Fig. 4

a Lengths from the vocal cord to the distal end of tracheal diverticula and its empirical cumulative distribution function. When the tracheal tube was fixed where the line of the vocal cord guide overlapped with the patient’s vocal cord and the tracheal tube’s length from the distal end of the tracheal cuff to the vocal cord guide of was 60 mm (e.g., Parker and Portex products as a 7.0-mm inner diameter), 85.3% of tracheal diverticula were considered to be sealed completely by the tracheal cuff which is located distal to the tracheal diverticula, whereas 14.7% were sealed incompletely and at risk of receiving positive-pressure ventilation. b Tracheal length and its empirical cumulative distribution function. When the length from the distal end of the tube to the vocal cord guide was 105 mm (e.g., Shiley products as an inner diameter of 7.0 mm), 12.6% of tracheas were at risk of receiving unintended bronchial intubation