BackgroundThe oral mucosa is an important defense barrier to penetration of microorganisms. Thus, changes in the oral epithelium might indicate risk for infection in intensive care patients receiving mechanical ventilation. Objective To evaluate the oral mucosa of intensive care patients who did or did not receive mechanical ventilation by using liquid-base exfoliative cytology. Methods The sample consisted of 3 groups: 27 patients admitted to intensive care during a 7-to 14-day period who received mechanical ventilation, 29 patients admitted during the same period who did not receive mechanical ventilation, and 27 healthy patients who had no lesions in the mouth. For all 3 groups, samples were collected from the buccal mucosa by using cytology brushes. Smears were applied to glass slides before Papanicolaou staining and were codified for blind analyses by a cytopathologist. Kruskal-Wallis and Dunn tests were used to analyze the results. Results Patients receiving mechanical ventilation had higher prevalence and intensity of karyomegaly, perinuclear halos, cell keratinization, deep cells, and leukocyte infiltrates than did patients in the other 2 groups (P < .05). No significant differences were observed between the control group and the group who did not receive mechanical ventilation. Conclusions Liquid-base exfoliative cytology can be used to detect preclinical alterations in the oral mucosa. Patients treated with mechanical ventilation are vulnerable to infections, and oral care may be valuable in their prognosis.