Systems and methods for accurately, substantially noninvasivelydetermining pulmonary capillary blood flow or cardiac output

• US 20060129055A1
• Filed: 02/03/2006
• Published: 06/15/2006
• Est. Priority Date: 02/22/2000
• Status: Active Grant

• Current Assignee: Joseph A. Orr, Kai Kuck
• Original Assignee: Joseph A. Orr, Kai Kuck
• Inventors: Kuck, Kai, Orr, Joseph A.
• Granted Patent: US 8,801,625 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• 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 5/0836 Measuring rate of CO2 production
• CPC Class Codes: G01N 2001/2244 Exhaled gas, e.g. alcohol detecting
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

Methods for noninvasively determining a pulmonary capillary blood flow or a cardiac output of a subject include determining data of the amount of gas exchanged between blood and gas in lungs of the subject, as well as data of an indicator of the content of the gas in blood of the subject. Such a determination may be made during two or more different states of ventilation. A geometric relationship is identified between data points, with any data points outlying the geometric relationship being disregarded. The remaining data points may be used to estimate or calculate a measure of pulmonary capillary blood flow or cardiac output. Systems that include elements that are configured to effect such methods are also disclosed.

Claims

1. A system for substantially non-invasively determining at least one of a pulmonary capillary blood flow and a cardiac output of a subject, comprising:

a breathing conduit;

a flow sensor in communication with the breathing conduit;

a gas sensor in communication with the breathing conduit;

at least one processing element for receiving signals from the flow sensor and the carbon dioxide sensor, the at least one processing element being programmed to;

calculate an estimate of an amount of gas exchanged between the blood and gas in lungs of the subject and a content of the gas in blood of the subject;

identify a geometric relationship between gas exchange data points of the amount of gas exchanged and corresponding content data points of the content of gas in blood; and

disregard any data points outside of the geometric relationship.

2. The system of claim 1, wherein the at least one processing element is programmed to identify the geometric relationship after data points of the amount of gas exchanged and of the content of the gas in blood have been evaluated to eliminate any outlying data points.

3. The system of claim 1, wherein the gas sensor comprises a carbon dioxide sensor.

4. The system of claim 1, wherein the at least one processing element is programmed to calculate an estimate of carbon dioxide elimination and an estimate of carbon dioxide content of the subject'"'"'s blood.

5. The system of claim 1, wherein the at least one processing element is programmed to filter the data points with an algorithmic filter.

6. The system of claim 1, wherein the at least one processing element is programmed to identify a substantially linear relationship between the data points.

7. The system of claim 1, wherein the at least one processing element is programmed to calculate a correlation coefficient between the gas exchange data and the content data.

8. The system of claim 7, wherein the at least one processing element is also programmed to increase the correlation coefficient between the gas exchange data and the content data.

9. The system of claim 1, wherein the at least one processor is programmed to disregard data points outside of the geometric relationship by eliminating one or more data points outside the geometric relationship.

10. The system of claim 1, wherein the at least one process is programmed to

normalize the gas exchange data and the content data;

and

cluster the normalized gas exchange data and the content data.

11. The system of claim 1, further comprising:

a ventilation control element configured to facilitate a change in effective ventilation by the subject.

12. The system of claim 1, further comprising:

an output element for outputting at least one of a pulmonary capillary blood flow and a cardiac output.

13. A method for determining at least one of a pulmonary capillary blood flow and a cardiac output of a subject, comprising:

determining a plurality of data comprising an amount of gas exchanged between blood and gas in lungs of the subject and data of an indicator of the content of the gas in blood of the subject during at least two different states of ventilation;

identifying a geometric relationship between data points of the data of the amount of gas exchanged and corresponding data points of the data of the indicator of content of the gas;

disregarding any outlying data points of the plurality of data; and

estimating the pulmonary capillary blood flow or the cardiac output based at least partially on the geometric relationship.

14. The method of claim 13, wherein identifying the geometric relationship comprises identifying a substantially linear relationship between the data of the amont of gas exchanged and the data of the indicator of the content of the gas.

15. The method of claim 13, wherein disregarding comprises selecting data points to use in the identifying the geometric relationship.

16. The method of claim 15, wherein selecting comprises clustering the data of the amount of gas exchanged and the data of the indicator of the content of the gas.

17. The method of claim 13, wherein disregarding comprises eliminating at least one data point.

18. A system for substantially non-invasively determining at least a pulmonary capillary blood flow of a subect, comprising:

a flow sensor in communication with a breathing circuit;

a gas sensor in communication with the breathing circuit;

means for causing a change in effective ventilation of the subject;

means for estimating gas exchange data and gas content data based on signals from the flow sensor and the gas sensor;

means for identifying a geometric relationship between the gas exchange data and the gas content data;

means for disregarding at least one of gas exchange data and gas content data outlying the geometric relationship.

19. The system of claim 18, wherein the means for disregarding comprises means for eliminating at least one data point of any outlying gas exchange data or any outlying gas content data.

20. The system of claim 18, further comprising:

means for outputting at least one of a pulmonary capillary blood flow and a cardiac output of the patient.