View of the Larynx Obtained using the Miller Blade and Paraglossal Approach, Compared to that with the Macintosh Blade

Abstract

The purpose of this study was to determine if laryngoscopy using a Miller blade with a paraglossal approach would yield an improved view of the larynx compared to that obtained with a Macintosh blade using the standard approach. One-hundred and sixty-one patients, scheduled for elective surgery requiring tracheal intubation, voluntarily participated in this study. Patients were randomly assigned to one of the two groups (Miller vs. Macintosh). A standard general anaesthetic was administered. Comparisons were made of the percentage of the vocal cords visible at laryngoscopy. The view of the airway was also graded using the Cormack and Lehane scale. Statistical analysis using Fisher's exact test was performed. A P value <0.05 was considered statistically significant. The time required to complete intubation and complications if any, were also recorded. Laryngoscopy using the Miller blade allowed 100% of the vocal cords to be viewed in 78%> of cases, whereas this was achievable in only 53% with the Macintosh blade (P=0.0014). The Miller blade enabled greater than 25% of the vocal cords to be seen in 95% of the cases, whereas this was achievable in only 80% with the Macintosh laryngoscope (P=0.003). A grade 1 Cormack and Lehane view of the larynx was obtained in 96.5% of cases in the Miller group compared with 85% in the Macintosh group (P=0.02). Direct laryngoscopy using the Miller blade and paraglossal approach, afforded a much-improved view of the larynx in the majority of cases. For this reason trainees should learn laryngoscopy using both blades.