There was significant difference in duration of invasive mechanical ventilation -LSB- @ ( @ , @ ) days vs. @ ( @ , @ ) days , Z = -@ , P = @ -RSB- , duration of total mechanical ventilation ( @ days vs. @ days , t = -@ , P = @ ) , and length of ICU stay ( @ days vs. @ days , t = -@ , P = @ ) between sequential group and control group , but there was no significant differences in the incidence of VAP -LSB- @ % ( @/@ ) vs. @ ( @/@ ) , ( @ ) = @ , P = @ -RSB- and mortality rate -LSB- @ % ( @/@ ) vs. @ % ( @/@ ) , P = @ -RSB- .