METHOD FOR CONTINUOUS AND NON-INVASIVE DETERMINATION OF EFFECTIVE LUNG VOLUME AND CARDIAC OUTPUT
First Claim
1. 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:
- measuring an inspiratory flow of inspiration gas inhaled by the subject and an expiratory flow of expiration gas exhaled by the subject, andmeasuring the carbon dioxide content of at least the expiration gas,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, based on the measured inspiratory flow, expiratory flow and carbon dioxide content; and
determining said at least one physiological parameter based on the correlation of the first, second and third parameters in the sequence of respiratory cycles.
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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.
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Citations
14 Claims
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1. 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:
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measuring an inspiratory flow of inspiration gas inhaled by the subject and an expiratory flow of expiration gas exhaled by the subject, and measuring the carbon dioxide content of at least the expiration gas, 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, based on the measured inspiratory flow, expiratory flow and carbon dioxide content; and determining said at least one physiological parameter based on the correlation of the first, second and third parameters in the sequence of respiratory cycles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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 device that also comprises at least one flow sensor for measuring an inspiratory flow of inspiration gas inhaled by the subject and an expiratory flow of expiration gas exhaled by the subject, at least one gas analyzer for measuring the carbon dioxide content of at least the expiration gas exhaled by the subject, said programming instructions causing said processor to:
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measure an inspiratory flow of inspiration gas inhaled by the subject and an expiratory flow of expiration gas exhaled by the subject, and measure the carbon dioxide content of at least the expiration gas, 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, based on the measured inspiratory flow, expiratory flow and carbon dioxide content; and determine said at least one physiological parameter based on the correlation of the first, second and third parameters in the sequence of respiratory cycles.
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11. A device 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, comprising:
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at least one flow sensor that measures an inspiratory flow of inspiration gas inhaled by the subject and an expiratory flow of expiration gas exhaled by the subject, during a sequence of respiratory cycles; at least one gas analyzer that measures the carbon dioxide content of at least the expiration gas; and a control unit configured to 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, based on the measured inspiratory flow, expiratory flow and carbon dioxide content, and to determine said at least one physiological parameter based on the correlation of the first, second and third parameters in the sequence of respiratory cycles. The device according to claim 11, comprising components forming a breathing-assist apparatus, and wherein said control unit is configured to operate said breathing-assist apparatus to provide a ventilatory treatment to the subject.
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- 13. The device according to claim 12 wherein the control unit is configured to cause a change in the effective ventilation of the subject to cause the carbon dioxide content of the expiration gas exhaled by the subject to vary in a range of 0.5%-1% during said sequence of respiratory cycles.
Specification