Non-invasive method and apparatus for measuring mixed venous carbon dioxide pressure (PvCO2) and other physiological variables

Claim 1

A method of determining the mixed venous PCO 2 (PvCO 2 ), the method of determining the mixed venous PCO 2 (PvCO 2 ) comprising the steps of: (a) measuring the PCO 2 of the gases in haled (PI CO2 ) exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ).

Claim 2

A method of determining the mixed venous PCO 2 (PvCO 2 ), the method of determining the mixed venous PCO 2 (PvCO 2 ) comprising the steps of: (a) measuring the PCO 2 of the gases in haled (PI CO2 ) exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ).

Claim 6

An apparatus for use in determining the mixed venous PCO 2 (PvCO 2 ) comprising: (a) means permitting gases to be inhaled and exhaled by a patient (b) means for measuring the PCO 2 of the gases inhaled and exhaled by the patient under controlled conditions without rebreathing (c) means for permitting the patient to inhale test gases containing at least a small concentration of CO 2 without rebreathing and means for measuring the PCO 2 of the inspired and expired gases that result from breathing the test gases (d) a reservoir for the test gases to be inhaled, the test gases containing at least a small concentration of CO 2 , the reservoir being in communication with the means permitting the gases to be inhaled (e) computers and requisite computer programming means for actually determining the mixed venous PCO 2 .

Claim 7

An apparatus for use in determining the mixed venous PCO 2 (PvCO 2 ) comprising: (a) means permitting gases to be inhaled and exhaled by a patient (b) means for measuring the PCO 2 of the gases inhaled and exhaled by the patient under controlled conditions without rebreathing (c) means for permitting the patient to inhale test gases containing at least a small concentration of CO 2 without rebreathing and means for measuring the PCO 2 of the inspired and expired gases that result from breathing the test gases (d) a reservoir for the test gases to be inhaled, the test gases containing at least a small concentration of CO 2 , the reservoir being in communication with the means permitting the gases to be inhaled (e) computers and requisite computer programming means for actually determining the mixed venous PCO 2 .

Claim 13

A method of determining cardiac output ##EQU9## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 14

A method of determining cardiac output ##EQU9## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 15

A method of determining cardiac output ##EQU10## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 16

A method of determining cardiac output ##EQU10## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 17

A method of determining cardiac output ##EQU11## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCo 2 when PECO 2 -PICO 2 =0, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-aerterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 18

A method of determining cardiac output ##EQU11## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI co2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCo 2 when PECO 2 -PICO 2 =0, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-aerterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 19

A method of determining cardiac output ##EQU12## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 20

A method of determining cardiac output ##EQU12## using a Fick technique comprising the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, further comprising the additional steps of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing where VCO 2 is the minute CO 2 production and C v-a is the mixed venous-arterial CO 2 content difference, VCO 2 is measured in standard ways including the integration of the expiratory PCO 2 versus volume curve, C v-a is calculated according to standard procedures from (a) PvCO 2 (the mixed venous PCO 2 ), (b) arterial blood gases, body temperature and blood hematocrit and thereafter determining the cardiac output Q according to the formula provided above.

Claim 21

An apparatus for determining cardiac output using a Fick technique comprising an apparatus for use in determining the mixed venous PCO 2 (PvCO 2 ) comprising: (a) means permitting gases to be inhaled and exhaled by a patient (b) means for measuring the PCO 2 of the gases inhaled and exhaled by the patient under controlled conditions without rebreathing (c) means for permitting the patient to inhale test gases containing at least a small concentration of CO 2 without rebreathing and means for measuring the PCO 2 of the inspired and expired gases that result from breathing the test gases (d) a reservoir for the test gases to be inhaled, the test gases containing at least a small concentration of CO 2 , the reservoir being in communication with the means permitting the gases to be inhaled (e) computers and requisite computer programming means for actually determining the mixed venous PCO 2 ; further comprising means to determine the difference between the end tidal PCO 2 and inspired PCO 2 under control and test conditions and means for relating said difference to the inspired PCO 2 used in the determination of said difference to mathematically determine the PvCO 2 , further comprising means of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing and means for determining the cardiac output comprising means utilizing the CO 2 production during the control phase and the mixed venous PCO 2 (PvCO 2 ).

Claim 22

An apparatus for determining cardiac output using a Fick technique comprising an apparatus for use in determining the mixed venous PCO 2 (PvCO 2 ) comprising: (a) means permitting gases to be inhaled and exhaled by a patient (b) means for measuring the PCO 2 of the gases inhaled and exhaled by the patient under controlled conditions without rebreathing (c) means for permitting the patient to inhale test gases containing at least a small concentration of CO 2 without rebreathing and means for measuring the PCO 2 of the inspired and expired gases that result from breathing the test gases (d) a reservoir for the test gases to be inhaled, the test gases containing at least a small concentration of CO 2 , the reservoir being in communication with the means permitting the gases to be inhaled (e) computers and requisite computer programming means for actually determining the mixed venous PCO 2 ; further comprising means to determine the difference between the end tidal PCO 2 and inspired PCO 2 under control and test conditions and means for relating said difference to the inspired PCO 2 used in the determination of said difference to mathematically determine the PvCO 2 , further comprising means of measuring the CO 2 production during the control phase (at times other than test conditions) without rebreathing and means for determining the cardiac output comprising means utilizing the CO 2 production during the control phase and the mixed venous PCO 2 (PvCO 2 ).

Claim 23

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 rebreathing to decrease effective alveolar ventilation to provide a change in the end tidal CO 2 concentration and (3) calculating output Q by: ##EQU13## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ) used to determine dPET wherein dPET is calculated utilizing the determination of the end tidal PCO 2 during control and test phases as referred to in subparagraphs (i) and (ii) as follows: (i) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (ii) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV.

Claim 24

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 rebreathing to decrease effective alveolar ventilation to provide a change in the end tidal CO 2 concentration and (3) calculating output Q by: ##EQU13## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ) used to determine dPET wherein dPET is calculated utilizing the determination of the end tidal PCO 2 during control and test phases as referred to in subparagraphs (i) and (ii) as follows: (i) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (ii) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV.

Claim 25

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU14## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.

Claim 26

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU14## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.

Claim 27

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU15## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, and the additional steps of calculating breath by breath, minute CO 2 production for different test gates without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.

Claim 28

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU15## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, and the additional steps of calculating breath by breath, minute CO 2 production for different test gates without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.

Claim 29

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU16## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.

Claim 30

A method of determining cardiac output using the method described by Gedeon in A New Method For Non-Invasive Determination of Pulmonary Blood Flow, Med. & Biol. Eng. and Compute., Volume 18, P. 411 (1980) which discloses the ventilating of a patient in steady state, the method of determining the cardiac output comprising the steps of: (1) monitoring minute CO 2 production and end tidal PCO 2 ; (2) introducing a change in minute CO 2 exhalation and observing the effect on end tidal PCO 2 by (a) providing an extra length of pause between breaths, keeping tidal volume and expiratory time constant; and (b) keeping tidal volume and expiratory time constant but adding CO 2 by rebreathing expired gases; and (3) calculating cardiac output Q by: ##EQU16## where S is the slope of the CO 2 dissociation curve at a PCO 2 equal to the end tidal PCO 2 ; dV is the change in minute CO 2 exhaled during the step in paragraph 2 and dPET is the change in end tidal PCO 2 during the step in paragraph 2 and the steps of: (a) measuring the PCO 2 of the gases inhaled (PI CO2 ) and exhaled by the patient under controlled conditions without rebreathing (b) causing the patient to inhale a test gas containing at least a small concentration of CO 2 and continuing to measure the PCO 2 of the inspired and expired gases, the patient taking at least two breaths without rebreathing (c) determining the PCO 2 of the inspired gases (P I ) and the end tidal PCO 2 of expired gases (PECO 2 ) (d) determining the differences between the end tidal PCO 2 and inspired PCO 2 under control and test conditions, relating these differences to the inspired PCO 2 to determine the mixed venous PCO 2 (PvCO 2 ), wherein the patient takes three or four breaths and the difference between the end tidal PCO 2 after the third breath and the inspired PCO 2 is determined at that time, wherein the determination being carried out is carried out mathematically using at least two points generated as described in sub-paragraphs (a) to (d) inclusive whereby the PICO 2 calculated using this relationship yields PvCO 2 when PECO 2 -PICO 2 =0, and the additional steps of calculating breath by breath, minute CO 2 production for different test gases without rebreathing to yield dV, and dPET is calculated by subtracting the end tidal PCO 2 under test conditions from the end tidal PCO 2 under control conditions.