Cricoid pressure, also known as the Sellick maneuver, is a procedure historically applied during certain emergency medical situations involving intubation. It involves applying external pressure to a specific cartilage in the neck. Its original purpose was to prevent aspiration, a serious complication where stomach contents enter the lungs during airway securement. The maneuver aimed to create a physical barrier to protect the airway.
The Theory and Application of Cricoid Pressure
The cricoid cartilage is a complete ring of cartilage located in the lower part of the larynx, just below the thyroid cartilage (Adam’s apple). Unlike other tracheal cartilages, which are C-shaped, its complete ring structure allows it to compress the esophagus against the vertebral column. This compression is theorized to occlude the esophagus, preventing stomach contents from entering the trachea and lungs.
In its traditional application, the cricoid cartilage is first identified by palpation. An assistant then applies backward pressure, typically using a two- or three-finger technique. The recommended force varies, starting at 10 Newtons (1 kg) while the patient is awake, increasing to 30-40 Newtons (3-4 kg) once consciousness is lost during rapid sequence intubation (RSI). This pressure is maintained until the breathing tube (endotracheal tube) is successfully placed in the trachea and its position is confirmed, safeguarding the airway.
Potential Complications and Difficulties
Cricoid pressure can introduce several challenges during intubation. One issue is the potential for the maneuver to worsen the intubator’s view of the larynx. This occurs because the applied pressure can distort the airway anatomy, making it harder to visualize the vocal cords and guide the breathing tube into the trachea.
Incorrect application of force or misplacement of pressure can lead to adverse outcomes. Applying excessive force can cause pain, gagging, retching, or vomiting in conscious patients, counteracting its purpose. There is also a risk of severe injuries, such as cricoid cartilage fracture or esophageal injury, particularly if the patient is actively vomiting or if the pressure is misdirected. Consistently applying the precise amount of force (e.g., 30-40 Newtons) in a high-stress emergency environment can be challenging, contributing to inconsistent application and complications.
The Debate Over Effectiveness
The initial support for cricoid pressure, introduced by Brian Arthur Sellick in 1961, stemmed from early observational studies with limited participant numbers. These findings suggested the maneuver could prevent regurgitation, but they lacked the rigorous methodology of modern randomized controlled trials. Over time, cricoid pressure became a standard practice, particularly during rapid sequence intubation.
Modern research, using advanced imaging techniques like MRI and ultrasound, has raised questions about the maneuver’s ability to reliably occlude the esophagus. These studies often show that the esophagus is frequently displaced laterally rather than being fully compressed against the spine, challenging the fundamental theory behind its effectiveness. Several observational studies and case reports have documented instances of gastric aspiration occurring despite the application of cricoid pressure, suggesting it may not consistently prevent its primary target complication. The current evidence is insufficient to conclude that cricoid pressure reduces aspiration or improves intubation success.
Current Clinical Recommendations
Given evolving evidence, major medical organizations have re-evaluated cricoid pressure. Guidelines from bodies like the Difficult Airway Society (DAS) and the American Society of Anesthesiologists no longer universally recommend its use. Instead, consensus has shifted away from considering it a mandatory standard of care in all rapid sequence intubations.
The current approach emphasizes that if cricoid pressure interferes with the intubator’s view of the larynx or impedes ventilation, it should be immediately reduced or released. This allows clinicians to prioritize securing the airway and maintaining oxygenation, even if it means discontinuing the maneuver. This change reflects a broader understanding that while historically practiced, the scientific backing for cricoid pressure’s benefit in preventing aspiration is not as robust as once believed, and its potential to hinder intubation attempts is a significant consideration.