Apparatus and method for non-invasively measuring cardiac output
First Claim
1. A method for estimating the cardiac output of an individual, comprising:
- determining a carbon dioxide elimination (VCO2) of the individual for a before re-breathing period and for a during re-breathing period;
calculating a carbon dioxide elimination difference between the carbon dioxide elimination of the before re-breathing period and the carbon dioxide elimination of the during re-breathing period;
estimating a partial pressure of carbon dioxide in alveoli (PACO2) of the individual for the before re-breathing period and for the during re-breathing period based on partial pressure of end tidal carbon dioxide (PetCO2) measurements of the individual during the before re-breathing period and during the during re-breathing period, respectively;
converting each estimation of the partial pressure of carbon dioxide in alveoli to a carbon dioxide content (CCO2);
calculating a carbon dioxide content difference between the carbon dioxide content of the before re-breathing period and the carbon dioxide content of the during re-breathing period; and
dividing the carbon dioxide elimination difference by the carbon dioxide content difference to estimate cardiac output.
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Accused Products
Abstract
Apparatus and methods for non-invasively determining the cardiac output or pulmonary capillary blood flow of a patient using partial re-breathing techniques. The apparatus includes a substantially instantaneously adjustable deadspace volume for accommodating differences in sizes or breathing capacities of various patients. The apparatus may be constructed of inexpensive elements, including one or more two-way valves, which render the apparatus very simple to use and inexpensive so that the unit may be employed as a disposable product. The method of the invention includes estimating the cardiac output or pulmonary capillary blood flow of a patient based on partial pressure of alveolar CO2, rather than on the partial pressure of end tidal CO2, as previously practiced. A computer program for calculating the cardiac output or pulmonary capillary blood flow of a patient is also disclosed.
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Citations
17 Claims
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1. A method for estimating the cardiac output of an individual, comprising:
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determining a carbon dioxide elimination (VCO 2 ) of the individual for a before re-breathing period and for a during re-breathing period;
calculating a carbon dioxide elimination difference between the carbon dioxide elimination of the before re-breathing period and the carbon dioxide elimination of the during re-breathing period;
estimating a partial pressure of carbon dioxide in alveoli (PACO2) of the individual for the before re-breathing period and for the during re-breathing period based on partial pressure of end tidal carbon dioxide (PetCO2) measurements of the individual during the before re-breathing period and during the during re-breathing period, respectively;
converting each estimation of the partial pressure of carbon dioxide in alveoli to a carbon dioxide content (CCO2);
calculating a carbon dioxide content difference between the carbon dioxide content of the before re-breathing period and the carbon dioxide content of the during re-breathing period; and
dividing the carbon dioxide elimination difference by the carbon dioxide content difference to estimate cardiac output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for estimating the cardiac output of a subject, comprising:
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estimating a carbon dioxide elimination of the subject for a before re-breathing period and for a during re-breathing period;
estimating a carbon dioxide content in blood passing by the alveoli of the subject for the before re-breathing period and for the during re-breathing period;
dividing a difference between carbon dioxide elimination from the before and during rebreathing periods by a difference between carbon dioxide content from the before and during rebreathing periods to estimate cardiac output. - View Dependent Claims (13)
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14. A method for estimating the cardiac output of a subject, comprising:
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estimating a carbon dioxide elimination of the subject and a carbon dioxide content of blood of the subject during baseline respiration;
providing for a change in effective ventilation of the subject;
estimating a carbon dioxide elimination of the subject and a carbon dioxide content of blood of the subject following the change in effective ventilation;
and dividing a change in the carbon dioxide elimination from before to after the change in effective ventilation by a change in the carbon dioxide content from before to after the change in effective ventilation to estimate cardiac ouput. - View Dependent Claims (15, 16, 17)
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Specification