[Exogenous pulmonary surfactant replacement combined with recruitment maneuver in prevention of alveolar derecruitment in rabbits with acute respiratory distress syndrome].

OBJECTIVE: To investigate the effects of exogenous pulmonary surfactant (PS), recruitment maneuver (RM) and the combination of RM with PS in rabbits with acute respiratory distress syndrome (ARDS). METHODS: ARDS models were induced in 28 New Zealand white rabbits by repeated airway lavage with normal warm saline, and the animals were ventilated with volume controlled ventilation [VCV, VT 8 ml/kg, RR 40/min, PEEP 3 cm HO2O (1 cm HO2O = 0.098 kPa)]. All the rabbits were randomly divided by random digit table into 4 groups (n=7 each): a control group, a PS group, a RM group and a PS + RM group. Arterial blood gas analysis, peak inflating pressure (PIP) and static compliance of the respiratory system (Cst) were measured. All the animals were sacrificed at 4h of experimental interventional therapy for the examination of pulmonary pathology. RESULTS: (1) The mean PaO2 in the PS group,the RM group and the PS+ RM group [(234 +/- 42)mm Hg,(231 +/- 17) mm Hg, (253 +/- 52)mm Hg(1 mm Hg = 0.133 kPa), respectively] was significantly higher than that in the control group [(74 +/- 15) mm Hg, F = 84.201, P < 0.01]. The improvement in the PS group and the PS + RM group was stable, but in the RM group, the PaO2 gradually decreased. (2) The PaCO2 in the control group [(56 +/- 11) mm Hg] was significantly higher than that in the PS group and the PS + RM group [(46 +/- 10) mm Hg, (46 +/- 10) mm Hg, respectively, F = 4.234, P < 0.05]. The PaCO2 in the RM group gradually increased. (3) The respective PIP in the 4 groups was (33 +/- 2), (23 +/- 1), (24 +/- 2), (22 +/- 1) cm H2O; Cst was (1.1 +/- 0.3), (1.7 +/- 0.3), (1.5 +/- 0.1), (1.9 +/- 0.4) ml/cm H2O. Compared with the baseline and with the control group, PIP and Cst in the 3 intervention groups improved significantly (F = 74.911, 15.863, P < 0.01). The improvement of Cst in the PS + RM group was better than that in the RM group (q = 2.58, P < 0.05). (4)The lung injury score in the PS group, the RM group and the PS +RM group (3.9 +/- 0.8, 6.1 +/- 0.7, 4.2 +/- 0.6, respectively) were significantly lower than that in the control group (13.5 +/- 0.7, F = 369.6, P < 0.01). The lung injury in the RM group was more severe than that in the PS and PS + RM group (q = 6.35, 5.70, all P < 0.01). CONCLUSIONS: Exogenous PS replacement therapy can improve oxygenation and the compliance of the respiratory system in ARDS rabbits . RM can also improve oxygenation and lung mechanics temporarily, but it may induce ventilator associated lung injury(VALI). PS replacement combined with RM therapy can alleviate VALI and is more effective in improving oxygenation and lung mechanics.