Objective: To investigate the effects of positive end-expiratory pressure (PEEP) ventilation upon respiratory function and lung surfactant protein B (SP-B)/SP-C in seawater respiratory distress syndrome (SW-RDS) rabbit.
Methods: Twenty-four female New Zealand rabbits were randomly equally divided into three groups:conventional mechanical ventilation (CMV) group, PEEP group, and control group. After anesthesia and tracheal intubation followed by 20 minutes of CMV, SW-RDS model was established by lung perfusion of artificial seawater through tracheal intubation. Then the CMV group ventilated for 6 hours (each parameter unchanged); PEEP group ventilated with PEEP of 8 cm H2O for 2 hours based on prior parameters and subsequently with CMV for 4 hours; control group without ventilation after modeling. Oxygenation indices and lung compliance were continuously monitored during ventilation. After ventilation, the rabbits in study groups were sacrificed while those dying a natural death in the control group selected. Bronchoalveolar lavage fluid of the left lung was collected to determine the alveolar surface tension and the right lung was harvested to measure the mRNA expression of SP-B/SP-C by real-time PCR as well as SP-B protein by Western blotting.
Results: After modeling, the data of lung compliance and oxygenation indices became significantly worse in every group but without statistical difference in three groups. All rabbits in control group died within 15 minutes of ventilator withdrawal. After receiving PEEP ventilation for 30 minutes, these indices significantly improved compared with CMV group in which there was no significant change of the indices (P < 0.05). Minimal alveolar surface tension in CMV group (mN/m, 30.8 +/- 6.3) was greater than in PEEP group (21.1 +/- 4.4, P < 0.05) and control group (23.6 +/- 4.6, P < 0.05); SP-B/SP-C mRNA relative expression (0.37 +/- 0.15/0.60 +/- 0.19) and SP-B relative protein abundance (0.38 +/- 0.17) in CMV group were obviously lower than in PEEP group (0.73 +/- 0.15/0.92 +/- 0.40, 0.52 +/- 0.22, P < 0.05).
Conclusions: PEEP ventilation can improve the oxygenation indices and lung compliance in SW-RDS animals. And such an effect is correlated with both the mRNA expressions of SP-B/SP-C and mechanical distension.