Apparatus and method for non-invasively measuring cardiac output
First Claim
1. An apparatus for determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising:
- a conduit adapted for flow communication with a respiratory system of the patient;
a deadspace adjustable between more than two volumes and positionable in flow communication with said conduit to receive a volume of gas comprising carbon dioxide for subsequent breathing by the patient; and
at least one detection component in communication with said conduit and capable of detecting changes in respiration of the patient.
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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
56 Claims
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1. An apparatus for determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising:
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a conduit adapted for flow communication with a respiratory system of the patient;
a deadspace adjustable between more than two volumes and positionable in flow communication with said conduit to receive a volume of gas comprising carbon dioxide for subsequent breathing by the patient; and
at least one detection component in communication with said conduit and capable of detecting changes in respiration of the patient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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- 32. An apparatus for determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising a conduit configured to communicate with a respiratory system of the patient and including an evacuation element comprising a valve for selectively releasing a volume of gas exhaled by the patient from said conduit or for facilitating introduction of gas into a deadspace including at least a portion of the conduit.
- 37. An apparatus for determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising a conduit configured to communicate with [an airway] a respiratory system of the patient, a gas source in communication with said conduit, and a gas insufflation component in communication with said airway.
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40. A method of determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising:
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measuring gas flow and carbon dioxide partial pressure during substantially normal respiration or ventilation of the patient;
calculating a carbon dioxide elimination and an end-tidal partial pressure of carbon dioxide from said gas flow and said carbon dioxide partial pressure;
measuring gas flow and carbon dioxide partial pressure during re-breathing to determine an end-tidal pressure change in said end-tidal partial pressure of carbon dioxide and a volume change in said carbon dioxide elimination;
estimating an anatomic deadspace partial pressure of carbon dioxide in an anatomic deadspace of the patient and a parallel deadspace partial pressure of carbon dioxide in a parallel deadspace of the patient;
selecting a functional residual capacity value;
correcting said carbon dioxide elimination based at least in part on said functional residual capacity value and on said end-tidal pressure change;
determining an alveolar partial pressure of carbon dioxide based at least in part on said end-tidal partial pressure of carbon dioxide and said parallel deadspace partial pressure of carbon dioxide;
determining an alveolar pressure change in said alveolar partial pressure of carbon dioxide effected by said re-breathing; and
determining the cardiac output or the pulmonary capillary blood flow from said volume change and said alveolar pressure change. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56)
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55. The method of claim 54, further comprising measuring said arterial partial pressure of carbon dioxide.
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56. The method of claim 55, wherein said measuring said arterial partial pressure of carbon dioxide comprises directly measuring said arterial partial pressure of carbon dioxide.
Specification