Influence of pharyngolaryngeal anomalies diagnosed through indirect laryngoscopy in the prediction of difficult intubation

Objective: To determine the pharyngolaryngeal anomalies not usually included in the evaluation of difficult airway, in order to investigate the influence of these anomalies in the prediction of difficult intubation. To do this, indirect laryngoscopy with a 70° rigid laryngoscope was performed on all patients during the preoperative period.

Methods: This is an observational, prospective study on 300 consecutive patients who were scheduled for endotracheal intubation under general anesthesia. In addition to assessing the airway in the preoperative period by demographic and clinical predictors of difficult airway, rigid indirect laryngoscopy was performed to diagnose pharyngolaryngeal anomalies. Later, under general anesthesia and direct laryngoscopy it was checked to see if there was difficulty in intubating the larynx, and its association with all previous variables was investigated. A logistic regression model for prediction purposes was developed, and its power of discrimination was achieved by assessing the area under the curve.

Results: During the examination by indirect laryngoscopy 46 anomalies were found, which were as follows: 31 abnormalities of the epiglottis (22 omega epiglottis, 9 flaccid or hypertrophic epiglottis); 6 findings of hypertrophic lingual tonsils, 3 cases of upper airway tumors, and 6 patients with tongue disorders. Intubation difficulty was found in 14 cases (4.66%). The regression model found, and its coefficients to develop it were: f(x)=1.322+(2.173 thyromental distance <6.5 cm)+(1.813 omega epiglottis)-(1.310*cm opening mouth). Global power of discrimination was 0.83, with a 95% confidence interval from 0.709 to 0.952).

Conclusion: Indirect laryngoscopy allowed pharyngolaryngeal anomalies to be diagnosed, including omega epiglottis, which was one of the variables included in the logistic regression model.