Bi-directional partial re-breathing method

US 6,200,271 B1
Filed: 09/09/1998
Issued: 03/13/2001
Est. Priority Date: 09/09/1998
Status: Expired due to Term

First Claim

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1. A method of non-invasively determining pulmonary capillary blood flow of a patient, comprising:

measuring a before re-breathing carbon dioxide elimination and a before re-breathing partial pressure of end tidal carbon dioxide prior to a re-breathing phase;

measuring a during re-breathing carbon dioxide elimination and a during re-breathing partial pressure of end tidal carbon dioxide during said re-breathing phase; and

measuring an after re-breathing carbon dioxide elimination and an after re-breathing partial pressure of end tidal carbon dioxide after said re-breathing phase.

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Abstract

A re-breathing method for determining pulmonary capillary blood flow that accounts for changes in the carbon dioxide content of a patient. The carbon dioxide elimination and partial pressure of end tidal carbon dioxide of the patient are measured prior to re-breathing, during re-breathing, and after re-breathing. A rate of change of carbon dioxide content of the venous blood of the patient is then calculated. The rate of change is then employed in calculating the pulmonary capillary blood flow of the patient.

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59 Claims

1. A method of non-invasively determining pulmonary capillary blood flow of a patient, comprising:
- measuring a before re-breathing carbon dioxide elimination and a before re-breathing partial pressure of end tidal carbon dioxide prior to a re-breathing phase;
  
  measuring a during re-breathing carbon dioxide elimination and a during re-breathing partial pressure of end tidal carbon dioxide during said re-breathing phase; and
  
  measuring an after re-breathing carbon dioxide elimination and an after re-breathing partial pressure of end tidal carbon dioxide after said re-breathing phase.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- - 2. The method of claim 1, further comprising determining a rate of change of a carbon dioxide content of venous blood of the patient.
  - 3. The method of claim 2, further comprising:
4. The method of claim 3, further comprising:
- determining a before time of said before re-breathing carbon dioxide elimination;
  
  determining a during time of said during re-breathing carbon dioxide elimination; and
  
  determining an after time of said after re-breathing carbon dioxide elimination.
5. The method of claim 2, further comprising:
- determining a before time of said before re-breathing partial pressure of end tidal carbon dioxide;
  
  determining a during time of said during re-breathing partial pressure of end tidal carbon dioxide; and
  
  determining an after time of said after re-breathing partial pressure of end tidal carbon dioxide.
6. The method of claim 3, further comprising:
- calculating said rate of change by employing the following equation;
  
  $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})} .$
  
  where Δ
  
  VCO_2BDcomprises a difference between said before re-breathing carbon dioxide elimination and said during re-breathing carbon dioxide elimination, Δ
  
  CACO_2DAcomprises a difference between said during re-breathing alveolar content and said after re-breathing alveolar content, Δ
  
  VCO_2DAcomprises a difference between said during re-breathing carbon dioxide elimination and said after re-breathing carbon dioxide elimination, Δ
  
  CACO_2BDcomprises a difference between said before re-breathing alveolar content and said during re-breathing alveolar content, t_Bcomprises a time of prior to said re-breathing phase, t_Dcomprises a time during said re-breathing phase, and t_Acomprises a time after said re-breathing phase.
7. The method of claim 3, further comprising calculating pulmonary capillary blood flow with said before re-breathing carbon dioxide elimination, said during re-breathing carbon dioxide elimination, said after re-breathing carbon dioxide elimination, said before re-breathing alveolar content, said during re-breathing alveolar content, said after re-breathing alveolar content, and said rate of change.
8. The method of claim 4, further comprising calculating pulmonary capillary blood flow with said before re-breathing carbon dioxide elimination, said during re-breathing carbon dioxide elimination, said after re-breathing carbon dioxide elimination, said before re-breathing alveolar content, said during re-breathing alveolar content, said after re-breathing alveolar content, said before time, said during time, said after time, and said rate of change.
9. The method of claim 7, further comprising calculating said pulmonary capillary blood flow by employing the following equation:
- $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{k \cdot (t_{B} + t_{A} - 2 t_{D}) - (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})},$
10. The method of claim 2, wherein said rate of change is substantially constant.
11. The method of claim 2, wherein said rate of change is substantially exponential over time.
12. The method of claim 1, further comprising:
- determining a before time of said before re-breathing carbon dioxide elimination;
  
  determining a during time of said during re-breathing carbon dioxide elimination; and
  
  determining an after time of said after re-breathing carbon dioxide elimination.
13. The method of claim 12, wherein a difference between said during time and said before time is equal to a difference between said after time and said during time.
14. The method of claim 13, further comprising calculating pulmonary capillary blood flow by employing the following equation:
- $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{- (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$

15. A method of non-invasively determining a pulmonary capillary blood flow of a patient, comprising:
- determining a before re-breathing carbon dioxide elimination (VCO_2B) of the patient, a before re-breathing alveolar partial pressure of carbon dioxide (PACO_2B) of the patient, and a before time (t_B);
  
  re-breathing to determine a during re-breathing carbon dioxide elimination (VCO_2D) of the patient, a during re-breathing alveolar partial pressure of carbon dioxide (PACO_2D) of the patient, and a during time (t_D);
  
  determining an after re-breathing carbon dioxide elimination (VCO_2A) of the patient, an after re-breathing alveolar partial pressure of carbon dioxide (PACO_2A) of the patient, and an after time (t_A); and
  
  calculating a rate of change (k) of a carbon dioxide content of venous blood of the patient.
- View Dependent Claims (16, 17, 18, 19, 20, 21)
- - 16. The method of claim 15, wherein said rate of change comprises a substantially linear change over time.
  - 17. The method of claim 15, wherein said rate of change comprises a substantially exponential change over time.
  - 18. The method of claim 15, wherein said calculating said rate of change comprises employing the following equation:
    - $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})} .$
  - 19. The method of claim 18, further comprising calculating pulmonary capillary blood flow by the following equation:
    - $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{k \cdot (t_{B} + t_{A} - 2 t_{D}) - (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$
  - 20. The method of claim 15, wherein t_D−
    - t_B=t_A−
      
      t_D.
  - 21. The method of claim 20, further comprising calculating pulmonary capillary blood flow by the following equation:
    - $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{- (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$

22. A method of non-invasively determining a pulmonary capillary blood flow of a patient, comprising:
- measuring a carbon dioxide elimination (VCO₂) of the patient before, during and after a re-breathing process; and
  
  determining an alveolar partial pressure of carbon dioxide (PACO₂) of the patient before, during and after said re-breathing process.
- View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
- - 23. The method of claim 22, further comprising determining a time (t) of each of said before, said during, and said after said re-breathing process.
  - 24. The method of claim 23, further comprising calculating a rate of change (k) of a content of carbon dioxide in venous blood of the patient.
  - 25. The method of claim 24, wherein said calculating comprises employing the following equation:
    - $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})} .$
  - 26. The method of claim 24, further comprising calculating pulmonary capillary blood flow (Q_pcbf).
  - 27. The method of claim 26, wherein said calculating comprises employing the following equation:
    - $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{k \cdot (t_{B} + t_{A} - 2 t_{D}) - (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})},$
  - 28. The method of claim 24, wherein said rate of change comprises a substantially linear change with respect to time.
  - 29. The method of claim 24, wherein said rate of change comprises a substantially exponential change over time.
  - 30. The method of claim 25, wherein t_D−
    - t_B=t_A−
      
      t_D.
  - 31. The method of claim 30, further comprising calculating pulmonary capillary blood flow by the following equation:
    - $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{- (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$

32. A method of determining a rate of change in carbon dioxide content of venous blood of a patient, comprising:
- measuring a carbon dioxide elimination (VCO₂) of the patient before (B), during (D) and after (A) a re-breathing process; and
  
  determining an alveolar partial pressure of carbon dioxide (PACO₂) of the patient before, during and after said re-breathing process.
- View Dependent Claims (33, 34)
- - 33. The method of claim 32, further comprising determining a time (t) of each of said before (t_B), said during (t_D), and said after (t_A) said re-breathing process.
  - 34. The method of claim 33, further comprising calculating said rate of change by employing the following equation:
    - $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})} .$

35. A method of determining a change in carbon dioxide content of venous blood of a patient, comprising:
- measuring a carbon dioxide elimination (VCO₂) of the patient before (B), during (D) and after (A) a re-breathing process; and
  
  determining an alveolar partial pressure of carbon dioxide (PACO₂) of the patient before, during and after said re-breathing process.
- View Dependent Claims (36, 37, 38, 39)
- - 36. The method of claim 35, further comprising determining a time (t) of each of said before (t_B), said during (t_D), and said after (t_A) said re-breathing process.
  - 37. The method of claim 36, further comprising calculating a rate of change by employing the following equation:
    - $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})} .$
  - 38. The method of claim 37, further comprising calculating a change in a carbon dioxide content of venous blood of the patient from t_Bto t_D(Δ
    - CvCO_2BD) by employing the following equation;
39. The method of claim 37, further comprising calculating a change in a carbon dioxide content of venous blood of the patient from t_Dto t_A(Δ
- CvCO_2DA) by employing the following equation;

40. A method of non-invasively determining pulmonary capillary blood flow of a patient, comprising:
- measuring a before carbon dioxide elimination and a before partial pressure of end tidal carbon dioxide prior to a change in effective ventilation;
  
  measuring a during carbon dioxide elimination and a during partial pressure of end tidal carbon dioxide during said change in effective ventilation; and
  
  measuring an after carbon dioxide elimination and an after partial pressure of end tidal carbon dioxide after said change in effective ventilation.
- View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59)
- - 41. The method of claim 40, wherein said change in effective ventilation comprises re-breathing.
  - 42. The method of claim 40, wherein said change in effective ventilation comprises a change in a respiratory rate.
  - 43. The method of claim 40, wherein said change in effective ventilation comprises a change in an inspiratory time.
  - 44. The method of claim 40, wherein said change in effective ventilation comprises a change in an expiratory time.
  - 45. The method of claim 40, wherein said change in effective ventilation comprises a change in a tidal volume.
  - 46. The method of claim 40, wherein said change in effective ventilation comprises a change in a quantity of carbon dioxide.
  - 47. The method of claim 40, further comprising determining a rate of change of a carbon dioxide content of venous blood of the patient.
  - 48. The method of claim 47, further comprising:
49. The method of claim 48, further comprising:
- determining a before time of said before carbon dioxide elimination;
  
  determining a during time of said during carbon dioxide elimination; and
  
  determining an after time of said after carbon dioxide elimination.
50. The method of claim 47, further comprising:
- determining a before time of said before partial pressure of end tidal carbon dioxide;
  
  determining a during time of said during partial pressure of end tidal carbon dioxide; and
  
  determining an after time of said after partial pressure of end tidal carbon dioxide.
51. The method of claim 48, further comprising:
- calculating said rate of change by employing the following equation;
  
  $k = \frac{Δ V_{{CO}_{2 BD}} \cdot Δ C_{A} {CO}_{2 DA} - Δ V_{{CO}_{2 DA}} \cdot Δ C_{A} {CO}_{2 BD}}{Δ V_{{CO}_{2 BD}} (t_{D} - t_{A}) - Δ V_{{CO}_{2 DA}} (t_{B} - t_{D})},$
  
  where Δ
  
  VCO_2BDcomprises a difference between said before carbon dioxide elimination and said during carbon dioxide elimination, Δ
  
  CACO_2DAcomprises a difference between said during alveolar content and said after alveolar content, Δ
  
  VCO_2DAcomprises a difference between said during carbon dioxide elimination and said after carbon dioxide elimination, Δ
  
  CACO_2BDcomprises a difference between said before alveolar content and said during alveolar content, t_Bcomprises a time of prior to said phase, t_Dcomprises a time during said change, and t_Acomprises a time after said change.
52. The method of claim 48, further comprising calculating pulmonary capillary blood flow with said before carbon dioxide elimination, said during carbon dioxide elimination, said after carbon dioxide elimination, said before alveolar content, said during alveolar content, said after alveolar content, and said rate of change.
53. The method of claim 49, further comprising calculating pulmonary capillary blood flow with said before carbon dioxide elimination, said during carbon dioxide elimination, said after carbon dioxide elimination, said before alveolar content, said during alveolar content, said after alveolar content, said before time, said during time, said after time, and said rate of change.
54. The method of claim 52, further comprising calculating said pulmonary capillary blood flow by employing the following equation:
- $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + V_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{k \cdot (t_{B} + t_{A} - 2 t_{D}) - (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$
55. The method of claim 47, wherein said rate of change is substantially constant.
56. The method of claim 47, wherein said rate of change is substantially exponential over time.
57. The method of claim 40, further comprising:
- determining a before time of said before carbon dioxide elimination;
  
  determining a during time of said during carbon dioxide elimination; and
  
  determining an after time of said after carbon dioxide elimination.
58. The method of claim 57, wherein a difference between said during time and said before time is equal to a difference between said after time and said during time.
59. The method of claim 58, further comprising calculating pulmonary capillary blood flow by employing the following equation:
- $Q_{pcbf} = \frac{V_{{CO}_{2 B}} + C_{{CO}_{2 A}} - 2 V_{{CO}_{2 D}}}{- (C_{A} {CO}_{2 B} + C_{A} {CO}_{2 A} - 2 C_{A} {CO}_{2 D})} .$

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Current Assignee
RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
Original Assignee
NTC Technology, Inc. (Dixtal Medical, Inc.)
Inventors
Haryadi, Dinesh G., Orr, Joseph A., Kück, Kai, Jaffe, Michael B.
Primary Examiner(s)
O'Connor, Cary
Assistant Examiner(s)
Astorino, Michael

Application Number

US09/150,135
Time in Patent Office

916 Days
Field of Search

600/500-504, 600/526, 600/528-538, 128/204-2-2, 128/897-899, 128/920-925
US Class Current

600/532
CPC Class Codes

A61B 5/029 Measuring or recording bloo...

A61B 5/083 Measuring rate of metabolis...

Bi-directional partial re-breathing method

First Claim

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Bi-directional partial re-breathing method

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