Effects of airway tree asymmetry on the emergence and spatial persistence of ventilation defects
Effects of airway tree asymmetry on the emergence and spatial persistence of ventilation defects
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DOI：
10.1152/japplphysiol.00881.2013
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发表时间：
2014-08-15
影响因子：
3.3
通讯作者：
Maksym, G. N.
中科院分区：
文献类型：
--
作者：
Leary, D.;Winkler, T.;Maksym, G. N.
非对称性和文献记载，但其对支气管收缩和通气分布的影响尚不清楚。在一系列开创性研究中，Venegas等人已经表明，支气管收缩可能导致计算模型中片状通气的自组织模式，该模型可以解释诱导支气管收缩期间在正电子发射断层扫描图像中观察到的通气不良[通气缺陷（VDFs）]区域。为了研究解剖不对称性对VDFs出现的影响，我们使用了Venegas和Winkler使用不同树开发的对称树计算模型，包括M. Tawhai（奥克兰大学），一棵对称树，以及三棵具有中间不对称性的树（Venegas JG，Winkler T，Musch G，Vidal梅洛MF，Layfield D，Tgavalekos N，Fischman AJ，卡拉汉RJ，Bellani G，Harris RS. Nature 434：777-782，2005和Winkler T，Venegas JG. J Appl Physiol 103：655-663，2007）。比较不同气道平滑肌激活水平下的通气模式、肺阻力（R-L）、肺弹性（E-L）和通气分布熵。我们发现VDEF出现在对称和不对称的树，但VDEF的位置在很大程度上是持久的不对称树，支气管收缩达到稳态比对称树。有趣的是，不对称树中的支气管收缩导致较低的R-L（类似于% 50）和较大的E-L（类似于% 25）。我们发现，VDef普遍是由气道不稳定引起的，但气道分支的不对称性导致了通气中自组织斑块的局部触发，并导致VDef的持续位置。这些发现有助于解释影像学研究中发现的VDFs的出现和持续存在。
Asymmetry and documented, but their effects on bronchoconstriction and ventilation distribution in asthma are unclear. In a series of seminal studies, Venegas et al. have shown that bronchoconstriction may lead to self-organized patterns of patchy ventilation in a computational model that could explain areas of poor ventilation [ventilation defects (VDefs)] observed in positron emission tomography images during induced bronchoconstriction. To investigate effects of anatomic asymmetry on the emergence of VDefs we used the symmetric tree computational model that Venegas and Winkler developed using different trees, including an anatomic human airway tree provided by M. Tawhai (University of Auckland), a symmetric tree, and three trees with intermediate asymmetry (Venegas JG, Winkler T, Musch G, Vidal Melo MF, Layfield D, Tgavalekos N, Fischman AJ, Callahan RJ, Bellani G, Harris RS. Nature 434: 777-782, 2005 and Winkler T, Venegas JG. J Appl Physiol 103: 655-663, 2007). Ventilation patterns, lung resistance (R-L), lung elastance (E-L), and the entropy of the ventilation distribution were compared at different levels of airway smooth muscle activation. We found VDefs emerging in both symmetric and asymmetric trees, but VDef locations were largely persistent in asymmetric trees, and bronchoconstriction reached steady state sooner than in a symmetric tree. Interestingly, bronchoconstriction in the asymmetric tree resulted in lower R-L (similar to%50) and greater E-L (similar to%25). We found that VDefs were universally caused by airway instability, but asymmetry in airway branching led to local triggers for the self-organized patchiness in ventilation and resulted in persistent locations of VDefs. These findings help to explain the emergence and the persistence in location of VDefs found in imaging studies.