A patient-specific finite element model of the smoker's lung during breathing

Lungs expand during breathing through increasing the space in the chest cavity. The mechanical properties of the lung play a pivotal role for space, which provides during breathing. Smoking via chronic obstructive pulmonary disease (COPD) can affect this mechanical function through the alteration of the mechanical properties of the lung tissue. Recently our group performed an experimental study to measure the axial and transversal mechanical properties of the human healthy and smokers' lung tissues (Karimi et al., Tech Health Care 2018). Our results revealed a higher stiffness for the smokers' lung tissues compared to the healthy ones. Here, we aimed to calculate the stresses, pressures, deformations, and kinetic energies in the healthy and smokers' lung tissues during breathing in interaction with the ribs and sternum. To do that, a patient-specific finite element (FE) model of the human lung was established and numerically subjected to an inhale-exhale pressure phase. The FE results revealed a higher pressure and a lower deformation in the smoking lung tissue compared to the healthy one. In addition, the stiffer smoking lung exerted a higher pressure and deformation in the sternum and ribs compared to the healthy lung. Furthermore, the smoking lung displayed a lower kinetic energy compared to the healthy lung and as a result, it transferred a higher amount of energy to the bones, which might increase the chance of bone remodeling and/or fracture during, e.g., coughing. These results have implications for not only understanding of the stresses and deformations induce in the lung tissues among the healthy and smokers during breathing but also for providing a preliminary information for the medical and biomechanical experts to have an assessment of the amount of injury occurs to the lung because of smoking.