What is the reason for applying cricoid pressure during a rapid sequence induction, and what are some of the problems associated with it?
The cricoid cartilage is the only complete cartilaginous circular ring in the trachea. As a result, posterior/rostral pressure applied to it will occlude the upper esophagus against the cervical vertebrae in an effort to prevent regurgitation of gastric contents into the oropharynx. Interestingly, cricoid pressure has been shown to decrease LES tone and may actually promote reflux. However, if gastro-esophageal reflux should occur while cricoid pres-sure is being held, regurgitation into the pharynx should be prevented. In the case of a difficult intubation, cricoid pressure can make ventilation more difficult.
Cricoid pressure is poorly tolerated in the awake patient and can cause the patient to retch. This retching can increase intra-esophageal pressure and result in an esophageal rupture. In the starved supine patient the max-imum intragastric pressure is 25 mmHg. Increasing gastric volume by 750 ml can increase the intragastric pressure to 35 mmHg. Regurgitation is associated with 40 mmHg of intragastric pressure and can be prevented by 30 newtons of force on the cricoid. Older studies recommend 40 N of force. However, this much force is poorly tolerated, often distorts the laryngeal anatomy making intubation difficult, and may predispose the patient to an esophageal rupture. One solution is to provide 20 N of force to the awake patient. This relatively small amount of force will give some protection against regurgitation; however, if intra-esophageal pressure gets too high, regurgitation will occur but esophageal rupture will not. When the patient loses consciousness, the force on the cartilage should be increased to 30 N until the trachea is successfully intubated.