Apparatus and method for non-invasively measuring cardiac output
First Claim
1. A method for noninvasively determining at least one of a cardiac output and a pulmonary capillary blood flow of a patient, comprising:
- determining a change in carbon dioxide elimination of the patient between carbon dioxide elimination of the patient during normal breathing and carbon dioxide elimination of the patient during re-breathing;
determining a change in partial pressure of end-tidal carbon dioxide of the patient between partial pressure of end tidal carbon dioxide of the patient during said normal breathing and partial pressure of end tidal carbon dioxide of the patient during said re-breathing; and
compensating for functional residual capacity in lungs of the patient.
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Abstract
Apparatus and methods for non-invasively determining cardiac output using partial re-breathing techniques are disclosed in which the apparatus is constructed with an instantaneously adjustable deadspace for accommodating differences in breathing capacities of various patients. The apparatus is constructed of inexpensive elements, including a single two-way valve which renders the apparatus very simple to use and inexpensive so that the unit may be readily disposable. The method of the invention provides a novel means of estimating cardiac output based on alveolar CO2 values rather than end-tidal CO2 values as previously practiced. A program for calculating cardiac output is also disclosed.
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Citations
8 Claims
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1. A method for noninvasively determining at least one of a cardiac output and a pulmonary capillary blood flow of a patient, comprising:
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determining a change in carbon dioxide elimination of the patient between carbon dioxide elimination of the patient during normal breathing and carbon dioxide elimination of the patient during re-breathing;
determining a change in partial pressure of end-tidal carbon dioxide of the patient between partial pressure of end tidal carbon dioxide of the patient during said normal breathing and partial pressure of end tidal carbon dioxide of the patient during said re-breathing; and
compensating for functional residual capacity in lungs of the patient. - View Dependent Claims (2, 3, 4, 5, 6, 7)
dissociation curve and said change in partial pressure of end tidal carbon dioxide.
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7. The method of claim 1, further comprising measuring carbon dioxide elimination and partial pressure of end tidal carbon dioxide over a plurality of breaths.
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8. 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;
estimating a partial pressure of carbon dioxide in alveolar blood (PACO2) of the individual for said before re-breathing period and for said during re-breathing period;
converting each estimation of said partial pressure of carbon dioxide in alveolar blood to a carbon dioxide content (CCO 2 );
calculating a carbon dioxide elimination difference between said carbon dioxide elimination of said before rebreathing period and said carbon dioxide elimination of said during re-breathing period;
calculating a carbon dioxide content difference between said carbon dioxide content of said before re-breathing period and said carbon dioxide content of said during re-breathing period; and
dividing said carbon dioxide elimination difference by said carbon dioxide content difference.
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Specification