Wang N, Banzett R B, Butler J P, Fredberg J J
Department of Environmental Science and Physiology, Harvard School of Public Health, Boston, MA 02115.
Respir Physiol. 1988 Jul;73(1):111-24. doi: 10.1016/0034-5687(88)90131-4.
We assessed various aerodynamic factors which might influence inspiratory valve function in the avian lung. During inspiration, no flow enters the proximal segments of the ventrobronchi connecting the primary bronchus to cranial sacs. Instead, all flow in the primary bronchus continues through the mesobronchus. This pattern of flow past the ventrobronchi into the mesobronchus is called inspiratory aerodynamic valving. Introducing steady inspiratory flows into simplified plastic models of a bifurcation, we altered geometry, downstream resistance, flow rate and gas density while we measured the resulting flow partitioning between downstream branches. We found that these models did reproduce the inspiratory valving phenomenon. Gas flow rate, gas density and geometry upstream of the bifurcation played important roles in flow partitioning, but the geometry and branching angles of the ventrobronchi did not. These findings are consistent with the idea that convective inertia of the inspiratory gas stream promotes preferential axial flow (Butler et al., 1988) and may be the principal mechanism accounting for inspiratory aerodynamic valving in the avian lung.
我们评估了各种可能影响鸟类肺部吸气瓣膜功能的空气动力学因素。在吸气过程中，没有气流进入连接主支气管与颅气囊的腹支气管近端部分。相反，主支气管中的所有气流继续通过中支气管。这种气流通过腹支气管进入中支气管的模式称为吸气空气动力学瓣膜作用。我们将稳定的吸气气流引入一个分叉的简化塑料模型中，在测量下游分支之间产生的气流分配时，改变了几何形状、下游阻力、流速和气体密度。我们发现这些模型确实再现了吸气瓣膜现象。分叉上游的气体流速、气体密度和几何形状在气流分配中起重要作用，但腹支气管的几何形状和分支角度不起作用。这些发现与吸气气流的对流惯性促进优先轴向流动的观点一致（巴特勒等人，1988年），并且可能是解释鸟类肺部吸气空气动力学瓣膜作用的主要机制。
