EFFECT OF MACROSCOPIC DEFORMATION ON LUNG MICROSTRUCTURE

Using an anisotropic theory of diffuse light scattering in lungs, we m easured the fractional changes in geometric mean linear intercepts in orthogonal directions when freshly excised rabbit lungs were subjected to isovolume uniaxial strains. Results from the optical technique wer e compared with morphometric estimates of fractional changes in mean l inear intercepts from the same strained and unstrained (control) lobes , with the conclusion that diffuse light scattering is adequate to est imate changes in mean free paths in different directions. We compared optical estimates of fractional changes in mean Linear intercepts with the macroscopic strain field measured by displacements of pleural mar kers; this relationship did not significantly differ from the line of identity. We conclude that the microscopic strain field is closely mat ched to the macroscopic strain field during uniaxial distortion. This suggests that surface reorientation may not play a large role in the o rigin of the low shear modulus of the lung, but this cannot be definit ively stated without comparison of these experimental results to speci fic model predictions of the changes in mean Linear intercepts in shea r deformation.