In the Literature

Summary of "Airway Ultrasound as Predictor of Difficult Direct Laryngoscopy: A Systematic Review and Meta-analysis"

Summary published April 27, 2023

Summary by Juan Li, MD; Yong G Peng, MD, PhD, FASE, FASA

Anesthesia & Analgesia | April 2022

Carsetti A, Sorbello M, Adrario E, Donati A, Falcetta S. Airway Ultrasound as Predictor of Difficult Direct Laryngoscopy: A Systematic Review and Meta-analysis. Anesth Analg. 2022 Apr 1;134(4):740-750. doi: 10.1213/ANE.0000000000005839. PMID: 34914641; PMCID: PMC8903216.

doi: https://doi.org/10.1213/ane.0000000000005839

  • In this systematic review and meta-analysis, the authors evaluate whether preoperative airway ultrasound can predict difficult direct laryngoscopy in adult patients undergoing elective surgery under general anesthesia.
  • The study found patients with difficult direct laryngoscopy have longer distance from skin to epiglottis (DSE) values than patients with easy laryngoscopy, with a mean difference of 0.38 cm (95% confidence interval [CI], 0.17-0.58 cm; P = .0004). The sensitivity was 0.82 (0.74-0.87) and the specificity was 0.79 (0.70-0.87).
  • Patients with difficult direct laryngoscopy also have longer distance from skin to vocal cords (DSVC) and distance from skin to hyoid bone (DSHB) values than patients with easy laryngoscopy, with a mean difference of 0.18 cm (95% CI, 0.01-0.35 cm; P = .04) and 0.23 cm (95% CI, 0.08-0.39 cm; P = .004); sensitivity 0.71 (0.58-0.82) and 0.75 (0.62-0.84); and specificity 0.71 (0.57-0.82) and 0.72 (0.45-0.89), respectively.
  • This is the first systematic review and meta-analysis to evaluate the diagnostic test accuracy of ultrasound in predicting difficult laryngoscopy in adult patients undergoing elective surgery. The study found that among the several upper airway ultrasound index tests considered in the literature, DSE accurately predicts difficult laryngoscopy in this population.
  • Because the meta-analysis found high clinical and methodological heterogeneity between studies, these results need to be interpreted with caution. However, ultrasound can assess sub-hyoid parameters that could help us to identify patients with potentially difficult airways due to the thickness of soft tissues despite normal routine clinical assessments. By providing an objective assessment of specific index tests and thus restricting interobserver variability, upper airway ultrasound may represent a powerful tool to improve the performance of difficult airway management predictive tests.