Author(s)

Fumio Nogata^1*, Yasunari Yokota², Yoko Kawamura², Hiroyuki Morita³, Yoshihiro Uno⁴, William R. Walsh⁵, Takahiko Kawamura⁶, Nigishi Hotta^7,8, Kenji Kagechika⁹

¹Gifu University, Gifu, Japan.
²Faculty of Engineering, Gifu University, Gifu, Japan.
³Department of General Medicine and General Internal Medicine, Gifu University School of Medicine, Gifu, Japan.
⁴Department of General Medicine, Gifu Prefectural General Medical Center, Gifu, Japan.
⁵Prince of Wales Hospital, University of New South Wales, Kensington, Australia.
⁶Diabetes and Endocrine Internal Medicine, Chubu Rosai Hospital, Nagoya, Japan.
⁷Nagoya University, Nagoya, Japan.
⁸Chubu Rosai Hospital, Nagoya, Japan.
⁹Anamizu General Hospital, Ishikawa, Japan.

Aneurysms can be classified into two main types based on their shape: saccular (spherical) and fusiform (cylindrical). In order to clarify the formation of aneurysms, we analyzed and examined the relationship between external force (internal pressure) and deformation (diameter change) of a spherical model using the Neo-Hookean model, which can be used for hyperelastic materials and is similar to Hooke’s law to predict the nonlinear stress-strain behavior of materials with large deformation. For a cylindrical model, we conducted an experiment using a rubber balloon. In the spherical model, the magnitude of the internal pressure Δp value is proportional to G (modulus of rigidity) and t (thickness), and inversely proportional to R (radius of the sphere). In addition, the maximum pressure Δp (max) is reached when λ (=expanded diameter/original diameter) is approximately 1.2, and the change in diameter becomes unstable (nonlinear change) thereafter. In the cylindrical model, localized expansion occurred at λ = 1.32 (λ = 1.98 when compared to the diameter at internal pressure Δp = 0) compared to the nearby uniform diameter, followed by a sudden rapid expansion (unstable expansion jump), forming a distinct bulge, and the radial and longitudinal deformations increased with increasing Δp, leading to the rupture of the balloon. Both models have a starting point where nonlinear deformation changes (rapid expansion) occur, so quantitative observation of the artery’s shape and size is important to prevent aneurysm formation.

Aneurysm Formation, Pressure-Inflation Characteristics, Elastic Instability, Expansion Signs, Saccular and Fusiform

Nogata, F. , Yokota, Y. , Kawamura, Y. , Morita, H. , Uno, Y. , Walsh, W. , Kawamura, T. , Hotta, N. and Kagechika, K. (2024) Signs of Aneurysm Formation Learned from Rubber Balloon Inflation. Journal of Biosciences and Medicines, 12, 556-571. doi: 10.4236/jbm.2024.1211042.