Ultrasonography predicts difficult airway management: A prospective double blinded study

Purpose

We evaluate ultrasonographic measurements and clinical criteria of difficult airway management to establish a new predictive score for difficult intubation.

Methods

We conducted a prospective observational double-blinded and monocentric study involving patients proposed for surgery under general anesthesia with orotracheal intubation. After collecting demographic and clinical data of difficult intubation, we evaluated 8 ultrasound measurements of airway assessment using an abdominal probe for the dimensions of the tongue and the hyomental distance. Then using a linear probe, we evaluated the thickness of the anterior neck soft tissues at three levels (hyoid bone, epiglottis, and trachea). After intubation, the sample was separated into 2 groups: easy laryngoscopy (EL) and difficult laryngoscopy (DL).

Univariate comparisons between variables were performed using t student test, Mann-Whitney test, and Pearson's Chi-square test. Statistical significance was defined as p < 0.05. Logistic regression was then performed to test correlations between sonographic measurements, clinical criteria, and difficult laryngoscopy.

These independent predictive criteria were the score parameters defined by values ​​corresponding to their respective odd ratios. Then we established the cutoff value of the score from its ROC curve.

Results

Difficult laryngoscopy and difficult intubation were found in 20.5% and 14.5% of patients respectively. In univariate analysis, the coronal diameter of the tongue and the thickness of anterior neck soft tissues at 3 levels (hyoid bone, epiglottis, and trachea) had areas under the ROC curves 0.70, 0.87, 0.89, and 0.83 respectively with cut-off values of 4.57 cm, 1.54 cm, 2.69 cm, and 1.15 cm. In multivariable analysis, the clinical and sonographic criteria independently associated with DL were Mallampati score >2 (OR = 3), a TANST at the epiglottis >2.69 cm (OR = 23) and a TANST at the trachea> 1.15cm (OR = 8). We determined a predictive score of difficult laryngoscopy with a sensitivity = 88%, a specificity = 88%, and an AUC = 0,9298. A score strictly superior to 10 multiplied the risk of a difficult laryngoscopy by 53.

Conclusion

A combination of clinical criteria and ultrasound measurements increases the ability to predict difficult airway management.

Clinical trial registration number

This study was registered in the Pan African Clinical Trials Registry (PACTR) under the reference (PACTR202109682609409)

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