Drainage of subglottic secretions decreased the incidence of VAP (P < 0.05). Also type of the pharmacologic medicine for stress ulcer prophylaxis has significant effect on VAP incidence. Among the patients in OTSS and CTSS groups, 20% and 12% developed VAP, respectively. Use of CTSS compared with OTSS did not show statistically significant effect on VAP incidence in multivariate analysis; however, OR (odds ratio) tended to identify OTSS as an exposure factor for the development of VAP (OR = 1.92; CI = 0.45-8.30; = 0.38) compared with the CTSS. Higher levels of APACHE II score, sinusitis and tracheostomy put the patients at the risk of VAP. However, using heat and moisture exchanger (HME) instead of humidifier decreased this risk.