title: Determination of pulmonary gases (O2 & CO2) metabolic-rates and lung diffusion coefficients based on the inspired and expired air compositions and venous blood and gas concentration.
abstract: The primary function of the lung is to (i) oxygenate the blood and thereby provide oxygen to the cells for metabolization purposes, and (ii) to remove the CO2 produced by the tissues from the pulmonary blood. Herein, we provide a noninvasive methodology to asses the capacity of the lung to oxygenate the pulmonary capillary blood and to reduce its CO2 concentration. For this purpose, we analyze the compositions of the inspired and expired air per breath, and therefrom compute the metabolic O2 consumption rate (VO2) and CO2 production rate (V CO2). Next we compute the cardiac out (CO) as CO = V O2(CAB O2 - CVB O2). We have derived the expressions for diffusion coefficients (i) DO2 in terms of VO2 and the alveolar and venous partial pressures, Pal O2 and PVB O2 and (ii) DCO2 in terms of VCO2, Pal CO2 and PVB CO2. The coefficients DO2 and DCO2 represent the gas transfer capacity of the lung. The paper provides a case study for the determination of Q, DO2 and DCO2. The derived information of DO2 and DCO2 as well as of O2 and CO2 metabolic rates can be of considerable clinical use including for SARS assessment.
authors.affiliation: School of Engineering, Nanyang Polytechnic, Singapor.
authors.forename: Loh
authors.initials: L
authors.lastname: Kah Meng
authors.forename: Dhanjoo N
authors.initials: DN
authors.lastname: Ghista
authors.forename: Heiko
authors.initials: H
authors.lastname: Rudolph