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October 14, 2007
9:00 AM - 11:00 AM
Room Hall D, Area D,
A Comparison of the Video and Macintosh Laryngoscopes in Potentially Difficult To Intubate Patients
Carin A. Hagberg, M.D., Didier Sciard, M.D., Richard M. Layman, M.D., Kristin M. Luong, B.S.
Anesthesiology, The University of Texas Medical School at Houston, Houston, Texas
Introduction: The Direct Coupler Interface (DCI) Video Laryngoscope System (VL, Karl Storz, Tuttlingen, Germany) is designed to optimize visualization of the airway by projecting an enlarged video image of the laryngeal structures onto a color monitor1. The purpose of this study is to determine if the VL is useful in patients at risk for difficult intubation, as compared to the traditional Macintosh Laryngoscope (ML).

Methods:Following approval by the Institutional Review Board, written informed consent, and randomization, either the VL or ML was used in 200 anesthetized patients that presented with one or more of the following features: (1) history of difficult intubation, (2) morbid obesity (BMI ≥ 35 kg/m2), (3) small mouth opening (<3 cm), (4) limited neck mobility, (5) Mallampati class III, (6) short thyromental distance (<6 cm). The direct view of the laryngeal structures using the Cormack-Lehane (CL) grading system, as modified by Yentis and Lee2, was noted for all cases. The monitor view was also scored for all VL cases. The use of optimal external laryngeal manipulation (OELM) and epiglottis lifting was noted and whether these maneuvers improved the CL grade. The level of difficulty in the performance of intubation, time to intubation, number of attempts, and intraoperative complications, such as SpO2 < 95%, blood, secretions, and soft tissue trauma, were recorded. Postoperative assessment of sore throat and hoarseness was also conducted at 2 hours.

Results:Patient demographics between the VL and ML groups were similar. Ninety-eight percent of VL cases exhibited a monitor view of ≤ 2b, as compared to 86% of the ML cases (p=0.002). In 90.7% of the VL cases with a direct view >1, the CL grade improved by one or more than one with the monitor view. OELM was required less often when using the VL, 34.3% vs. 58% (p<0.001). Although the incidence of O2 saturation < 95% was greater in the VL group, there was no increased morbidity. Further comparison between the two groups is depicted in Table 1.

Discussion: The monitor view of the laryngeal structures using the VL is superior in comparison to the traditional view with the ML for potentially difficult intubations. Although epiglottis lifting consistently allows a superior view when utilized with the VL, less laryngeal manipulation is required with its use. This study suggests that the VL is an effective tool in patients at risk for difficult intubation.


1. J Clin Anesth 2002; 14: 620-6.

2. Anaesthesia 1998; 53: 1041-4.[table1]

Anesthesiology 2007; 107: A593
A comparison of the VL versus the ML in potentially difficult to intubate patients.
VL (n=100)ML (n=100)p-value
CL Direct View I:IIa:IIb:III:IV27:23:23:26:241:25:20:13:10.004
CL Monitor View I:IIa:IIb:III:IV67:17:14:2:041:25:20:13:1<0.001
Duration of Laryngoscopy (s)39.5 ± 68.7 (2-521)26.9 ± 22.9 (5-150)0.09
# of Attempts 1:2:3: Failed87:11:2:686:7:3:60.99
SpO2 < 95%500.02
Esophageal Intubation010.3
Difficulty Level (None:Mild:Moderate:Severe)60:24:13:346:36:14:40.7
*Significant p ≤ 0.05