Fluid-structure interaction modeling of lactating breast.
There are two theories for the dynamics of milk expression by the infant. One hypothesis is that milk expression is due to the negative pressure applied by the infant sucking; the alternative hypothesis is that the tongue movement and squeezing of nipple/areola due to mouthing is responsible for the extraction of milk from the nipple. In this study, 3-D two-way Fluid-Structure Interaction (FSI) simulations are conducted to investigate the factors that play the primary role in expressing milk from the nipple. The models include the solid deformation and periodic motion of the tongue and jaw movement. To obtain the boundary conditions, ultrasound images of the oral cavity and motion of the tongue movement during breastfeeding are extracted in parallel to the intra-oral vacuum pressure. The numerical results are cross-validated with clinical data. The results show that, while vacuum pressure plays an important role in the amount of milk removal, the tongue/jaw movement is essential for facilitating this procedure by decreasing the shear stress within the main duct in the nipple. The developed model can contribute to a better understanding of breastfeeding complications due to infant or breast abnormalities and for the design of medical devices such as breast pumps and artificial teats.