CATHETER FOR USE IN DETECTING DISSOLVED GAS IN FLUIDS SUCH AS BLOOD

• US 3,658,053 A
• Filed: 08/28/1969
• Issued: 04/25/1972
• Est. Priority Date: 08/28/1969
• Status: Expired due to Term

• Current Assignee: Allegheny International Medical Technology Incorporated
• Original Assignee: Austin L. Wahrhaftig, Gordon J. Fergusson
• Inventors: Fergusson, Gordon J., Wahrhaftig, Austin L.
• Primary Examiner(s): Truluck, Dalton L.
• Application Number:
  US04/853,784
• Time in Patent Office: 971 Days
• Field of Search: 128/2,2.05,2.1,344,348 73/23
• US Class Current: 600/364
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61M 25/0069 Tip not integral with tube

Abstract

A blood catheter including a cannula covered with a thin layer of silicone rubber or other material permeable to one or more of the gases that are or might be found in blood and wherein the cannula preferably includes a helical arrangement of apertures for enabling the diffusion of gas through the membrane and into the center portion of the cannula. The helical pattern of apertures around the periphery of the cannula enables the catheter to contact the interior wall of a blood vessel without restricting blood flow past more than a small fraction of the total number of apertures. Other hole configurations can be used, for example, when a plurality of holes are located at spaced axial locations along the cannula and at spaced intervals around the circumference of the cannula at the various axial locations.

Claims

2. A catheter as defined in claim 1 wherein said apertures are spaced with respect to each other both longitudinally and circumferentially about said exterior periphery of said cannula and are provided in a sufficient number to enable substantially the same amount of gas to pass through the sum of all of the gas diffusion paths per unit time irrespective of the blockage of certain of said gas diffusion paths resulting from local contact of the exterior periphery of said membrane with the blood vessel walls when said cannula and said membrane are disposed in said operative position therein.

3. A catheter as defined in claim 2 wherein the ratio of the longitudinal spacing between apertures aligned longitudinally to the longitudinal dimension of each aperture is substantially five to one.

4. A catheter as defined in claim 3 wherein the longitudinal dimension of each of said apertures is in the range of from 0.006 inch to 0.012 inch.

5. A catheter as defined in claim 4 wherein the longitudinal dimension of each of said apertures is approximately 0.008 inch.

6. A catheter as defined in claim 2 wherein said elongated tubular structure comprises a unitary cylindrical tube of metal having a closed distal end formed in the portion thereof defining said cannula.

7. A catheter as defined in claim 6 wherein said apertures are formed by a coping saw to a depth substantially one-third the outside diameter of said cannula to provide adequate opening into said gas passage consistent with minimum structural weakening of said cannula.

8. A catheter as defined in claim 7 wherein said apertures are arranged sequentially in a generally helical pattern throughout the exterior periphery of said cannula, adjacent apertures being angularly spaced with respect to each other approximately 120* and longitudinally spaced from one another a distance generally five times the longitudinal dimension of each aperture.

9. A catheter as defined in claim 8 wherein the longitudinal dimension of each of said apertures is approximately 0.008 inch and the number of apertures is approximately 14.

10. A catheter as defined in claim 9 wherein said membrane extends throughout the longitudinal extent of said cylindrical tube.

11. A catheter as defined in claim 10 wherein said cylindrical tube is formed of stainless steel and said membrane is comprised of silicone rubber.