Left-molar approach for direct laryngoscopy: is it easy?

Abstract

For direct laryngoscopy, we compared midline and left-molar approaches with respect to ease of intubation, using a Macintosh blade. We investigated the relationship between failure of the left-molar approach and preoperative risk factors for difficult intubation. With local ethics committee approval, 200 consecutive adult, nonpregnant patients were included in the study. The demographic data, body mass index, Mallampati modified score, interincisor gap, and mentohyoid and thyromental distances were measured preoperatively. First, the Macintosh blade was inserted using the midline approach, and then optimal external laryngeal manipulation (OELM) was applied. Second, the blade was inserted using the left-molar approach. The glottic views were assessed according to the Cormack-Lehane classification before and after OELM in both approaches. In cases where tracheal intubation failed with the left-molar approach, the midline approach was applied again and endotracheal intubation took place. The grade I glottic view obtained using the midline approach without OELM did not change in 94.3% of the patients with the left-molar approach without OELM; in addition, the grade II glottic view improved to grade I in 52.8% of the patients with the same technique (P < 0.001). Although the number of patients with a grade I or II glottic view in the left-molar approach was 197, only 37 patients could be intubated using the left-molar approach. In addition, 59.5% of them were intubated at the second attempt with the left-molar approach, while the incidence of a second attempt was 1.2% with the midline approach (P < 0.001). There was no correlation between the preoperative risk factors for difficult intubation and failure of the left-molar approach. Difficulty in the insertion of the endotracheal tube limits the efficacy of the left-molar approach. It is not possible to predict the failure of intubation with the left-molar approach by considering the preoperative risk factors.