Method for continuous measurement of flux of gases in the lungs during breathing

• US 7,913,690 B2
• Filed: 03/21/2003
• Issued: 03/29/2011
• Est. Priority Date: 03/28/2002
• Status: Active Grant

• Current Assignee: Thornhill Scientific Inc.
• Original Assignee: Alex Vesely, David Preiss, Eitan Prisman, Joseph Fisher, Takafumi Azami, Tehilla Adams
• Inventors: Preiss, David, Vesely, Alex, Fisher, Joseph, Azami, Takafumi, Adams, Tehilla, Prisman, Eitan
• Primary Examiner(s): Douglas; Steven O
• Application Number:
  US10/509,068
• Publication Number:
  US 20050217671A1
• Time in Patent Office: 2,930 Days
• Field of Search: 702/22, 702/31, 702/32, 702/19, 128/204.19, 12820421-20429, 128/205.12
• US Class Current: 128/204.23
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• 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 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61M 16/0045 Means for re-breathing exhaled gases, e.g. for hyperventilation treatment
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/0833 T- or Y-type connectors, e.g. Y-piece
• CPC Class Codes: A61M 16/202 electrically actuated
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 16/206 Capsule valves, e.g. mushroom, membrane valves
• CPC Class Codes: A61M 16/208 Non-controlled one-way valves, e.g. exhalation, check, pop-off non-rebreathing valves
• CPC Class Codes: A61M 16/209 Relief valves
• 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 2230/432 partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 partial O2 pressure (P-O2)
• CPC Class Codes: A61M 2230/437 the anaesthetic agent concentration

Abstract

A method of calculating the flux of any gas (x) in a CBC circuit for a ventilated or a spontaneous breathing subject, for example said gas(x) being; a) an anesthetic such as but limited to; i)N₂O; ii) sevoflurane; iii) isoflurane; iv) halothane; v) desflurame; or the like b) Oxygen; c) Carbon dioxide; or the like utilizing the following relationships; Flux of gas(x)=SGF (F_SX−F_EX) wherein SGF=Source of gas flow into the breathing circuit (CBC circuit) in liters/minute as read from the gas flow meter as set by the anesthesiologist; F_SX=Fractional concentration of gas X in the source gas (which is set by the anesthesiologist); F_EX=Fractional concentration of gas X in the end expired gas as determined by a portable gas analyzer, or the like.

Claims

1. A method of determining the flux of a gas “

X”

in a subject that is ventilated or breathing spontaneously, comprising the steps of;

a. providing to the subject, via a Conditional Breathing Circuit (CBC), a source gas and a second gas that has substantially the same concentration of gas “

X”

as in the alveoli of the lung, wherein the source gas for a given breath is provided at a flow rate (SGF) that results in the source gas entering the CBC being equal to or less than the subject'"'"'s alveolar ventilation, any balance of the gas provided for the same breath being the second gas;

b. determining the flux of gas “

X”

by;

(i) determining the source gas flow (SGF) into the CBC;

(ii) determining the concentration, F_SX, of gas “

X”

in the source gas flow;

(iii) determining the concentration, F_EX, of gas “

X”

in the end expired gas; and

(iv) processing data utilizing the relationship;

Flux of gas “

X”

=SGF(F_SX−

F_EX);

or

Flux of gas “

X”

=SGF(F_EX−

F_SX);

wherein;

SGF=the rate of source gas flow into the CBC in liters/minute;

F_SX=Fractional concentration of gas “

X”

in the source gas;

F_EX=Fractional concentration of gas “

X”

in the end expired gas.

2. The method of claim 1, wherein the second gas is gas expired by the subject in the preceding breath.

3. The method of claim 2, wherein values for SGF, F_SX and F_EX are determined by a device comprising a gas flow meter and a tidal gas analyzer and wherein the data is processed by a processor operatively associated with the device.

4. The method of claim 1, wherein the Conditional Breathing Circuit is Magill circuit.

5. The method of claim 1, wherein the Conditional Breathing Circuit is a-rebreathing circuit.

6. The method of claim 1, wherein the CBC circuit is a non-rebreathing circuit.

7. The method of claim 2 used to determine oxygen consumption.

8. The method of claim 2 used to determine oxygen consumption in an operating room setting.

9. The method of claim 2 or 8 used to optimize oxygen consumption.

10. The method of claim 2 or 8 utilized as an early indication of malignant hyperthermia.

11. A method according to claim 1, wherein gas “

X”

is any gas other than carbon dioxide and wherein the Conditional Breathing Circuit (CBC) comprises a carbon dioxide absorber

and wherein the term F_EX in the equation Flux of gas “

X”

=SGF (F_SX−

F_EX) is replace by the term F_RBX

where F_RBX =Concentration of gas X in the expired limb of circuit before the gas passes through the carbon dioxide absorber and mixes with gas coming from the flow meter.

12. The method of claim 11 used to determine how much anesthetic is being absorbed by the patient.

13. The method of claim 12 wherein said anesthetic is N₂O.

14. The method of claim 1, 2, or 11, wherein said method is incorporated in an algorithm spreadsheet, formula or the like contained within software which is capable of running on a computing device, or is installed therein.

15. The method of claim 1, wherein the gas “

X”

is carbon dioxide and the CBC is a re-breathing circuit.

16. The method of claim 11, wherein the gas “

X”

is an anesthetic and the CBC is a re-breathing circuit.

17. The method of claim 16, wherein the anesthetic is:

i) N₂O;

ii) sevoflurane;

iii) isoflurane;

iv) halothane;

v) desflurame.

18. An apparatus configured for use with a Conditional Breathing Circuit (CBC) for determining the flux of a gas “

X”

in a subject that is ventilated or breathing spontaneously, comprising;

c. at least one gas analyzer;

d. a gas flow meter for determining the rate of flow of a source gas;

e. a processor programmed for;

(i) determining the source gas flow (SGF) into the CBC;

(ii) determining the concentration, F_SX, of gas “

X”

in the source gas flow;

(iii) determining the concentration, F_EX, of gas “

X”

in the expired gas; and

(iv) processing data utilizing the relationship;

Flux of gas “

X”

=SGF(F_SX−

F_EX);

or

Flux of gas “

X”

=SGF(F_EX−

F_SX);

wherein;

SGF=the rate of source gas flow into the CBC in liters/minute;

F_SX=Fractional concentration of gas “

X”

in the source gas;

F_EX=Fractional concentration of gas “

X”

in the end expired gas.

19. An apparatus according to claim 18 in the form of an anesthetic machine wherein gas “

X”

is an anesthetic gas and wherein the CBC includes a carbon dioxide absorber and wherein the processor is configured to determine consumption of the anesthetic gas using the relationship Flux of gas “

X”

=SGF(F_SX−

F_EX) by determining F_RBX and by replacing the term F_EX in the equation Flux of gas “

X”

=SGF (F_SX−

F_EX) by the term F_RBX;

where F_RBX=Concentration of gas X in the expired limb of circuit before the gas passes through the carbon dioxide absorber and mixes with gas coming from the flow meter.

20. An apparatus according to claim 18 further comprising a CBC.

21. The use of a conditional breathing circuit (CBC) for determining the flux of a gas “

X”

in a subject that is ventilated or breathing spontaneously, comprising the steps of;

a. analyzing the concentration of gas “

X”

in the end tidal gas;

b. controlling the rate of flow of a source gas;

c. determining the concentration, F_SX, of gas “

X”

in the source gas flow;

d. processing data utilizing the relationship;

Flux of gas “

X”

=SGF(F_SX−

F_EX);

or

Flux of gas “

X”

=SGF(F_EX−

F_SX);

wherein;

SGF=the rate of source gas flow into the CBC in liters/minute;

F_SX=Fractional concentration of gas “

X”

in the source gas;

F_EX=Fractional concentration of gas “

X”

in the end expired gas.

23. The use according to claim 21, wherein gas “

X”

is an anesthetic gas and wherein the CBC includes a carbon dioxide absorber and wherein the data is processed to determine consumption of the anesthetic gas using the relationship;

Flux of gas “

X”

=SGF (F_SX−

F_EX) by determining F_RBX and by replacing the term F_EX in the equation Flux of gas “

X”

=SGF (F_SX−

F_EX) by the term F_RBX;

where F_RBX=Concentration of gas X in the expired limb of circuit before the gas passes through the carbon dioxide absorber and mixes with gas coming from the flow meter.

22. A processor programmed for receiving source gas flow rate data and gas concentration data generated by a gas analyzer, and programmed for:

(v) determining the source gas flow (SGF) into a CBC;

(vi) determining the concentration, F_SX, of gas “

X”

in the source gas flow;

(vii) determining the concentration, F_EX, of gas “

X”

in the expired gas; and

(viii) processing data utilizing the relationship;

Flux of gas “

X”

=SGF(F_SX−

F_EX);

or

Flux of gas “

X”

=SGF(F_EX−

F_SX);

wherein;

SGF=the rate of source gas flow into the CBC in liters/minute;

F_SX=Fractional concentration of gas “

X”

in the source gas;

F_EX=Fractional concentration of gas “

X”

in the end expired gas.

24. A processor according to claim 22, wherein gas “

X”

is an anesthetic gas and wherein the CBC includes a carbon dioxide absorber and wherein the data is processed to determine consumption of the anesthetic gas using the relationship;

Flux of gas “

X”

=SGF (F_SX−

F_EX) by determining F_RBX and by replacing the term F_EX in the equation Flux of gas “

X”

=SGF (F_SX−

F_EX) by the term F_RBX;

where F_RBX =Concentration of gas X in the expired limb of circuit before the gas passes through the carbon dioxide absorber and mixes with gas coming from the flow meter.