The incidence rate of early onset ventilator-associated pneumonia in the intermittent drainage group ( 13.0 % ) and the continuous drainage group ( 14.6 % ) was significantly lower than that in the control group ( 40.4 % ) , and the difference was statistically significant ( ( 2 ) = 9.914 , 7.978 ;P = 0.002,0.005 ) , but there was no difference between the former 2 groups ( ( 2 ) = 0.056 ; P = 0.812 ) .