European journal of applied physiology
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Eur. J. Appl. Physiol. · Nov 2003
Determination of rate-constants as a method to describe passive expiration.
To describe the relaxed expiration by a two-compartment model, we introduced a gas/energy transfer between the lung compartment ( V(1)) and a second one ( V(2)). If V(2) were a real volume, the rate-constants (i.e. the flow/volume ratios) of the compartments would describe a real gas-exchange. Alternatively, if a viscoelastic behaviour of the lung or an energy-exchange between compartments was simulated, V(2) would become a "pseudo-volume". ⋯ In conclusion, our analysis demonstrated that the energy/volume of the second compartment may increase at the beginning of expiration and then decrease, showing a maximum, even though the total curve can only be a decreasing one. In other words, the slowing down of the curve representing expiratory volume is due not only to the longer emptying of the second compartment, but also to the interaction between the two compartments. As presently proposed, this interaction can be represented by either a gas exchange between two actual volumes, or a mechanical energy transfer between the lung and the tissue compartment.