Wilson T A, De Troyer A
Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis 55455.
J Appl Physiol (1985). 1992 Dec;73(6):2283-8. doi: 10.1152/jappl.1992.73.6.2283.
The chest wall is modeled as a linear system for which the displacements of points on the chest wall are proportional to the forces that act on the chest wall, namely, airway opening pressure and active tension in the respiratory muscles. A standard theorem of mechanics, the Maxwell reciprocity theorem, is invoked to show that the effect of active muscle tension on lung volume, or airway pressure if the airway is closed, is proportional to the change of muscle length in the relaxation maneuver. This relation was tested experimentally. The shortening of the cranial-caudal distance between a rib pair and the sternum was measured during a relaxation maneuver. These data were used to predict the respiratory effect of forces applied to the ribs and sternum. To test this prediction, a cranial force was applied to the rib pair and a caudal force was applied to the sternum, simulating the forces applied by active tension in the parasternal intercostal muscles. The change in airway pressure, with lung volume held constant, was measured. The measured change in airway pressure agreed well with the prediction. In some dogs, nonlinear deviations from the linear prediction occurred at higher loads. The model and the theorem offer the promise that existing data on the configuration of the chest wall during the relaxation maneuver can be used to compute the mechanical advantage of the respiratory muscles.
胸壁被建模为一个线性系统，在该系统中，胸壁上各点的位移与作用在胸壁上的力成正比，这些力即气道开口压力和呼吸肌中的主动张力。运用力学中的一个标准定理——麦克斯韦互易定理，来表明主动肌张力对肺容积的影响，或者如果气道关闭时对气道压力的影响，与松弛动作中肌肉长度的变化成正比。这种关系通过实验进行了验证。在松弛动作期间测量一对肋骨与胸骨之间头-尾距离的缩短情况。这些数据被用于预测施加在肋骨和胸骨上的力的呼吸效应。为了验证这一预测，向肋骨对施加一个头向力，并向胸骨施加一个尾向力，模拟胸骨旁肋间肌主动张力施加的力。在肺容积保持恒定的情况下，测量气道压力的变化。测量得到的气道压力变化与预测结果吻合良好。在一些狗身上，在较高负荷下出现了与线性预测的非线性偏差。该模型和定理表明，在松弛动作期间关于胸壁构型的现有数据有望用于计算呼吸肌的机械优势。
