Endotracheal intubation is the process of placing a flexible plastic tube through the mouth and into the trachea, or windpipe. This procedure is performed to maintain an open airway for patients who are critically ill, injured, or under anesthesia. To aid in this process, clinicians use a stylet, which is a slender, malleable rod inserted into the endotracheal tube to help guide it into the correct position.
The Role of the Stylet in Endotracheal Intubation
An intubating stylet gives the flexible endotracheal tube (ETT) a more rigid and specific shape, which helps in guiding it through a patient’s airway. The stylet allows a clinician to stiffen the tube and mold its shape to better navigate the patient’s unique anatomy. This added control can be helpful during difficult laryngoscopy procedures.
The most common shape created with the stylet is the “hockey-stick” curve. This involves keeping the main body of the tube straight with a distinct bend of about 25 to 35 degrees at the distal tip. This angulation directs the end of the ETT toward the opening of the trachea, which is situated in the front part of the neck.
Shaping the tube is useful in patients where visualizing the vocal cords is challenging. An “anterior airway,” for instance, describes when the larynx is positioned higher in the neck than usual, making it difficult to see with a standard laryngoscope. By using a stylet to create a specific curve, the operator can more effectively maneuver the tip of the tube through the vocal cords.
The Intubation Procedure Using a Stylet
The stylet is lubricated for easy insertion into and removal from the endotracheal tube (ETT). It is then advanced into the ETT, with the clinician ensuring that the tip of the stylet does not extend beyond the end of the tube to prevent trauma to the airway. The combined ETT and stylet are then bent into the desired shape, such as the “hockey-stick” curve.
A clinician uses a laryngoscope, a device with a light and a blade, to gently lift the tongue and epiglottis to get a direct view of the vocal cords. The pre-shaped ETT with the stylet inside is carefully advanced through the mouth. The curve of the tube helps the operator to guide its tip through the glottis, the opening between the vocal cords, and into the trachea.
Once the ETT has passed through the vocal cords to the appropriate depth, the stylet must be removed while the ETT is held firmly in place. This step often involves an assistant who withdraws the stylet as the primary clinician secures the tube. Removing the stylet softens the tube, allowing it to conform to the trachea’s natural shape.
After stylet removal, the clinician confirms that the tube is correctly placed in the trachea and not the esophagus. This is done by inflating a small cuff at the end of the ETT to create a seal against the tracheal wall. The clinician then checks for placement by listening for breath sounds in the lungs and using a capnograph to detect carbon dioxide in the exhaled air, which confirms tracheal placement.
Types of Intubation Stylets
Several types of stylets exist to address various clinical scenarios. The most common is the standard malleable stylet, which consists of a pliable metal core housed within a smooth plastic sheath. This design allows clinicians to easily bend the stylet into the required shape for a specific patient’s anatomy, making it a versatile tool.
Another category is the lighted stylet, or lightwand, which incorporates a high-intensity light source at its tip. When used for intubation, the bright light transilluminates, or shines through, the soft tissues of the neck. A well-defined, bright glow on the front of the neck indicates that the tip is correctly positioned in the trachea, while a diffuse and dull light suggests it has entered the esophagus.
Video stylets are an advanced option that integrate a miniature camera at the distal end. The camera transmits a live video feed to an external monitor, providing a direct view of the airway structures as the stylet is advanced. This allows the clinician to visualize the vocal cords and confirm passage of the tube without needing a separate laryngoscope.
Procedural Considerations and Airway Management
When using a stylet for intubation, specific techniques are employed to enhance safety. To minimize the risk of the rigid tip causing trauma, some clinicians withdraw the stylet by one to two centimeters after the ETT has passed through the vocal cords but before it is fully advanced. This maneuver softens the leading edge of the tube, making its final passage gentler.
During insertion, the tip of the ETT can get caught on the cartilaginous rings of the anterior tracheal wall, which is more common when the tube has a pronounced curve. To overcome this, the clinician might rotate the tube slightly, which can help the beveled tip navigate past the obstruction smoothly. This technique can prevent failed intubation attempts and reduce airway trauma.
The stylet is not the only tool available to assist with intubation. A tracheal tube introducer, often called a bougie, is another common device. A bougie is a thin, flexible plastic rod that is first passed into the trachea, and then the ETT is threaded over it. The choice to use a stylet versus a bougie depends on the clinical circumstances and the experience of the medical provider.