A Pilot Study of Balloon Dilation in an Animal Model Resulting in Cricoid Cartilage Fracture: Implications for the Stenotic Pediatric Airway

Objective: Endoscopic balloon dilation is increasingly popular as primary therapy for infants with subglottic stenosis. We aim to determine the maximum balloon diameter and pressure where no fracture of the cricoid would occur, minimum balloon size and pressures where a gross fracture of the cricoid occurs, and location of these fractures. We tested these objectives by performing balloon dilation in laryngotracheal complexes of eight euthanized adult male New Zealand white rabbits, with airway characteristics similar to a 3- to 9-month-old infant. Methods: Subglottic airway diameter of each specimen was determined using endotracheal tubes (Cotton-Myer grading system). Preexistent subglottic disease was excluded by rigid endoscopy. Serial dilation with balloon catheters was performed, employing incremental balloon sizes and pressures, to determine balloon size and pressure, which resulted in a cricoid fracture. Locations of gross fractures were validated by two independent observers. Results: Airway diameter of all specimens was 5.4 mm (size 4.0 endotracheal tube). Four of the seven cricoid cartilages exhibited gross fractures. Dilation with balloon diameters less than 6.0 mm failed to induce a fracture despite maximal inflation to 16.0 atmospheres. The minimum balloon size required to create a fracture was 7.0 mm, at a pressure of 6.0 atmospheres. All fractures occurred at the anterior lamina of cricoid ring. Conclusions: No fractures occurred when balloon dilation was performed with a balloon 0.6 mm or smaller than the measured subglottic diameter. Fractures of the cricoid occurred when balloon dilation was performed with a balloon 1.6 mm or larger than the subglottic diameter.