Cricothyroid Membrane Location
The cricothyroid membrane is located inferior to the thyroid cartilage and superior to the cricoid cartilage. 1, 2
Anatomical Boundaries
The cricothyroid membrane occupies the space between two critical cartilaginous structures:
- Superior border: The anterior inferior border of the thyroid cartilage 3
- Inferior border: The anterior superior border of the cricoid cartilage 3
- Lateral boundaries: The cricothyroid muscles define the working width of the membrane 4
Clinical Dimensions
The working dimensions of the cricothyroid membrane are critical for emergency airway access:
- Vertical height: Ranges from 8-19 mm (mean 13.7 mm) 4
- Horizontal width: Ranges from 9-19 mm (mean 12.4 mm) between the cricothyroid muscles 4
- Distance to vocal cords: Approximately 9.8 mm from the upper limit of the membrane to the vocal cords 4
Relationship to Other Structures
The thyroid gland sits inferior to the thyroid cartilage, making the cricothyroid membrane positioned superior to the thyroid gland 5. The membrane is the recommended site for emergency front-of-neck airway access in cannot intubate, cannot oxygenate (CICO) situations 1, 2.
Emergency Access Technique
The Difficult Airway Society recommends a 4-step surgical cricothyroidotomy approach: identification of the cricothyroid membrane, stab incision through skin and membrane, caudal traction on the cricoid cartilage with a tracheal hook, and insertion of a small cuffed tube 5, 1, 2.
Critical Pitfalls
- Gender differences: The cricothyroid membrane is significantly more difficult to identify by palpation in females (incorrect identification in 81% vs 31% in males), with greater posterior thyroid cartilage angulation in females (118.6° vs 95.9°) 6
- Vascular considerations: Approximately 62% of individuals have an artery crossing the cricothyroid membrane transversely 4
- Post-procedure considerations: Patients who undergo cricothyroid approximation surgery (a voice feminization procedure) may have complete loss of the cricothyroid membrane, making emergency cricothyroidotomy impossible 5