Positional relationships between a tracheal diverticulum and the tracheal tube under general anesthesia: a single-center observational and simulation study

Background Incomplete sealing of tracheal diverticula by a tracheal tube cuff during positive-pressure ventilation causes barotrauma but the concrete possibility of incomplete sealing has not been indicated. We aimed to assess the possibility of incomplete sealing in a simulated situation of tracheal intubation for patients with tracheal diverticula with tube fixation where the tracheal tube's vocal cord guide overlaps with the patient's vocal cord.Methods We retrospectively assessed the characteristics of tracheal diverticula based on thoracic computed tomography data in our institution from January 2018 to July 2020. Then, we assessed the structural parameters of three single-lumen tracheal tubes (Parker Flex-Tip [Parker Medical, Bridgewater, CT, USA], Portex Soft Seal [ICU Medical, San Clemente, CA, USA], and Shiley TaperGuard [Medtronic, Dublin, Ireland]; 6.0-8.0 mm inner diameter size) and simulated the positional relationships between tracheal diverticula and the tracheal tube during tracheal intubation where the vocal cord guide overlaps with the patient's vocal cord. We assessed each tube product's possibility of incompletely sealing tracheal diverticula and the possibility of unintended bronchial intubation.Results In 5,854 patients, the prevalence of tracheal diverticula was 5.7%. The mean (SD) length from the vocal cord to the distal end of the tracheal diverticula was 52.2 (12.8) mm. Tracheal tubes with length from the distal end of the tracheal cuff to the vocal cord guide of >= 70 mm had a low risk of incompletely sealing tracheal diverticula (< 5%) and length from the distal end of the tube to the vocal cord guide of <= 95 mm had a low risk of unintended bronchial intubation (< 5%). No products in this study satisfied both outcomes.Conclusions Tube fixation, where the vocal cord guide overlaps with the patient's vocal cord, is associated with risk of incompletely sealing of tracheal diverticula depending on the tube's manufacturer and tube's inner diameter size, although it was not a high risk. The use of small inner diameter sized tube relative to patient's body size is high risk of incomplete sealing of tracheal diverticula.