Patent ID: 6991607

Claim:
A device for measuring a metabolic function of a patient, said device comprising: a first measuring system for measuring velocity of sound v S in exhaled air from a patient; an electronic storage device for storing a molecular weight M i and an adiabatic coefficient k G of at least two gas components of the exhaled air; and an electronic computer connected to said first measuring system for receiving a signal corresponding to a measured velocity v S and for calculating a proportion A a,1 of a first gas component of the exhaled air based on a measured velocity v S , said first gas component being selected from the group consisting of oxygen and carbon dioxide, said computer being adapted to calculate the proportion of said first gas component in exhaled air by the formula M G /k G =R×T /( v S 2 ) where M G is a molecular weight of the exhaled air, k G is an adiabatic coefficient of the exhaled air, R is a universal gas constant, and T is a temperature of the exhaled air, and by the formula M G =sum( A a,i ×M i ) where i is an integer corresponding to a number of gas components of the exhaled air, and 1/(1 −k G )−sum( A a,i /(1 −k G )) where k i is the adiabatic coefficient of the gas components of the exhaled air.