Kim M J, Druz W S, Danon J, Machnach W, Sharp J T
J Appl Physiol. 1976 Sep;41(3):369-82. doi: 10.1152/jappl.1976.41.3.369.
Diaphragmatic force-length behavior was assessed in anesthetized dogs using two techniques. One employed measurements in a diaphragm strip with intact nerve and blood supply; the second related transdiaphragmatic pressure (Pdi) to direct estimates of diaphragmatic tension from strain gauge arches during bilateral, tetanic, supramaximal phrenic nerve stimulation. In strip preparations the diaphragm exerted active force at lengths as short as 40% of resting in situ length (Lo), and maximal force was registered at a length averaging 25% greater than Lo. This suggested a broader effective length range for the diaphragm as compared to other skeletal muscles. In the intact preparation both Pdi and directly measured diaphragmatic tension were inversely related to lung volume and when they were used to calculate the diaphragm's effective radius of curvature (r), r was found to change little or decrease at large lung volumes rather than increase as theory would predict. These findings suggest that length tension characteristics outweigh geometric considerations in explaining the diaphragm's function in normal dogs and probably normal men.
采用两种技术评估了麻醉犬的膈肌力-长度行为。一种方法是在具有完整神经和血液供应的膈肌条带上进行测量；另一种方法是在双侧强直性膈神经超强刺激期间，将跨膈压（Pdi）与通过应变片弓直接估算的膈肌张力相关联。在膈肌条带制备中，膈肌在短至静息原位长度（Lo）的40%时就能产生主动力，最大力出现在比Lo平均长25%的长度处。这表明与其他骨骼肌相比，膈肌的有效长度范围更广。在完整的实验准备中，Pdi和直接测量的膈肌张力均与肺容积呈负相关，当用它们来计算膈肌的有效曲率半径（r）时，发现r在大肺容积时变化很小或减小，而不是像理论预测的那样增加。这些发现表明，在解释正常犬以及可能正常人类的膈肌功能时，长度-张力特性比几何因素更为重要。
