Using the bubble inclinometer to measure laryngeal tilt and predict difficulty of laryngoscopy

Abstract

Study objective: To evaluate a simple device, the bubble inclinometer, to measure degrees of laryngeal tilt (LT) for predicting difficulty of direct laryngoscopy using a Macintosh #3 laryngoscope.

Design: Randomized, double-blind study.

Setting: Inpatient surgery center at a university medical center.

Patients: 50 renal lithotripter patients.

Interventions: Patients were measured with the bubble inclinometer and the laryngeal indices caliper. A sleep dose of thiopental sodium (4 mg/kg) and a muscle-relaxing dose of succinylcholine (1 mg/kg) were then given to each patient.

Measurements and main results: LT was measured by both methods (directly and indirectly). Difficulty of laryngoscopy was graded as follows: Grade 1 = all of vocal cords seen; Grade 2 = part of vocal cords seen; Grade 3 = no part of vocal cords seen.

Conclusions: The bubble inclinometer accurately and reproducibly measures relative LT, and the anterior tilt of the larynx directly correlates with the ability to see the laryngeal opening during direct laryngoscopy with a Macintosh #3 laryngoscope.