NITRIC OXIDE MEASUREMENTS IN PATIENTS USING FLOWFEEDBACK

• US 20090247891A1
• Filed: 03/16/2009
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Wood, Lockett E.
• Granted Patent: US 8,425,428 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption

Abstract

The present invention provides a method for measuring FeNO in a subject, wherein the FeNO data derived from a subject patient is normalized to compensate for variations of FeNO with flow rate.

Claims

1. A method of measuring FeNO in a patient comprising:

measuring FeNO concentration in an exhaled breath of the patient;

measuring the exhalation flow rate of the exhaled breath as a function of time; and

generating FeNO concentration data as a function of time based on the measured FeNO concentration, the measured exhalation flow rate, and predetermined information describing the relationship between FeNO concentration measurements and exhalation flow rate for a healthy patient.

2. The method of claim 1 wherein measuring FeNO concentration comprises measuring FeNO concentration as a function of time.

3. The method of claim 1 wherein measuring FeNO concentration comprises collecting a sample of exhaled breath and thereafter measuring FeNO concentration of the sample.

4. The method of claim 3 wherein the sample is collected in a bag.

5. The method of claim 3 wherein the sample is collected in a cylinder with a piston.

6. The method of claim 2 further comprising collecting the exhaled breath as a sample and thereafter measuring FeNO concentration of the sample.

7. The method of claim 1 further comprising normalizing the measured FeNO concentration.

8. The method of claim 7 wherein the normalization occurs around a predetermined flow rate.

9. The method of claim 8 wherein the predetermined flow rate is approximately 50 ml/sec.

17. The method of claim 1 wherein said selected flow rate is about 50 ml/sec.

18. The method of claim 1 wherein said subject is caused to exhale at a substantially constant flow rate.

19. The method of claim 3 wherein said substantially constant flow rate is determined by ATS standards.

20. The method of claim 3 wherein said substantially constant flow rate is about 50 ml/sec±

10.

10. An NO monitoring system comprising:

a mouthpiece capable of receiving a breath from a patient;

a flow rate measuring device capable of measuring the flow rate of the breath from the patient;

a FeNO measuring device capable of determining a FeNO measurement from the breath from the patient;

an adjuster capable of adjusting the FeNO measurement based, at least in part, on the flow rate of the breath from the patient.

11. The system of claim 10 further comprising a breath storage device.

12. The system of claim 11 further comprising a normalizer capable of normalizing the FeNO measurement based, at least in part, on one or more FeNO measurements from a person other than the patient.

13. The system of claim 10 wherein the adjuster is capable of adjusting the FeNO measurement based, at least in part, on a difference calculation between the flow rate of the breath from the patient and predetermined flow rate.

14. The system of claim 10 wherein the adjuster is capable of adjusting the FeNO measurement to determine a new FeNO measurement that estimates the FeNO measurement if the patient had exhaled at a constant flow rate.

15. The system of claim 14 wherein the constant flow rate is approximately 50 ml/sec.

16. A method for measuring FeNO in a subject, the method comprising

a. causing a subject to exhale into an apparatus for receiving exhaled breath;

b. collecting at least some of the exhaled breath;

c. measuring FeNO in the collected exhaled breath;

d. measuring the flow rate of exhaled breath as a function of time;

e. determining an average flow rate of the exhaled breath from the measured flow rate of exhaled breath as a function of time;

f. calculating a baseline correction factor “

X”

according to the formula;

X=A/B where A is the measured FeNO; and

B is FeNO for a normal subject at the average flow rate;

g. normalizing the measured FeNO using the baseline correction factor X to obtain a normalized FeNO;

h. adjusting the normalized FeNO to a selected flow rate;

i. scaling back the normalized FeNO using the baseline correction factor;

j. thereby measuring FeNO in a subject.