Device and method for the detection and evaluation of expirograms

• US 7,885,771 B2
• Filed: 08/11/2005
• Issued: 02/08/2011
• Est. Priority Date: 08/12/2004
• Status: Expired due to Fees

• Current Assignee: Universitaetsklinikum Freiburg (Albert-Ludwigs-Universitaet Freiburg)
• Original Assignee: Universitätsklinikum Freiburg
• Inventors: Roecker, Kai, Prettin, Stephan
• Primary Examiner(s): Raymond; Edward
• Application Number:
  US11/573,631
• Publication Number:
  US 20080114551A1
• Time in Patent Office: 2,007 Days
• Field of Search: 702/24, 702/30, 702/50, 702182-185, 600/526
• US Class Current: 702/24
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

The invention relates to an apparatus for the acquisition and interpretation of expirograms comprising:

• • a gas measuring probe that is designed to determine the gas concentration ƒ_mess of a gas in exhaled respiratory air;
  • a reading device that is connected to the gas measuring probe via signal and is designed to read for a plurality of values x₁, . . . , x_N of an exhaled volume of the exhaled respiratory air the respective determined gas concentrations ƒ_mess(x₁), . . . , ƒ_mess(x_N) from the gas measuring probe;
  • a storage device that is designed to store the values x₁, . . . , x_N assigned to the gas concentrations ƒ_mess(x₁), . . . , ƒ_mess(x_N);
  • a function fitting unit that is connected to the storage device via signal and that is designed to determine a non-linear fit function
    ƒ(x)=g(x)·h(x)+Offset_Gas
  •  for the stored gas concentrations ƒ_mess(x₁), . . . , ƒ_mess(x_N) by determining functions g(x) and h(x) wherein
    • h(x)=a+b·x
    • g(x) is a continuously differentiable, non-linear function with

$g\left(0\right)=0\mathrm{and}\underset{x->\infty }{\lim }g\left(x\right)=\mathrm{const},$

• • • a, b and const being constants and
    • Offset_Gas being a constant, mean concentration of the gas in room air.

Claims

1. An apparatus for the acquisition and interpretation of expirograms comprising:

a gas measuring probe configured to determine the gas concentration ƒ

_mess of a gas in exhaled respiratory air;

a reading device that is configured to read, for a plurality of values x₁, . . . , x_N of an exhaled volume of the exhaled respiratory air, the respective determined gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) from the gas measuring probe;

a storage device configured to store the values x₁, . . . , x_N assigned to the gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N); and

a function fitting unit that is configured to determine a non-linear fit function

ƒ

(x)=g(x)·

h(x)+Offset_Gas

 

for the stored gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) by determining functions g(x) and h(x) wherein

h(x)=a+b·

x

g(x) is a continuously differentiable, non-linear function, where;

2. The apparatus according to claim 1 further comprising

an evaluation unit configured to determine the physiological dead space x_VD of a respective lung, where

3. The apparatus according to claim 1, wherein g(x) is a monotonic function.

4. The apparatus according to claim 3 wherein

5. The apparatus according to claim 1, wherein the function fitting unit is configured to determine the fit function f(x)=g(x)h(x)+Offset_Gas, according to the Marquardt-Levenberg algorithm.

6. The apparatus according claim 1, wherein the storage unit is an electronic storage unit.

7. The apparatus according claim 1, further comprising

an evaluation device configured to calculate the alveolar recruitment rate g′

(x) by deriving the function g(x) based on the exhaled volume x.

8. The apparatus according to claim 7, further comprising

a display device configured to display the alveolar recruitment rate g′

(x) in a graphic manner.

17. The apparatus according to claim 2, wherein g(x) is a monotonic function, and wherein:

18. The apparatus according to claim 2, wherein the function fitting unit is configured to determine the fit function f(x)=g(x)·

h(x)+Offset _Gas according to the Marquardt-Levenberg algorithm.

21. The apparatus according to claim 8, wherein the display device is configured to display the alveolar recruitment rate g′

(x) in a graphic manner such that the alveolar recruitment rate g′

(x) is graphically presented as a density of randomly distributed points.

9. A method for the acquisition and interpretation of expirograms, the method comprising:

measuring gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) for a plurality of values x₁, . . . , x_N of an exhaled volume of exhaled respiratory air;

saving the measured gas concentrations; and

determining a non-linear fit function

ƒ

(x)=g(x)·

h(x)+Offset_Gas

 

for the stored gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) by determining functions g(x) and h(x) wherein;

h(x)=a+b·

x,

g(x) is a continuously differentiable, non-linear function, where;

10. The method according to claim 9 further comprising

determining the physiological dead space x_VD of a respective lung, wherein:

11. The method according to claims 9, wherein:

12. The method according to claim 9, wherein determining the fit function f(x)=g(x)h(x)+Offset_Gas, comprises determining the fit function according to the Marquardt-Levenberg algorithm.

13. The method according to claim 9, further comprising

calculating the alveolar recruitment rate g′

(x) by deriving the function g(x).

14. The method according to claim 13, further comprising

graphically presenting the alveolar recruitment rate g′

(x) on a display device.

19. The method according to claim 10, wherein:

20. The method according to claim 10, wherein determining the fit function f(x)=g(x)·

h(x)+Offset_Gas comprises determining the fit function according to the Marqardt-Levenberg algorithm.

22. The method according to claim 14, wherein the alveolar recruitment rate g′

(x) is graphically presented on a display device such that the alveolar recruitment rate g′

(x) is graphically presented as a density of randomly distributed points.

15. A computer program product for interpreting expirograms that includes computer-executable instructions that, when executed by a computer processor, cause one or more processors to:

receive gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) for a plurality of values x₁, . . . , x_N of an exhaled volume of exhaled respiratory air;

store the received gas concentrations; and

determine a non-linear fit function

ƒ

(x)=g(x)·

h(x)+Offset_Gas

 

for the stored gas concentrations ƒ

_mess(x₁), . . . , ƒ

_mess(x_N) by determining functions g(x) and h(x)

wherein

h(x)=a+b·

x,

g(x) is a continuously differentiable, non-linear function with

16. The computer program product according to claim 15, wherein the computer executable instructions further case one or more processors to determine the physiological dead space x_VD of a respective lung wherein: