肺泡复张后不同通气模式和自主呼吸对防止肺泡再萎陷的实验研究

目的探讨肺泡复张后不同通气模式和自主呼吸在防止肺泡再萎陷中的作用。方法选择健康杂种犬18只,建立油酸所致急性呼吸窘迫综合征（ARDS）模型,行容积控制通气（VCV）,呼气末正压（PEEP）16cmH2O,潮气量（VT）10ml／kg,通气频率30次／min,稳定后作为基础状态。以压力控制通气（PCV,PEEP35cmH2O,PCV15cmH2O,持续60s）行肺泡复张（RM）,分为3组：VCV组（VCV通气,VT15ml／kg）,PCV组（PCV通气,调节压力控制水平使VT保持在15ml／kg）和sB组（PCV通气,保留一定程度的自主呼吸,调节压力控制水平使VT保持在15ml／kg）。3组通气频率（20次／min）、PEEP（10cmH2O）和吸／呼比（1：2）均相同。观察4h后处死动物。结果VCV组、PCV组及SB组低位拐点分别为（16．1±1．9）cmH2O,（17．4±1．5）cmH2O和（17．1±1．6）cmH2O。在使用肺泡复张后,VCV组PaO2维持在与基础状态相近的水平,而PCV组和SB组PaO2显著高于基础状态。与VCV组相比,SB组PaO2在第30min明显增高（P〈0．05）,肺内分流在第5、30与60min有明显降低趋势（P值分别为0．077、0．058、0．076）。（3）与基础状态相比,肺泡复张后各组平台压及平均气道压均明显降低,其中sB组平台压明显低于VCV组（P〈0．05）,平均气道压从第120min直至实验结束均明显低于其他两组（P〈0．05）。结论在肺泡复张后选用PCV并保留一定程度的自主呼吸,能弥补较低PEEP在防止肺泡再萎陷方面的不足,较VCV更有效、安全。

The effects of different ventilatory modes and spontaneous breathing after recruitment maneuver in acute respiratory distress syndrome. Experiment with dogs

OBJECTIVE: To investigate the role of different ventilatory modes and spontaneous breathing (SB) in prevention of derecruitment in acute respiratory distress syndrome (ARDS). METHODS: Eighteen dog ARDS models were established by injection of oleic acid into the central vein and ventilated with volume controlled ventilation (VCV,) with the positive end expiratory pressure (PEEP) of 16 cm H(2)O, tidal volume (V(T)) of 10 ml/kg, and respiratory rate (RR) of 30 bpm, and the steady state in this mode was defined as baseline (0 min). After the baseline state was reached, all dogs accepted recruitment maneuver (RM) in pressure controlled ventilation (PCV) mode at the level of 15 cm H(2)O and PEEP of 35 cm H(2)O for 1 min, and then assigned into three groups and ventilated for 4 hs: VCV group (VCV with V(T) of 15 ml/kg), PCV group in which the peak inspiratory airway pressure was adjusted for keeping 15 ml/kg of V(T), and SB grouping which PCV with SB activity and inspiratory airway pressure were adjusted for keeping 15 ml/kg of V(T). PEEP of 10 cm H(2)O, RR of 20 bpm, and inspiratory/expiratory ratio of 1/2 were kept for all animals. Four hours later the dogs were killed and their lungs were taken out. RESULTS: (1) The lower inflection points were identified as 16.1 +/- 1.9, 17.4 +/- 1.5, and 17.1 +/- 1.6 cm H(2)O for the VCV, PCV, and SB group respectively. (2) After RM, the PaO(2) levels of the PCV and SB groups were kept higher than baseline, but the PaO(2) level was as same as that in the baseline state in the VCV group. Compared with the VCV group, higher PaO(2) the PaO(2) level 30 min after RM in the SB group was found (P < 0.05). The intrapulmonary shunt 5 min, 30 min and 1 hr after RM in the SB group were all lower than those in the VCP group, however, not significantly (P = 0.077, 0.058, 0.076). (3) Compared with baseline levels, the plateau pressure and mean airway pressure in all animals were decreased significantly after RM. The plateau pressure in the SB group was significantly lower than that in the VCV group (P < 0.05). CONCLUSION: PCV with spontaneous breathing activity can offset the effect of antiderecruitment for lower PEEP; it would be more safe and effective than VCV.