Certified Registered Nurse Anesthetist (CRNA) Practice Exam

Where should the tip of the endotracheal tube be positioned relative to the carina?

1. At the level of the carina

2. 4 cm below the carina

3. 4 cm above the carina

4. 2 cm from the vocal cords

The correct answer is: 4 cm above the carina

The ideal positioning of the tip of the endotracheal tube (ETT) is approximately 4 to 5 cm above the carina. This placement is crucial because it ensures that both mainstem bronchi are adequately ventilated while minimizing the risk of accidental intubation into one of the bronchi, which can lead to hypoventilation or atelectasis of the opposite lung. Positioning the ETT too close to the carina risks causing irritation or injury to surrounding structures and can also lead to obstruction of airflow if the tube migrates further during patient movement or operations. The 4 cm above the carina measurement is a guideline commonly adopted by anesthesia providers to guarantee optimal lung inflation and protection of the airway. Understanding this positioning is essential for practitioners, as it impacts patient safety and overall outcomes during surgery, particularly in complex cases requiring general anesthesia.