Straight blades improve visualization of the larynx while curved blades increase ease of intubation: a comparison of the Macintosh, Miller, McCoy, Belscope and Lee-Fiberview blades.

Purpose: To compare the Macintosh (M), McCoy (MC), Miller (MIL), Belscope (BP) and Lee-Fiberview (LF) laryngoscopes with respect to the grade of laryngeal visualization and the difficulty of intubation.
Methods: We included 500 patients scheduled to undergo elective surgery and who required tracheal intubation. Patients were randomly assigned to five groups of 100 patients each. Anesthesia was induced intravenously using 1-3 mg.kg(-1) of propofol, fentanyl 1.5 microg.kg(-1) and atracurium 0.5 mg.kg(-1) or suxamethonium 1 mg.kg(-1). The laryngeal view was classified according to Cormack and Lehane. The degree of difficulty with intubation was rated as: Grade 1, intubation easy; Grade 2, intubation requiring an increased anterior lifting force and assistance to pull the right corner of the mouth upwards to increase space; Grade 3, intubation requiring multiple attempts and a curved stylet; Grade 4, failure to intubate with the assigned laryngoscope. Data were examined using analysis of variance, chi(2) or Fisher test, Student's t test and odds ratio. P < 0.05 was considered statistically significant.
Results: Laryngoscopic views obtained with the BP and MIL laryngoscopes were similar, and better than with the other types of laryngoscopes (P < 0.001). The levering tip of the MC blade (P = 0.02) and the fibreoptic device of the LF (P < 0.001) significantly improved the laryngoscopic view. Regarding the degree of difficulty with intubation, the best results were obtained with the MC and M blades (P < 0.001).
Conclusion: Laryngoscopy was better with straight blades but curved blades provided better intubating conditions.