Static mechanics of excised whole lung: pleural mechanics

Continuum analyses of lung mechanics require that the boundary condition of stress transmitted to the outermost alveoli be known. Depending upon the exact geometry of the pleural-parenchymal coupling, this stress could possibly be influenced by the pleural mechanical properties. The relation between pleural tension and extension ratio was obtained from tissue specimens from mongrel dog lungs. Using the worst-case geometry, this relationship was compared with the equivalent relation between pressure and volume ratio for the whole lung of the same mongrel dogs. The results of this comparison and a suitable mathematical analysis indicate that the pleura transmits applied pressure differences to the underlying alveolar walls essentially without modification.