Accuracy of ultrasound in measurement of the pediatric cricothyroid membrane.

Background: Emergency front of neck airway is a recommended airway rescue strategy in children over 1 year old. Surgical tracheostomy is advocated as the first-line technique, but in the absence of an ear, nose and throat surgeon cricothyroidotomy or tracheostomy is proposed. Recent research shows that clinical identification of the cricothyroid membrane is frequently inaccurate in older children and adults and has prompted investigation of ultrasound as a potential clinical tool for emergency front of neck airway. Advance knowledge of the dimensions of the pediatric cricothyroid membrane may assist clinicians in determining the feasibility of emergency front of neck airway, optimum technique, and equipment.

Aims: The aim of this study was to assess the accuracy of ultrasound-assisted pediatric cricothyroid membrane localization and dimension measurement using magnetic resonance imaging as the reference standard.

Methods: After structured training, two pediatric anesthesiology trainees used ultrasound to identify and measure the dimensions of the cricothyroid membrane in pediatric patients undergoing elective magnetic resonance imaging of the head and neck under general anesthesia. A pediatric radiologist reviewed the corresponding magnetic resonance imaging scans and measured the height of the cricothyroid membrane. The accuracy of the cricothyroid membrane height as measured by ultrasound was compared to that measured by magnetic resonance imaging.

Results: Twenty-two patients were included in the study. The cricothyroid membrane was accurately identified by ultrasound in all cases. The correlation coefficient for cricothyroid membrane height measured by ultrasound and that measured by magnetic resonance imaging was 0.98 (95% C.I 0.95-0.99, P < 0.0001). The bias was -0.16 mm and the precision was 0.19 mm. All differences were within the a priori limits of agreement. The 95% limits of agreement were -0.54 to 0.22 mm.

Conclusion: Ultrasound can be used to accurately identify and measure cricothyroid membrane height in pediatric patients. This approach could have clinical and research utility.