Background. To simulate the short-term dynamics of soluble gas exchange (e.g. CO 2 rebreathing), model structure, ventilation-perfusion ( Vdot A/Q̇) and ventilation-volume (V̇/VA) parameters must be selected correctly. Some diseases affect mainly V̇A/VA distribution while others affect both V̇A/Q̇ and V̇A/VA distributions. Results from the multiple inert gas elimination technique (MIGET) and multiple breath nitrogen washout (MBNW) can be used to select V̇AQ̇ and V̇A/VA parameters, but no method exists for combining V̇AQ̇ and V̇A/ VA parameters in a multicompartment lung model. Methods. We define a tidally breathing lung model containing shunt and up to eight alveolar compartments. Quantitative and qualitative understanding of the diseases is used to reduce the number of model compartments to achieve a unique solution. The reduced model is fitted simultaneously to inert gas retentions calculated from published V̇A/Q̇ distributions and normalized MBNWs obtained from similar subjects. Normal lungs and representative cases of emphysema and embolism are studied. Results. The normal, emphysematous and embolism models simplify to one, three and two alveolar compartments, respectively. Conclusions. The models reproduce their respective MIGET and MBNW patient results well, and predict disease-specific steady-state and dynamic soluble and insoluble gas responses.
- Ventilation inhomogeneity
- Ventilation/perfusion distribution