In Response

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Excerpt

The first criticism of our Italian colleagues is that neck circumference was not measured in our study.1 They surmised that an increased neck circumference may necessitate the use of greater cricoid force to effectively occlude the esophageal entrance. However, they did not quote any study to support their claim. In our investigation, morbidly obese patients were not included, and we were satisfied that the body mass index in both men and women was comparable. The many factors that potentially influence the effectiveness of cricoid pressure (CP) have been detailed recently.2 These include the force used, how the force is applied, contact point, deformability and surface area of the cricoid plate, distance between the skin and cricoid cartilage and type of tissue between them, size of the esophageal inlet, intraesophageal pressure, and location of the esophageal inlet in relation to the cricoid cartilage and vertebral body. The availability of new, easy-to-use devices will allow us to use the appropriate force reliably and to study the relative impact of these various factors.
Their second criticism is that our use of the GlideScope Video Laryngoscope (GVL) prevents the extrapolation of our findings to the use of rigid laryngoscopy. They assert that the use of GVL can result in a change in the laryngeal-esophageal anatomical relationship. We believe this is a moot point for 3 reasons. First, our study was performed in the sniffing position, which is the ideal position for axis alignment. Second, the GVL yields a panoramic view of the glottis and esophageal entrance and permits easy cannulation of the esophagus.3 Third, we believe that, in the future, the use of video laryngoscopy will surpass the use of conventional laryngoscopy.
Their third criticism is that failed gastric tube insertion during CP is not proof of effective CP. It is clearly mentioned in the Methods section that in all patients in whom esophageal cannulation could not be done (effective CP), cannulation was attempted again after the release of CP and was successfully performed. This was an important part of the protocol to ensure that the inability to cannulate was solely due to CP and not because of other causes. Thirteen of 73 patients were excluded, and the reason for this was because of the prolonged time required to visualize the esophageal inlet. Our goal was to complete the experiment in <2 minutes in our anesthetized and paralyzed patients. For safety concerns, when it became apparent that the experiment would last longer than 2 minutes (because of the time required to identify the esophageal inlet in some patients), the experiment was terminated.
Regarding their fourth criticism, we believe our investigation provided evidence that the cricoid force necessary to prevent regurgitation is less in women compared with men with normal body habitus. The fact that the cricoid cartilage is smaller in women as compared with men was adequately addressed in our article. We are satisfied with our explanation that less applied cricoid force occludes the esophageal entrance in women as compared with men is related to the differences in the size of the cricoid plate.
It is clearly stated in the Methods sections of our 2 articles1,3 that training of the operator performing gastric tube insertion trials commenced months before the studies began. In addition, it is has been shown in a randomized clinical trial that the glidescope facilitates gastric tube insertions.4 It is no surprise that ignoring these important aspects of our strict protocol has led the Italian group to incorrect or misleading conclusions.
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