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October 14, 2007
9:00 AM - 11:00 AM
Room Hall D, Area D,
Video Laryngoscopy Improves Intubating Conditions in Patients with Simulated Difficult Airway
Christian Byhahn, M.D., Thomas Kirschning, M.D., Jens Meier, M.D., Manfred Kaufmann, M.D., Bernhard Zwissler, M.D.
Departments of Anesthesiology and Gynecology, J.W. University Medical School, Frankfurt, Germany
Objective: Video technology used for endotracheal intubation has been reported to significantly enhance the visualization of the glottic structures when compared to direct laryngoscopy in routine patients without predictors for a difficult airway (1). We tested the hypothesis that, with video laryngoscopy, the visibility of the glottis and thereby intubating conditions can also be improved in patients with simulated difficult airway.

Methods: With IRB approval and written, informed consent, 38 adult patients undergoing elective surgery were included in the study. After induction of general anesthesia, all patients had a cervical immobilization collar (Stifneck Select, Laerdal Medical GmbH, Puchheim, Germany) put on to simulate a difficult airway by suspending neck extension and downsizing mouth opening. Laryngoscopy was performed using a video laryngoscope with a size 3 Macintosh blade attached (DCI Scope, Karl Storz, Tuttlingen, Germany). The view of the glottis was rated using 5 grades according to the modified Cormack-Lehane scoring system: I=full view of the glottis; IIa = partial view of the glottis; IIb = arytenoids or posterior portion of cords only visible; III = only epiglottis visible; IV = neither epiglottis nor glottis visible. First, direct laryngoscopy was performed with the naked eye (direct view), and the best view obtained was graded by the laryngoscopist (senior anesthesiologist) without looking at the video monitor. Subsequently, the view on the video monitor, located in front of the intubator was then immediately graded by the same anesthesiologist. Fisher's Exact test was used for statistical analysis.

Results: 38 adult female patients (mean body mass index 25.3±3.1kg/m2) were studied. Upon preoperative airway examination, no patient had predictors for or a history of difficult intubation. With direct (video-assisted) view, intubating conditions were graded challenging or difficult (grades IIb-IV) in n=33/38 (n=24/38) patients (P=0.0324). An improvement in grade of the view between the direct vision and the video-assisted view was noted in n=16/38 patients (+1 grade n=13, +2 grades n=3). Grades IIa and IIb were thereby taken as distinct grades (i.e., the difference between a view of IIa on video and that of IIb on direct vision would be a grade difference of 1).

Discussion: As shown in a previous multi-center study when video laryngoscopy significantly improved the glottic view during routine intubations, we could demonstrate that this was also the case in patients with anticipated difficult airway, i.e. in those with immoblized cervical spine (e.g. trauma victims). Video laryngoscopy thereby proved its value in the operating room environment. Its use in emergency situations or in an out-of-hospital setting seems, however, barely possible due to the fact that a cold light source running on 220V and a heavy video monitor are required. Downsizing the equipment to an easily portable format and running it on battery power could render its in-the-field use possible, thereby decreasing the likelihood of out-of-hospital airway disasters during emergency endotracheal intubations.

Reference: (1) Kaplan MB, et al., J Clin Anesth 2006;18:357-62.

Anesthesiology 2007; 107: A585