Abstract
Two different exponential descriptions, Salazar-Knowles: V=Vmax(1-e-kp) and Colebatch-Gibson: V=Vo-Ae-kp, for the static deflationary pressure volume curve were applied for ten normal rat lungs and their mathematical characteristics were evaluated.
1) At low and high lung volume, theoretical values obtained by the Salazar-Knowles formula showed significantly large discrepancies compared with the actual measured values. However, the difference was minimal at mid-lung volume in both the Colebatch-Gibson and Salazar-Knowles formulae.
2) Even by the Colebatch-Gibson formula, the discrepancies between theoretical and actual value was fairly large at a low lung volume, so that this may suggest that application of the single exponential form of the pressure volume curves had some limitations in term of the expression of lung elasticity in mathematical terms.
3) A tangent at the 50% of maximum lung volume on the pressure-volume curve showed good correlation with the compliance obtained from the actual measured values between 40% and 70% of V30, suggesting that it may be a useful index for the evaluation of lung elasticity.
