Dynamic metabolism monitoring system

• US 20070073182A1
• Filed: 09/22/2006
• Published: 03/29/2007
• Est. Priority Date: 09/23/2005
• Status: Active Grant

• Current Assignee: Kitchener Wilson
• Original Assignee: Kitchener Wilson
• Inventors: Wilson, Kitchener
• Granted Patent: US 8,109,884 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption

Abstract

A metabolism monitoring system, data analyzer, and method is disclosed for processing data to very quickly estimate metabolic parameters. The analyzer of the invention uses a dynamic observer state estimator to estimate the parameters and tracks their values as they change with alterations in the patient metabolism or testing conditions. The state estimator does not use the conventional steady state solutions. The observer predicts the patient consumption of oxygen and exhalation of carbon dioxide at a subsequent point in time, corrects these values using measurements of air flow rate and chamber levels of oxygen and carbon dioxide taken at that subsequent time, and repeats for the next time. The corrected values are used for estimation of the metabolic parameters.

Claims

1. A metabolism monitor in ambient air having a chamber, a patient connected to the chamber, a flow of air through the chamber, an air analyzer providing measurements of chamber air characteristics at a plurality of times, and a metabolic parameter estimator operating on the plurality of measurements comprising:

a predictor of metabolic parameters; and

a corrector of the predicted metabolic parameters.

2. The monitor of claim 1 where the patient connection comprises having a portion of the patient enclosed by the chamber.

3. The monitor of claim 1 where the characteristics comprise the air flow rate selected from the group consisting of the rate entering the chamber and the rate leaving the chamber.

4. The monitor of claim 3 where characteristics comprise the ambient pressure and the chamber air pressure and where the air flow rate entering the chamber is determined by the difference in these pressures.

5. The monitor of claim 1 where the predictor comprises:

the estimation of the net oxygen flow rate into the chamber as contributed by ambient and the patient;

the estimation of the net carbon dioxide flow rate into the chamber as contributed by ambient and the patient; and

the estimation of the net air flow rate into the chamber as contributed by ambient and the patient.

6. The monitor of claim 1 where the characteristics comprise:

the volumetric fraction of oxygen and

the volumetric fraction of carbon dioxide and where the predictor comprises;

the prediction of the volumetric fraction of oxygen and

the prediction of the volumetric fraction of carbon dioxide and the corrector comprises;

a first correction factor dependent on the difference between the measured and predicted oxygen volumetric fractions, and

a second correction factor dependent on the difference between the measured and predicted carbon dioxide volumetric fractions.

7. The monitor of claim 1 further comprises a chamber volume estimator using the measurements.

8. A method to estimate metabolic parameters comprising the steps of:

placing a chamber in ambient air;

connecting the chamber to a patient;

flowing air through the chamber;

sampling the chamber air at a plurality of times and for each sample;

measuring characteristics of the gas in the sample;

predicting the metabolic parameters;

predicting the measurements; and

correcting the predicted metabolic parameters using the predicted measurements and the measurements.

9. The method of claim 8 where the connection is by enclosing a portion of the patient within the chamber.

10. The method of claim 8 where the characteristics comprise the air flow rate selected from the group consisting of the rate into the chamber and the rate out of the chamber.

11. The method of claim 8 where predicting the anticipated metabolic parameters comprises the steps of:

estimating the net oxygen flow rate into the chamber as contributed by ambient and the patient;

estimating the net carbon dioxide flow rate into the chamber as contributed by ambient and the patient; and

estimating the net air flow rate into the chamber as contributed by ambient and the patient.

12. The method of claim 8 where the characteristics comprise:

the volumetric fraction of oxygen and

the volumetric fraction of carbon dioxide and where predicting the anticipated metabolic parameters comprises the steps;

predicting the volumetric fraction of oxygen and

predicting the volumetric fraction of carbon dioxide and where correcting the predicted metabolic parameters comprises the steps of;

applying a first correction factor dependent on the difference between the measured and predicted oxygen volumetric fractions, and

applying a second correction factor dependent on the difference between the measured and predicted carbon dioxide volumetric fractions.

13. A metabolic parameter estimator receiving measurements of patient connected chamber air characteristics at a plurality of times comprising:

a predictor of metabolic parameters; and

a corrector of the predicted metabolic parameters.

14. The estimator of claim 13 where the characteristics comprise the chamber air flow rate selected from the group consisting of the rate entering the chamber and the rate leaving the chamber.

15. The estimator of claim 14 where characteristics comprise the ambient pressure and the chamber air pressure and where the air flow rate entering the chamber is determined by the difference in these pressures.

16. The estimator of claim 13 where the predictor comprises:

the estimation of the net oxygen flow rate into the chamber as contributed by ambient and the patient;

the estimation of the net carbon dioxide flow rate into the chamber as contributed by ambient and the patient; and

the estimation of the net air flow rate into the chamber as contributed by ambient and the patient.

17. The estimator of claim 13 where the characteristics comprise:

the volumetric fraction of oxygen and

the volumetric fraction of carbon dioxide and where the predictor comprises;

the prediction of the volumetric fraction of oxygen and

the prediction of the volumetric fraction of carbon dioxide and the corrector comprises;

a first correction factor dependent on the difference between the measured and predicted oxygen volumetric fractions, and

a second correction factor dependent on the difference between the measured and predicted carbon dioxide volumetric fractions.

18. The estimator of claim 13 further comprises a chamber volume estimator using the measurements.