Massaro D, Clerch L, Temple D, Baier H
J Clin Invest. 1983 Jun;71(6):1536-43. doi: 10.1172/jci110909.
Low volume ventilation without periodic large inflations leads to diminished alveolar stability and to the accumulation of increased amounts of airway disaturated phosphatidylcholine (DSPC) in large aggregates that sediment at 1,000 g; surfactant in this form lowers surface tension less rapidly than surfactant present in the 1,000-g supernatant fraction. These observations led to the present work in which we tested the notion that alveolar instability may develop in the presence of an undiminished quantity of total airway surfactant, if the amount of surfactant found in the 1,000-g supernatant fraction is diminished. Pulmonary compliance fell and the alveolar-arterial O2 gradient widened in normothermic rats during constant ventilation in the resting tidal volume range, and, in hyperthermic rats (approximately 39 degrees C) similarly ventilated but with the addition of periodic sighs. The total amount of airway DSPC was undiminished in each group, but in each less DSPC was present in the 1,000-g supernatant fraction compared with controls. Alveolar instability and hypoxemia also developed in hyperthermic rats during low volume ventilation without periodic sighs. Although the total amount of airway DSPC was decreased in these rats, enough remained to theoretically form a continuous monomolecular film over the entire alveolar surface at functional residual capacity; however, there was insufficient surfactant in the 1,000-g supernatant fraction to form such a continuous film. These findings demonstrate that the mode of ventilation, and moderate hyperthermia, may lead to decreased alveolar stability despite the presence of normal amounts of airway surfactant, and, by inference, indicate the extracellular form or state of surfactant has an important effect on alveolar stability.
低容量通气且无周期性大潮气量通气会导致肺泡稳定性降低，并使大量聚集的气道不饱和磷脂酰胆碱（DSPC）沉积，这些聚集物在1000g离心力下会沉淀；这种形式的表面活性剂降低表面张力的速度比1000g上清液部分中的表面活性剂要慢。这些观察结果引发了本研究，在本研究中我们测试了这样一种观点，即如果1000g上清液部分中发现的表面活性剂数量减少，那么在气道表面活性剂总量未减少的情况下，肺泡不稳定仍可能会发生。在静息潮气量范围内持续通气的正常体温大鼠中，以及在同样通气但添加了周期性叹息的高温大鼠（约39摄氏度）中，肺顺应性下降，肺泡 - 动脉氧分压差增大。每组气道DSPC的总量未减少，但与对照组相比，每组1000g上清液部分中的DSPC含量均减少。在无周期性叹息的低容量通气期间，高温大鼠也出现了肺泡不稳定和低氧血症。虽然这些大鼠气道DSPC的总量减少了，但理论上仍有足够的量在功能残气量时在整个肺泡表面形成连续的单分子层；然而，1000g上清液部分中没有足够的表面活性剂来形成这样的连续膜。这些发现表明，通气模式和中度高温可能会导致肺泡稳定性下降，尽管气道表面活性剂含量正常，并且由此推断，表明表面活性剂的细胞外形式或状态对肺泡稳定性有重要影响。
