Cricoid Pressure: Do No Harm, But Do It Correctly

To the Editor As clinicians with interest in cricoid pressure (CP), we read “The Clinical Use of Cricoid Pressure: First Do No Harm.”1 The authors detailed unsettled aspects, including “the use of thumb-index versus index-middle versus 3-finger occlusion.”1 They alluded to Sellick’s2 description “...the cricoid is palpated and lightly held between the thumb and second finger.”1 They added, “…Interestingly, Figure 4 in the seminal report by Sellick2 actually depicts CP using a 3-finger (thumb, index, and middle) technique!”1 We wish to clarify this misunderstanding. First, the “British” naming of the third digit (middle finger) as the second finger contributed to the confusion. Second, CP is a 2-step maneuver. Sellick2 wrote, “whilst the patient is still conscious the cricoid cartilage is palpated and lightly held between the second finger and the thumb, and the index finger is placed on the anterior surface. As consciousness is lost, pressure is increased by the index finger maintaining the cricoid in its central position.” The authors misinterpreted holding the cricoid between 2 fingers as the entire CP technique. One of us (M.R.S.), who wrote 2 articles with Sellick,2 attests that he always used the 3-finger maneuver (essential for proper application). Patient positioning during CP is no longer a matter of dispute. Sellick2 used the head-down position after intubation as a maneuver to induce regurgitation.3 CP and intubation were performed in the supine position.2 The sniffing position is preferred because it allows effective CP and optimal visualization.3 The 30°–40° head-up position (practiced before CP) postulates that the pressure in the stomach does not exceed 20 cm H2O. In this position, gastric contents are retained in place and if regurgitation occurs, they will not reach the larynx.2,3 The authors presented 5 considerations when designing studies. The first is optimal application and consistent CP performance.1 Although technology-enhanced simulation improves application of the correct force, we propose actual measurement of the force rather than estimating it. The progressive loss of force, variations in application, and complications associated with excessive or inadequate force are all reasons why reliable devices should be used to measure the exact force.3,4 We salute the call for appropriate power calculations. This requirement has been addressed in editorials, reviews, and letters. Investigations that are not sufficiently powered can lead to erroneous and misleading conclusions.3 Because pulmonary aspiration can occur before CP and after release of CP, the fundamental question that needed to be answered was whether properly applied CP effectively compressed the conduit between the stomach and the pharynx? Two studies have answered this question. The authors alluded to the study by Rice and colleagues1 in awake volunteers but overlooked the study by Zeidan et al4 that provided real-time visual and mechanical evidence for the effectiveness of CP in anesthetized and paralyzed patients. We invite the readers to observe the effect of CP in occluding the esophageal entrance during video laryngoscopy (Figure).Figure.: Esophageal entrance as seen during video laryngoscope: (A) before application of CP and (B) after application of 30 N force during CP. CP indicates cricoid pressure.We congratulate the authors for collecting a wealth of information and suggest additional issues, including contraindications, role of nasogastric tubes, ethical considerations, and legal implications Arjang Khorasani, MDDepartment of AnesthesiologyRush Medical CollegeChicago, Illinois[email protected] M. Ramez Salem, MDDepartment of AnesthesiologyUniversity of Illinois College of MedicineChicago, Illinois Ahed Zeidan, MDAhmed Al-Faraj, MDDepartment of AnesthesiologyKing Fahad Specialist HospitalDammam, Saudi Arabia