Process and device for measuring exhaled air to determine metabolic function of a living being

摘要

A process and a device are provided for determining the proportion of a component of the air exhaled by a breathing living being that is characteristic of the metabolic function of such living being. The invention relates to a process for determination of a first component A_a,1 in the air exhaled by a patient that is characteristic of the metabolic function of the patient such as carbon dioxide (CO₂) or oxygen (O₂), where the exhaled air having at least two components (i=1, 2, . . . ) each having a proportion A_a,i. The molecular weights M; and the adiabatic coefficients k_i of the components are known. The process measures the velocity of sound v_S in the exhaled air, and the portion A_i,1 of the first component in the exhaled air is calculated by use of the measured velocity, at a temperature T of the exhaled air. The proportion of the component is determined by the equation M_G/k_G=R×T/(v_s²), where M_G=sum(A_a,i×M_i), i=1, 2, . . . , and where M_G is the molecular weight of the exhaled air, and 1/(1−k_G)=sum(A_a,i/(1−k_i)), i=1, 2, . . . , where k_G is the adiabatic coefficient, and R is the universal gas constant.