Habteyes Firdaweke G, Komari S Omid, Nagle Anna S, Klausner Adam P, Heise Rebecca L, Ratz Paul H, Speich John E
Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA 23284, United States.
Department of Surgery, Virginia Commonwealth University, Richmond, VA 23298, United States.
J Mech Behav Biomed Mater. 2017 Jul;71:192-200. doi: 10.1016/j.jmbbm.2017.02.020. Epub 2017 Feb 20.
Tension-sensitive nerves in the bladder wall are responsible for providing bladder sensation. Bladder wall tension, and therefore nerve output, is a function of bladder pressure, volume, geometry and material properties. The elastic modulus of the bladder is acutely adjustable, and this material property is responsible for adjustable preload tension exhibited in human and rabbit detrusor muscle strips and dynamic elasticity revealed during comparative-fill urodynamics in humans. A finite deformation model of the bladder was previously used to predict filling pressure and wall tension using uniaxial tension test data and the results showed that wall tension can increase significantly during filling with relatively little pressure change. In the present study, published uniaxial rabbit detrusor data were used to quantify regulated changes in the elastic modulus, and the finite deformation model was expanded to illustrate the potential effects of elasticity changes on pressure and wall tension during filling. The model demonstrates a shift between relatively flat pressure-volume filling curves, which is consistent with a recent human urodynamics study, and also predicts that dynamic elasticity would produce significant changes in wall tension during filling. The model results support the conclusion that acute regulation of bladder elasticity could contribute to significant changes in wall tension for a given volume that could lead to urgency, and that a single urodynamic fill may be insufficient to characterize bladder biomechanics. The model illustrates the potential value of quantifying wall tension in addition to pressure during urodynamics.
膀胱壁中的张力敏感神经负责传递膀胱感觉。膀胱壁张力，进而神经输出，是膀胱压力、容积、几何形状和材料特性的函数。膀胱的弹性模量可快速调节，这种材料特性导致人和兔逼尿肌条中出现可调节的预负荷张力，以及在人体比较充盈尿动力学期间揭示的动态弹性。先前使用膀胱的有限变形模型，利用单轴拉伸试验数据预测充盈压力和壁张力，结果表明，在充盈过程中，壁张力可在压力变化相对较小的情况下显著增加。在本研究中，利用已发表的兔逼尿肌单轴数据来量化弹性模量的调节变化，并扩展有限变形模型以说明弹性变化对充盈过程中压力和壁张力的潜在影响。该模型显示了相对平坦的压力-容积充盈曲线之间的转变，这与最近一项人体尿动力学研究一致，并且还预测动态弹性会在充盈过程中导致壁张力发生显著变化。模型结果支持以下结论：膀胱弹性的急性调节可能导致给定容积下壁张力的显著变化，进而引发尿急，并且单次尿动力学充盈可能不足以表征膀胱生物力学特性。该模型说明了在尿动力学过程中除了压力之外量化壁张力的潜在价值。
