明确高呼气末正压（PEEP）条件下肺泡微循环的变化情况以及液体复苏在高PEEP情况下对肺泡微循环的影响。

选用北京当地的15条健康成年杂种狗进行实验，分别观察基线（PEEP 5 cmH₂O，1 cmH₂O=0.098 kPa）、高PEEP（平均动脉压下降≥20 mmHg，1 mmHg=0.133 kPa）及液体复苏后的呼吸、系统循环及肺泡微循环情况，肺泡微循环利用旁流暗视野成像（SDF）技术进行观察、留取视频结果，线下利用AVA3.2软件进行分析，不同条件下的实验数据之间的差异利用Wilcoxon秩和检验进行分析。

高PEEP可导致中心静脉压（CVP）升高（P=0.001）及心输出量（CO）下降（P=0.002），肺泡微循环表现为总微血管数量（TVDa，P=0.036）、灌注血管数量（PVDa，P=0.002）、灌注血管比例（PPVa，P=0.003）、血流状态（MFIa，P=0.002）显著下降，肺泡周围毛细血管密度下降不明显（TVDs，P=0.319）；液体复苏恢复整体循环后，微循环参数均无显著改善。

过高的PEEP水平可导致肺泡微循环的显著恶化，通过液体复苏不能改善由此产生的微循环障碍。

To reveal the changes of alveolar microcirculation in mechanical ventilation with high PEEP and the influence of fluid resuscitation on alveolar microcirculation.

This study was carried in 15 healthy, adult mongrel dogs in Beijing, to observe the breathing, systemic circulation and alveolar microcirculation respectively in baseline(PEEP 5 cmH₂O), high PEEP (MAP dropped more than 20 mmHg, before resuscitation) and high PEEP after fluid resuscitation. The alveolar microcirculation was observed by the SDF(sidestream dark-field, SDF), record videos and then analyzed by software of AVA3.2 off-line, comparisons of experimental data in different conditions was used the Wilcoxon test.

CVP elevated and CO dropped in mechanical ventilation with high PEEP, total vascular density (TVDa, P=0.036), perfused vessel density (PVDa, P=0.002), proportion of perfused vessels (PPVa, P=0.003) and microvascular flow index (MFIa, P=0.002) of alveolar microcirculation were significant reduced, the capillary density surrounding the alveolar decline was not obvious(TVDs, P=0.319). The alveolar microcirculation is not improved after the fluid resuscitation.

Alveolar microcirculation is significantly worsed in mechanical ventilation with high PEEP and fluid resuscitation can not improve the alveolar microcirculation disorders.