US 6,227,196 B1 · Apparatus and method for non-invasively measuring cardiac output

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.

Claims56

Dependent claims

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.

1 more element

A method of determining a cardiac output or a pulmonary capillary blood flow of a patient, comprising:

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.

7 more elements

Dependencies are inferred from the claim text.

Apparatus and method for non-invasively measuring cardiac output

Life of this patent

Apparatus and method for non-invasively measuring cardiac output

Life of this patent

Abstract

Claims56