# US 7,465,275 B2 · Method and apparatus for measuring functional residual capacity (FRC) and cardiac output(CO)

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- Number: US 7,465,275 B2
- Document ID: US7465275B2
- Status: Granted
- Kind: B2
- Application number: 10/479,390
- Filed: 2002-05-29
- Published: 2004-12-09
- Granted: 2008-12-16
- Earliest claimed: 2001-05-29
- Assignees: GE Healthcare Finland Oy
- Inventors: Ola Stenqvist
- Web page: https://patentgrep.com/patent/US7465275B2

## CPC

- A61B 5/0836: {Measuring rate of CO2 production}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

The present invention relates to a method and an apparatus for measuring Functional Residual Capacity (CO). Further, it relates to a method and an apparatus for measuring cardiac output (CO). The method comprises the steps of determining the amount of oxygen and carbon dioxide being inhaled and exhaled during at least two breathing cycles, identifying at least one difference between said breathing cycles, and estimating the FRC and/or CO based on the determined uptake of oxygen and excretion of carbon dioxide and said identified difference.

## Claims

### Claim 1

A method for estimation of functional residual capacity (FRC) in a person, comprising:
establishing a breathing pattern;
determining the amount of oxygen and carbon dioxide being inhaled and exhaled during a first breathing cycle comprised by said breathing pattern;
accomplishing a first change in said breathing pattern of known magnitude;
determining the amount of oxygen and carbon dioxide being inhaled and exhaled during a second breathing cycle;
estimating the FRC based on the determined amounts of oxygen and carbon dioxide in said first and second breathing cycles.

### Claim 2 (depends on 1)

The method of claim 1, wherein said first change of breathing pattern is selected from apnea, a breath volume larger than the breath volume of said first breathing cycle, a breath volume smaller than the breath volume of said first breathing cycle, a duration difference between the different phases in said first and second breathing cycles, a difference in dead space volume.

### Claim 3 (depends on 1)

The method of claim 1, wherein said second breathing cycle is followed by a second change in breathing pattern of known magnitude compensatory to said first change in breathing pattern of known magnitude to re-establish a steady state allowing a new estimation of FRC with minimal delay.

### Claim 4 (depends on 3)

The method of claim 3, wherein said first change in breathing pattern is an increase of the time period between exhalation and inhalation or a breath with substantially decreased breath volume and said second change in breathing pattern is a breath with substantially increased breath volume.

### Claim 5 (depends on 3)

The method of claim 3, wherein said first change in breathing pattern is a breath with substantially increased breath volume and said second change in breathing pattern is an increase of the time period between inhalation and exhalation or a breath with substantially decreased breath volume.

### Claim 6 (depends on 2)

The method of claim 2, comprising an apnea period of from 5 to 25 seconds.

### Claim 7 (depends on 6)

The method of claim 6, comprising an apnea period of from 8 to 15 seconds.

### Claim 8 (depends on 1)

The method of claim 1, wherein the amount of oxygen and carbon dioxide being inhaled and exhaled is determined by measuring the end-tidal concentration of oxygen and carbon dioxide and the inspirational concentration of oxygen.

### Claim 9 (depends on 2)

The method of claim 2, wherein said difference in dead space volume is increased during a limited period of time.

### Claim 10 (depends on 9)

The method of claim 9, wherein said period of time is short enough to avoid re-circulation of carbon dioxide in mixed venous blood.

### Claim 11 (depends on 1)

The method of claim 1, comprising the determination of oxygen uptake and carbon dioxide excretion during said first breathing cycle based on the determined amount of oxygen and carbon dioxide being inhaled and exhaled.

### Claim 12 (depends on 1)

The method of claim 1, wherein the estimation of FRC is repeated for continuous monitoring of FRC.

### Claim 13 (depends on 1)

The method of claim 1, wherein the estimation of FRC comprises several of said determinations so as to provide an average FRC estimation.

### Claim 14 (depends on 1)

The method of claim 1, wherein said person is a ventilator treated patient and wherein said first change in breathing pattern is based on a predetermined breathing pattern of the ventilator.

### Claim 15 (depends on 14)

The method of claim 14, comprising the determination of post expiration end pressure (PEEP) of the ventilator based on FRC.

### Claim 16

An apparatus for measuring functional residual capacity (FRC), comprising:
means for establishing a breathing pattern;
means for determining the amount of oxygen and carbon dioxide being inhaled and exhaled during a first breathing cycle comprised by said breathing pattern;
means for accomplishing a first change in said breathing pattern of known magnitude;
means for determining the amount of oxygen and carbon dioxide being inhaled and exhaled during a second breathing cycle;
means for estimating the FRC based on the determined amounts of oxygen and carbon dioxide in said first and second breathing cycles.

### Claim 17 (depends on 16)

The apparatus of claim 16, wherein said means for estimating FRC are capable of estimating the base metabolism from said determination of oxygen and carbon dioxide.

### Claim 18 (depends on 17)

The apparatus of claim 17, wherein said first change of breathing pattern is selected from apnea, a breath volume larger than the breath volume of said first breathing cycle, a breath volume smaller than the breath volume of said first breathing cycle, a duration difference between the different phases in said first and second breathing cycles, a difference in dead space volume.

### Claim 19 (depends on 16)

The apparatus of claim 16, comprising means for accomplishing a second change in breathing pattern of known magnitude after completion of said second breathing cycle, the means for accomplishing said second change being compensatory to the means for accomplishing said first change in breathing pattern and being capable of re-establishing a steady state allowing a new estimation of FRC with minimal delay.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein said first change in breathing pattern is an increase of the time period between exhalation and inhalation or a breath with substantially decreased breath volume and said second change in breathing pattern is a breath with substantially increased breath volume.

### Claim 21 (depends on 19)

The apparatus of claim 19, wherein said first change in breathing pattern is a breath with substantially increased breath volume and said second change in breathing pattern is an increase of the time period between inhalation and exhalation or a breath with substantially decreased breath volume.

### Claim 22 (depends on 20)

The apparatus of claim 20, comprising an apnea period of from 5 to 25 seconds.

### Claim 23 (depends on 22)

The apparatus of claim 22, comprising an apnea period of from 8 to 15 seconds.

### Claim 24 (depends on 16)

The apparatus of claim 16, wherein the amount of oxygen and carbon dioxide being inhaled and exhaled is determined by measuring the end-tidal concentration of oxygen and carbon dioxide and the inspirational concentration of oxygen.

### Claim 25 (depends on 16)

The apparatus of claim 16, wherein the estimation of FRC is repeated for continuous monitoring of FRC.

### Claim 26 (depends on 16)

The apparatus of claim 16, wherein the estimation of FRC comprises several of said determinations so as to provide an average FRC estimation.

### Claim 27 (depends on 16)

The apparatus claim 16, wherein said first change in breathing pattern is based on a predetermined breathing pattern of the ventilator.

### Claim 28 (depends on 16)

The apparatus of claim 16, comprising means for the determination of post expiration end pressure.

### Claim 29 (depends on 18)

The apparatus of claim 18, wherein said difference in dead space volume is increased during a limited period of time.

### Claim 30

A method for estimation of functional residual capacity (FRC), comprising the steps of determining the amount of oxygen and carbon dioxide being inhaled and exhaled during at least two breathing cycles, identifying at least one difference between said breathing cycles, and estimating the FRC based on the determined amount of oxygen and carbon dioxide and said identified difference.

### Claim 31 (depends on 30)

A method according to claim 30, further comprising the step of estimating the base metabolism from the oxygen and carbon dioxide determination.

### Claim 32 (depends on 30)

A method according to claim 30, wherein the amount of oxygen and carbon dioxide being inhaled and exhaled is determined by measuring the end-tidal concentration of oxygen and carbon dioxide and the inspirational concentration of oxygen.

### Claim 33 (depends on 30)

A method according to claim 30, wherein the difference between the breathing cycles comprises a difference in the time period between exhalation and inhalation.

### Claim 34 (depends on 33)

A method according to claim 33, wherein one of the breathing cycles comprises an apnea period, preferably having a duration of 5-25 seconds, and most preferably 8-15 seconds.

### Claim 35 (depends on 30)

A method according to claim 30, wherein the difference between the breathing cycles comprises a difference in air volume being inhaled.

### Claim 36 (depends on 30)

A method according to claim 30, wherein the difference between the breathing cycles comprises a duration difference between the different phases in the breathing cycles.

### Claim 37 (depends on 30)

A method according to claim 30, wherein the difference between the breathing cycles comprises a controlled difference in the dead space volume.

### Claim 38 (depends on 37)

A method according to claim 37, wherein the dead space is increased during a limited period, said time period preferably being long enough to reach a steady state and short enough to avoid recirculation of CO2 in mixed venous blood.

### Claim 39 (depends on 30)

A method according to claim 30, wherein the determined amount of oxygen and carbon dioxide being inhaled and exhaled is used to determine the uptake of oxygen and excretion of carbon dioxide during the breathing cycles.

### Claim 40 (depends on 30)

A method according to claim 30, wherein the estimation of the FRC is repeated for continuous monitoring of the FRC.

### Claim 41 (depends on 30)

A method according to claim 30, wherein the estimation of the FRC comprises several measurements, whereby the estimation is determined as an average value of said measurements.

### Claim 42 (depends on 30)

A method for estimation of functional residual capacity (FRC) in ventilator treated patients according to claim 30, wherein the difference between the breathing cycles is based on a predetermined breathing pattern of the ventilator equipment.

### Claim 43 (depends on 42)

A method according to claim 42, wherein the estimation of the FRC is used to determine the post expiration end pressure (PEEP) for the ventilator equipment.

### Claim 44

An apparatus for estimation of functional residual capacity (FRC), comprising measuring means for determining the amount of oxygen and carbon dioxide being inhaled and exhaled during at least two breathing cycles, means for identifying at least one difference between said breathing cycles, and processing means for calculation of an estimated FRC based on the measured amount of oxygen and carbon dioxide and said identified difference.

### Claim 45 (depends on 44)

An apparatus according to claim 44, wherein the processing means further being adapted to estimate the base metabolism from the oxygen and carbon dioxide determination.

### Claim 46 (depends on 44)

An apparatus according to claim 44, wherein the means for determining the amount of oxygen and carbon dioxide being inhaled and exhaled comprises means for measuring the end-tidal concentration of oxygen and carbon dioxide and the inspirational concentration of oxygen.

### Claim 47 (depends on 44)

An apparatus according to claim 44, wherein the difference between the breathing cycles comprises a difference in the time period between exhalation and inhalation.

### Claim 48 (depends on 47)

An apparatus according to claim 47, wherein one of the breathing cycles comprises an apnea period, preferably having a duration of 5-25 seconds, and most preferably 8-15 seconds.

### Claim 49 (depends on 44)

An apparatus according to claim 44, wherein the difference between the breathing cycles comprises a difference in air volume being inhaled.

### Claim 50 (depends on 44)

An apparatus according to claim 44, wherein the difference between the breathing cycles comprises a duration difference between the different phases in the breathing cycles.

### Claim 51 (depends on 44)

An apparatus according to claim 44, wherein the means for measuring the uptake of oxygen and excretion of carbon dioxide during the breathing cycles comprises means for determining the fluxes of oxygen and carbon dioxide during inhalation and exhalation.

### Claim 52 (depends on 44)

An apparatus for estimation of functional residual capacity (FRC) in ventilator treated patients according to claim 44, wherein the difference between the breathing cycles is based on a predetermined breathing pattern of the ventilator equipment.