Supine to upright lung mechanics: do changes in lung shape influence lung tissue deformation?

In this study we analyze lung shape change between the upright and supine postures and the effect of this shape change on the deformation of lung tissue under gravity. We use supine computed tomography images along with upright tomosynthesis images obtained on the same day to show that there is significant diaphragmatic movement between postures. Using a continuum model of lung tissue deformation under gravity we show that the shape changes due to this diaphragmatic movement could result in different lung tissue expansion patterns between supine and upright lungs. This is an essential consideration when interpreting imaging data acquired in different postures or translating data acquired in supine imaging to upright function.