Intracuff Pressure and Tracheal Morbidity - Influence of Filling Cuff with Saline during Nitrous Oxide Anesthesia

Background. Diffusion of nitrous oxide into the cuff of the endotracheal tube results in an increase in cuff pressure. Excessive endotracheal tube cuff pressure may impair tracheal mucosal perfusion and cause tracheal damage and sore throat. Filling the cuff of the endotracheal tube with saline instead of air prevents the increase in cuff pressure due to nitrous oxide diffusion. This method was used to test whether tracheal morbidity is related to excess in tracheal cuff pressure during balanced anesthesia. Methods: Fifty patients with American Society of Anesthesiologists physical status I or II were randomly allocated to two groups with endotracheal tube cuffs initially inflated to 20-30 cm H2O with either air (group A) or saline (group S). Anesthesia was maintained with isoflurane and nitrous oxide. At the time of extubation, a fiberoptic examination of the trachea was performed by an independent observer, and abnormalities of tracheal mucosa at the level of the cuff contact area were scored. Patients assessed their symptoms (sore throat, dysphagia, and hoarseness) at the time of discharge from the postanesthesia care unit and 24 h after extubation on a 101-point numerical rating scale. Results. Cuff pressure increased gradually during anesthesia in group A but remained stable in group S. The incidence of sore throat was greater in group A than in group S in the postanesthesia care unit (76 vs. 20%) and 24 h after extubation (42 vs. 12%; P < 0.05). Tracheal lesions at time of extubation were seen in all patients of group A and in eight patients (32%) of group S (P < 0.05). Conclusion: Excess in endotracheal tube cuff pressure during balanced anesthesia due to nitrous oxide diffusion into this closed gas space causes sore throat that is related to tracheal mucosal erosion.