Proper insertion depth of endotracheal tubes in adults by topographic landmarks measurements

Study Objective: To evaluate a new method of endotracheal tube (ETT) positioning relative to carina, based on external topographic landmarks. Design: Prospective, randomized, crossover study. Setting: Operating room, university hospital. Patients: 200 American Society of Anesthesiologists (ASA) physical status I-II patients (100 women and 100 men) scheduled for elective surgery with general anesthesia. Interventions: ETT insertion depth was topographically determined by adding the distance measured (in cm) from the right mouth corner to right mandibular angle to the distance measured from the right mandibular angle to a point situated on the center of a line running transversally through the middle of the sternal manubrium. This method was compared to the 21/23 cm insertion depth method. Measurements: ETT position was assessed fiberoptically. The main end point was considered the percentage of ETT tips situated more than 25% higher or lower than a predetermined "best" tip position (4 cm above the carina). Main Results: There were 58.5% ETT tips positioned too closely (<3 cm above the carina) to the carina with the control method and 24% with the study method (P = 0.0001). No ETT tip was too high (>5 cm above the carina). The tip-carina distance was shorter in women (2.7 ± 2.5 vs 3.6 ± 2.2 cm in men P = 0.0001) and in those aged more than 65 years (2.8 ± 2.4 vs 3.4 ± 2.4 cm with age less than 65 years; P = 0.012) only with the 21/23 cm method. Conclusions: With our new ETT positioning method, there were fewer ETTs positioned outside the desired range of distance to carina. Our method may be especially valuable in women and in patients older than 65 years.