Comparative study of a standard Macintosh blade III and a modified Optic Viewmax blade II for endotracheal intubation

ABSTRACT

The availability of a laryngoscope blade that could improve visualization of glottic structures without requiring excess traction force during tracheal intubation would be helpful in reducing the perioperative complications related to laryngoscopy. The Viewmax laryngoscope blade II [Rusch] is a modified laryngoscope blade which incorporates an unmagnified optic side port to a standard Macintosh [MAC] blade III. This modification allows for an alternative view of the glottis from a position 1 cm behind the left tip of the blade while still allowing the standard direct view provided with MAC-3 blade during tracheal intubation. In this study, we compared the Viewmax to a standard MAC-3 blade using a randomized cross-over study design. Fifty six patients ASA physical status I and II requiring tracheal intubation were enrolled in this study. The preanesthesia airway evaluation included Mallimpoti score, thyromental distance, and maximal mouth opening. Anesthesia was induced with propofol 2 mg/kg and fentanyl 50-100 mg, followed by rocuronium 0.6 mg/kg IV for muscle relaxation. According to a randomization, either the standard MAC-3 blade [Mac Group] or Viewmax II blade [Viewmax Group] was first chosen for laryngoscopy. After viewing the laryngeal structures, the first blade was withdrawn and the second blade [MAC or Viewmax] was used to repeat the laryngoscopy. A strain gauge laryngoscope handle was used with both blades to measure the peak axial force applied at the handle by the anesthesiologist during the laryngoscopy. After viewing the laryngeal structures with the second blade, tracheal intubation was performed in all patients. The views of laryngeal structure during laryngoscopy were classified by the anesthesiologist as Grade 1= most of the glottis is visible; Grade 2 = only the posterior portion of the glottis is visible; Grade 3 = only the epiglottis is visible; and grade 4 = only the soft palate is visible. Anesthesiologist's satisfaction with the Viewmax laryngoscope was evaluated using a verbal score from 0 to 100. Our results showed that there were no significant differences in the laryngoscopic views between the two blades. However, the use of Viewmax blade was associated with lower percentage of laryngoscopic views grade III and IV compared to MAC blade. The recorded force applied to the laryngoscope handle during laryngoscopy was significantly less in Viewmax group compared to MAC group. The view of the laryngeal structures with Viewmax 11 blade was comparable to the MAC-3 blade. However, the use of Viewmax blade required less axial force applied at-the handle during the laryngoscopy