SYSTEM AND METHOD FOR MONITORING CARDIAC OUTPUT

• US 20110004108A1
• Filed: 11/14/2008
• Published: 01/06/2011
• Est. Priority Date: 11/16/2007
• Status: Active Grant

• Current Assignee: Austin Health
• Original Assignee: Austin Health
• Inventors: Peyton, Philip John
• Granted Patent: US 8,613,707 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61M 16/0045 Means for re-breathing exhaled gases, e.g. for hyperventilation treatment
• CPC Class Codes: A61M 16/01 specially adapted for anaesthetising A61M16/104, A61M16/18 take precedence
• 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 16/085 Gas sampling
• CPC Class Codes: A61M 16/1065 in the expiratory path
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 16/202 electrically actuated
• CPC Class Codes: A61M 16/22 Carbon dioxide-absorbing devices ; Other means for removing carbon dioxidecartridges with absorbing substances for respiratory apparatus A62B19/00
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/103 the CO2 concentration
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)

Abstract

A method for monitoring cardiac output (pulmonary blood flow) of a subject, the method including: measuring a first net pulmonary uptake or elimination of a breathed gas species by the subject and a first partial pressure of the gas species at a first time, and at a second time later than the first time, determining a first pulmonary blood flow of the patient at the first time, and determining a pulmonary blood flow of the subject at the second time on the basis of the first pulmonary blood flow, the first net pulmonary uptake or elimination, the second net pulmonary uptake or elimination, the first partial pressure, and the second partial pressure.

Claims

1. A method for monitoring cardiac output (pulmonary blood flow) of a subject, the method including:

(i) measuring a first net pulmonary uptake or elimination of a breathed gas species by said subject at a first time;

(ii) measuring a first partial pressure of said gas species in lungs of said subject at said first time;

(iii) determining a first pulmonary blood flow of said patient at said first time;

(iv) measuring a second net pulmonary uptake or elimination of said breathed gas species by said subject at a second time later than said first time;

(v) measuring a second partial pressure of said gas species in lungs of said subject at said second time; and

(vi) determining a pulmonary blood flow of said subject at said second time on the basis of said first pulmonary blood flow, said first net pulmonary uptake or elimination, said second net pulmonary uptake or elimination, said first partial pressure, and said second partial pressure.

2. A method as claimed in claim 1, including:

determining a first rate of change of partial pressure of said gas species in lungs of said subject at said first time; and

determining a second rate of change of partial pressure of said gas species in lungs of said subject at said second time;

wherein said pulmonary blood flow of said subject at said second time is determined on the basis of said first and second rates of change of partial pressure of said gas species in lungs of said subject at said first and second times.

3. A method as claimed in claim 1, including:

determining an effective lung volume of said subject at said first time;

wherein the pulmonary blood flow of said subject at said second time is determined on the basis of said effective lung volume.

4. A method according to claim 1, wherein the pulmonary blood flow of said subject is determined for each of a plurality of second times later than said first time and corresponding to successive breaths of said subject to provide breath-by-breath determination of said pulmonary blood flow of said subject.

5. A method according to claim 1, wherein {dot over (Q)}t_k, the pulmonary blood flow ({dot over (Q)}t) for a breath k ({dot over (Q)}t_k), is determined according to:

6. A method according to claim 1, wherein {dot over (Q)}t_k, the pulmonary blood flow ({dot over (Q)}t) for a breath k ({dot over (Q)}t_k), is determined according to:

determining pulmonary blood flow

8. A method according to claim 1, wherein {dot over (Q)}t_k, the pulmonary blood flow ({dot over (Q)}t) for a breath k ({dot over (Q)}t_k), is determined according to:

9. A method according to claim 1, wherein {dot over (Q)}t_k, the pulmonary blood flow ({dot over (Q)}t) for a breath k ({dot over (Q)}t_k), is determined according to:

10. A method according to claim 9, wherein said at least one correction factor corr includes a correction factor to correct for a change in metabolic rate due to a change in body temperature of said subject.

11. A method according to claim 9, wherein said at least one correction factor corr includes a correction factor to correct for a change in the level of alveolar ventilation of said subject.

12. A method according to claim 6, wherein the net rate of pulmonary uptake or elimination of said gas species G for each breath is approximated by a difference between an inspired partial pressure of said gas species G (PI_G) and its partial pressure in end-tidal gas (PE′

_G) for a corresponding breath, so that said pulmonary blood flow {dot over (Q)}t_k for a breath k of said subject is determined from {dot over (Q)}t_i, a pulmonary blood flow of said subject for an earlier breath i, according to;

13. A method according to claim 1 wherein the gas species is carbon dioxide (CO₂).

14. A method according to claim 1, wherein the subject is human.

15. A system having components for executing the methods of claim 1.

16. A computer-readable storage medium having stored therein programming instructions for executing the methods of claim 1.

7. (canceled)

17. A system for monitoring cardiac output (pulmonary blood flow) of a subject, the system including means for:

(i) measuring a first net pulmonary uptake or elimination of a breathed gas species by said subject at a first time;

(ii) measuring a first partial pressure of said gas species in lungs of said subject at said first time;

(iii) determining a first pulmonary blood flow of said patient at said first time;

(iv) measuring a second net pulmonary uptake or elimination of said breathed gas species by said subject at a second time later than said first time;

(v) measuring a second partial pressure of said gas species in lungs of said subject at said second time; and

(vi) determining a pulmonary blood flow of said subject at said second time on the basis of said first pulmonary blood flow, said first net pulmonary uptake or elimination, said second net pulmonary uptake or elimination, said first partial pressure, and said second partial pressure.

18. A system according to claim 17, including

a gas analyser for measuring partial pressures of said gas species inhaled and/or exhaled by said subject;

and a gas flow or volume measurement device for measuring flow of said gas species inhaled and/or exhaled by said subject, and further including means for determining alveolar partial pressures at said first and second times and net rates of uptake or elimination by the lungs of said gas species at said first and second times.

19. A system according to claim 17, including means for performing one or more data averaging or smoothing operations to determine the pulmonary blood flow of the subject.

20. A system according to claim 17, wherein the system is operable to determine the pulmonary blood flow of said subject for each of a plurality of second times later than said first time and corresponding to successive breaths of said subject to provide breath-by-breath determination of said pulmonary blood flow of said subject.

21. A computer-readable storage medium having stored therein programming instructions for executing the steps of:

(i) accessing first gas species data representing a first net pulmonary uptake or elimination of a breathed gas species by said subject at a first time, and a first partial pressure of said gas species in lungs of said subject at said first time;

(ii) determining a first pulmonary blood flow of said patient at said first time;

(iii) accessing second gas species data representing a second net pulmonary uptake or elimination of said breathed gas species by said subject at a second time later than said first time, and a second partial pressure of said gas species in lungs of said subject at said second time; and

(iv) processing said first gas species data and said second gas species data to determine a pulmonary blood flow of said subject at said second time on the basis of said first pulmonary blood flow, said first net pulmonary uptake or elimination, said second net pulmonary uptake or elimination, said first partial pressure, and said second partial pressure.