Routine use of ultrasonography in prediction of uncuffed endotracheal tube size in pediatric patients

Endotracheal intubation is a crucial skill in anesthesia. Uncuffed pediatric endotracheal tube (ETT) size can be calculated by various methods like age-based formula or by using ultrasound to measure minimal transverse subglottic diameter (MTSD). This study aimed to compare both age-based formula and ultrasound to assess the advantage of routine use of ultrasound to determine pediatric ETT size. Forty children of 2–10 years of age, ASA class ≤ II, Mallampati airway classes I and II, scheduled for surgery away from the head and neck, were included. Uncuffed ETT size for each child was calculated using age-based formula. After induction of balanced general anesthesia, an ultrasound was done to measure MTSD and an endotracheal tube was selected accordingly. After intubation, an air leak test was done and the ETT was accordingly changed (if needed). ETT size by age-based formula strongly correlated with the size measured by ultrasound (Pearson correlation 0.913; P < 0.001). The percentage of the need to change the endotracheal tube according to the leak test was only 7.5%. The ETT size calculation was similar for both age-based formula and ultrasound. So, we could not justify the routine use of ultrasound for calculating ETT size for intubation in pediatric patients.