Automatic lung parameter estimator

• US 7,008,380 B1
• Filed: 02/01/2000
• Issued: 03/07/2006
• Est. Priority Date: 02/03/1999
• Status: Expired due to Term

• Current Assignee: Mermaid Care A/S
• Original Assignee: Egon Steen Toft, Per Thorgaard, Soren Christensen Kjaergaard, Steen Andreassen, Stephen Edward Rees
• Inventors: Rees, Stephen Edward, Andreassen, Steen, Toft, Egon Steen, Thorgaard, Per, Kjaergaard, Soren Christensen
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/890,801
• Time in Patent Office: 2,226 Days
• Field of Search: 600/322, 600/323, 600529-538, 128/204.23
• US Class Current: 600/532
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/082 Evaluation by breath analysis, e.g. determination of the chemical composition of exhaled breath A61B5/083, A61B5/091 take precedence
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/435 partial O2 pressure (P-O2)

Abstract

A device for determining one or more respiratory parameters relating to an individual is disclosed, as well as a method for determining one or more respiratory parameters by means of the device, wherein the individual is suffering from hypoxemia or is at risk of hypoxemia. However, the method and the device may also be applied to healthy individual e.g. for testing of medicaments. The device is controlled by a computer equipped with suitable software and includes functionality for on-line continuous data collection, automatic assessment of the timing of measurements, automatic assessment of the next target (oxygen saturation of arterial blood (SpO2)), automatic assessment of the appropriate fraction of oxygen in inspired gas (FIO2) settings to achieve the target SpO2, automatic control of the FIO2, on-line parameter estimation, and automatic assessment of the number of measurememts requied.

Claims

1. A device for determining one or more respiratory parameters relating to an individual, comprising

a gas flow device having means for conducting a flow of inspiratory gas from an inlet opening to the respiratory system of the individual and a flow of expiratory gas from the respiratory system of the individual to an outlet opening,

a gas-mixing unit for supplying a substantially homogeneous gas to the inlet opening of the gas flow device,

first supply means for supplying a first gas to an inlet of the gas mixing unit and having first control means for controlling the flow of the first gas,

second supply means for supplying a second gas having an oxygen fraction different to the gas supplied from the first supply means to an inlet of the gas mixing unit and having second control means for controlling the flow of the second gas,

a computer for determining said one or more respiratory parameters,

first detection means for detecting the level of oxygen (SaO₂, SpO₂, PaO₂, PpO₂) in the blood circulation of the individual and producing an output to the computer accordingly, and

second detection means for detecting the level of oxygen (FIO₂, FE′

O₂, FĒ

O₂, PIO₂, PE′

O₂, PĒ

O₂) in the gas flow passing into or out of the respiratory system of the individual and producing an output to the computer accordingly,

the computer being adapted for retrieving and storing at least two measurements being the concurrent output produced by the first detection means and the second detection means within a data structure, in which the two stored outputs are mutually related, in data storage associated with the computer, the at least two measurements being conducted at corresponding levels of oxygen in the gas flow passing into the respiratory system, the computer further being adapted for determining at least two respiratory parameter (Rdiff, shunt, , H-shift, V-shift) being descriptive of the pulmonary gas exchange of the individual, the determination being based on the at least two measurements.

2. A device according to claim 1, wherein said parameter(s) (Rdiff, shunt, , H-shift, V-shift) is/are generalised parameters being comparable to similar parameter(s) determined for other individuals.

3. A device according to claim 1, wherein the computer further is adapted for performing a procedure at least once, the procedure comprising

determining, based on at least two measurements, whether additional measurements are required,

asserting a possible desired target defining a desired output of the first detection means,

producing a possible control data item based on the target, and

retrieving and storing, in the data structure, additional measurement results being the concurrent output produced by the first detection means and the second detection means.

4. A device according to claim 1, wherein the second detection means are arranged for detecting the level (FIO2, PIO2) of oxygen in the gas flow passing into the respiratory system, and the device further comprises

third detection means for detecting the level (FE′

O2, FĒ

O2, PE′

O2, PĒ

O2) of oxygen in the gas flow passing out of the respiratory system and producing an output to the computer accordingly, and

fourth detection means for detecting variables (Vt, f, ) of the gas flow passing the respiratory system and producing an output to the computer accordingly, said output being sufficient for the computer to establish the volume flow of gas passing the respiratory system,

the computer being adapted for retrieving and storing output from the third detection means and the fourth detection means within the data structure relating these stored output mutually as well as with the output from the first detection means and the second detection means retrieved simultaneously.

5. A device according to claim 4, wherein the computer further being adapted for establishing, based on said measurement(s), the oxygen consumption (VO₂) of the individual.

6. A device according to claim 1, wherein the computer is adapted to determine a parameter relating to an equilibrium state of the overall oxygen uptake or consumption of the individual based on the output of at least one of the detection means, to compare said parameter with a predefined threshold value and to produce a control data item accordingly if said parameter exceeds said threshold value.

7. A device according to claim 1, wherein the computer is adapted to assess the appropriate change in oxygen level in the inspired gas (FIO2) from the current oxygen level (FIO2) so as to achieve a given desired target oxygen level in the blood (SaO2, SpO2, PaO2, PpO2) and produce a control data item accordingly.

8. A device according to claim 7, wherein the assessment of change in oxygen level in the inspired gas is based on a predefined set of data representing statistical distributions of parameters stored within data storage associated with the computer and on said measurements.

9. A device according to claim 7, wherein the assessment of change in oxygen level in the inspired gas is based on the rate of change of the output of at least one of the detection means in response to a change in oxygen level (FIO₂) in the inspired gas flow.

10. A device according to claim 7, wherein the computer is adapted to operate the control means for controlling the flow to the gas mixing unit of at least one gas, in response to said control data item relating to the assessed change in oxygen level from the computer so as to change the oxygen level (FIO2) in the inspired gas flow accordingly.

11. A device according to claim 1, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air.

12. A device according to claim 11, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air and in the range of 0.85 to 1.00.

13. A device according to claim 1, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range of 0.00 to 0.21.

14. A device according to claim 13, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range 0.00 to 0.05.

15. A device according to claim 1, wherein the oxygen saturation in the blood circulation of the individual is in the range of 65 to 100%.

16. A device according to claim 15, wherein the oxygen saturation in the blood circulation of the individual is in the range of 85 to 100%.

17. A device according to claim 1, wherein the first detection means is arranged for detecting a parameter relating to the saturation level of oxygen in the arterial blood stream.

18. A device for determining one or more respiratory parameters relating to an individual, comprising

a gas flow device having means for conducting a flow of inspiratory gas from an inlet opening to the respiratory system of the individual and a flow of expiratory gas from the respiratory system of the individual to an outlet opening,

a gas-mixing unit for supplying a substantially homogeneous gas to the inlet opening of the gas flow device,

first supply means for supplying a first gas to an inlet of the gas mixing unit and having first control means for controlling the flow of the first gas,

second supply means for supplying a second gas having an oxygen fraction different to the gas supplied from the first supply means to an inlet of the gas mixing unit and having second control means for controlling the flow of the second gas,

a computer for determining said one or more respiratory parameters,

first detection means for detecting the level of oxygen (SaO₂, SpO₂, PaO₂, PpO₂) in the blood circulation of the individual and producing an output to the computer accordingly, and

second detection means for detecting the level of oxygen (FIO₂, FE′

O₂, FĒ

O₂, PIO₂, PE′

O₂, PĒ

O₂) in the gas flow passing into or out of the respiratory system of the individual and producing an output to the computer accordingly,

the computer being adapted for retrieving and storing a first measurement being the concurrent output produced by the first detection means and the second detection means within a data structure, in which the two stored outputs are mutually related, in data storage associated with the computer, the computer being further adapted for performing a procedure at least once, the procedure comprising

determining, based on data stored within the data structure, whether additional measurements are required,

asserting a possible desired target defining a desired output of the first detection means,

producing a possible control data item based on the target, and

retrieving and storing, in the data structure, additional measurement results being the concurrent output produced by the first detection means and the second detection means.

19. A device according to claim 18, wherein the second detection means are arranged for detecting the level (FIO₂, PIO₂) of oxygen in the gas flow passing into the respiratory system, and the device further comprises

third detection means for detecting the level (FE′

O₂, FĒ

O₂, PE′

O₂, PĒ

O₂) of oxygen in the gas flow passing out of the respiratory system and producing an output to the computer accordingly, and

fourth detection means for detecting variables (Vt, f, ) of the gas flow passing the respiratory system and producing an output to the computer accordingly, said output being sufficient for the computer to establish the volume flow of gas passing the respiratory system,

the computer being adapted for retrieving and storing output from the third detection means and the fourth detection means within the data structure in data storage associated with the computer, in which the stored outputs are mutually related and related to the output from the first detection means and the second detection means, and the output from the four detection means can be retrieved simultaneously.

20. A device according to claim 19, wherein the computer further being adapted for establishing, based on said measurement(s), the oxygen consumption (VO₂) of the individual.

21. A device according to claim 18, wherein the computer is adapted for determining at least one respiratory parameter (Rdiff, shunt, , H-shift, V-shift) being descriptive of the condition of the individual, the determination being based on at least two measurements.

22. A device according to claim 21, wherein at least two respiratory parameters (Rdiff, shunt, , H-shift, V-shift) are determined.

23. A device according to claim 21, wherein said parameter(s) (Rdiff, shunt, , H-shift, V-shift) is/are generalised parameters being comparable to similar parameter(s) determined for other individuals.

24. A device according to claim 18, wherein the computer is adapted to determine a parameter relating to an equilibrium state of the overall oxygen uptake or consumption of the individual based on the output of at least one of the detection means, to compare said parameter with a predefined threshold value and to produce a control data item accordingly if said parameter exceeds said threshold value.

25. A device according to claim 18, wherein the computer is adapted to assess the appropriate change in oxygen level in the inspired gas (FIO2) from the current oxygen level (FIO2) so as to achieve a given desired target oxygen level in the blood (SaO2, SpO2, PaO2, PpO2) and produce a control data item accordingly.

26. A device according to claim 25, wherein the assessment of change in oxygen level in the inspired gas is based on a predefined set of data representing statistical distributions of parameters stored within data storage means associated with the computer and on said measurement(s).

27. A device according to claim 25, wherein the assessment of change in oxygen level in the inspired gas is based on the rate of change of the output of at least one of the detection means in response to a change in oxygen level (FIO₂) in the inspired gas flow.

28. A device according to claim 25, wherein the computer is adapted to operate the control means for controlling the flow to the gas mixing unit of at least one gas, in response to said control data item relating to the assessed change in oxygen level from the computer so as to change the oxygen level (FIO2) in the inspired gas flow accordingly.

29. A device according to claim 18, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air.

30. A device according to claim 29, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air and in the range 0.85 to 1.00.

31. A device according to claim 18, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range of 0.00 to 0.21.

32. A device according to claim 31, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range of 0.00 to 0.05.

33. A device according to claim 18, wherein the oxygen saturation in the blood circulation of the individual is in the range of 65 to 100%.

34. A device according to claim 33, wherein the oxygen saturation in the blood circulation of the individual is in the range of 85 to 100%.

35. A device according to claim 18, wherein the first detection means is arranged for detecting a parameter relating to the saturation level of oxygen in the arterial blood stream.

36. A device for determining one or more respiratory parameters relating to an individual, comprising

a gas flow device having means for conducting a flow of inspiratory gas from an inlet opening to the respiratory system of the individual and a flow of expiratory gas from the respiratory system of the individual to an outlet opening,

a gas-mixing unit for supplying a substantially homogeneous gas to the inlet opening of the gas flow device,

first supply means for supplying a first gas to an inlet of the gas mixing unit and having first control means for controlling the flow of the first gas,

second supply means for supplying a second gas having an oxygen fraction different to the gas supplied from the first supply means to an inlet of the gas mixing unit and having second control means for controlling the flow of the second gas,

a computer for determining said one or more respiratory parameters,

first detection means for detecting the level of oxygen (SaO₂, SpO₂, PaO₂, PpO₂) in the blood circulation of the individual and producing an output to the computer accordingly, and

second detection means for detecting the level of oxygen (FIO₂, FE′

O₂, FĒ

O₂, PIO₂, PE′

O₂, FĒ

O₂) in the gas flow passing into or out of the respiratory system of the individual and producing an output to the computer accordingly,

the computer being adapted for retrieving and storing at least a first measurement being the concurrent output produced by the first detection means and the second detection means within a data structure, in which the two stored outputs are mutually related, in data storage associated with the computer, the computer further being adapted to assess the appropriate change in oxygen level in the inspired gas (FIO₂) from the current oxygen level (FIO₂) so as to achieve a given desired target oxygen level in the blood (SaO₂, SpO₂, PaO₂, PpO₂) and produce a control data item accordingly, wherein the assessment of change in oxygen level in the inspired gas is based on a predefined set of data representing statistical distributions of parameters stored within data storage means associated with the computer and on said measurement(s).

37. A device according to claim 36, wherein the assessment of change in oxygen level in the inspired gas is based on the rate of change of the output of at least one of the detection means in response to a change in oxygen level (FIO₂) in the inspired gas flow.

38. A device according to claim 36, wherein the computer is adapted to operate the control means for controlling the flow to the gas mixing unit of at least one gas, in response to said control data item from the computer so as to change the oxygen level (FIO2) in the inspired gas flow accordingly.

39. A device according to claim 36, wherein the computer further is adapted for performing a procedure at least once, the procedure comprising

determining, based on at least one measurement, whether additional measurements are required,

asserting a possible desired target defining a desired output of the first detection means,

producing a possible control data item based on the target, and

retrieving and storing, in the data structure, additional measurement results being the concurrent output produced by the first detection means and the second detection means.

40. A device according to claim 36, wherein the second detection means are arranged for detecting the level (FIO2, PIO2) of oxygen in the gas flow passing into the respiratory system, and the device further comprises

third detection means for detecting the level (FE′

O2, FĒ

O₂, PE′

O2, PĒ

O2) of oxygen in the gas flow passing out of the respiratory system and producing an output to the computer accordingly, and

fourth detection means for detecting variables (Vt, f, ) of the gas flow passing the respiratory system and producing an output to the computer accordingly, said output being sufficient for the computer to establish the volume flow of gas passing the respiratory system,

the computer being adapted for retrieving and storing output from the third detection means and the fourth detection means within the data structure relating these stored output mutually as well as with the output from the first detection means and the second detection means retrieved simultaneously.

41. A device according to claim 40, wherein the computer further being adapted for establishing, based on said measurement(s), the oxygen consumption (VO₂) of the individual.

42. A device according to claim 36, wherein the computer is adapted for determining at least one respiratory parameter (Rdiff, shunt, , H-shift, V-shift) being descriptive of the condition of the individual, the determination being based on at least two measurements.

43. A device according to claim 42, wherein at least two respiratory parameters (Rdiff, shunt, , H-shift, V-shift) are determined.

44. A device according to claim 42, wherein said parameter(s) (Rdiff, shunt, , H-shift, V-shift) is/are generalized parameters being comparable to similar parameter(s) determined for other individuals.

45. A device according to claim 36, wherein the computer is adapted to determine a parameter relating to an equilibrium state of the overall oxygen uptake or consumption of the individual based on the output of at least one of the detection means, to compare said parameter with a predefined threshold value and to produce a control data item accordingly if said parameter exceeds said threshold value.

46. A device according to claim 36, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air.

47. A device according to claim 36, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range of 0.00 to 0.21.

48. A device according to claim 36, wherein the oxygen saturation in the blood circulation of the individual is in the range of 65 to 100%.

49. A device according to claim 36, wherein the first detection means is arranged for detecting a parameter relating to the saturation level of oxygen in the arterial blood stream.

50. Method for determining one or more respiratory parameters using a device according to claim 36, wherein the individual is an apparently healthy individual.

51. Method for determining one or more respiratory parameters using a device according to claim 36, wherein the individual is considered to have a risk of suffering from hypoxemia.

52. Method for determining one or more respiratory parameters using a device according to claim 36, wherein the individual is suffering from hypoxemia.

53. Method according to claim 52, wherein the individual is suffering from one or more disease(s) selected from the group(s) comprising left sided heart failure, adult respiratory distress syndrome, pneumonia, postoperative hypoxemia, pulmonary fibrosis, toxic pulmonary lymphoedema, pulmonary embolisms, chronic obstructive pulmonary disease and cardiac shunting.

54. A device according to claim 36, wherein one gas is atmospheric air and another gas has an oxygen fraction higher than that of atmospheric air and in the range of 0.85 to 1.00.

55. A device according to claim 36, wherein one gas is atmospheric air and another gas has an oxygen fraction in the range of 0.00 to 0.05.

56. A device according to claim 36, wherein the oxygen saturation in the blood circulation of the individual is in the range of 85 to 100%.

57. A computer system comprising at least one general purpose computer having one or more computer programs stored within data storage means associated therewith, the computer system being arranged for as well as being adapted for determining one or more respiratory parameters relating to an individual, the computer system being intended for use with

an associated gas flow device having means for conducting a flow of inspiratory gas from an inlet opening to the respiratory system of the individual and a flow of expiratory gas from the respiratory system of the individual to an outlet opening,

an associated gas-mixing unit for supplying a substantially homogeneous gas to the inlet opening of the gas flow device,

associated first supply means for supplying a first gas to an inlet of the gas mixing unit and having first control means for controlling the flow of the first gas,

associated second supply means for supplying a second gas having an oxygen fraction different to the gas supplied from the first supply means to an inlet of the gas mixing unit and having second control means for controlling the flow of the second gas,

associated first detection means for detecting the level of oxygen (SaO₂, SpO₂, PaO₂, PpO₂) in the blood circulation of the individual and producing an output to the computer system accordingly, and

associated second detection means for detecting the level of oxygen (FIO₂, FE′

O₂, FĒ

O₂, PIO₂, PE′

O₂, PĒ

O₂) in the gas flow passing into or out of the respiratory system of the individual and producing an output to the computer system accordingly,

the computer system being adapted for retrieving and storing at least two measurements being the concurrent output produced by the first detection means and the second detection means within a data structure, in which the two stored outputs are mutually related, in data storage associated with the computer system, the at least two measurements being conducted at corresponding levels of oxygen in the gas flow passing into the respiratory system, the computer system further being adapted for determining at least two respiratory parameters (Rdiff, shunt, , H-shift, V-shift) being descriptive of the pulmonary gas exchange of the individual, the determination being based on the at least two measurements.

58. A computer program product embodied on a computer readable medium being adapted to enable a computer system according to claim 57 to determine one or more respiratory parameters of an individual.