Patent ID: 6506608
Filing Date: 2003-01-14
Classification: A61B,A61M,G01F,G01N,Y10T

Abstract:
A method of analyzing exhaled breath produced by a subject over a measurement period, the method comprising:determining an exhaled mass of the exhaled breath by integrating a plurality of flow rate determinations and a plurality of density determinations for the exhaled breath passing through a flow tube during the measurement period, wherein the plurality of flow rate determinations for the exhaled breath and the plurality of density determinations for the exhaled breath are determined by passing a plurality of ultrasonic pulses through at least part of the flow tube as the exhaled breath passes therethrough; determining an exhaled volume of the exhaled breath by integrating a plurality of flow rate determinations for the exhaled breath passing through the flow tube during the measurement period; determining an inhaled nitrogen mass using an inhaled volume of inhaled gases during the measurement period and an inhaled composition of inhaled gases, and determining an exhaled nitrogen mass as equal to the inhaled nitrogen mass; subtracting the exhaled nitrogen mass from the exhaled mass of the exhaled breath, so as to determine a mass of residue exhaled gas, wherein the residue exhaled gas is substantially a mixture of carbon dioxide and oxygen; and determining a composition of the residue exhaled gas from the exhaled volume of the exhaled gas and the mass of residue exhaled breath.