A tidally breathing model of ventilation, perfusion and volume in normal and diseased lungs.
BACKGROUND
To simulate the short-term dynamics of soluble gas exchange (e.g. CO2 rebreathing), model structure, ventilation-perfusion (VA/Q) and ventilation-volume (VA/VA) parameters must be selected correctly. Some diseases affect mainly the VA/Q distribution while others affect both VA/Q and VA/VA distributions. Results from the multiple inert gas elimination technique (MIGET) and multiple breath nitrogen washout (MBNW) can be used to select VA/Q and VA/VA parameters, but no method exists for combining VA/Q and VA/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 VA/Q 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.
Yem
J S
JS
Department of Anaesthetics, The University of Sydney, Royal Prince Alfred Hospital Missenden Road, Camperdown, NSW 2050, Australia.
Turner
M J
MJ
Baker
A B
AB
Young
I H
IH
Crawford
A B H
AB
D000328:Adult; D001944:Breath Tests; D006801:Humans; D008297:Male; D008954:Models, Biological; D011650:Pulmonary Alveoli / Q000503:physiopathology; D011655:Pulmonary Embolism / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012995:Solubility; D014692:Ventilation-Perfusion Ratio