

7. The tonometry catheter apparatus of claim 1, further including means for displaying one or more variables indicative of physiological condition of the patient.

8. The tonometry catheter of claim 1, further including one or more safety pressure relief lumens.

15. The tonometry catheter of claim 1, further comprising:

one or more safety pressure relief lumens, each having a distal end and a proximal end, each distal end opening into a plurality of orifices, which may be proximate to the distal tip thereof along the tonometry catheter near its distal tip, none of the orifices communicating with the vessel space, or with the pressure lumen, or with the vacuum lumen.

16. The tonometry catheter of claim 1, wherein the gas contained within the closed path comprises ambient air prior to placement of the apparatus within the body of a patient, and thereafter the gas after equilibration comprises a gas mixture having a composition approximating that of body tissues adjacent the vessel.

17. The tonometry catheter of claim 1, wherein the means for propelling gas into the vessel comprises a means for injecting additional gas into the closed path.

19. A method for continuous indirect monitoring of organ or tissue oxygenation gas exchange, or pH comprising:

positioning a tonometry catheter apparatus according to claim 1 into the body of a patient;

providing a continuous recirculation of gas through a closed circuit including the vessel;

introducing gas into the circuit under positive pressure to distend the vessel;

monitoring connections within the circuit to assure integrity thereof as a closed system;

connecting the catheter to a monitoring circuit for monitoring the level, percentage, proportion, or partial pressure of CO₂ gas within the circuit;

allowing entry of the bicarbonate ion concentration of the blood, serum, or plasma into the electronic portion of the system;

deriving the value pH or related values from the measured level, percentage, proportion, or partial pressure of CO₂ gas within the circuit and the entered value of the concentration of bicarbonate ions in the blood, serum, or plasma;

displaying and/or recording the measured and/or derived values on a continuous basis; and

triggering an audible or visual alarm when a malfunction in the system is sensed, or when the measured or derived values are above or below pre-selected critical values.

9. A tonometry catheter apparatus comprising:

an elongate flexible tube having a proximal extracorporeal end and a distal intracorporeal end;

the distal end of the tube having

a distensible, inflatable, gas-permeable tonometry vessel, the vessel and the distal end defining therebetween a space which is filled with a gas,

an in-flow orifice in communication with the space, through which gas may enter the vessel,

an in-flow lumen with a distal end and a proximal end, the distal end being in communication with the in-flow orifice,

an out-flow orifice in communication with the space, through which the gas may exit the vessel, and

an out-flow lumen with a distal end and a proximal end, the distal end being in communication with the out-flow orifice,

the proximal end of the tube having

means for propelling gas into the vessel,

means for continuously quantifying the level of carbon dioxide (CO₂) gas exiting the vessel,

a hollow connecting member linking the propelling and quantifying means to define with the vessel, the in-flow lumen and the out-flow lumen a closed path through which the gas may continuously recirculate under a relatively constant pressure, thereby resulting in a substantially error-free, stable reading,

one or more safety pressure relief lumens, and

one or more pressure relief valves in communication with in-flow, the out-flow, and the one or more safety pressure relief lumens to regulate pressure within the closed path in the event of malfunction that could otherwise lead to an undesirable and hazardous progressive accumulation of gas within a body cavity of a human subject in which the vessel is inserted.

12. The tonometry catheter of claim 9, including a pressure sensing means in communication with the hollow connecting member.

10. A tonometry catheter apparatus comprising:

an elongate flexible tube having a proximal extracorporeal end and a distal intracorporeal end;

the distal end of the tube having

a distensible, inflatable, gas-permeable tonometry vessel, the vessel and the distal end defining therebetween a space which is filled with a gas,

an in-flow orifice in communication with the space, through which gas may enter the vessel,

an in-flow lumen with a distal end and a proximal end, the distal end being in communication with the in-flow orifice,

an out-flow orifice in communication with the space, through which the gas may exit the vessel, and

an out-flow lumen with a distal end and a proximal end, the distal end being in communication with the out-flow orifice,

the proximal end of the tube having

means for propelling gas into the vessel,

means for continuously quantifying the level of carbon dioxide (CO₂) gas exiting the vessel, and

a hollow connecting member linking the propelling and quantifying means to define with the vessel, the in-flow lumen and the out-flow lumen a closed path through which the gas may continuously recirculate under a relatively constant pressure, thereby resulting in a substantially error-free, stable reading,

one or more safety pressure relief lumens, and

a pressure sensing means in communication with the one or more safety pressure relief lumens for quantifying pressure in the closed path and detecting undesirable or hazardous increases in pressure within a body cavity of a human subject in whom the vessel has been inserted.

11. The tonometry catheter of claim 10, wherein the pressure sensing means comprises a pressure transducer.

13. The tonometry catheter of claim 10, including a pressure sensing means in communication with the hollow connecting member.

14. The tonometry catheter of claim 11, including a pressure sensing means in communication with the hollow connecting member.

18. A method for continuous indirect monitoring of organ or tissue oxygenation, gas exchange, and pH comprising:

providing a catheter having an elongate flexible tube;

introducing the catheter into an organ of interest so that a gas-permeable, inflatable vessel is disposed at a desired sampling site;

positioning the vessel at the sampling site for a length of time sufficient to allow carbon dioxide gas at the sampling site to diffuse across the vessel'"'"'s wall and into an out-flow lumen provided within the flexible tube;

circulating gas under a relatively constant pressure within a closed circuit defined by the vessel, the in-flow lumen, the out-flow lumen, and a hollow connecting member connecting the in-flow and out-flow lumens;

analyzing gas on a continuous basis within the closed circuit for the level of carbon dioxide gas within the gas mixture contained in the circuit;

determining the intracellular pH of the organ or tissue at or near the sampling site on a continuous basis from the level of carbon dioxide gas and a measure or estimate of body bicarbonate concentration; and

determining whether organ or tissue hypercapnia, acidosis, hypoxia, or ischemia are present on the basis of the determination of carbon dioxide gas level within the vessel and on the basis of intracellular pH determination.

20. The method of claim 18, further comprising the step of inserting the catheter by a transnasal, transoral, transrectal, surgical, or other route of placement into some portion of the gastrointestinal tract, which includes the esophagus, stomach, duodenum, small intestines, jejunum, ileum, colon or large intestine, or rectum.