A 32-year-old woman with a 6-month history of gastroesophageal reflux disease presents to the emergency department with acute appendicitis. She is scheduled for emergency appendectomy under general anesthesia. Her vitals are: BP 128/82 mmHg, HR 92/min, RR 18/min, SpO₂ 98% on room air. She last ate a light breakfast 2 hours ago. During rapid sequence induction, after pre-oxygenation and administration of induction agent and succinylcholine, the anesthesiologist applies cricoid pressure. Which of the following best describes the PRIMARY mechanism by which cricoid pressure reduces aspiration risk in this patient?

Explanation

## Mechanism of Cricoid Pressure in Rapid Sequence Induction **Key Point:** Cricoid pressure (Sellick maneuver) works by compressing the esophagus posteriorly against the cervical vertebral bodies, occluding the esophageal lumen and preventing passive regurgitation of gastric contents from entering the pharynx and subsequently the trachea. ### Anatomical Basis The cricoid cartilage is the only complete cartilaginous ring in the larynx. When external pressure is applied posteriorly over the cricoid cartilage: 1. The esophagus lies directly posterior to the cricoid ring 2. Backward compression of the cricoid cartilage compresses the esophageal lumen against the cervical spine (C3–C4 level) 3. This creates a mechanical seal preventing upward movement of gastric contents ### Clinical Application in RSI | Phase | Action | Purpose | |-------|--------|----------| | Pre-oxygenation | Cricoid pressure not applied | Allows normal breathing | | Induction agent administration | Cricoid pressure initiated (10 N) | Prevent regurgitation during loss of consciousness | | After intubation | Cricoid pressure released | Confirm tube position, restore normal anatomy | **High-Yield:** The pressure applied should be approximately 10 N (1 kg force) during induction, increasing to 30 N (3 kg force) if regurgitation occurs. Excessive pressure can distort the laryngeal view and impede intubation. **Clinical Pearl:** Cricoid pressure is particularly critical in this patient because she has GERD (increased gastric acidity and volume) and a recent meal (2 hours), both risk factors for aspiration pneumonitis (Mendelson syndrome). ### Why Cricoid Pressure Fails Sometimes - Incorrect hand placement (over thyroid cartilage instead of cricoid) - Insufficient force application - Anatomical variations (obesity, short neck) - Esophageal intubation (pressure then occludes the tube instead of esophagus) [cite:Gupta & Sharma Airway Management Ch 8]