Method of measuring an acoustic impedance of a respiratory system and diagnosing a respiratory disease or disorder or monitoring treatment of same

• US 20090062672A1
• Filed: 06/09/2006
• Published: 03/05/2009
• Est. Priority Date: 06/10/2005
• Status: Active Grant

• Current Assignee: Telethon Institute for Child Health Research
• Original Assignee: Telethon Institute for Child Health Research
• Inventors: Sly, Peter, Hantos, Zoltan, Thamrin, Cindy
• Granted Patent: US 8,641,637 B2
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/0051 by applying vibrations
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise
• CPC Class Codes: G01H 15/00 Measuring mechanical or acoustic impedance

Abstract

The present invention provides a method of measuring an acoustic impedance of a respiratory system. The method comprises selecting a frequency range for an acoustic wave, directing the acoustic wave into the respiratory system and receiving an acoustic wave from the respiratory system. The method also comprises determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system. Each volume, or the volumes within each volume range, is larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges. Further, the method includes determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system and charaterising the respiratory system by analysing the dependency of the acoustic impedance on the volume or volume range.

Claims

1. A method of measuring an acoustic impedance of a respiratory system, the method comprising:

selecting a frequency range for an acoustic wave,

directing the acoustic wave into the respiratory system,

receiving an acoustic wave from the respiratory system and

determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system, each volume, or the volumes within each volume range, being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges,

determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system and

charaterising the respiratory system by analysing the dependency of the acoustic impedance on the volume or volume range.

2. The method as claimed in claim 1 wherein the acoustic impedance is determined at or near resonance or anti-resonance condition.

3. The method as claimed in claim 1 wherein the frequency of the acoustic wave is selected so that the acoustic impedance of the respiratory system is predominantly determined by a predetermined internal region of the human respiratory system.

4. The method as claimed in claim 3 wherein the predetermined internal region comprises the airways, but not the periphery of the lungs.

5. The method as claimed in claim 1 wherein the selected frequency is greater than 40 Hz.

6. The method as claimed in claim 1 wherein the selected frequency is greater than 60 Hz.

7. The method as claimed in claim 1 wherein the selected frequency is greater than 100 Hz.

8. The method as claimed in claim 1 wherein the acoustic wave is directed into the respiratory system and received from the respiratory system during a volume change of the respiratory system.

9. The method as claimed in claim 1 comprising:

determining the acoustic impedance for a plurality of volumes of the respiratory system, each volume being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes.

10. The method as claimed in claim 1 comprising:

determining the acoustic impedance for a plurality of volume ranges of the respiratory system, the volumes within each volume range being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volume ranges.

15. The method as claimed in claim 9 wherein the frequency of the acoustic wave is selected so that the acoustic impedance can be determined at or near resonance or anti-resonance.

16. The method as claimed in claim 9 comprising:

determining the acoustic impedance for a plurality of volumes of the respiratory system, each volume being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes.

17. The method as claimed in claim 9 comprising:

determining the acoustic impedance for a plurality of volume ranges of the respiratory system, the volumes within each volume range being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volume ranges.

18. The method as claimed in claim 2 wherein:

the frequency of the acoustic wave is selected so that the acoustic impedance of the respiratory system is predominantly determined by a predetermined internal region of the human respiratory system;

the predetermined internal region comprises the airways, but not the periphery of the lungs;

wherein the selected frequency is greater than 40 Hz;

the selected frequency is greater than 60 Hz; and

the selected frequency is greater than 100 Hz.

19. The method as claimed in claim 18 wherein the acoustic wave is directed into the respiratory system and received from the respiratory system during a volume change of the respiratory system.

20. The method as claimed in claim 18 comprising:

determining the acoustic impedance for a plurality of volumes of the respiratory system, each volume being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes.

21. The method as claimed in claim 18 comprising:

determining the acoustic impedance for a plurality of volume ranges of the respiratory system, the volumes within each volume range being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volume ranges.

11. A method of diagnosing a respiratory disease or disorder in a subject comprising:

selecting a frequency range for an acoustic wave,

directing the acoustic wave into the respiratory system of the subject,

receiving an acoustic wave from the respiratory system,

determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system, each volume, or the volumes within each range, being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges,

determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system and

comparing the acoustic impedance to a reference acoustic impedance obtained from a subject not having the respiratory disease or disorder.

12. A method of monitoring the progress of therapy targeted at a respiratory disease or disorder in a subject comprising:

a) selecting a frequency range for an acoustic wave,

b) directing the acoustic wave into the respiratory system of the subject,

d) receiving an acoustic wave from the respiratory system,

e) determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system, each volume, or the volumes within each range, being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges,

f) determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system

g) administering therapy to the subject,

h) reassessing the subject using method steps a) to e),

wherein a change in acoustic impedance during or following therapy monitors the progression of the therapy.

13. A method for determining the potential responsiveness of a subject to particular forms of therapy for a respiratory disease or disorder comprising:

a) selecting a frequency range for an acoustic wave,

b) directing the acoustic wave into the respiratory system of a subject,

c) receiving an acoustic wave from the respiratory system,

d) determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system, each volume, or the volumes within each range, being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges,

e) determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system and

f) comparing the acoustic impedance to a reference acoustic impedance obtained from a subject not having the respiratory disease or disorder which thereby predicts the potential responsiveness of the subject to a particular form of therapy.

14. A method for predicting the risk of progression to severe and/or persistent respiratory disease or disorder in a subject, comprising:

a) selecting a frequency range for an acoustic wave,

b) directing the acoustic wave into the respiratory system of the subject,

c) receiving an acoustic wave from the respiratory system,

d) determining the acoustic impedance for a plurality of volumes or volume ranges of the respiratory system, each volume, or the volumes within each range, being larger than RV or FRC and smaller than TLC whereby the determined acoustic impedances are specific for respective volumes or volume ranges,

e) determining a volume, or volume range, dependency of the acoustic impedance of the respiratory system and

f) comparing the acoustic impedance to a reference acoustic impedance obtained from a subject not having the respiratory disease or disorder,

wherein a level of impedance greater than the reference is associated with increased risk of progression to severe and/or persistent respiratory disease or disorder.