Hoppin F G, Hughes J M, Mead J
J Appl Physiol Respir Environ Exerc Physiol. 1977 May;42(5):773-81. doi: 10.1152/jappl.1977.42.5.773.
Dog airways in situ are longer and extend more with inflation than when dissected out. The associated deformation of the parenchyma, from considerations of elasticity, appears to be small. The associated axial forces, to the extent they are transmitted along the tree, are governed by branching angles. Overall, average angles are such as would maintain constant axial stress along the tree and thus favor symmetrical lengthening. But locally, angles indicate considerable variation of transmitted stresses. Since radiography shows relatively homogeneous lengthening, we infer powerful local axial stabilization. In confirmation, dog airways were much less extended by locally applied forces in situ than excised. Do forced expirations apply substantial axial forces? In one subjects, during forced expiration, airway pressure fell abruptly near the carina but calculations showed relatively small axial forces applied to the airway. However, we speculate that large forces may be applied by airway plugs. We conclude that parenchyma stabilizes airway length against variably transmitted axial forces, and, perhaps, forces on airway plugs.
犬原位气道比解剖分离出的气道更长，且充气时伸展得更多。从弹性角度考虑，实质组织的相关变形似乎很小。相关的轴向力，就其沿气道树传递的程度而言，受分支角度的控制。总体而言，平均角度能使气道树沿轴向保持恒定应力，从而有利于对称延长。但在局部，角度表明传递应力存在相当大的变化。由于X射线摄影显示延长相对均匀，我们推断存在强大的局部轴向稳定作用。经证实，犬原位气道在局部施加力时的伸展程度远小于切除后的气道。用力呼气时会施加大量轴向力吗？在一名受试者中，用力呼气时，隆突附近的气道压力突然下降，但计算表明施加到气道的轴向力相对较小。然而，我们推测气道阻塞物可能会施加较大的力。我们得出结论，实质组织可稳定气道长度，以抵抗轴向力的可变传递，或许还能抵抗气道阻塞物施加的力。
