STUDY OBJECTIVE: (1) To evaluate a device of the authors' design, the laryngeal indices caliper, which quantitates the position of the anterior edges of the larynx relative to the upper teeth and the external auditory canals; (2) to determine how relative laryngeal position affects ease of direct laryngoscopy with a Macintosh #3 laryngoscope. DESIGN: Randomized, double-blind study. SETTING:Inpatient surgery center at a university medical center. PATIENTS: 101 renal lithotripter patients. INTERVENTIONS: Patients were measured with the laryngeal indices caliper prior to induction of general endotracheal anesthesia. They were then given a sleep dose of thiopental sodium (4 mg/kg) and paralyzed with a bolus dose of succinylcholine (1 mg/kg). MEASUREMENTS AND MAIN RESULTS: Of the measurements taken or calculated, only laryngeal tilt (LT) showed a significant correlation with grade of difficulty of laryngoscopy. When the anterior surface of the thyroid cartilage was tilted more than 20 degrees anteriorly to a line perpendicular to the laryngeal indices line, the vocal cords could not be seen in 83% of the patients. CONCLUSIONS: (1) Laryngeal tilt is a good predictor of difficulty of laryngoscopy with a Macintosh #3 laryngoscope; (2) the laryngeal indices caliper is a simple pocket device to measure LT indirectly.
RCT Entities:
STUDY OBJECTIVE: (1) To evaluate a device of the authors' design, the laryngeal indices caliper, which quantitates the position of the anterior edges of the larynx relative to the upper teeth and the external auditory canals; (2) to determine how relative laryngeal position affects ease of direct laryngoscopy with a Macintosh #3 laryngoscope. DESIGN: Randomized, double-blind study. SETTING: Inpatient surgery center at a university medical center. PATIENTS: 101 renal lithotripter patients. INTERVENTIONS:Patients were measured with the laryngeal indices caliper prior to induction of general endotracheal anesthesia. They were then given a sleep dose of thiopental sodium (4 mg/kg) and paralyzed with a bolus dose of succinylcholine (1 mg/kg). MEASUREMENTS AND MAIN RESULTS: Of the measurements taken or calculated, only laryngeal tilt (LT) showed a significant correlation with grade of difficulty of laryngoscopy. When the anterior surface of the thyroid cartilage was tilted more than 20 degrees anteriorly to a line perpendicular to the laryngeal indices line, the vocal cords could not be seen in 83% of the patients. CONCLUSIONS: (1) Laryngeal tilt is a good predictor of difficulty of laryngoscopy with a Macintosh #3 laryngoscope; (2) the laryngeal indices caliper is a simple pocket device to measure LT indirectly.