Filter unit for end tidal carbon monoxide monitor

• US 5,357,971 A
• Filed: 03/07/1994
• Issued: 10/25/1994
• Est. Priority Date: 06/16/1992
• Status: Expired due to Fees

• Current Assignee: Sandoz Inc. (Novartis Ag)
• Original Assignee: Natus Medical Incorporated
• Inventors: Stone, Robert T., Sheehan, Neil J., Rouw, Scott R.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/207,892
• Time in Patent Office: 232 Days
• Field of Search: 128/716, 128/718, 128/719, 128/912, 128/205.11, 128/205.12, 128/205.29, 137/544, 73/863.21, 73/23.2, 422/28.04, 422/83, 422/84, 422/107
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: G01N 33/004 for CO, CO2
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A noninvasive device and methods for measuring the end-tidal carbon monoxide concentration in a patient'"'"'s breath, particularly newborn and premature infants. The patient'"'"'s breath is monitored. An average carbon monoxide concentration is determined based on an average of discrete samples in a given time period. The ratio of the end-tidal portion of the breath flow sample is separately determined, preferably based on monitoring the level of carbon dioxide in the gas sample and identifying the carbon dioxide concentration levels corresponding to the end-tidal portion of the breath sample. The sensed carbon monoxide level is converted to the end-tidal carbon monoxide level by subtracting the ambient carbon monoxide level and dividing the remainder by the ratio of end-tidal breath to breath in the breath sample. An easy to use microcontroller-based device containing a carbon dioxide detector, a carbon monoxide detect and a pump for use in a hospital, home, physician'"'"'s office or clinic by persons not requiring high skill and training is described. A replaceable filter unit made of a single tri-lumen PVC extrusion and a tube segment inter-connecting two of the lumens used to provide the consumable filtration material. The filtration material is interposed between the carbon dioxide sensor and the carbon monoxide sensor which are mounted inside the monitor housing. The filter unit also interfaces the canula for receiving the patient'"'"'s breath sample and a hydrophobic filter between the patient and the carbon dioxide monitor. The filter unit is replaceable when the filtration medium is no longer effective or for use with different patients and may be disposable.

Claims

1. A filter unit for use with a non-invasive end-tidal gas flow monitor having a first sensor for detecting the amount of a first gas component in a gas sample, a second sensor for detecting the amount of a second gas component in a gas sample taken from a patient, a first connector in communication with the first sensor, a second connector in communication with the first sensor, a third connector in communication with the second sensor, comprising:

a body having a first end and a second end and first, second, and third lumens extending through the body between the first and second ends;

a first filter for removing undesired selected components from the gas sample, the first filter comprising a consumable filtration medium and being located in one of the second and third lumens; and

a tube segment connecting the second and third lumens at one of the first and second ends, wherein the first lumen forms a first gas flow path between the first and second ends of the body and the second lumen, the tube segment, and the third lumen form a second gas flow path through the body.

2. The filter unit of claim 1 wherein the body is a single extruded tri-lumen body.

3. The filter unit of claim 2 wherein the first, second, and third lumens generally have walls of about the same thickness.

4. The filter unit of claim 2 wherein the first, second, and third lumens have respective first, second, and third longitudinal axes that are in a common plane.

5. The filter unit of claim 1 wherein the first second and third lumens have different inner dimensions.

6. The filter unit of claim 5 further comprising a plug inserted in one of the second and third lumens at the one end receiving the tube segment, the plug having an interior flow passageway having an inner dimension that corresponds to the inner dimension of the other of the second and third lumens so that the tube segment is inserted into the plug flow passageway and the other lumen.

7. The filter unit of claim 6 wherein the inner dimensions of the lumens have generally circular cross sections.

8. The filter unit of claim 7 wherein the body is an extruded tri-lumen body.

9. The filter unit of claim 7 wherein the tube segment is bonded to the plug and one of the second and third lumens.

10. The filter unit of claim 5 wherein the first, second, and third lumens have respective longitudinal axes that are aligned in a common plane.

11. The filter unit of claim 5 wherein the first, second, and third lumens are dimensioned to fit over the first, second, and third connectors to form a secure frictional engagement.

12. The filter unit of claim 11 wherein the first, second, and third lumens have respective longitudinal axes that are aligned in a common plane.

13. The filter unit of claim 5 wherein the first filter is located interior to the second lumen.

14. The filter unit of claim 1 wherein the first filter further comprises:

a first length of cellulose acetate;

a first length of activated carbon having an outer circumference; and

a second length of cellulose acetate.

15. The filter unit of claim 14 further comprising a thin cap sealingly interposed between the outer circumference of the activated carbon and an interior wall of the second gas flow path, the cap having an aperture at each end of the carbon for providing a gas flow path therethrough.

16. A filter assembly for use with a non-invasive end-tidal gas monitor having a first sensor for detecting the amount of a first gas component in a gas sample, a second sensor for detecting the amount of a second gas component in a gas sample taken from a patient, a first connector in communication with the first sensor, a second connector in communication with the first sensor, a third connector in communication with the second sensor, comprising:

a body having a first end and a second end and first, second, and third lumens extending through the body between the first and second ends;

a first filter for removing undesired selected components from the gas sample, the first filter comprising a consumable filtration medium and being located in one of the second and third lumens;

a tube segment connecting the second and third lumens at one of the first and second ends, wherein the first lumen forms a first gas flow path between the first and second ends of the body and the second lumen, the tube segment, and the third lumen form a second gas flow path through the body;

a fitting having a barbed end connected to one end of the first lumen; and

means on said fitting for receiving a hydrophobic filter.

17. The filter unit of claim 16 further comprising a hydrophobic filter, means for connecting the hydrophobic filter to the fitting, and means on said filter for receiving a cannula for providing a gas sample taken from the patient.

18. The filter unit of claim 17 wherein the connecting means further comprises a threaded interconnection for connecting the hydrophobic filter to the fitting and the receiving means further comprises a tapered protrusion for receiving the cannula in frictional engagement.

19. A kit for use with a non-invasive end-tidal gas monitor having a first sensor for detecting the amount of a first gas component in a gas sample, a second sensor for detecting the amount of a second gas component in a gas sample taken from a patient, a first connector in communication with the first sensor, a second connector in communication with the first sensor, a third connector in communication with the second sensor, comprising:

a body having a first end and a second end and first, second, and third lumens extending through the body between the first and second ends;

a first filter for removing undesired selected components from the gas sample, the first filter comprising a consumable filtration medium and being located in one of the second and third lumens;

a tube segment connecting the second and third lumens at one of the first and second ends, wherein the first lumen forms a first gas flow path between the first and second ends of the body and the second lumen, the tube segment, and the third lumen form a second gas flow path through the body;

a fitting having a barbed end for connecting to one end of the first lumen;

a hydrophobic filter;

an interconnection for connecting the hydrophobic filter to the fitting;

a tapered protrusion on said hydrophobic filter; and

a cannula having a first end and a second end, the first end having first and second apertures for receiving a sample of gas from the patient, and the second end having an aperture frictionally connectable to the tapered protrusion, the cannula further comprising an insertion mark spaced a predetermined distance from the first end on the order of 1.0 centimeters.

20. A filter assembly for use with a non-invasive end-tidal gas monitor having a first sensor for detecting the amount of a first gas component in a gas sample, a second sensor for detecting the amount of a second gas component in a gas sample taken from a patient, a first connector in communication with the first sensor, a second connector in communication with the first sensor, a third connector in communication with the second sensor, comprising:

a body having a first end and a second end and first, second, and third lumens extending through the body between the first and second ends;

a first filter for removing undesired selected components from the gas sample, the first filter comprising a consumable filtration medium and being located in one of the second and third lumens;

a tube segment connecting the second and third lumens at one of the first and second ends, wherein the first lumen forms a first gas flow path between the first and second ends of the body and the second lumen, the tube segment, and the third lumen form a second gas flow path through the body;

a fitting having a barbed end connecting to one end of the first lumen;

a hydrophobic filter;

an interconnection connecting the hydrophobic filter to the fitting;

a tapered protrusion on said hydrophobic filter; and

a cannula having a first end and a second end, the first end having first and second apertures for receiving a sample of gas from the patient, and the second end having an aperture frictionally connected to the tapered protrusion, the cannula further comprising an insertion mark spaced a predetermined distance from the first end on the order of 1.0 centimeters.