不同呼气末正压与潮气量对离体损伤鼠肺泡稳定性的影响

目的采用肺泡显微镜观察不同的PEEP-VT组合的机械通气模式对无灌注损伤鼠肺及正常鼠肺的肺泡动力学的影响。方法游离肺后,损伤组采用Tween-20灌注制作损伤肺模型。损伤肺与正常肺采用三种不同水平的PEEP（5、10、20 cmH2O,1 cmH2O=0.098 kPa）及三种不同的VT（6、10、15 ml/kg）共9种不同的PEEP-Vt组合的机械通气模式。采用肺泡显微镜观察肺泡动力学。结果正常肺的肺泡动力学十分稳定（I-E%为3.2%±11.0%）,各组之间差异无统计学意义（P〉0.01）。而损伤肺中,只有机械通气采用的PEEP为20 cmH2O时,肺泡保持稳定性（I-E%为0.2%±9.3%）;而当采用5 cm、10 cmH2O PEEP时,损伤肺的肺泡动力学不稳定I-E%分别为100%±0%及30.7%±16.8%。结论不论机械通气采用何种PEEP和VT组合,正常肺的肺泡动力学十分稳定。而对于损伤肺,只有PEEP为20 cmH2O时肺泡动力学稳定,而采用其他两种PEEP,肺泡稳定性有显著改变。

Effect of positive end-expiratory pressure and tidal volume on alveolar stability in isolated injured rat lungs

Objective To investigate the effect of positive end-expiratory pressure（ PEEP） and tidal volume（ Tv） on alveolar stability in isolated rat lungs. Methods The lungs w ere isolated from female Wistar rats and injured by Tw een-20 treatment. The isolated non-perfused normal and injured lungs w ere mechanically ventilated w ith combinations of 3 PEEP settings（ 5,10,20 cmH2O） w ith 3 VT settings（ 6,10,15 ml / kg）. The alveolar stability w as observed by using alveolar microscopy. Results In normal lungs alveolar stability persisted in all PEEP-VT combinations w ith a mean I-E% of 3. 2% ± 11. 0%. In injured lungs alveoli w ere extremely instable at PEEP levels of 5 and 10 cmH2O w ith mean I-E% of 100. 0% ± 0% and 30. 7% ± 16. 8%,respectively; only at a PEEP of 20 cmH2O alveolar stability w ith a mean I-E% of 0. 2% ± 9. 3% w as observed. Conclusion In isolated normal lungs alveolar stability is almost unaffected by PEEP and VT. In isolated injured lungs alveolar stability can reached only at high PEEP level,w hereas low er PEEP levels are associated w ith alveolar instability regardless of the applied tidal volume.