Chapter 24: Airway and Facial Applications

INTRODUCTION

Multiple point-of-care ultrasound (POCUS) applications may be used in the acute care setting to evaluate and manage airway and facial conditions. These include difficult airway assessment, confimation of endotracheal tube placement, surgical airway landmark identification, diagnosing epiglottitis, salivary gland evaluation, and maxillary sinus evaluation.

AIRWAY

CLINICAL CONSIDERATIONS

The anatomic structures of the larynx and upper airway are superficially located, and therefore well suited for POCUS assessment. Although airway ultrasound techniques are not universally used for upper airway assessment and procedures, there is growing evidence that ultrasound can provide valuable information about the anatomy of the upper airway and can be used to confirm proper placement of an endotracheal tube.

CLINICAL INDICATIONS

The indications for POCUS in airway management are as follows:

1. Preintubation assessment of the upper airway

2. Assessment of anatomic structures for surgical airway management

3. Postintubation confirmation of endotracheal tube placement

4. Assessment of vocal cord function

5. Evaluation for epiglottitis

Preintubation Assessment of the Upper Airway

POCUS of the airway has been shown to be a useful tool for preintubation assessment in both adult and pediatric patients to determine appropriate tube size and predict difficult airways. Sonographic measurements of infrahyoid airway structures have been found to correlate well with computed tomography (CT) or magnetic resonance imaging (MRI).¹ Ultrasound imaging of the width of the air column at the level of the cricoid cartilage was found to have a correlation coefficient of 0.99 with MRI measurement.¹ This parameter was designed to help clinicians estimate proper endotracheal tube size and avoid the complications that occur when an excessively large endotracheal tube is employed. In a study of 192 pediatric patients of 1 month to 6 years of age, sonographically measured subglottic airway diameter was a better predictor of proper endotracheal tube size than standard age- and height-based formulas.² Studies also support the idea that ultrasound can help predict the presence of a difficult airway by assessment of the thickness of the anterior neck soft tissues. Patients who have a mean distance from hyoid bone to skin of 0.88 cm or less had easier intubations than patients with a mean distance greater than 1 cm.^3–5

Assessment of Anatomic Structures for Surgical Airway Management

Ultrasound of the upper airway can play an important role when placement of a percutaneous cricothyrotomy or tracheostomy is being considered. Using surface landmarks can be unreliable, especially in obese patients. Several studies reveal the need for a better approach in patients with poorly defined anatomy by highlighting the challenges of using the landmark technique alone. In one particular study, the cricothyroid membrane was correctly identified only 30% of the time via the landmark technique, and the desired target location for percutaneous cricothyrotomy was correctly identified only 10% ...