Examining the pediatric subglottic airway by ultrasound: A systematic review

Abstract

Objective: The purpose of this review was to determine the ability of ultrasound (US) to assess the subglottic airway in pediatric patients to estimate the appropriate size of endotracheal tube (ETT).

Data sources: Pubmed, Scopus, and Embase databases.

Methods: A search of the literature was performed for studies that utilized ultrasonography to examine the minimal transverse diameter of the subglottic airway (MTDSA) in the pediatric (age < 18) population to estimate endotracheal tube (ETT) size. Articles were excluded if they involved adults or non-humans, had no comparison method, or were case reports. The primary outcome was the successful use of ultrasound compared to the reference standard defined by the study.

Results: Sixteen studies were included, for a total of 1,633 pediatric subjects in whom transcervical laryngeal ultrasound was used prospectively to examine the MTDSA to estimate ETT size prior to intubation. Ultrasound reliably predicted the clinically best fit endotracheal tube by air leak test in 48-100% of subjects, while age-based formulas were accurate 24-95% of the time. Ultrasound was highly predictive of proper size, with R2 ranging between 0.684 to 0.980. Of those reintubated (n = 104), 86 (83%) required larger-sized tubes, while 18 (17%) required smaller-sized tubes. Both methods tended to underestimate ETT size, but the age-based formulas accounted for most of these differences.

Conclusion: Transcervical laryngeal ultrasound appears to be a reliable predictor of endotracheal tube size in children undergoing elective surgery, which has implications for preventing intubation-related trauma and ensuring adequate ventilation for those who may require prolonged intubation.

Keywords: Endotracheal tubes; Otolaryngology; Pediatric otolaryngology; Subglottic airway; Systematic review; Ultrasound.