Method for continuous and non-invasive determination of effective lung volume and cardiac output
First Claim
1. A non-invasive method for simultaneously determining at least two physiological parameters related, respectively, to the effective lung volume and the cardiac output of a subject, the method comprising the steps of, during a sequence of respiratory cycles:
- changing ventilation of a subject provided by a breathing apparatus, wherein the change of ventilation is performed by a control unit of the breathing apparatus and wherein the change in ventilation causes a substantial change in carbon dioxide content in expiration gas exhaled by the subject during the sequence of respiratory cycles;
after changing ventilation, measuring at least an expiratory flow of expiration gas exhaled by the subject, and measuring the carbon dioxide content of at least the expiration gas, wherein the expiratory flow of the expiration gas is measured by at least one flow sensor of a monitoring device, and the carbon dioxide content is measured by at least one gas analyzer of the monitoring device;
determining, for each respiratory cycle in the sequence of respiratory cycles, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is performed by the control unit of the breathing apparatus and is based on the measured expiratory flow and the measured carbon dioxide content;
for each respiratory cycle in the sequence of respiratory cycles, the control unit inserts the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the simultaneous determination of the at least two physiological parameters is performed by the control unit, and the simultaneous determination of the at least two physiological parameters involves finding an approximate solution to the overdetermined system of equations; and
continuously monitoring the at least two physiological parameters simultaneously determined by the control unit, wherein the control unit is a component of the monitoring device.
1 Assignment
0 Petitions
Accused Products
Abstract
In a method for continuous and non-invasive determination of the effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of a subject during a sequence of respiratory cycles, the inspiratory and expiratory flow, and the carbon dioxide content of at least the expiration gas are measured. In each respiratory cycle, a first parameter related to the subject'"'"'s fraction of alveolar carbon dioxide, a second parameter related to the carbon dioxide content of the subject'"'"'s arterial blood, and a third parameter related to the subject'"'"'s carbon dioxide elimination are determined based on the measured inspiratory flow, expiratory flow and carbon dioxide content. The effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of the subject is determined based on the correlation of the first, second and third parameters.
16 Citations
24 Claims
-
1. A non-invasive method for simultaneously determining at least two physiological parameters related, respectively, to the effective lung volume and the cardiac output of a subject, the method comprising the steps of, during a sequence of respiratory cycles:
-
changing ventilation of a subject provided by a breathing apparatus, wherein the change of ventilation is performed by a control unit of the breathing apparatus and wherein the change in ventilation causes a substantial change in carbon dioxide content in expiration gas exhaled by the subject during the sequence of respiratory cycles; after changing ventilation, measuring at least an expiratory flow of expiration gas exhaled by the subject, and measuring the carbon dioxide content of at least the expiration gas, wherein the expiratory flow of the expiration gas is measured by at least one flow sensor of a monitoring device, and the carbon dioxide content is measured by at least one gas analyzer of the monitoring device; determining, for each respiratory cycle in the sequence of respiratory cycles, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is performed by the control unit of the breathing apparatus and is based on the measured expiratory flow and the measured carbon dioxide content; for each respiratory cycle in the sequence of respiratory cycles, the control unit inserts the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the simultaneous determination of the at least two physiological parameters is performed by the control unit, and the simultaneous determination of the at least two physiological parameters involves finding an approximate solution to the overdetermined system of equations; and continuously monitoring the at least two physiological parameters simultaneously determined by the control unit, wherein the control unit is a component of the monitoring device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A non-transitory, computer-readable data storage medium encoded with programming instructions for non-invasive determination of at least one physiological parameter related to the effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of a subject, said storage medium being loaded into a processor of a breathing apparatus that also comprises at least one flow sensor of a monitoring device for measuring at least an expiratory flow of expiration gas exhaled by the subject, at least one gas analyzer of the monitoring device measuring the carbon dioxide content of at least the expiration gas exhaled by the subject, said programming instructions causing said processor to:
-
change ventilation of a subject provided by the breathing apparatus so as to cause a substantial change in carbon dioxide content in expiration gas exhaled by the subject during a sequence of respiratory cycles; following the change in ventilation, process a measure of at least an expiratory flow of expiration gas exhaled by the subject, and process a measure of the carbon dioxide content of at least the expiration gas, wherein the expiratory flow of the expiration gas is measured by the at least one flow sensor, and the carbon dioxide content is measured by the at least one gas analyzer; determine, for each respiratory cycle in the sequence of respiratory cycles, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is based on the measured expiratory flow and the measured carbon dioxide content; and for each respiratory cycle in the sequence of respiratory cycles, the processor inserts the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the determination of the at least one physiological parameter is performed by the processor, and the determination of the at least one physiological parameter involves finding an approximate solution to the overdetermined system of equations; and calculate an error indicative of uncertainty in the determination of the at least one physiological parameter; and cause an alarm signal to be generated by the monitoring device when the error exceeds a predetermined threshold value; and provide continuous monitoring of the at least one physiological parameter determined by the processor, wherein the processor is a component of the monitoring device. - View Dependent Claims (12, 13)
-
-
14. A breathing apparatus adapted to provide a non-invasive determination of at least one physiological parameter related to the effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of a subject, the breathing apparatus comprising:
-
a breathing assist apparatus selected from the group consisting of a ventilator and an anesthesia machine; and a monitoring device, wherein the monitoring device comprises at least one flow sensor disposed to measure at least an expiratory flow of expiration gas exhaled by the subject, during a sequence of respiratory cycles; at least one gas analyzer disposed to measure the carbon dioxide content of at least the expiration gas; and a control unit configured to control ventilation of the subject provided by the breathing assist apparatus and to determine, for each respiratory cycle in the sequence of respiratory cycles following a ventilation change by the control unit that causes a substantial change in the carbon dioxide content in the expiration gas, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is based on the measured expiratory flow provided by the at least one flow sensor and the measured carbon dioxide content provided by the at least one gas analyzer, and the control unit is configured to, for each respiratory cycle in the sequence of respiratory cycles, insert the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the determination of the at least one physiological parameter by the control unit involves finding an approximate solution to the overdetermined system of equations, and the control unit is configured to provide non-invasive continuous monitoring of the at least one determined physiological parameter during respiratory treatment provided by the breathing assist apparatus. - View Dependent Claims (15, 16, 17)
-
-
18. A non-invasive method for determining at least one physiological parameter related to the effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of a subject, the method comprising the steps of, during a sequence of respiratory cycles:
-
changing ventilation of a subject provided by a breathing apparatus, wherein the change of ventilation is performed by a control unit of the breathing apparatus and wherein the change in ventilation causes a substantial change in carbon dioxide content in expiration gas exhaled by the subject during the sequence of respiratory cycles; after changing ventilation, measuring at least an expiratory flow of expiration gas exhaled by the subject, and measuring the carbon dioxide content of at least the expiration gas, wherein the expiratory flow of the expiration gas is measured by at least one flow sensor of a monitoring device, and the carbon dioxide content is measured by at least one gas analyzer of the monitoring device; determining, for each respiratory cycle in the sequence of respiratory cycles, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is performed by the control unit of the breathing apparatus and is based on the measured expiratory flow and the measured carbon dioxide content; for each respiratory cycle in the sequence of respiratory cycles, the control unit inserts the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the determination of the at least one physiological parameter is performed by the control unit, and the determination of the at least one physiological parameter involves finding an approximate solution to the overdetermined system of equations; and calculating an error indicative of uncertainty in the determination of the at least one physiological parameter, wherein the control unit calculates the error and causes an alarm signal to be generated by the monitoring device when the error exceeds a predetermined threshold value, wherein the control unit is a component of the monitoring device and the monitoring device continuously monitors the at least one physiological parameter determined by the control unit. - View Dependent Claims (19)
-
-
20. A non-transitory, computer-readable data storage medium encoded with programming instructions for non-invasive and simultaneous determination of at least two physiological parameters related, respectively, to the effective lung volume and the cardiac output of a subject, said storage medium being loaded into a processor of a breathing apparatus that also comprises at least one flow sensor of a monitoring device for measuring at least an expiratory flow of expiration gas exhaled by the subject, and at least one gas analyzer of the monitoring device for measuring the carbon dioxide content of at least the expiration gas exhaled by the subject, said programming instructions causing said processor to:
-
change ventilation of a subject provided by the breathing apparatus so as to cause a substantial change in carbon dioxide content in expiration gas exhaled by the subject during a sequence of respiratory cycles; following the change in ventilation, process a measure of at least an expiratory flow of expiration gas exhaled by the subject, and process a measure of the carbon dioxide content of at least the expiration gas, wherein the expiratory flow of the expiration gas is measured by the at least one flow sensor, and the carbon dioxide content is measured by the at least one gas analyzer; determine, for each respiratory cycle in the sequence of respiratory cycles, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is based on the measured expiratory flow and the measured carbon dioxide content; and for each respiratory cycle in the sequence of respiratory cycles, the processor inserts the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the simultaneous determination of the at least two physiological parameters is performed by the processor, and the determination of the at least two physiological parameters involves finding an approximate solution to the overdetermined system of equations; and provide continuous monitoring of the at least two physiological parameters determined by the processor, wherein the processor is a component of the monitoring device.
-
-
21. A breathing apparatus adapted to provide a non-invasive determination of at least one physiological parameter related to the effective lung volume, the cardiac output, and/or the carbon dioxide content of venous blood of a subject, the breathing apparatus comprising:
-
a breathing assist apparatus selected from the group consisting of a ventilator and an anesthesia machine; and a monitoring device, wherein the monitoring device comprises at least one flow sensor disposed to measure at least an expiratory flow of expiration gas exhaled by the subject, during a sequence of respiratory cycles; at least one gas analyzer disposed to measure the carbon dioxide content of at least the expiration gas; and a control unit configured to control ventilation of the subject provided by the breathing assist device and to determine, for each respiratory cycle in the sequence of respiratory cycles following a ventilation change by the control unit that causes a substantial change in the carbon dioxide content in the expiration gas, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is based on the measured expiratory flow provided by the at least one flow sensor and the measured carbon dioxide content provided by the at least one gas analyzer, and the control unit is configured to, for each respiratory cycle in the sequence of respiratory cycles, insert the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the determination of the at least one physiological parameter by the control unit involves finding an approximate solution to the overdetermined system of equations, the control unit further being configured to calculate an error indicative of uncertainty in the determination of the at least one physiological parameter, and cause an alarm signal to be generated by the monitoring device when the error exceeds a predetermined threshold value. - View Dependent Claims (22, 23)
-
-
24. A breathing apparatus adapted to provide non-invasive and simultaneous determination of at least two physiological parameters related, respectively, to the effective lung volume and the cardiac output of a subject, the breathing apparatus comprising:
-
a breathing assist apparatus selected from the group consisting of a ventilator and an anesthesia machine; and a monitoring device, wherein the monitoring device comprises at least one flow sensor disposed to measure at least an expiratory flow of expiration gas exhaled by the subject, during a sequence of respiratory cycles; at least one gas analyzer disposed to measure the carbon dioxide content of at least the expiration gas; and a control unit configured to control ventilation of the subject provided by the breathing assist apparatus and to determine, for each respiratory cycle in the sequence of respiratory cycles following a ventilation change by the control unit that causes a substantial change in the carbon dioxide content in the expiration gas, a first parameter related to the fraction of alveolar carbon dioxide of the subject, a second parameter related to the carbon dioxide content of the arterial blood of the subject, and a third parameter related to carbon dioxide elimination of the subject, wherein the determination of each of the first parameter, the second parameter, and the third parameter is based on the measured expiratory flow provided by the at least one flow sensor and the measured carbon dioxide content provided by the at least one gas analyzer, and the control unit is configured to, for each respiratory cycle in the sequence of respiratory cycles, insert the determined values of the first, second and third parameters into a capnodynamic equation so as to form an overdetermined system of equations, wherein the simultaneous determination of the at least two physiological parameters by the control unit involves finding an approximate solution to the overdetermined system of equations, and the control unit is configured to provide non-invasive continuous monitoring of the at least two simultaneously determined physiological parameters during respiratory treatment provided by the breathing assist apparatus.
-
Specification