Method and apparatus for reducing purge volume in a blood chemistry monitoring system

• US 5,947,911 A
• Filed: 01/09/1997
• Issued: 09/07/1999
• Est. Priority Date: 01/09/1997
• Status: Expired due to Term

• Current Assignee: Segars California Partners, LP
• Original Assignee: VIA Medical Corporation (Medtronic Plc)
• Inventors: Lai, Benjamin B., Wong, David K.
• Primary Examiner(s): Hindenburg, Max
• Assistant Examiner(s): MARMOR II, CHARLES ALAN
• Application Number:
  US08/780,799
• Time in Patent Office: 971 Days
• Field of Search: 600/309, 600/322, 600/345, 600/573, 604/4, 604/49, 604/50, 604/51, 604/52, 604/53, 604/131, 204/403, 204/409, 204/411
• US Class Current: 600/573
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits

Abstract

A method and apparatus for reducing the volume of fluid required to purge a patient'"'"'s blood from a blood sampling site after the blood has been sampled for measurement. A coil is formed in the fluid flow line between the source of fluid and the blood sampling site by looping the fluid flow line around on itself in order to generate turbulence in the fluid flow to help purge the patient'"'"'s blood from the blood sampling site after sampling. This turbulence-inducing coil is conveniently formed in a fluid flow line extending from the upstream end of a blood chemistry sensor module which is adapted to be installed in the fluid flow line of a standard IV infusion set as part of a combined infusion fluid delivery and blood chemistry monitoring system.

Claims

1. Apparatus for monitoring a predetermined parameter of a patient'"'"'s blood while infusing an infusion fluid into the patient, comprising:

a sensor assembly having an upstream end and a downstream end;

a first fluid flow line extending from the downstream end of the sensor assembly and including a connector for connecting the first fluid flow line in fluid communication with a catheter configured for insertion into a blood vessel of the patient;

a second fluid flow line extending from the upstream end of the sensor assembly and including a connector for connecting the second fluid flow line in fluid communication with a source of fluid, wherein the second fluid flow line has a coil formed therein by looping the line around on itself;

a pump conditioned to pump the infusion fluid from the source of fluid to the patient, through the second fluid flow line, the sensor assembly, and the first fluid flow line, and further conditioned to intermittently draw blood from the patient through the first fluid flow line and the sensor assembly and into, but not beyond, the coil of the second fluid flow line; and

one or more sensors, disposed in the sensor assembly in fluid communication with the first and second fluid flow lines, for providing a signal indicative of a predetermined parameter of a patient'"'"'s blood when drawn into the sensor assembly;

wherein the coil of the second fluid flow line is configured to generate turbulence in the fluid flow, to help purge the patient'"'"'s blood from the sensor assembly after sampling.

2. Apparatus as set forth in claim 1, wherein the coil in the second fluid flow line comprises a series of loops formed in a spiral.

3. Apparatus as defined in claim 1, wherein:

the coil of the second fluid flow line is located immediately adjacent to the sensor assembly; and

the pump is conditioned to draw blood from the patient as far as a point about one-half to three-quarters through the length of the coil of the second fluid flow line.

4. Apparatus for monitoring a predetermined parameter of a patient'"'"'s blood while infusing an infusion fluid into the patient, comprising:

a source of fluid;

a fluid flow line in fluid communication with the source of fluid, for infusing fluid into the patient;

a sensor assembly in fluid communication with the fluid flow line;

wherein a coil is formed in the fluid flow line between the source of fluid and the sensor assembly by looping the fluid flow line around on itself; and

a pump conditioned to pump the infusion fluid from the source of fluid to the patient, through the fluid flow line and the sensor assembly, and further conditioned to intermittently draw blood from the patient through the fluid flow line and the sensor assembly and into, but not beyond, the coil of the fluid flow line, whereupon the sensor assembly senses characteristics of the blood;

wherein the coil of the fluid flow line is configured to generate turbulence in the fluid flow to help purge the patient'"'"'s blood from the sensor assembly after sampling.

5. Apparatus as set forth in claim 4, wherein the coil is looped around on itself more than once to form a plurality of loops in the fluid flow line.

6. Apparatus as set forth in claim 5, wherein the coil comprises a series of loops formed in a spiral.

7. Apparatus as set forth in claim 5, wherein the coil comprises at least three loops of the fluid flow line.

8. Apparatus as set forth in claim 4, wherein the coil in the fluid flow line comprises one or more loops having a diameter of less than about two inches.

9. Apparatus as defined in claim 4, wherein:

the coil of the fluid flow line is located immediately adjacent to the sensor assembly; and

the pump is conditioned to draw blood from the patient as far as a point about one-half to three-quarters through the length of the coil of the fluid flow line.

10. A method for measuring one or more predetermined parameters of a patient'"'"'s blood, comprising steps of:

providing a sensor assembly having one or more sensors, each configured to measure a predetermined parameter of an adjacent fluid;

connecting the sensor assembly to an infusion line, such that a pump can direct an infusion fluid through the infusion line to the sensor assembly and, in turn, into the patient'"'"'s vascular system, wherein a predetermined portion of the infusion line is configured in the shape of a coil, to induce turbulence in any fluid flowing through it;

intermittently conditioning the pump to draw blood from the patient through the sensor assembly and into, but not beyond, the predetermined portion of the infusion line, whereupon the one or more sensors of the sensor assembly can measure the one or more predetermined parameters of the patient'"'"'s blood; and

thereafter conditioning the pump to purge the drawn blood from the infusion line and sensor assembly, back into the patient'"'"'s vascular system, wherein the coil of the infusion line ensures that the infusion fluid passing therethrough is sufficiently turbulent to help purge the blood from the infusion line and the sensor assembly.

11. A method as defined in claim 10, wherein:

the coil of the infusion line is located immediately adjacent to the sensor assembly; and

the step of intermittently conditioning the pump to draw blood from the patient includes a step of drawing blood as far as a point about one-half to three-quarters through the length of the coil of the infusion line.