Systems and methods for concomitant CO2 sampling and O2 delivery

Patent metadata

Field	Value
Publication number	US-10925514-B2
Application number	US-201815898797-A
Country	US
Kind code	B2
Filing date	Feb 19, 2018
Priority date	Feb 20, 2017
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A CO2 monitoring system provides oxygen (O2) to a subject's mask with known characteristics. The CO2 monitoring system receives, from the mask, gas samples including exhaled CO2 diluted by O2. The CO2 monitoring system uses an adaptive noise canceller to cancel the diluting O2 by using the known characteristics of the O2 provided to the mask, the result of which process is restoration of the original concentration level of the CO2 as exhaled by the subject into the mask.

First claim

The invention claimed is:

1. A method of restoring an exhaled carbon dioxide (CO 2 ) concentration level, comprising:
providing an input oxygen flow to a mask attached to a subject;
using, a CO 2 monitoring system configured to monitor CO 2 exhaled by the subject into the mask during a respiration cycle, to perform the steps of:
drawing, from the mask, a gas sample including exhaled CO 2 and oxygen (O 2 ) admixture originating from the input oxygen flow;
detecting, in the gas sample, a concentration level for the CO 2 and for the O 2 admixture; and
restoring a concentration level of the CO 2 as exhaled by the subject during the respiration cycle based on characteristics of the input oxygen flow and the concentration level of the oxygen admixture detected in the gas sample, wherein restoring the concentration level of the exhaled CO 2 comprises determining the characteristics of the input oxygen flow based on a set parameter and/or on a measured parameter; and

displaying, on a computer display, for the respiration cycle, a signal representing the restored concentration level of the exhaled CO 2 .

2. The method of claim 1 , wherein restoring the concentration level of the CO 2 exhaled by the subject during the respiration cycle comprises modifying the concentration level of the CO 2 detected in the gas sample.

3. The method of claim 1 , wherein detecting the concentration level of the CO 2 and the concentration level of the O 2 admixture in the gas sample comprises: providing the gas sample, or a portion of the gas sample, to a common gas sampling chamber, and simultaneously detecting both the concentration level of the CO 2 and O 2 admixture in the gas sample contained in the common gas sampling chamber.

4. The method of claim 1 , wherein determining the characteristics of the input oxygen flow comprises setting the set parameter of the input oxygen flow and maintaining the set parameter of the input oxygen flow, wherein the set parameter comprises a frequency at which the input oxygen flow is provided to the mask, an amplitude of the input oxygen flow, or a combination thereof.

5. The method of claim 1 , wherein determining the characteristics of the input oxygen flow comprises measuring the measured parameter of the input oxygen flow, wherein the measured parameter comprises a frequency at which the input oxygen flow is provided to the mask, an amplitude of the input oxygen flow, or a combination thereof.

6. The method of claim 1 , wherein restoring the concentration level of the exhaled CO 2 comprises cancelling an oxygen noise signal representative of the O 2 admixture in the gas sample.

7. The method of claim 6 , wherein cancelling the oxygen noise signal comprises using an adaptive noise canceller.

8. The method of claim 7 , wherein using the adaptive noise canceller comprises changing coefficients of the adaptive noise canceller based on a signal or data output by the adaptive noise canceller.

9. The method of claim 8 , wherein cancelling the oxygen noise signal comprises:
providing first data representing both the CO 2 and the O 2 admixture in the gas sample to a first input of the adaptive noise canceller;
providing second data representing the characteristics of the input oxygen flow to a second input of the adaptive noise canceller; and
cancelling the oxygen noise signal that represents the O 2 admixture in the gas sample by using the first and second data.

10. The method of claim 9 , comprising calibrating the CO 2 monitoring system, the calibrating comprising: providing to the mask only an initial input oxygen flow and detecting an oxygen dispersion level in a respective gas sample and setting parameters of the input oxygen flow based on the oxygen dispersion level and/or providing to the mask only exhaled CO 2 and detecting an initial CO 2 concentration level in a respective gas sample in order to estimate CO 2 rebreathing and setting parameters of the input oxygen flow based on the estimated CO 2 rebreathing.

11. A system configured to monitor an exhaled carbon dioxide (CO 2 ) concentration level, comprising:
a gas sampling chamber configured to receive a gas sample from a mask attached to a face of a subject, the gas sample including an oxygen (O 2 ) admixture originating from an input oxygen flow provided to the mask and CO 2 exhaled by the subject into the mask;
a CO 2 detector configured to detect a concentration level of CO 2 in the gas sample;
an O 2 detector configured to detect a concentration level of O 2 admixture in the gas sample;
a CO 2 restoration unit configured to determine a restored concentration level of the CO 2 exhaled by the subject based on characteristics of the input O 2 flow and the concentration level of the O 2 admixture detected in the gas sample; and
a computer display configured to display a signal representing the exhaled CO 2 with the restored concentration level.

12. The system of claim 11 , wherein the CO 2 detector and the O 2 detector are, respectively, configured to simultaneously detect CO 2 and O 2 in a same gas sample.

13. The system of claim 11 , wherein the CO 2 restoration unit comprises an adaptive noise canceller.

14. The system of claim 11 , comprising an O 2 flow re-shaper configured to receive an O 2 flow from an O 2 source and to control the characteristics of the inflow O 2 so as to output to the mask the input oxygen flow.

15. The system of claim 11 , comprising the mask.

16. A system configured to monitor a non-diluted concentration level of carbon dioxide (CO 2 ), comprising:
a gas sampling chamber configured to receive a dilute CO 2 gas sample from a mask attached to a face of a subject, wherein the dilute CO 2 gas sample comprises a mixture of an oxygen (O 2 ) admixture and CO 2 , and wherein the CO 2 is exhaled by the subject during a respiration cycle;
a CO 2 detector disposed within the gas sampling chamber and configured to detect CO 2 in the dilute CO 2 gas sample;
an O 2 detector disposed within the gas sampling chamber and configured to detect the O 2 admixture in the dilute CO 2 gas sample; and
a CO 2 restoration unit comprising a processor configured to monitor a concentration level of the CO 2 and a concentration level of the O 2 admixture in the dilute CO 2 gas sample and to determine the non-diluted concentration level of CO 2 as exhaled by the subject during the respiration cycle based on characteristics of a flow of O 2 into the mask and the concentration level of O 2 admixture detected in the dilute CO 2 gas sample.

17. The system of claim 16 , wherein the processor is configured to modify the concentration level of the CO 2 detected in the dilute CO 2 gas sample to determine the non-diluted concentration level of CO 2 .

18. The system of claim 16 , comprising an adaptive noise canceller configured to cancel an oxygen noise signal representative of the O 2 admixture in the dilute CO 2 gas sample to determine the non-diluted concentration level of the CO 2 .

19. The system of claim 16 , wherein the characteristics of the flow of O 2 comprises measuring a parameter of the flow, the parameter comprises a frequency at which the flow of O 2 is provided to the mask, an amplitude of the flow of O 2 , or a combination thereof.

Assignees

• Oridion Medical 1987 Ltd

Inventors

• Kertser Michael

Classifications

• A61B5/7214

  using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths · CPC title

• A61M16/085

  Gas sampling · CPC title

• A61B5/725

  using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316) · CPC title

• A61M2205/702

  automatically during use · CPC title

• A61M2202/0208

  Oxygen · CPC title