Sellick's Maneuver (cricoid pressure)
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It is true that cricoid pressure during induction of sedation and paralysis in
rapid-sequence intubation is a recommended technique for protecting the airway
and reducing the risk of vomiting and aspiration.[1][2]  However, the
recommended practice of cricoid pressure has never been studied in an
evidence-based manner to determine whether or not manual pressure on the
cricoid cartilage can effectively occlude the esophagus and protect the airway
from vomit and aspiration.[3][4][5]   In fact, there is experimental evidence
that cricoid pressure can reduce the lower esophageal sphincter tone and
actually increase the risk of vomiting and aspiration.[6]

The evidence to date suggests that the airway is best protected from vomit and
aspiration by reducing the time required to intubation and increasing the
initial-attempt success rate.[7] [8] [9]   This is most effectively
accomplished by rapid-sequence oral-tracheal intubation.

 Doug  Ragland, MD
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 REFERENCES

 [1] Sakles JC: Airway management in the emergency department: a one-year
 study of 610 tracheal intubations [see comments].  Ann Emerg Med; 31(3):
 325-32 (Mar1998)
 [...The technique of choice for oral intubation is rapid sequence induction
 (RSI).  RSI consists of preoxygenation/denitrogenation followed by
 administration of a short-acting hypnotic agent (i.e., thiopental) and a
 neuromuscular blocking agent (traditionally succinylcholine). An assistant
 holds cricoid pressure (Sellick's maneuver) to prevent aspiration as
 consciousness is lost.

 [2] Talucci RC, Shaikh KA, Schwab CW: Rapid sequence induction with
 orotracheal intubation in the multiply injured patient. Am Surg 54:185-187,
 1998

 [3]  Warner MA, Warner ME, Weber JG: Clinical significance of pulmonary
 aspiration during the perioperative period. ANESTHESIOLOGY 1993; 78:56-62

 [4] Schwartz DE, Matthay MA, Cohen NH: Death and other complications of
 emergency airway management in critically ill adults. ANESTHESIOLOGY 1995;
 82:367-76

 [5]  Efficacy and safety of cricoid pressure needs scientific validation
 [letter]
 Jackson SH - Anesthesiology - 1996 Mar; 84(3): 751-2

 [6] Tournadre JP: Cricoid cartilage pressure decreases lower esophageal
 sphincter tone.
 Anesthesiology; 86(1): 7-9 (Jan 1997)
 [...The phenomenon we observed may provide a possible explanation for gastric
 content aspiration during induction of anesthesia despite the application of
 cricoid cartilage pressure. For example, if only moderate cricoid pressure,
 as recommended before loss of consciousness (about 20 N), is applied when the
 upper esophageal sphincter is not completely intact, the efficacy of LES
 (lower esophagel sphincter) barrier pressure may be reduced, leading to
 regurgitation....]

 [7] Sakles JC: Airway management in the emergency department: a one-year
 study of 610 tracheal intubations [see comments].  Ann Emerg Med; 31(3):
 325-32 (Mar1998)
 [...A recent study compared blind nasotracheal intubation with
 succinylcholine-assisted intubation in drug-intoxicated patients. Blind nasal
 intubation had a success rate of 65% with a mean time to intubation of 276
 seconds. In contrast, succinylcholine-assisted intubation had a 100% success
 rate with a mean intubation time of 64 seconds.  The blind nasal intubation
 group experienced complications, including epistaxis, vomiting, and
 aspiration; there were no complications in the group treated with
 succinylcholine.  A second, large, prospective study compared rapid sequence
 induction with blind nasal intubation, in patients in whom no paralytic
 agents were administered. The unparalyzed group experienced complications,
 including airway trauma, aspiration, and death. No complications occurred in
 the rapid sequence group.

 [8]  Droner SC, Merigian KS, Hedges JR, et al: A comparison of blind
 nasotracheal and succinylcholine assisted intubation is the poisoned
 patient. Ann Emerg Med 16:650-652, (1987)

 [9] Li J, Murphy-Lavoie H, Bugas C, et al: Complications of emergency
 intubation with and without paralysis. American Journal of Emergency
 Medicine 17:141-143, (1999)