Can tidal breathing with deep inspirations of intact airways create sustained bronchoprotection or bronchodilation?
Can tidal breathing with deep inspirations of intact airways create sustained bronchoprotection or bronchodilation?
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DOI：
10.1152/japplphysiol.00009.2013
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发表时间：
2013-08-01
影响因子：
3.3
通讯作者：
Lutchen, Kenneth R.
中科院分区：
文献类型：
--
作者：
Harvey, Brian C.;Parameswaran, Harikrishnan;Lutchen, Kenneth R.
由于呼吸而施加在气道平滑肌上的波动力被认为可以调节体内的高反应性。然而，最近的动物和人类离体气道研究表明，围绕固定平均值的典型呼吸大小跨壁压 (Ptm) 振荡对于减轻气道收缩是无效的。为了帮助理解这种差异，我们假设 Ptm 振荡能够产生与气道平滑肌条研究中观察到的相同程度的支气管扩张，需要施加比预期在体内发生的更大的应变。首先，我们从模拟 5 cmH(2)O 正常功能残气量的 Ptm 向静态收缩气道施加越来越大幅度的 Ptm 振荡。潮汐式振荡 (5-10 cmH(2)O) 施加 4.9 +/- 2.0% 应变，并导致 11.6 +/- 4.8% 恢复，而模拟每次呼吸深吸气的 Ptm 振荡 (5-30 cmH(2)O) 实现 62.9 +/- 12.1% 恢复。然后从 Ptm = 1 cmH(2)O 开始应用这些相同的 Ptm 振荡，导致每个振荡幅度的应变大约加倍。当施加极端压力时，我们观察到完全恢复。结合这两个数据集，我们发现应变和最终恢复之间存在线性关系。最后，我们比较了收缩前后 Ptm 振荡与仅在收缩后施加的 Ptm 振荡的影响，发现两种载荷条件对收缩具有相似的影响。我们的结论是，虽然施加到气道壁的足够大的应变能够产生显着的支气管扩张，但实现这些应变所需的 Ptm 振荡预计不会在体内发生。
Fluctuating forces imposed on the airway smooth muscle due to breathing are believed to regulate hyperresponsiveness in vivo. However, recent animal and human isolated airway studies have shown that typical breathing-sized transmural pressure (Ptm) oscillations around a fixed mean are ineffective at mitigating airway constriction. To help understand this discrepancy, we hypothesized that Ptm oscillations capable of producing the same degree of bronchodilation as observed in airway smooth muscle strip studies requires imposition of strains larger than those expected to occur in vivo. First, we applied increasingly larger amplitude Ptm oscillations to a statically constricted airway from a Ptm simulating normal functional residual capacity of 5 cmH(2)O. Tidal-like oscillations (5-10 cmH(2)O) imposed 4.9 +/- 2.0% strain and resulted in 11.6 +/- 4.8% recovery, while Ptm oscillations simulating a deep inspiration at every breath (5-30 cmH(2)O) achieved 62.9 +/- 12.1% recovery. These same Ptm oscillations were then applied starting from a Ptm = 1 cmH(2)O, resulting in approximately double the strain for each oscillation amplitude. When extreme strains were imposed, we observed full recovery. On combining the two data sets, we found a linear relationship between strain and resultant recovery. Finally, we compared the impact of Ptm oscillations before and after constriction to Ptm oscillations applied only after constriction and found that both loading conditions had a similar effect on narrowing. We conclude that, while sufficiently large strains applied to the airway wall are capable of producing substantial bronchodilation, the Ptm oscillations necessary to achieve those strains are not expected to occur in vivo.