Hubmayr R D, Hill M J, Wilson T A
Thoracic Research Unit, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
J Appl Physiol (1985). 1996 Feb;80(2):522-30. doi: 10.1152/jappl.1996.80.2.522.
The parenchymal marker technique was used to measure regional tidal volumes of samples of lung parenchyma in four open-chest supine dogs. Radiopaque markers that had been implanted in the lower lobe were tracked by biplane video fluoroscopy during sinusoidal volume oscillations at tidal volumes of approximately 20% of total lung capacity and frequencies of 1-40 breaths/min before and after methacholine was administered by aerosol. The volumes of tetrahedrons with apexes at four markers were computed, and sine waves were fit to the data for volume vs. time for each tetrahedron. The ratio of mean regional volume to mean airway pressure decreased by 10-45% after exposure to methacholine. Dynamic lung elastance and resistance of the constricted lungs were larger than control, and both were frequency dependent. Regional elastance and resistance varied considerably among tetrahedrons, and these were also frequency dependent. The data were fit by a model in which tissue elastance was uniform and nearly equal to elastance in the control state, but small-airway resistance was high and variable. We conclude that the lung contracts under bronchoconstriction but that the increased dynamic elastance and resistance of the constricted lung may be primarily the result of nonuniform increased airway resistance at the level of the terminal bronchioles.
采用实质标记技术，对4只开胸仰卧犬肺实质样本的局部潮气量进行测量。通过双平面视频荧光镜观察，在雾化吸入乙酰甲胆碱前后，对植入下叶的不透射线标记物进行追踪，观察其在潮气量约为肺总量20%、频率为1 - 40次/分钟的正弦波容积振荡过程中的情况。计算以四个标记物为顶点的四面体体积，并对每个四面体的体积与时间数据拟合正弦波。暴露于乙酰甲胆碱后，平均局部容积与平均气道压力之比下降了10% - 45%。收缩肺的动态肺弹性和阻力大于对照组，且两者均与频率相关。各四面体之间的局部弹性和阻力差异很大，且这些也与频率相关。数据由一个模型拟合，该模型中组织弹性均匀且几乎等于对照状态下的弹性，但小气道阻力高且可变。我们得出结论，支气管收缩时肺会收缩，但收缩肺动态弹性和阻力增加可能主要是终末细支气管水平气道阻力不均匀增加的结果。
