Lambert R K, Paré P D, Okazawa M
Institute of Fundamental Sciences-Physics, Massey University, Palmerston North, 5331 New Zealand.
J Appl Physiol (1985). 2001 Jun;90(6):2041-7. doi: 10.1152/jappl.2001.90.6.2041.
We have observed that small, membranous bronchioles from rabbits, in which the smooth muscle is not activated, experience a critical elastic buckling involving the whole airway wall during deflation of the lung. This implies that, at some point during the deflation, the airway wall goes from being in a state of tension to a state of compression. At the transition, there is neither net tension nor net compression in the wall, and the transmural pressure difference must, therefore, be zero. Thus at this point, the pressure difference across the muscle that results from the passive stress in the muscle is just balanced by the pressure difference across the folded mucosal membrane. We estimated the muscle stress, and hence the pressure across the muscle, from published data on rabbit trachealis (Opazo-Saez A and Paré PD, J Appl Physiol 77: 1638-1643, 1994) and equated this to the pressure across the folded membrane. By using a theoretical prediction of this pressure (Lambert RK, Codd SL, Alley MR, and Pack RJ, J Appl Physiol 77: 1206-1216, 1994), together with the results of our morphometric measurements on these airways, we estimated that the flexural rigidity of the folding membrane in peripheral rabbit airways is of the order of 10(-12) Pa x m3. This value implies that, in these airways, membrane folding provides significant resistance to airway smooth muscle shortening.
我们观察到，来自兔子的小型膜性细支气管，其中平滑肌未被激活，在肺萎陷期间会经历涉及整个气道壁的临界弹性屈曲。这意味着，在萎陷过程中的某个时刻，气道壁从张力状态转变为压缩状态。在转变过程中，壁内既没有净张力也没有净压缩，因此跨壁压差必须为零。因此，在这一点上，由肌肉中的被动应力产生的跨肌肉压差正好被折叠黏膜上的压差所平衡。我们根据已发表的关于兔气管肌的数据（奥帕佐 - 塞斯A和帕雷PD，《应用生理学杂志》77: 1638 - 1643, 1994）估算了肌肉应力，进而估算了跨肌肉的压力，并将其与跨折叠膜的压力相等同。通过使用对该压力的理论预测（兰伯特RK、科德SL、艾利MR和帕克RJ，《应用生理学杂志》77: 1206 - 1216, 1994），结合我们对这些气道进行的形态测量结果，我们估算出兔外周气道中折叠膜的弯曲刚度约为10^(-12) 帕·立方米。这个值意味着，在这些气道中，膜折叠对气道平滑肌缩短提供了显著的阻力。
