De Troyer Andre, Cappello Matteo, Meurant Nathalie, Scillia Pierre
Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine, Brussels, Belgium.
J Appl Physiol (1985). 2003 May;94(5):1757-65. doi: 10.1152/japplphysiol.01013.2002.
Expansion of the lung during inspiration results from the coordinated contraction of the diaphragm and several groups of rib cage muscles, and we have previously shown that the changes in intrathoracic pressure generated by the latter are essentially additive. In the present studies, we have assessed the interaction between the right and left hemidiaphragms in anesthetized dogs by comparing the changes in airway opening pressure (DeltaPao) obtained during simultaneous stimulation of the two phrenic nerves (measured DeltaPao) to the sum of the DeltaPao values produced by their separate stimulation (predicted DeltaPao). The measured DeltaPao was invariably greater than the predicted DeltaPao, and the ratio between these two values increased gradually as the stimulation frequency was increased; the ratio was 1.10 +/- 0.01 (P < 0.05) for a frequency of 10 Hz, whereas for a frequency of 50 Hz it amounted to 1.49 +/- 0.05 (P < 0.001). This interaction remained unchanged after the rib cage was stiffened and its compliance was made linear, thus indicating that the load against which the diaphragm works is not a major determinant. However, radiographic measurements showed that stimulation of one phrenic nerve extends the inactive hemidiaphragm toward the sagittal midplane and reduces the caudal displacement of the central portion of the diaphragmatic dome. As a result, the volume swept by the contracting hemidiaphragm is smaller than the volume it displaces when the contralateral hemidiaphragm also contracts. These observations indicate that 1) the left and right hemidiaphragms have a synergistic, rather than additive, interaction on the lung; 2) this synergism operates already during quiet breathing and increases in magnitude when respiratory drive is greater; and 3) this synergism is primarily related to the configuration of the muscle.
吸气时肺的扩张源于膈肌和几组胸廓肌肉的协同收缩，并且我们之前已经表明，后者产生的胸内压变化基本上是累加的。在本研究中，我们通过比较在同时刺激双侧膈神经时获得的气道开口压力变化（ΔPao）（实测ΔPao）与分别刺激双侧膈神经产生的ΔPao值之和（预测ΔPao），评估了麻醉犬左右半膈肌之间的相互作用。实测ΔPao总是大于预测ΔPao，并且随着刺激频率增加，这两个值之间的比率逐渐升高；对于10Hz的频率，该比率为1.10±0.01（P<0.05），而对于50Hz的频率，该比率达到1.49±0.05（P<0.001）。在胸廓变硬且其顺应性变为线性后，这种相互作用保持不变，因此表明膈肌工作时所对抗的负荷不是主要决定因素。然而，影像学测量显示，刺激一侧膈神经会使静止的半膈肌向矢状中平面延伸，并减少膈肌穹窿中央部分的尾侧位移。结果，收缩的半膈肌扫过的容积小于对侧半膈肌也收缩时它所移位的容积。这些观察结果表明：1）左右半膈肌对肺具有协同作用，而非累加作用；2）这种协同作用在安静呼吸时就已存在，并且在呼吸驱动增强时其程度增加；3）这种协同作用主要与肌肉的形态有关。
