It is the application of cricoid pressure(CP), originally published by Sellick in 1961 to “control regurgitation of gastric or esophageal contents until intubation with a cuffed endotracheal tube was completed” with the goal of reducing the risk of aspiration of gastric contents, during Rapid Sequence Induction(RSI). Also,sometimes referred to as Rapid Sequence Induction Intubation (RSII), is an important part of airway management technique in emergencies.
Properly applied pressure over the cricoid cartilage over the cricoid cartilage compresses the esophagus against the vertebral body thereby preventing the aspiration.Sellick observed that the cricoid pressure occluded the esophagus at C5 vertebra level.
The technique is a part of RSI, meant for rapid access and control of the airway in emergency where patient is considered to have full stomach.
An assistant applies the cricoid pressure with thumb on one side and index and middle finger on the other side of the trachea starting before induction of anesthesia and removing the pressure only after inflation of cuff of endotracheal tube.
The technique should be explained to the patient and the assistant should be trained in the proper way of applying the CP.
Controversies,contradictions and complications
Large number of studies and review articles have attempted to address these issues,appropriate in the context of introduction of new equipment,algorithm and better understanding of concepts,all related to emergency airway management.
Is it consistently effective?
MRI studies,in 2003 showed that the esophagus is lateral,not posterior to trachea in 50% of healthy volunteers involved in this study.But,another MRI study argued that it is the post cricoid hypo pharynx which matters in cricoid pressure and is effectively compressed by cricoid pressure.
Studies of review of mortality and incidence of aspiration have shown significant incidence of aspiration even in patients where CP was used.
Conversely,there was a decline in the incidence of aspiration related deaths in the decades following introduction if CP for RSI.However,it is to be noted that,during that period there was simultaneous progess in the understanding and management of other aspects of obstetric anesthetic management too.
Can CP Interfere with effective airway management?
Possible,more so if it is applied incorrectly.
Available literature has shown that it can interfere with all aspects of airway management including mask ventilation,airway insertion,insertion of supraglottic airway devices(SAD),intubation through SAD and laryngoscopy.
Recommendation is to reduce the pressure or release completely if the CP interferes with effective ventilation,since oxygenation is the priority number one in any airway management.
How much pressure should be exerted?
20N is the recommonded force,but it is not objectively possible to measure the same.Higher pressure may be required in presence of a nasogastric tube.
A higher force of 30N is recommonded with NG tube in place
Can patient be ventilated with face mask during CP?
original techniques precludes any positive pressure breaths during RSI,of which CP is a part.However,a properly applied CP prevents transmission of the pressure applied at oral cavity to the stomach.For regurgitation to occur,a pressure of more than 20cmH2O is required.
Current practice,also endorsed by Difficult Airway Society of the UK and Canadian Airway Focus Group(CAFG),is that patient can be gently ventilated during the RSI as it a)helps to know the ability to ventilate the patient b)helps to maintain better oxygenation during intubation,especially should there be difficult in intubation.
Can CP be effective in presence of NG tube?
In the original description,the recommendation was to empty the stomach and remove the NG tube before RSI.Later,Sellick Himself observed that the NG tube can safely be left in place during RSI and the practice continues to be acceptable today.
Studies and evidence,including MRI studies, have shown that presence of NG tube does not reduce the effectiveness of CP in compressing the esophagus,which happens around the NG tube.Further, the NG Tube itself is not compressed, and provides a pathway for the gastric contents to be brought out should there be a regurgitation.
What complications have been reported?
Reported problems and complications include worsening of airway obstruction, regurgitation ,vomiting and aspiration.There is also a report of esophageal rupture during CP which however is extremely rare.
CP in patients with subcutaneous esophageal grafts.
Conventional technique would not occlude the esophagus.In these patients,direct pressure over the graft against anterior chest wall can be applied with the palm of the hand,to occlude the graft lumen during RSI.
Should we abandon the Sellick Manoever or use it in every RSI?
The recommendation is to use it in all RSI but CP is to be reduced or released if it interfers with ventilation.
Sellick BA Cricoid pressure to control regurgitation of stomach contents during induction of anesthesia.Lancet 1961;2:404-6
Ramez Salem et al gastric Tubes and Airway Management in Patients at Risk of Regurgitation:History,Current Concepts and Proposals for an Algorithm Anesth Analg 2014;118:No3