DETERMINING FUNCTIONAL RESIDUAL LUNG CAPACITY

• US 20110112424A1
• Filed: 04/23/2009
• Published: 05/12/2011
• Est. Priority Date: 04/23/2008
• Status: Abandoned Application

• Current Assignee: Mark Shahar, Yitzhak Kesselman
• Original Assignee: Mark Shahar, Yitzhak Kesselman
• Inventors: Kesselman, Yitzhak, Shahar, Mark
• Application Number:
  US12/988,931
• Publication Number:
  US 20110112424A1
• Time in Patent Office: Days
• US Class Current: 600/532
• 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: A61M 16/021 operated by electrical means A61M16/202 – A61M16/205 take precedence
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2205/3584 using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 partial O2 pressure (P-O2)

Abstract

Determining functional residual lung capacity (FRC) by changing a subject'"'"'s inspirium FiO₂ by a predetermined amount, and a) for each breath in a series of breaths subsequent to changing the FiO₂, determining expiratory tidal volume, determining expiratory fractional N₂ tidal volume, multiplying the expiratory tidal volume by an absolute difference between the expiratory fractional N₂ tidal volume of the breath and that of an immediately preceding breath for a first multiplication result, dividing the first multiplication result by the sum of the differences for a first division result, and multiplying the fractional N₂ tidal volume by the sum of the first division results of the breaths for a second multiplication result, and b) dividing the sum of the second multiplication results of the breaths by the absolute difference between the fractional N₂ tidal volume of the first and last breaths to produce a measurement of the subject'"'"'s FRC.

Claims

1. A method for determining the functional residual lung capacity of a subject, the method comprising:

changing the FiO₂ of a subject'"'"'s inspirium by a predetermined amount;

for each breath in a series of breaths of said subject subsequent to changing said FiO₂,

determining an expiratory tidal volume measurement value of said breath,

determining an expiratory fractional N₂ tidal volume measurement value of said breath,

multiplying said expiratory tidal volume measurement value of said breath by an absolute difference between said expiratory fractional N₂ tidal volume measurement value of said breath and that of a breath immediately preceding said breath, thereby yielding a first multiplication result,

dividing said first multiplication result by the sum of said absolute differences of each of said breaths, thereby yielding a first division result, and

multiplying said expiratory fractional N₂ tidal volume measurement value of said breath by the sum of said first division results of each of said breaths, thereby yielding a second multiplication result; and

dividing the sum of said second multiplication results of each of said breaths by the absolute difference between said expiratory fractional N₂ tidal volume measurement values of the first and last breaths in said series of breaths, thereby producing a functional residual lung capacity measurement of said subject.

2. A method according to claim 1 wherein said changing step comprises increasing said FiO₂.

3. A method according to claim 1 wherein said changing step comprises decreasing said FiO₂.

4. A method according to claim 1 wherein said changing step comprises changing said FiO₂ by an amount that is within the range of about 20% to about 25% of total inspired volume of said subject.

5. A method according to claim 1 wherein said changing step comprises changing said FiO₂ in accordance with a single step function.

6. A method according to claim 1 and further comprising:

determining a fractional expiratory CO₂ tidal volume of expirium of said subject; and

determining a fractional expiratory O₂ tidal volume of expirium of said subject,

wherein said step of determining said fractional expiratory N₂ tidal volume comprises determining said fractional expiratory N₂ tidal volume as a function of said O₂ and CO₂ fractional expiratory O₂ tidal volumes.

7. A method according to claim 6 wherein said step of determining said fractional expiratory CO₂ tidal volume comprises determining prior to changing said FiO₂.

8. A method according to claim 6 wherein said step of determining said fractional expiratory CO₂ tidal volume comprises determining said fractional expiratory CO₂ tidal volume separately for each of said breath in said series of breaths.

9. A method according to claim 1 wherein said determining steps comprise determining until any of said expiratory fractional tidal volumes reaches a steady state.

10. A method according to claim 9 wherein said determining steps comprise determining until consecutive ones of any of said expiratory fractional tidal volumes differ by less than a predefined amount.

11. A method according to claim 10 wherein said determining steps comprise determining until consecutive ones of any of said expiratory fractional tidal volumes differ by less than <

1%.

12. A method according to claim 1 wherein said determining steps comprise determining for predefined number of breaths after any of said expiratory fractional tidal volumes reaches a steady state.

13. A method according to claim 6 wherein said step of determining said fractional expiratory O₂ tidal volume comprises determining using a minimal level of O₂ in said breath after said FiO₂ is increased.

14. A method according to claim 6 wherein said step of determining said fractional expiratory O₂ tidal volume comprises determining using a maximal level of O₂ in said breath after said FiO₂ is decreased.

15. A method according to claim 1 wherein said determining steps comprise associating any of said tidal volumes with any of said breaths where the measurement of said tidal volume is closest in time to the occurrence of said breath after a change in detected in inspirium FiO₂ of said subject.

16. A functional residual lung capacity measurement system, the system comprising:

a ventilation system; and

a functional residual capacity analyzer configured to co-operate with said ventilation system to determine the functional residual lung capacity of a subject that is insufflated with O₂ by said ventilation system, wherein said analyzer is configured to,

a) for each breath in a series of breaths of said subject subsequent to the occurrence of a change in the FiO₂ of a subject'"'"'s inspirium by a predetermined amount,

determine an expiratory tidal volume measurement value of said breath,

determine an expiratory fractional N₂ tidal volume measurement value of said breath,

multiply said expiratory tidal volume measurement value of said breath by an absolute difference between said expiratory fractional N₂ tidal volume measurement value of said breath and that of a breath immediately preceding said breath, thereby yielding a first multiplication result,

divide said first multiplication result by the sum of said absolute differences of each of said breaths, thereby yielding a first division result, and

multiply said expiratory fractional N₂ tidal volume measurement value of said breath by the sum of said first division results of each of said breaths, thereby yielding a second multiplication result, and

b) divide the sum of said second multiplication results of each of said breaths by the absolute difference between said expiratory fractional N₂ tidal volume measurement values of the first and last breaths in said series of breaths, thereby producing a functional residual lung capacity measurement of said subject.

17. A system according to claim 16 wherein said ventilation system comprises:

an O₂ source;

an O₂ sensor configured to measure inspiratory O₂ between said O₂ source and a subject; and

a flow transducer configured to measure pressure along expiratory and inspiratory channels intermediate said O₂ source and said subject,

wherein said functional residual capacity analyzer is configured to determine any of said tidal volumes using any of said pressure measurement and said inspiratory O₂ measurement.

18. A system according to claim 16 wherein said analyzer is configured to automatically initiate a measurement of said functional residual lung capacity after said change in said FiO₂ occurs.

19. A system according to claim 17 wherein said analyzer is configured to cause said O₂ source to change said FiO₂ of said subject inspirium by said predetermined amount.

20. A system according to claim 19 wherein said O₂ source is configured to change said FiO₂ of said subject inspirium by increasing said FiO₂.

21. A system according to claim 19 wherein said O₂ source is configured to change said FiO₂ of said subject inspirium by decreasing said FiO₂.

22. A system according to claim 19 wherein said O₂ source is configured to change said FiO₂ by an amount that is within the range of about 20% to about 25% of total inspired volume of said subject.

23. A system according to claim 16 wherein said O₂ source is configured to change said FiO₂ in accordance with a single step function.

24. A system according to claim 16 wherein said analyzer is configured to

determine a fractional expiratory CO₂ tidal volume of expirium of said subject,

determine a fractional expiratory O₂ tidal volume of expirium of said subject, and

determine said fractional expiratory N₂ tidal volume as a function of said O₂ and CO₂ fractional expiratory O₂ tidal volumes.

25. A system according to claim 24 wherein said analyzer is configured to determine said fractional expiratory CO₂ tidal volume prior to said change in FiO₂.

26. A system according to claim 24 wherein said analyzer is configured to determine said fractional expiratory CO₂ tidal volume separately for each of said breath in said series of breaths.

27. A system according to claim 16 wherein said analyzer is configured to make any of said determinations until any of said expiratory fractional tidal volumes reaches a steady state.

28. A system according to claim 27 wherein said analyzer is configured to make any of said determinations until consecutive ones of any of said expiratory fractional tidal volumes differ by less than a predefined amount.

29. A system according to claim 28 wherein said analyzer is configured to make any of said determinations until consecutive ones of any of said expiratory fractional tidal volumes differ by less than <

1%.

30. A system according to claim 16 wherein said analyzer is configured to make any of said determinations for predefined number of breaths after any of said expiratory fractional tidal volumes reaches a steady state.

31. A system according to claim 24 wherein said analyzer is configured to determine said fractional expiratory O₂ tidal volume using a minimal level of O₂ in said breath after said FiO₂ is increased.

32. A system according to claim 24 wherein said analyzer is configured to determine said fractional expiratory O₂ tidal volume using a maximal level of O₂ in said breath after said FiO₂ is decreased.

33. A system according to claim 16 wherein said analyzer is configured to associate any of said tidal volumes with any of said breaths where the measurement of said tidal volume is closest in time to the occurrence of said breath after a change in detected in inspirium FiO₂ of said subject.

34. A computer program product for determining the functional residual lung capacity of a subject, the computer program product comprising:

a computer readable medium; and

computer program instructions operative to

a) for each breath in a series of breaths of said subject subsequent to the occurrence of a change in the FiO₂ of a subject'"'"'s inspirium by a predetermined amount,

determine an expiratory tidal volume measurement value of said breath,

determine an expiratory fractional N₂ tidal volume measurement value of said breath,

multiply said expiratory tidal volume measurement value of said breath by an absolute difference between said expiratory fractional N₂ tidal volume measurement value of said breath and that of a breath immediately preceding said breath, thereby yielding a first multiplication result,

divide said first multiplication result by the sum of said absolute differences of each of said breaths, thereby yielding a first division result, and

multiply said expiratory fractional N₂ tidal volume measurement value of said breath by the sum of said first division results of each of said breaths, thereby yielding a second multiplication result, and

b) divide the sum of said second multiplication results of each of said breaths by the absolute difference between said expiratory fractional N₂ tidal volume measurement values of the first and last breaths in said series of breaths, thereby producing a functional residual lung capacity measurement of said subject,

wherein said program instructions are stored on said computer readable medium.