Stress ulcer prophylaxis is proposed to be a risk factor due to the alkalinization of gastric content. The effect of stress ulcer prophylaxis with H 2 -antagonists or antacids on VAP is still controversial. In some studies [145, 146] , the use of sucralfate was associated with a decreased incidence of VAP, however the other reports did not support this [147, 148] . Also, H 2 -antagonists are more efficient for anti-ulcer prophylaxis than the sucralfate [148] . Therefore, the choice of agent for prophylaxis should be done according to the patient and cost-effectiveness.