Apparatus and method for non-invasively measuring cardiac output
First Claim
1. A re-breathing method, comprising:
- evaluating a characteristic of a patient, said characteristic comprising at least one of a lung capacity of the patient, a size of the patient, a respiratory flow condition, and a respiratory carbon dioxide condition; and
adjusting a deadspace volume based on said characteristic, said adjusting being effected without substantially changing airway pressure.
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Accused Products
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
25 Claims
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1. A re-breathing method, comprising:
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evaluating a characteristic of a patient, said characteristic comprising at least one of a lung capacity of the patient, a size of the patient, a respiratory flow condition, and a respiratory carbon dioxide condition; and
adjusting a deadspace volume based on said characteristic, said adjusting being effected without substantially changing airway pressure. - View Dependent Claims (2, 3, 4)
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5. 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 (6, 7, 8, 9, 10, 11)
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12. A re-breathing method, comprising:
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insufflating an airway of a patient with gas insufflation apparatus;
monitoring at least one aspect of the patient'"'"'s breathing during said insufflating;
reducing said insufflating; and
monitoring said at least one aspect of the patient'"'"'s breathing with said insufflating reduced. - View Dependent Claims (13, 14)
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15. An apparatus for introducing deadspace into a breathing circuit, comprising:
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a deadspace portion of the breathing circuit located to receive gases exhaled by a patient upon positioning the breathing circuit in communication with an airway of the patient;
a primary expiratory pathway through the breathing circuit;
a flow restrictor positioned along said primary expiratory pathway downstream from a junction of said deadspace portion with said primary expiratory pathway; and
a two-way valve positioned along or at an end of said deadspace portion, said two-way valve having;
a first, closed position for causing exhaled gases to flow through said flow restrictor; and
a second, opened position for causing at least a portion of exhaled gases to flow into said deadspace portion. - View Dependent Claims (16, 17)
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18. A method for estimating the partial pressure of carbon dioxide in the alveolar blood (PACO2) of an individual, comprising:
- calculating a concentration of carbon dioxide in the parallel deadspace (PDSCO2) of an airway of the individual; and
determining an end tidal partial pressure of carbon dioxide (etCO2) of the individual. - View Dependent Claims (19, 20, 21, 22, 23, 24)
- calculating a concentration of carbon dioxide in the parallel deadspace (PDSCO2) of an airway of the individual; and
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25. A method for estimating the cardiac output of an individual, comprising:
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determining a carbon dioxide elimination (VCO2) of the patient 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 (CCO2);
calculating a carbon dioxide elimination difference between said carbon dioxide elimination of said before re-breathing 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