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Redundant Safety and Videolaryngoscopy.

Critical Care Medicine www.ccmjournal.org 1463 During the last 20 years, video laryngoscopy has taken on an increasingly important role in airway management. Multiple studies have compared direct laryngoscopy to video laryngoscopy but few have accomplished this under the austere conditions of prehospital air rescue medicine. In this issue of Critical Care Medicine, Kreutziger et al (1) add to our knowledge with their work. The authors’ randomized critically ill patients requiring prehospital airway management to direct laryngoscopy or McGrath Mac video laryngoscopy under the most difficult circumstances possible, helicopter rescue. The study by Kreutziger et al (1) is relevant to all critical care and emergency airway managers. Experienced prehospital physicians with extensive training in anesthesiology intubated unfasted patients with soiled airways, hemodynamic instability, cervical spine precautions, and limited pulmonary reserve. These challenges are common to patients intubated in the ICU, emergency department, and after unexpected decompensation on the general hospital ward. The authors (1) adhered to a well-planned and safe protocol. Intubation attempts were stopped when oxygen saturation fell by 10%. Second attempts could be made with the same method, but the physicians were mandated to switch techniques after a failed second attempt. The investigators’ primary outcome was intubation success with video versus direct laryngoscopy. They designed the study to have 90% power to detect a difference of ± 6.5% with a p value of 0.01. They calculated that 992 patients would be needed to achieve this but stopped the study after performing a preplanned interim analysis when 514 patients (50%) were enrolled. At that point, there was no difference in effectiveness between the techniques (98.5% direct laryngoscopy, 98.1% video laryngoscopy) and further enrollment would not have resulted in meaningful outcome differences. This finding is consistent with multiple studies that show, across several different video laryngoscopes and in different patient populations, that video laryngoscopy and direct laryngoscopy tend to perform equally well (2). These authors and others have previously found video laryngoscopy to be inferior to direct laryngoscopy (3–5), but other studies have found the opposite (6–10). Video laryngoscopy tends to be superior with relatively inexperienced operators (7, 11, 12). This is relevant to the study by Kreutziger et al (1), as these very experienced prehospital air rescue physicians likely are more familiar with direct laryngoscopy than most intensivists and emergency physicians. Other experienced flight crews have demonstrated higher than average success rates for other difficult procedures, such as cricothyrotomy (13). That said, even for experienced airway managers, video laryngoscopy may be superior for intubating morbidly obese patients (9) and others with predicted difficult airways (6). Using video laryngoscopy with an anterior optic that is opposed to the tongue and above secretions that pool in the hypopharynx of the supine patient, video laryngoscopy and direct laryngoscopy performed equally well in soiled airways (14). Video laryngoscopes that require the optic to pass through the hypopharynx are more liable to become fouled by saliva, blood, and vomitus and fail in soiled airways (4). This is especially important for clinicians who care for unfasted, traumatized, and other patients suffering from unexpected, emergent respiratory failure. Video laryngoscopes with anterior optics include the Glidescope, the McGrath Mac, and the C-Mac. Although the McGrath Mac employed in the study by Kreutziger et al (1) is shaped like a standard MacIntosh blade, it is in fact much thicker than a metal blade and does not lend itself to direct laryngoscopy. Direct laryngoscopy creates both visual and physical space in which to pass an endotracheal tube. The cost of this is difficulty with glottic visualization, as seen in the study by Kreutziger et al (1). Video laryngoscopy places an optic at the glottis and requires a more rigid stylet or other means to displace tissue and successfully pass the endotracheal tube. The result is often a mismatch between excellent glottic view and difficulty with tube placement, also seen in the study by Kreutziger et al (1). This may have occurred because the same malleable stylet was used for both techniques. A more rigid stylet might have facilitated tube placement with the McGrath Mac. A recent ICU study that concluded that direct *See also p. 1362.