Who is “Sellick” and when did his method become ubiquitous?
It is hard to think of anything that is more iconic in the practice of emergency medicine than the Sellick Maneuver: application of cricoid pressure to prevent aspiration during intubation and to improve laryngeal visualization. Attending physicians teach it to residents, paramedics use it, and it is an intrinsic part of rapid sequence intubation. So where did this classic maneuver come from?
In 1961, British anesthesiologist Dr. Brian A. Sellick conducted a study in which cadaver stomachs were filled with water and placed in steep Trendelenburg – this was the common practice in those days to reduce the chance of aspiration should a patient vomit. Sellick then applied pressure over the cricoid cartilage. He found he could prevent fluid from getting into the pharynx by applying firm backwards pressure on the cricoid. The theory was that by pressing on the cricoid, the esophagus was compressed against the cervical vertebrae, closing it off and thereby reducing the chance of aspiration. With little further study, the eponymous Sellick maneuver entered into medical practice. It seemed to make such obvious common sense that it became “gospel.” I also became routine while bagging a patient with a BVM and during rapid sequence intubation (RSI), which is often performed on a patient with a full stomach.
Sellick was not the first physician to describe pressure on the laryngeal area to close off the esophagus, however. In 1774, Dr. William Cullen described the “ingenious” experiments of a Dr. Munro on “ascertaining the best manner of inflating the lungs of drowned persons.” In those days, such ventilation was accomplished by using a bellows inserted into the mouth to inflate the lungs or a “pipe” inserted into the nose through which the rescuer would blow. Monro noted air insufflated into the oropharynx went into the stomach resulting in vomiting but by pressing on the lower larynx he could direct air into the lungs.
A few recent studies have brought into question whether this old standard should be accepted so fully. The bottom line is that Sellick’s maneuver works by closing off the opening of the esophagus by compressing the hypopharynx against the cervical vertebrae. It takes some 40N of pressure on the cricoid to reliably close off the opening to the esophagus. Such pressure may compress the airway itself and close it off as well. This might occur more often in pediatric patients who have more flexible cartilage. In many cases, cricoid pressure degrades the ability to visualize the cords making it more difficult to intubate the patient. In such a situation one should immediately release compression over the cricoid. As such, the Sellick maneuver may play a more important role when using a bag-valve mask to ventilate a patient so that the stomach is not distended with air as long as the airway is not compressed. It may actually play a lesser role during the act of intubation itself.