Gauthier S P, Wolfson M R, Deoras K S, Shaffer T H
Department of Physiology and Pediatrics, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Pediatr Res. 1992 Feb;31(2):157-62. doi: 10.1203/00006450-199202000-00013.
Five generations of airways from 15 preterm lambs of 130-137 d (90% term) gestation were studied to investigate the effect of generation on structure-function of preterm airways. Airway rings were measured to determine the internal radius (r), and wall thickness (t). The ratio r/t was then calculated as a morphometric index used in the determination of wall stress. Airway rings from each generation were placed in tissue baths to compare passive, active, and total force development. Contraction via membrane depolarization (KCl) and muscarinic receptor stimulation (acetylcholine) were evaluated. As r and t decreased, r/t declined by a factor of 3.48 down the generations. At the optimal length for active force development, the passive, active, and total stresses decreased significantly as a function of generation. The receptor-mediated response to acetylcholine was significantly less in generations 0, 1, and 2 than in generations 3 and 4. No differences were found among the various generations in contractility as measured by the response to KCl. These data suggest that based on the interrelationship between airway morphometry and force development the trachea is exposed to greater wall stress than the lower airways during continuous positive airway pressure. Taken together, these data may help to explain the structural changes, such as tracheomegaly, as well as the physiologic changes in airway reactivity seen in the premature infant after mechanical ventilation.
对15只妊娠130 - 137天（足月的90%）的早产羔羊的五代气道进行了研究，以探讨代数对早产气道结构 - 功能的影响。测量气道环以确定内径（r）和壁厚（t）。然后计算r/t比值，作为用于确定壁应力的形态学指标。将每一代的气道环置于组织浴中，以比较被动、主动和总力的发展。评估通过膜去极化（氯化钾）和毒蕈碱受体刺激（乙酰胆碱）引起的收缩。随着r和t减小，r/t沿代际下降了3.48倍。在主动力发展的最佳长度下，被动、主动和总应力随代际显著降低。0代、1代和2代对乙酰胆碱的受体介导反应明显低于3代和4代。通过对氯化钾的反应测量的各代之间在收缩性方面未发现差异。这些数据表明，基于气道形态学与力发展之间的相互关系，在持续气道正压通气期间，气管比下呼吸道承受更大的壁应力。综上所述，这些数据可能有助于解释早产婴儿机械通气后出现的结构变化，如气管扩大，以及气道反应性的生理变化。
