Effects of different modes of mechanical ventilation on expression of ?-defensin-2 gene and protein in ventilator-associated pneumonia / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of conventional mechanical ventilation (CMV) and mechanical ventilation with ideal PEEP and permissive hypercapnia (PHY + PEEPi) on expression of ?-defensin-2 (HBD-2) gene and protein in ventilator-associated pneumonia (VAP). Methods Forty-eight male SD rats weighing 280-320 g were randomly divided into 2 groups (1) CMV group (VT = 12 ml? kg-1 , RR = 70bpm, FiO2 = 1.0) (n = 24) and (2) PHY + PEEPi group (VT =6 ml?kg-1 , RR = 90bpm, PEEP = 0.2 kPa, FiO2 = 1,0) (n = 24) . The animals were anesthetized with intraperitoneal 20% urethane 1 ml?100 g-1 , tracheotomized and mechanically ventilated. After being ventilated for 24 h P. aeruginosa (3 ? 108 CFU/ml) 0.2 ml was introduced into trachea to induce pulmonary infection. Three animals were sacrificed at following intervals before and 1.5 h, 3h,6h,12h,3d and 5 d after introduction of P. aeruginosa. Lung tissaes were obtained from middle and lower lobes of left lung for microscopic examination and determination of expression of mRNA of HBD-2 by RT-PCR and HBD-2 protein level by Western blot analysis. Right lung was lavaged and broncho-alveolar lavage fluid (BALF) was collected for bacteriological examination. Results There were significantly more severe pathological changes in the lung in CMV group as compared with PHY + PEEPi group. In CMV group the levels of up-regulation of HBD-2 mRNA and protein expression were significantly lower after 3h than those in PHY + PEEPi group. The positive rate of blood and BALF bacterial culture was also higher in CMV group. The survival rate of PHY + PEEPi group was 76% , significantly higher than that of CMV group (40% ) ( P