MANAGING FLOW/VOLUME LOOP INFORMATION

• US 20100222693A1
• Filed: 02/27/2009
• Published: 09/02/2010
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: Volusense AS
• Original Assignee: Volusense AS
• Inventors: Enger, Oivind, Eriksen, Morten
• Granted Patent: US 8,357,100 B2
• Time in Patent Office: Days
• US Class Current: 600/538
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: G16H 40/63 for local operation

Abstract

Embodiments of the present invention provide methods of extracting optimal information from a flow/volume loop concerning the patient'"'"'s respiratory condition by examining the overall shape of the space under the flow/volume loop'"'"'s expiration portion. In some embodiments, this is done with reference to the center of mass of that space. In some embodiments, this is done with reference to the area of that space. Some embodiments are significantly less affected by random/statistical variations and/or noise within the measurement system than existing methods.

Claims

1. A method of gathering data related to breathing patterns of a patient, comprising the steps of:

(a) acquiring flow data and volume data, wherein flow data relates to a rate of air flow into and out of the patient'"'"'s lungs and volume data relates to changes in volume of the patient'"'"'s lungs;

(b) generating a flow/volume loop based on at least some of the flow data and at least some of the volume data, the flow/volume loop having an expiration portion and an inspiration portion, the expiration portion beginning with a full-inhale point and ending with a full-exhale point, which both lie along a zero-flow line; and

(c) calculating an exhale pattern parameter based on an overall shape of an expiration space, which is bounded by the expiration portion of the flow/volume loop and the zero-flow line.

2. The method of claim 1, wherein acquiring flow data and volume data comprises measuring flow data and calculating volume data from measured flow data.

3. The method of claim 1, wherein acquiring flow data and volume data comprises measuring volume data and calculating flow data from measured volume data.

4. The method of claim 1, wherein the flow data and the volume data on which the flow/volume loop is based comprises average flow data and average volume data from multiple patient breathing cycles.

5. The method of claim 1, further comprising (d) comparing the exhale pattern parameter to a predetermined parameter to determine whether the volume data and/or the flow data are indicative of a respiratory irregularity.

6. The method of claim 1, wherein the exhale pattern parameter is based on a center of mass of the expiration space.

7. The method of claim 6, wherein the full-inhale point corresponds to a full-inhale volume value, the full-exhale point corresponds to a full-exhale volume value, and the center of mass of the expiration space corresponds to a center-of-mass volume value and wherein the exhale pattern parameter is based on the full-inhale volume value, the full-exhale volume value, and the center-of-mass volume value.

8. The method of claim 7, wherein the center-of-mass volume value is calculated according to the following formula:

${\mathrm{CM}}_V=\frac{{\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{fe}}}<br><br>V<br><br>\left(t\right)·<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t}{{\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{fe}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t}$

wherein CM_V=the center-of-mass volume value;

t_fi=time at the full-inhale point;

t_fe=time at the full-exhale point;

V(t)=exhaled volume as a function of time; and

F(t)=air flow as a function of time.

9. The method of claim 7, wherein the center-of-mass volume value is based on discrete sample points representing measured values taken at equidistant points in time according to the following formula:

${\mathrm{CM}}_V\approx <br><br>\frac{\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>\left(V_p<br><br>F_p^2\right)}{\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>F_p^2}$

wherein CM_V=the center-of-mass volume value;

n_fi is a sample point count number at the full-inhale point;

n_fe is a sample point count number at the full-exhale point; and

V and F are sample point series describing volume and flow waveforms.

10. The method of claim 7, wherein the exhale pattern parameter comprises a volume value ratio of (i) a difference between the center-of-mass volume value and the full-inhale volume value to (ii) a difference between the full-exhale volume value and the full-inhale volume value.

11. The method of claim 10, further comprising (d) determining whether the volume value ratio is less than a predetermined threshold ratio, the predetermined threshold ratio being indicative of a respiratory irregularity.

12. The method of claim 11, wherein the predetermined threshold ratio is approximately 0.45.

13. The method of claim 1, wherein a half-exhale point lies on the zero-flow line halfway between the full-inhale point and the full-exhale point and wherein calculating the exhale pattern parameter comprises:

(i) calculating a first-half-exhale area, the first-half-exhale area being the area of a shape bounded by (A) the expiration portion, (B) a first line segment that extends between the full-inhale point and the half-exhale point along the zero-flow line, and (B) a second line segment that extends perpendicularly to the zero-flow line between the half-exhale point and a corresponding point on the expiration portion of the flow/volume loop,

(ii) calculating a second-half-exhale area, the second-half-exhale area being the area of a shape bounded by (A) the expiration portion, (B) the second line segment, and (C) a third line segment that extends between the half-exhale point and the full-exhale point along the zero-flow line, and

(iii) determining the exhale pattern parameter based on the first-half-exhale area and the second-half-exhale area.

14. The method of claim 13, wherein calculating the first-half-exhale area is according to the following formula:

$A_{\mathrm{fh}}={\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{he}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t$

and calculating the second-half-exhale area is according to the following formula;

$A_{\mathrm{sh}}={\int <br><br>}_{t_{\mathrm{he}}}^{t_{\mathrm{fe}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t$

wherein A_fh=the first-half-exhale area;

A_sh=the second-half-exhale area;

t_fi=time at the full-inhale point;

t_he=time at the half-exhale point;

t_fe=time at the full-exhale point; and

F(t)=air flow as a function of time.

15. The method of claim 13, wherein calculating the first-half-exhale area is based on discrete sample points representing measured values taken at equidistant points in time according to the following formula:

$A_{\mathrm{fh}}\approx <br><br>\mathrm{\Delta <br><br>}<br><br><br><br>t<br><br>\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{he}}}{\sum <br><br>}}<br><br><br><br>F_p^2$

and calculating the second-half-exhale area is based on discrete sample points representing measured values taken at equidistant points in time according to the following formula;

$A_{\mathrm{sh}}\approx <br><br>\mathrm{\Delta <br><br>}<br><br><br><br>t<br><br>\underset{p=n_{\mathrm{he}}+1}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>F_p^2$

wherein A_fh=the first-half-exhale area;

A_sh=the second-half-exhale area;

Δ

t=a time interval between the equidistant points in time;

n_fi is a sample point count number at the full-inhale point;

n_he is a sample point count number at the half-exhale point;

n_fe is a sample point count number at the full-exhale point; and

F is a sample point series describing a flow waveform.

16. The method of claim 13, wherein calculating the exhale pattern parameter comprises calculating an area ratio of the first-half-exhale area to the first-half-exhale area plus the second-half-exhale area, the exhale pattern parameter comprising the area ratio.

17. The method of claim 16, further comprising (d) determining whether the area ratio is less than a predetermined threshold ratio, the predetermined threshold ratio being indicative of a respiratory irregularity.

18. The method of claim 17, wherein the predetermined threshold ratio is approximately 0.45.

19. A computer-readable medium programmed with instructions for performing a method of gathering data related to breathing patterns of a patient, the medium comprising instructions for causing a programmable processor to:

(a) access a flow/volume loop that displays flow data and volume data, the flow data relating to a rate of air flow into and out of the patient'"'"'s lungs and the volume data relating to changes in volume of the patient'"'"'s lungs, wherein the flow/volume loop includes an expiration portion and an inspiration portion, the expiration portion beginning with a full-inhale point and ending with a full-exhale point, which both lie along a zero-flow line; and

(b) calculate an exhale pattern parameter based on an overall shape of an expiration space, which is bounded by the expiration portion of the flow/volume loop and the zero-flow line.

20. The computer-readable medium of claim 19, wherein the flow data and the volume data comprises average flow data and average volume data from multiple patient breathing cycles.

21. The computer-readable medium of claim 19, further comprising instructions for causing the programmable processor to:

(c) compare the exhale pattern parameter to a predetermined parameter to determine whether the volume data and/or the flow data are indicative of a respiratory irregularity.

22. The computer-readable medium of claim 19, wherein the exhale pattern parameter is based on a center of mass of the expiration space.

23. The computer-readable medium of claim 22, wherein the full-inhale point corresponds to a full-inhale volume value, the full-exhale point corresponds to a full-exhale volume value, and the center of mass of the expiration space corresponds to a center-of-mass volume value and wherein the exhale pattern parameter is based on the full-inhale volume value, the full-exhale volume value, and the center-of-mass volume value.

24. The computer-readable medium of claim 23, wherein the center-of-mass volume value is calculated according to the following formula:

${\mathrm{CM}}_V=\frac{{\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{fe}}}<br><br>V<br><br>\left(t\right)·<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t}{{\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{fe}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t}$

wherein CM_V=the center-of-mass volume value;

t_fi=time at the full-inhale point;

t_fe=time at the full-exhale point;

V(t)=exhaled volume as a function of time; and

F(t)=air flow as a function of time.

25. The computer-readable medium of claim 23, wherein the center-of-mass volume value is based on discrete sample points representing measured values taken at equidistant points in time according to the following formula:

${\mathrm{CM}}_V\approx <br><br>\frac{\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>\left(V_p<br><br>F_p^2\right)}{\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>F_p^2}$

wherein CM_V=the center-of-mass volume value;

n_fi is a sample point count number at the full-inhale point;

n_fe is a sample point count number at the full-exhale point; and

V and F are sample point series describing volume and flow waveforms.

26. The computer-readable medium of claim 23, wherein the exhale pattern parameter comprises a volume value ratio of (i) a difference between the center-of-mass volume value and the full-inhale volume value to (ii) a difference between the full-exhale volume value and the full-inhale volume value.

27. The computer-readable medium of claim 26, further comprising (d) determining whether the volume value ratio is less than a predetermined threshold ratio, the predetermined threshold ratio being indicative of a respiratory irregularity.

28. The computer-readable medium of claim 27, wherein the predetermined threshold ratio is approximately 0.45.

29. The computer-readable medium of claim 19, wherein a half-exhale point lies on the zero-flow line halfway between the full-inhale point and the full-exhale point and wherein the instructions for causing the programmable processor to calculate the exhale pattern parameter comprise instructions for causing the programmable processor to:

(i) calculate a first-half-exhale area, the first-half-exhale area being the area of a shape bounded by (A) the expiration portion, (B) a first line segment that extends between the full-inhale point and the half-exhale point along the zero-flow line, and (C) a second line segment that extends perpendicularly to the zero-flow line between the half-exhale point and a corresponding point on the expiration portion of the flow/volume loop,

(ii) calculate a second-half-exhale area, the second-half-exhale area being the area of a shape bounded by (A) the expiration portion, (B) the second line segment, and (C) a third line segment that extends between the half-exhale point and the full-exhale point along the zero-flow line, and

(iii) determine the exhale pattern parameter based on the first-half-exhale area and the second-half-exhale area.

30. The computer-readable medium of claim 29, wherein the instructions for causing the programmable processor to calculate the first-half-exhale area comprise instructions for causing the programmable processor to use the following formula:

$A_{\mathrm{fh}}={\int <br><br>}_{t_{\mathrm{fi}}}^{t_{\mathrm{he}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t$

and the instructions for causing the programmable processor to calculate the second-half-exhale area comprise instructions for causing the programmable processor to use the following formula;

$A_{\mathrm{sh}}={\int <br><br>}_{t_{\mathrm{he}}}^{t_{\mathrm{fe}}}<br><br>{\left[F<br><br>\left(t\right)\right]}^2<br><br><br><br><br><br>t$

wherein A_fh=the first-half-exhale area;

A_sh=the second-half-exhale area;

t_fi=time at the full-inhale point;

t_he=time at the half-exhale point;

t_fe=time at the full-exhale point; and

F(t)=air flow as a function of time.

31. The computer-readable medium of claim 29, wherein the instructions for causing the programmable processor to calculate the first-half-exhale area comprise instructions for causing the programmable processor to use discrete sample points representing measured values taken at equidistant points in time according to the following formula:

$A_{\mathrm{fh}}\approx <br><br>\mathrm{\Delta <br><br>}<br><br><br><br>t<br><br>\underset{p=n_{\mathrm{fi}}}{\overset{n_{\mathrm{he}}}{\sum <br><br>}}<br><br><br><br>F_p^2$

and the instructions for causing the programmable processor to calculate the second-half-exhale area comprise instructions for causing the programmable processor to use discrete sample points representing measured values taken at equidistant points in time according to the following formula;

$A_{\mathrm{sh}}\approx <br><br>\mathrm{\Delta <br><br>}<br><br><br><br>t<br><br>\underset{p=n_{\mathrm{he}}+1}{\overset{n_{\mathrm{fe}}}{\sum <br><br>}}<br><br><br><br>F_p^2$

wherein A_fh=the first-half-exhale area;

A_sh=the second-half-exhale area;

Δ

t=a time interval between the equidistant points in time;

n_fi is a sample point count number at the full-inhale point;

n_he is a sample point count number at the half-exhale point;

n_fe is a sample point count number at the full-exhale point; and

F is a sample point series describing a flow waveform.

32. The computer-readable medium of claim 29, wherein the instructions for causing the programmable processor to calculate the exhale pattern parameter comprise instructions for causing the programmable processor to calculate an area ratio of the first-half-exhale area to the first-half-exhale area plus the second-half-exhale area, the exhale pattern parameter comprising the area ratio.

33. The computer-readable medium of claim 32, further comprising instructions for causing the programmable processor to (c) determine whether the area ratio is less than a predetermined threshold ratio, the predetermined threshold ratio being indicative of a respiratory irregularity.

34. The computer-readable medium of claim 33, wherein the predetermined threshold ratio is approximately 0.45.