IMPACT OF RESPIRATORY MECHANICS MODEL PARAMETERS ON GAS EXCHANGE EFFICIENCY

Mathematical and numerical modelling of the human lung

S. Martin ; T. Similowski ; C. Straus ; B. Maury

Others  :  http://www.esaim-proc.org/articles/proc/pdf/2008/02/proc082303.pdf
PID  :  49642

来源: CEUR

【 摘 要 】

In this article, we are interested in the impact of the mechanical characteristics of the bronchial tree and lung parenchyma on the gas exchange capacity of the human lungs.Objectives. The precise role of the airway smooth muscle (ASM) remains a matter of debate. ASM could have a structural function, to confer transport optimized mechanical properties to the bronchial tree. To test this hypothesis, the present model analysis investigates how ASM-dependent changes in respiratory mechanics can influence the efficiency of the lung as gas exchangers.Method. To this aim, two models have been elaborated. The first one is a single compartment model of the respiratory system that is accurate enough to predict the behaviour of the system during a complex dynamical situation (the forced inspiratory-expiratory maneuver that is performed during spirometric evaluations). The second one is an oxygen absorption model. The two models are coupled in series. The effects of changes in the parameters of the mechanical model on the performance of the gas exchange model are described.Results. The model shows that the mechanical response of the bronchial tree to the dilating forces related to inspiration is among the determinants of this efficiency. At one extreme, a fully rigid bronchial tree would be counterproductive by preventing sufficient amounts of gas to flow through it and reach the alveoli. At the other extreme, a fully distensible bronchial tree would allow greater inspiratory volumes to enter the thorax, but would compromise gas exchange efficiency by decreasing the alveolar volume, hence the membrane surface available for oxygen transfer (deadspace effect). This supports the hypothesis that ASM has a transport optimizing structural function.Conclusions. This is supported by physiological observations compatible with deadspace increases following the administration of ASM-relaxing agents, i. e. bronchodilators.