There has always been some controversy about the utility of applying cricoid pressure (aka Sellick Maneuver) during rapid sequence intubation for the purpose of preventing aspiration. Theoretically, applying pressure on the cricoid cartilage posteriorly should occlude the esophagus against the vertebrae and therefore prevent passive regurgitation of gastric contents into the oropharynx. Unfortunately, has never been proven to reduce aspiration. In fact, there are some studies using both CT scanning and MRI scanning that demonstrate that cricoid pressure does not reliably occlude the esophagus during direct laryngoscopy., In addition, cricoid pressure is poorly performed by many practitioners. Another drawback is that at times cricoid pressure applied to firmly can obscure the view obtained by direct laryngoscopy. Furthermore, aggressive cricoid pressure can make placement of a supraglottic airway (laryngeal mask airway or King tube airway) or bag valve mask ventilation more difficult. The 2010 ACLS guidelines make the strong statement that, “the routine use of cricoid pressure in cardiac arrest is not recommended.”
With this as a background, a new study out of Saudi Arabia was just published that demonstrates that the proper application of cricoid pressure using a force of 30 N to the cricoid cartilage effectively occludes the esophageal entrance during Glidescope intubation. However, a major issue with this study is that it only evaluated nonobese patients with an ASA score of I-II and it only evaluated Glidescope intubation. The investigators assessed ability to pass a gastric tube through the esophageal opening (used as a marker of the potential for regurgitation) with and without application of cricoid pressure in 107 nonobese, American Society of Anesthesiologists class I and II elective surgery patients who were sedated, paralyzed, and manually ventilated.
The gastric tube could not be advanced in any patient when cricoid pressure was applied and could be advanced in every patient when cricoid pressure was not applied. Therefore, the investigators concluded that cricoid pressure using this force could effectively occlude the esophagus during Glidescope intubation in this patient population.
One problem that I see with this study is that the results can not necessarily be applied to obese patients or for rapid sequence intubation using direct laryngoscopy. Direct laryngoscopy often uses more anterior force to visualize the glottis compared with a Glidescope intubation. For now, I think the use of cricoid pressure remains operator dependent. I would emphasize that the Sellick maneuver should NOT be used in cases of cardiac arrest and consider lightening the pressure if you are having problems with visualization during direct laryngoscopy or for placement of supraglottic airways.
 Annals Emergency Medicine, 2007; 50: 653-666