Respiratory analysis with capnography

• US 20030073919A1
• Filed: 10/15/2001
• Published: 04/17/2003
• Est. Priority Date: 10/15/2001
• Status: Active Grant

• Current Assignee: Physio-Control Incorporated (Stryker Corporation)
• Original Assignee: Baruch S. Krauss, David R. Hampton
• Inventors: Hampton, David R., Krauss, Baruch S.
• Granted Patent: US 6,648,833 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production

Abstract

The invention presents techniques for identifying and guiding treatment for medical conditions, based upon the carbon dioxide concentration in the patient'"'"'s breath. In an exemplary application, the techniques of the invention may be used to distinguish obstructive lung disease from restrictive lung disease, even though the symptoms of the conditions are similar. The techniques of the invention may further be used to monitor the effectiveness of the treatment.

Claims

1. A method comprising:

measuring a concentration of carbon dioxide in a breath expired by a patient; and

determining the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement.

2. The method of claim 1, wherein measuring a concentration of carbon dioxide in a breath expired by a patient comprises generating a capnogram with a capnograph.

3. The method of claim 1, wherein measuring the concentration of carbon dioxide in a breath expired by a patient comprises measuring the concentration of carbon dioxide as a function of time.

4. The method of claim 3, wherein determining the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement comprises measuring the ascending slope of a curve traced by the measurements of the concentration of carbon dioxide over time.

5. The method of claim 1, wherein determining the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement comprises:

measuring the duration of a steady rise of the concentration of carbon dioxide;

determining the presence of obstructive lung disease when the duration is longer than a threshold duration; and

determining the presence of restrictive lung disease when the duration is shorter than the threshold duration.

6. The method of claim 1, wherein determining the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement comprises:

measuring the rate of increase of the concentration of carbon dioxide;

determining the presence of obstructive lung disease when the rate of increase is lower than a threshold rate; and

determining the presence of restrictive lung disease when the rate of increase is higher than the threshold rate.

7. The method of claim 1, wherein determining the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement comprises:

measuring the concentration of carbon dioxide as a function of time;

comparing the measurement of the concentration of carbon dioxide as a function of time to a characteristic curve; and

determining the presence of obstructive lung disease when the correlation of the measurement of the concentration of carbon dioxide as a function of time to the characteristic curve exceeds a threshold value.

8. The method of claim 1, further comprising reporting the determination.

9. The method of claim 1, wherein the breath expired by the patient is a first breath, the method further comprising:

measuring a concentration of carbon dioxide in a second breath expired by the patient following treatment;

evaluating a change in concentration of carbon dioxide between the first breath and the second breath.

10. The method of claim 9, further comprising reporting the evaluation.

11. The method of claim 1, further comprising treating the patient as a function of the determination.

12. The method of claim 1, further comprising recommending treatment of the patient as a function of the determination.

13. A device comprising:

a gas sensor that measures the concentration of carbon dioxide in a breath expired by a patient; and

a processor that determines the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement.

14. The device of claim 13, further comprising an output device that reports the determination.

15. The device of claim 13, further comprising an intake apparatus that conveys the expired breath from the patient to the gas sensor.

16. The device of claim 13, further comprising an analog-to-digital converter that converts analog measurements from the gas sensor to digital values, wherein the processor analyzes the digital values to determine the presence of one of obstructive lung disease and restrictive lung disease.

17. The device of claim 13, further comprising a capnograph that includes the gas sensor.

18. The device of claim 13, wherein the gas sensor comprises an infrared sensor.

19. A method comprising:

measuring a concentration of carbon dioxide in a breath expired by a patient; and

guiding treatment of the patient as a function of the measurement.

20. The method of claim 19, wherein guiding treatment comprises determining the presence of obstructive lung disease.

21. The method of claim 20, wherein guiding treatment further comprises assessing the severity of the obstructive lung disease.

22. The method of claim 19, wherein guiding treatment comprises determining the presence of restrictive lung disease.

23. The method of claim 22, wherein guiding treatment further comprises assessing the severity of the restrictive lung disease.

24. The method of claim 19, wherein measuring the concentration of carbon dioxide in the breath expired by a patient comprises measuring the concentration of carbon dioxide as a function of time.

25. The method of claim 19, further comprising reporting a recommendation for treatment.

26. The method of claim 19, further comprising:

measuring a second concentration of carbon dioxide in a second breath expired by the patient after a treatment; and

monitoring the response of the patient to the treatment as a function of the measurement of the second concentration.

27. An apparatus device comprising:

a sensing means that measures the concentration of carbon dioxide over time in a breath expired by a patient;

a processing means that determines the presence of one of obstructive lung disease and restrictive lung disease as a function of the measurement; and

an output means that reports the determination.

28. The apparatus of claim 27, further comprising:

a filtering means that receives a signal from the sensing means and generates a filtered signal comprising low frequency components of the signal; and

a converting means that receives the filtered signal and generates a digital signal received by the processing means.

29. The apparatus of claim 27, further comprising memory means that stores data characteristic of at least one of obstructive lung disease and restrictive lung disease.