Acoustic features as novel predictors of difficult laryngoscopy in orthognathic surgery: an observational study

BACKGROUND: The evaluation of the difficult intubation is an important process before anaesthesia. The unanticipated difficult intubation is associated with morbidity and mortality. This study aimed to determine whether acoustic features are valuable as an alternative method to predict difficult laryngoscopy (DL) in patients scheduled to undergo orthognathic surgery. METHODS: This study included 225 adult patients who were undergoing elective orthognathic surgery under general anaesthesia with tracheal intubation. Preoperatively, clinical airway evaluation was performed, and the acoustic data were collected. Twelve phonemes {[a], [o], [e], [i], [u], [ü], [ci], [qi], [chi], [le], [ke], and [en]} were recorded, and their formants (f1-f4) and bandwidths (bw1-bw4) were extracted. Difficult laryngoscopy was defined as direct laryngoscopy with a Cormack-Lehane grade of 3 or 4. Univariate and multivariate logistic regression analyses were used to examine the associations between acoustic features and DL. RESULTS: Difficult laryngoscopy was reported in 59/225 (26.2%) patients. The area under the curve (AUC) of the backward stepwise model including en_f2 [odds ratio (OR), 0.996; 95% confidence interval (CI), 0.994–0.999; P=0.006], ci_bw4 (OR, 0.997; 95% CI, 0.993–1.000; P=0.057), qi_bw4 (OR, 0.996; 95% CI, 0.993–0.999; P=0.017), le_f3 (OR, 0.998; 95% CI, 0.996–1.000; P=0.079), o_bw4 (OR, 1.001; 95% CI, 1.000–1.003; P=0.014), chi_f4 (OR, 1.003; 95% CI, 1.000–1.005; P=0.041), a_bw4 (OR, 0.999; 95% CI, 0.998–1.000; P=0.078) attained a value of 0.761 in the training set, but a value of 0.709 in the testing set. The sensitivity and specificity of the model in the testing set are 86.7% and 63.0%, respectively. CONCLUSIONS: Acoustic features may be considered as useful predictors of DL during orthognathic surgery.