The cricothyroid membrane is located between the thyroid and cricoid cartilages (Figure 30-2A). Both structures are easily palpated but are not directly seen because they are covered with the pretracheal fascia. In men, the thyroid cartilage is prominent and creates the "Adam's apple"; in women and children, the thyroid and cricoid cartilages can be hard to distinguish from each other.
A. Neck anatomy. B. Location of the cricothyroid membrane.
Locate the cricothyroid membrane. [Photo used with permission of Jennifer McBride, PhD, and Michael D. Smith, MD.]
Make a midline vertical incision. The pretracheal fascia is seen through the incision. Bleeding is less likely with a vertical incision. [Photo used with permission of Jennifer McBride, PhD, and Michael Phelan, MD.]
Perforate the cricoid membrane with a horizontal incision. [Photo used with permission of Jennifer McBride, PhD, and Michael Phelan, MD.]
Widen the opening. [Photo used with permission of Jennifer McBride, PhD, and Michael Phelan, MD.]
Insert a tracheostomy tube with obturator. [Photo used with permission of Jennifer McBride, PhD, and Michael Phelan, MD.]
The cricothyroid membrane is found approximately one-third the distance from the manubrium to the chin in the midline in patients with normal habitus (Figure 30-2B). In a patient with a short, obese neck, the membrane may be hidden at the level of the manubrium. In a patient with a thin, long neck, it may be midway between the chin and the manubrium. The thyroid gland overlies the trachea; both structures are difficult to palpate. One easy way to find the cricoid membrane is to slowly palpate the trachea as you move up toward the head from the sternal notch; when your fingers "fall off" after a firm structure, you have palpated the thyroid cartilage. Next, slowly palpate downward toward the feet, and the first "soft spot" after that thyroid cartilage is the cricoid membrane.
The vascular structure potentially injured during the course of a properly performed cricothyrotomy is a thyroid artery, a branch of the aorta running up to the thyroid gland in the midline. This vessel infrequently reaches the level of the cricothyroid membrane. A carotid injury is potential when landmarks are not seen or not adhered to or when technique is poor; this can be catastrophic and requires immediate direct pressure to avoid harm.
The equipment needed to perform a surgical cricothyrotomy is listed in Table 30-2.
TABLE 30-2Equipment Needed to Perform a Surgical Cricothyrotomy ||Download (.pdf) TABLE 30-2 Equipment Needed to Perform a Surgical Cricothyrotomy
Personal protective equipment
Scalpel with a #10 (preferable because of its greater width) or #11 blade
A 6-mm endotracheal tube or tracheostomy tube (latter preferred), plus a smaller one available
Tape to secure the tube in place
Cloth ribbon and sutures to secure tracheostomy tube in place
Bag-valve mask device and oxygen source
Gum elastic bougie for guiding tube
PATIENT PREPARATION AND POSITIONING
Place the patient supine, with the neck slightly hyperextended if no cervical trauma is present (neutral if there is suspected trauma) so neck structures can be palpated and identified. If time permits, apply antiseptic solution to the skin. Ventilate with a bag-valve mask connected to 100% oxygen while preparing.
The procedure for performing a surgical cricothyrotomy is summarized in Table 30-3.
TABLE 30-3Performing a Surgical Cricothyrotomy ||Download (.pdf) TABLE 30-3 Performing a Surgical Cricothyrotomy
|Step ||Comment |
|1. Stand to one side of the patient at the level of the neck. || |
Right-handed practitioner—stand on the patient's right side.
Left-handed practitioner—stand on the patient's left side.
|2. Locate the cricothyroid membrane. || |
Locate the cricoid ring.
Place the index finger at the sternal notch and palpate cephalad until the first rigid structure is felt (cricoid ring), or use "fall off and return" approach noted earlier.
Roll the index finger one finger breadth above to locate the membrane between the cricoid and thyroid cartilages (Figure 30-3).
|3. Using the thumb and middle finger of the nondominant hand, stabilize the two cartilages. ||— |
|4. Use the scalpel to make a vertical incision in the midline between the two cartilages, extending if needed. || |
Incise through the skin and subcutaneous tissues.
The structures are superficial, so do not incise deep to avoid damage to the cricoid or thyroid cartilage or vascular structures (Figure 30-4). The membrane is felt, not directly seen, after incision.
|5. With the scalpel blade positioned horizontally, perforate the cricothyroid membrane so that the blade goes in approximately half its length. ||The horizontal orientation is in anatomic alignment with the membranes to avoid vascular injury (Figure 30-5). Once the membrane is perforated, do not leave it empty; slide forceps or dilator around the blade or place a bougie before removing the scalpel. |
|6. Widen the incision opening. ||A dilator or mosquito or Kelly clamp may be used (Figure 30-6). |
|7. Place the tube in the opening. ||Although instinct may guide you to direct the tracheostomy tube posterior, remember that the trachea is superficial and the tube should follow the tracheal axis (Figure 30-7). |
|8. Connect to a bag-valve mask device for ventilation. Check for breath sounds with ventilation. || |
If no ventilation is heard bilaterally, pull the tube out and reinsert it.
Recheck for breath sounds to ensure that the endotracheal tube is correctly positioned after any manipulation.
When inserting a standard endotracheal tube, listen for asymmetry of breath sounds. If breath sounds are absent on the left side, then the tube has been inserted down the right mainstem bronchus and needs to be pulled back a few centimeters. If using an endotracheal tube, insert no more than 2–3 cm to avoid mainstem bronchus placement.
|9. Secure the tube carefully with a ribbon and/or adhesive tape. ||More challenging with a standard endotracheal tube. |
|10. Apply dressing and further secure the tube. || |
If a tracheostomy tube has been used, fashion a simple dressing by cutting a slit halfway down the middle of a 4×4 gauze dressing and placing it under the tracheostomy tube.
Secure the tube with a ribbon placed through the flanges of the tracheostomy tube.
For added security, use 2-0 nylon sutures to fix the tube to the skin.
Consider changing endotracheal tubes to tracheostomy tubes whenever possible.
SURGICAL CRICOTHYROTOMY USING SELDINGER TECHNIQUE
This method uses the Seldinger technique (Figure 30-8). Make a small vertical incision through the skin at the cricothyroid membrane. Insert the needle and aspirate air to make sure the needle is in the trachea. Next, pass the guide wire through the needle, directing the guide wire caudally. Place a tracheostomy tube over the dilator, and make a "nick" in the skin to ease penetration. Then pass the dilator, with the tracheostomy tube, over the guide wire into the trachea. Once the dilator is in the trachea, remove the guide wire, direct the tracheostomy tube into the trachea, and verify correct placement. Indications and complications are similar to the open method, and direct comparisons in real use do not exist. Multiple commercial kits exist, but proper use requires deliberate, repetitive training.
Placement of a percutaneous cricothyrotomy with a commercial kit and the Seldinger technique. [Photo used with permission of David Effron, MD.]
Introduce the catheter into the larynx. A. Introduce the catheter into the larynx skin at a 90-degree angle to the skin. B. When air returns, change the angle to 45 degrees. [Photo used with permission of Jennifer McBride, PhD, and Michael D. Smith, MD.]
Attach the high-flow regulator via connective tubing to the catheter and start ventilation with high-pressure 100% oxygen source. Note: Stabilize catheter at the base to avoid dislodgement (not done in figure for display purposes). [Photo used with permission of David Effron, MD.]
Acute complications after emergency cricothyrotomy occur in up to 15% of cases.6 Venous bleeding usually occurs from small veins and stops spontaneously. Using a vertical neck incision that is not too long decreases the chance of ongoing bleeding. Arterial bleeding can be from the thyroid artery or from a small artery at the base of the cricothyroid membrane. The first step in controlling ongoing bleeding is to apply gentle pressure. If bleeding persists, topical hemostatic agents or ligation may be necessary. A small amount of bleeding usually creates no hemodynamic concerns, but it can make the procedure more challenging.
In an obese patient, it is possible to place the tube anterior to the larynx and trachea into the mediastinum, making ventilation impossible. Signs of an incorrectly positioned tube are high airway pressures, absent breath sounds, and massive subcutaneous emphysema. If this complication is suspected, remove the tube and make a second attempt at insertion. Endotracheal tubes passed through the cricoid membrane may curl toward the mouth, making ventilation impossible. A gum elastic bougie can help direct the endotracheal tube.5
Laceration of the trachea, esophagus, or recurrent laryngeal nerves is rare and is more likely to occur if one is unfamiliar with the neck anatomy. Pneumothorax is usually secondary to barotrauma caused by ventilation initiated immediately after tube placement.
A tube left in the narrow space between the cricoid and thyroid cartilages can erode both cartilages, and bacterial chondritis may occur. The cartilages will be destroyed and eventually scar, leading to stenosis and loss of the function of the larynx. Because cricothyrotomy has a high incidence of airway stenosis,6 a change to tracheostomy is common after 2 to 3 days.