Endotracheal tubes (ETTs) are used to deliver mechanical ventilation for patients with respiratory failure, as well as during procedures requiring general anesthesia. Due to the complex geometry of the human throat, it is often difficult for medical professionals to insert the ETT (or "intubate") into a patient with an ETT directly. Therefore, physicians use stylets, or semi-malleable guides, to bend the ETT into a shape that better matches the curvature of the throat and can be advanced into the trachea. Once it is successfully inserted into the trachea, the stylet is removed, leaving the endotracheal tube for the airway path. 

When the angle of the stylet does not match the path into the trachea, medical professionals must retract the endotracheal tube, re-bend the stylet, and reinsert both into the patient until a successful intubation is achieved. This increases both the time of the intubation and the risk of intubation related complications such as hypoxemia or damage to the vocal cords.