Intubation guide marks for correct tube placement. A clinical study.

The tracheas of 140 adult patients were intubated with either TFX or Portex tracheal tubes. Guide marks were printed at variable distances proximal to the tube cuffs, and during intubation the guide mark was positioned at the level of the vocal cords. The distance between the bevel end of the tube and the carina was determined with a fibreoptic bronchoscope. The mean distance between the tip of the tracheal tube and the carina varied between 3.7 and 4.1 cm with the head in the neutral position. The tip of the tracheal tube approaches the carina by a mean distance of 0.5 cm when the head is moved from the extended position to the neutral position. It is recommended that a guide mark be placed 2.5 cm from the proximal end of the cuff in tubes used for adult males and 2.25 cm in tubes used for adult females. The use of guide marks is a simple, safe and reliable method for correct tracheal tube placement.