Evaluation of Errors in Expiratory Flow Method of Breath-by-breath Gas Exchange Measurement

Abstract

A computer simulation in the expiratory flow method was utilized to obtain information on the effects of error factors on the gas exchange during breath-by-breath measurement.The error sensitivites of gas exchange variables (V_O_2, V_CO₂, and R) to the error in expiratory flow integration were always one, while the error sensitivities to the flow base-line drift decreased with the reduction of expiratory period.V_O_2 values were affected by dhfts in both expired oxygen and carbon dioxide concentration.A combined error of the integrals of flow and the integrals of product of flow times gas concentration caused multiple effects on V_O_2, depending on the sign and magnitude of theintegrals.Problems in this simulation were selection of average gas consentration in the integrals, application to the transient response, and lack of the wave form analysis of distorted signals.