Pulmonary impedance and alveolar instability during injurious ventilation in rats
Pulmonary impedance and alveolar instability during injurious ventilation in rats
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DOI：
10.1152/japplphysiol.01339.2004
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发表时间：
2005-08-01
影响因子：
3.3
通讯作者：
Nieman, GF
中科院分区：
文献类型：
--
作者：
Allen, GB;Pavone, LA;Nieman, GF
长期以来，急性损伤肺中的机械紊乱在很大程度上被归因于肺泡水平机械功能的改变。然而，这还没有被直接证明，所以我们在过度通货膨胀损伤的大鼠模型中研究了这个问题。开胸手术后，大鼠采用1)高潮气量(VT)或2)低潮气量(VT)并周期性深度充气(DIS)的机械通气。每分钟用强迫振荡法测量肺阻抗，由此计算出弹性(H)和滞后(ETA)。胸膜下肺泡每隔15分钟用活体视频显微镜成像一次。在吸气峰和呼气末测量单个肺泡横截面积，并以百分比变化作为肺泡不稳定的指标(%I-E Delta)。低VT从未导致%I-E Delta的增加，但确实导致了进行性肺不张，这与H的增加相吻合，但不是ETA的增加。DI逆转低VT所致的肺不张，使H恢复到基线水平。高VT 30min时，%I-E Delta、H和Eta均开始升高，DI对此无明显影响。我们的结论是，H和ETA的同时增加反映了肺泡不稳定形式的肺损伤，而在低VT时H的单独和可逆的增加仅仅反映了肺泡的脱屑。
The mechanical derangements in the acutely injured lung have long been ascribed, in large part, to altered mechanical function at the alveolar level. This has not been directly demonstrated, however, so we investigated the issue in a rat model of overinflation injury. After thoracotomy, rats were mechanically ventilated with either 1) high tidal volume (VT) or 2) low VT with periodic deep inflations (DIs). Forced oscillations were used to measure pulmonary impedance every minute, from which elastance (H) and hysteresivity (eta) were derived. Subpleural alveoli were imaged every 15 min using in vivo video microscopy. Cross-sectional areas of individual alveoli were measured at peak inspiration and end exhalation, and the percent change was used as an index of alveolar instability (%I-E Delta). Low VT never led to an increase in %I-E Delta but did result in progressive atelectasis that coincided with an increase in H but not eta. DI reversed atelectasis due to low VT, returning H to baseline. %I-E Delta, H, and eta all began to rise by 30 min of high VT and were not reduced by DI. We conclude that simultaneous increases in both H and eta are reflective of lung injury in the form of alveolar instability, whereas an isolated and reversible increase in H during low VT reflects merely derecruitment of alveoli.