Diaphragm curvature modulates the relationship between muscle shortening and volume displacement.
Diaphragm curvature modulates the relationship between muscle shortening and volume displacement.
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隔膜曲率调节肌肉缩短和容量位移之间的关系。
DOI：
10.1152/ajpregu.00673.2010
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Boriek,AladinM
中科院分区：
文献类型：
--
作者：
Greybeck,BradJ;Wettergreen,Matthew;Hubmayr,RolfD;Boriek,AladinM
在生理性自主呼吸动作期间，隔膜在保持曲率的同时置换体积。然而，在最大横膈膜激活时，曲率急剧减小。我们测试的假设，膈肌缩短和体积位移（VD）之间的关系是非线性的，曲率是这种关系的决定因素。将不透射线标记物通过手术放置在6只犬膈肌肋中部区域的3根相邻肌纤维上。使用双平面荧光透视确定三维位置，并在自主呼吸（SB）、气道阻塞后肺容量范围从功能残气量（FRC）到总肺容量的自主吸气努力以及在相同肺容量的双侧最大膈神经刺激期间，计算俯卧位和仰卧位时的膈肌VD、曲率和肌肉缩短。在仰卧位的狗，隔膜VD是大约两到三倍更大的最大膈神经刺激期间比SB。VD的肌肉缩短的贡献非线性增加与独立的姿势与水平的隔膜激活。在次最大膈肌激活期间，由于俯卧和仰卧姿势中的膈肌曲率的恒定性，贡献基本上是线性的。然而，在肌肉缩短值大于40%（ΔL/LFRC）的最大双侧膈神经刺激期间曲率的突然损失导致肌肉缩短对膈肌VD的贡献的非线性增加，这伴随着膈肌曲率的非线性变化。我们得出结论，膈肌缩短和VD之间的非线性关系，部分是由于在极端肌肉缩短的曲率损失。
During physiological spontaneous breathing maneuvers, the diaphragm displaces volume while maintaining curvature. However, with maximal diaphragm activation, curvature decreases sharply. We tested the hypotheses that the relationship between diaphragm muscle shortening and volume displacement (VD) is nonlinear and that curvature is a determinant of such a relationship. Radiopaque markers were surgically placed on three neighboring muscle fibers in the midcostal region of the diaphragm in six dogs. The three-dimensional locations were determined using biplanar fluoroscopy and diaphragm VD, curvature, and muscle shortening were computed in the prone and supine postures during spontaneous breathing (SB), spontaneous inspiration efforts after airway occlusion at lung volumes ranging from functional residual capacity (FRC) to total lung capacity, and during bilateral maximal phrenic nerve stimulation at those same lung volumes. In supine dogs, diaphragm VD was approximately two- to three-fold greater during maximal phrenic nerve stimulation than during SB. The contribution of muscle shortening to VD nonlinearly increases with level of diaphragm activation independent of posture. During submaximal diaphragm activation, the contribution is essentially linear due to constancy of diaphragm curvature in both the prone and supine posture. However, the sudden loss of curvature during maximal bilateral phrenic nerve stimulation at muscle shortening values greater than 40% (ΔL/LFRC) causes a nonlinear increase in the contribution of muscle shortening to diaphragm VD, which is concomitant with a nonlinear change in diaphragm curvature. We conclude that the nonlinear relationship between diaphragm muscle shortening and its VD is, in part, due to a loss of its curvature at extreme muscle shortening.