Sellick maneuver assisted real-time to achieve target force range in simulated environment-A prospective observational cross-sectional study on manikin.

A force sensor system was developed to give real-time visual feedback on a range of force. In a prospective observational cross-section study, twenty-two anaesthesia nurses applied cricoid pressure at a target range of 30-40 Newtons for 60 seconds in three sequential steps on manikin: Group A (step 1 blinded, no sensor), Group B (step 2 blinded sensor), Group C (step 3 sensor feedback). A weighing scale was placed below the manikin. This procedure was repeated once again at least 1 week apart. The feedback system used 3 different colours to indicate the force range achieved as below target, achieve target, above target. Significantly higher proportion of target cricoid pressure was achieved with the use of sensor feedback in Group C; 85.9% (95%CI: 82.7%-88.7%) compared to when blinded from sensor in Group B; 31.3% (95%CI: 27.4-35.4%). Cricoid force achieved blind (Group B) exceeded force achieved with feedback (Group C) by a mean of 8.0 (95%CI: 5.9-10.2, p<0.0001) and 6.2 (95%CI:4.1-8.3, p< 0.0001) Newtons in round 1 and 2 respectively. Weighing scale read lower than corresponding force sensor by a mean of 8.4 Newtons (95% CI: 7.1-9.7, p<0.0001) in group B and 5.8 Newtons (95% CI: 4.5-7.1, p<0.0001) in Group C. Force sensor visual feedback system enabled application of reproducible target cricoid pressure with less variability and has potential value in clinical use. Using weighing scale to quantify and train cricoid pressure requires a review. Understanding the force applied is the first step to make cricoid pressure a safe procedure.

Spatial Motion of Arytenoid Cartilage Using Dynamic Computed Tomography Combined with Euler Angles.

OBJECTIVE: To investigate the feasibility of dynamic computed tomography in recording and describing the spatial motion characteristics of the arytenoid cartilage. METHODS: Dynamic computed tomography recorded the real-time motion trajectory of the arytenoid cartilage during inspiration and phonation. A stationary coordinate system was established with the cricoid cartilage as a reference and a motion coordinate system was established using the movement of the arytenoid cartilage. The Euler angles of the arytenoid cartilage movement were calculated by transformation of the two coordinate systems, and the spatial motion characteristics of the arytenoid cartilage were quantitatively studied. RESULTS: Displacement of the cricoid cartilage was primarily inferior during inspiration. During phonation, the displacement was mainly superior. When the glottis closed, the superior displacement was about 5-8 mm within 0.56 s. During inspiration, the arytenoid cartilage was displaced superiorly approximately 1-2 mm each 0.56 s. The rotation angle was subtle with slight rotation around the XYZ axis, with a range of 5-10 degrees. During phonation, the displacement of the arytenoid cartilage was mainly inferior (about 4-6 mm), anterior (about 2-4 mm) and medial (about 1-2 mm). The motion of the arytenoid cartilage mainly consisted of medial rolling, and there was an alternating movement of anterior-posterior tilting. The arytenoid cartilage rolled medially (about 20-40 degrees within 0.56 s), accompanied by anterior-posterior tilting (about 15-20 degrees within 0.56 s). CONCLUSION: Dynamic computed tomography recordings of arytenoid cartilage movement can be combined with Euler transformations as a tool to study the spatial characteristics of laryngeal structures during phonation. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:E646-E653, 2020.

A survey of cricoid pressure application in a single institution in Ethiopia.

OBJECTIVE: The aim of this survey is to determine the standard of practice of cricoid pressure application on rapid sequence induction in Ayder comprehensive specialized hospital from April 3 to May 3, 2019. RESULTS: A total of 30 anesthetists were involved in the study with a response rate of 87%. Ninety percent of the respondents do not mask ventilate during rapid sequence induction and they do aspirate the naso-gastric tube if present. Almost half of the respondents have witnessed regurgitation during application of cricoid pressure and 93% do not remove the naso-gastric tube before rapid sequence induction. Seventy percent had experienced difficulty of endotracheal intubation during application of cricoid pressure. All of the respondents had less than 10 years of working experience as anesthetist.

The effect of force applied to the left paratracheal oesophagus on air entry into the gastric antrum during positive-pressure ventilation using a facemask.

Cricoid force is widely applied to decrease the risk of pulmonary aspiration and gastric antral insufflation of air during positive-pressure ventilation, yet its efficacy remains controversial. We compared manual oesophageal compression at the low left paratracheal and cricoid levels for the prevention of gastric antral air insufflation during positive-pressure ventilation by facemask in patients scheduled for elective surgery under general anaesthesia. After gaining written consent, participants were randomly allocated by sealed envelope to one of three groups: oesophageal compression by 30 N paratracheal force (paratracheal group); oesophageal compression by 30 N cricoid force (cricoid group); or no oesophageal compression (control group). Gastric insufflation of air was assessed before and after positive-pressure ventilation by ultrasound measurement of the antral cross-sectional area and/or presence of air artefacts in the antrum. The primary outcome measure was the proportion of participants with ultrasound evidence of gastric insufflation. We recruited 30 patients into each group. Before facemask ventilation, no air artefacts were visible in the antrum in any of the participants. After facemask ventilation of the participant's lungs, no air artefacts were seen in the paratracheal group, compared with six subjects in the cricoid group and eight subjects in the control group (p = 0.012). Our results suggest that oesophageal compression can be achieved by the application of manual force at the low left paratracheal level and that this is more effective than cricoid force in preventing air entry into the gastric antrum during positive-pressure ventilation by facemask.

Effect of Cricoid Pressure Compared With a Sham Procedure in the Rapid Sequence Induction of Anesthesia: The IRIS Randomized Clinical Trial.

Importance: The use of cricoid pressure (Sellick maneuver) during rapid sequence induction (RSI) of anesthesia remains controversial in the absence of a large randomized trial. Objective: To test the hypothesis that the incidence of pulmonary aspiration is not increased when cricoid pressure is not performed. Design, Setting, and Participants: Randomized, double-blind, noninferiority trial conducted in 10 academic centers. Patients undergoing anesthesia with RSI were enrolled from February 2014 until February 2017 and followed up for 28 days or until hospital discharge (last follow-up, February 8, 2017). Interventions: Patients were assigned to a cricoid pressure (Sellick group) or a sham procedure group. Main Outcomes and Measures: Primary end point was the incidence of pulmonary aspiration (at the glottis level during laryngoscopy or by tracheal aspiration after intubation). It was hypothesized that the sham procedure would not be inferior to the cricoid pressure. The secondary end points were related to pulmonary aspiration, difficult tracheal intubation, and traumatic complications owing to the tracheal intubation or cricoid pressure. Results: Of 3472 patients randomized, mean (SD) age was 51 (19) years and 1777 (51%) were men. The primary end point, pulmonary aspiration, occurred in 10 patients (0.6%) in the Sellick group and in 9 patients (0.5%) in the sham group. The upper limit of the 1-sided 95% CI of relative risk was 2.00, exceeding 1.50, failing to demonstrate noninferiority (P = .14). The risk difference was -0.06% (2-sided 95% CI, -0.57 to 0.42) in the intent-to-treat population and -0.06% (2-sided 95% CI, -0.56 to 0.43) in the per protocol population. Secondary end points were not significantly different among the 2 groups (pneumonia, length of stay, and mortality), although the comparison of the Cormack and Lehane grade (Grades 3 and 4, 10% vs 5%; P <.001) and the longer intubation time (Intubation time >30 seconds, 47% vs 40%; P <.001) suggest an increased difficulty of tracheal intubation in the Sellick group. Conclusions and Relevance: This large randomized clinical trial performed in patients undergoing anesthesia with RSI failed to demonstrate the noninferiority of the sham procedure in preventing pulmonary aspiration. Further studies are required in pregnant women and outside the operating room. Trial Registration: ClinicalTrials.gov Identifier: NCT02080754.

Pressure measurement in the upper esophagus during cricoid pressure: A high-resolution solid-state manometry study.

BACKGROUND: The use of cricoid pressure is controversial, and its ability to occlude the esophagus has been questioned. In this study, high-resolution solid-state manometry was used to analyze pressure changes in the upper esophagus from cricoid pressure during modified rapid sequence induction. This is a secondary analysis of data from a previous study. METHODS: Seventeen healthy volunteers participated in a double-blind, randomized, placebo-controlled, cross-over study with primary aim to compare differences in the barrier pressure on the lower esophageal sphincter during rapid sequence induction with or without alfentanil. Standardized cricoid pressure of 30 N was applied 2 minutes after propolipid injection and held for 15 seconds and pressures in the esophagus were measured. RESULTS: Cricoid pressure resulted in a pressure increase of 127 ± 98 mmHg (95% CI: 73-182) (placebo) and 123 ± 74 mmHg (95% CI: 84-162) (alfentanil) at the level of the upper esophageal sphincter (UES), compared to baseline. The pressure difference around the UES compared to the proximal esophagus during cricoid pressure application was 165 ± 100 mmHg (placebo) and 159 ± 87 mmHg (alfentanil) (mean ± 1 SD). CONCLUSION: This study using high-resolution solid-state manometry under clinically relevant conditions shows that 30 N cricoid pressure generates high pressure in the area of the UES, far exceeding the levels previously considered necessary to prevent regurgitation. Additional studies are needed to clarify the effectiveness of cricoid pressure in preventing passive regurgitation before it is rejected as a part of rapid sequence induction.

Ideal Cricoid Pressure Is Biomechanically Impossible During Laryngoscopy.

OBJECTIVE: This study was a prospective, randomized controlled trial of rapid sequence intubation (RSI) with cricoid pressure (CP) within the emergency department (ED). The primary aim of the study was to examine the link between ideal CP and the incidence of aspiration. METHOD: Patients > 18 years of age undergoing RSI in the ED of two hospitals in New South Wales, Australia, were randomly assigned to receive measured CP using weighing scales to target the ideal CP range (3.060-4.075 kg) or control CP where the weighing scales were used, but the CP operator was blinded to the amount of CP applied during the RSI. A data logger recorded all CP delivered during each RSI. Immediately after intubation, tracheal and esophageal samples were taken and underwent pepsin analysis. RESULTS: Fifty-four RSIs were analyzed (25 measured/29 control). Macroscopic contamination of the larynx at RSI was observed in 14 patients (26%). During induction (0-50 seconds), both groups delivered in-range CP. During intubation (51-223 seconds), laryngoscopy was associated with a reduction in mean CP below 3.060 kg in both groups. When compared, there was no statistically significant difference between the groups. For 11 patients, pepsin was detected in the oropharyngeal sample, while three were positive for tracheal pepsin. Seven patients (four control/three measured) were treated for clinical aspiration during hospitalization. As a result of the finding that neither group could maintain ideal range CP during laryngoscopy, the trial was abandoned. CONCLUSION: Laryngoscopy provides a counter force to CP, which is negated to facilitate tracheal intubation. The concept that a static 3.060 to 4.075 kg CP could be maintained during laryngoscopy and intubation was rejected by our study. Whether a lower CP range could prevent aspiration during RSI was not explored by this study.

Cricothyroid joint type as predictor for vocal fold elongation in professional singers.

OBJECTIVE: Vocal fold (VF) elongation vocal folds depends on two factors: the activity of the laryngeal muscles and the cricothyroid joint (CTJ). The aim of the study was to show the influence of the CTJ on VF elongation while singing a sustained vowel at different pitches. STUDY DESIGN: Prospective study. METHODS: Forty-nine female professional singers (25 sopranos, 24 altos) were recruited. Three-dimensional images of the larynx derived from high-resolution computed tomography scanning were obtained at the mean speaking fundamental frequency (F0) and one (F1) and two octaves (F2) above this pitch. RESULTS: From F0 to F1, all three CTJ types showed equal elongation of the VF (type A: 14%, type B/C: 13%). From F1 to F2, VF elongation was 8% in singers with type A and 4% in those with type B/C (P < 0.0001). CONCLUSION: The stability of the CTJ directly influences VF during singing. This is the first study to show this relationship in vivo. LEVEL OF EVIDENCE: 4. Laryngoscope, 128:1176-1181, 2018.

Cricoid Pressure Controversies: Narrative Review.

Since cricoid pressure was introduced into clinical practice, controversial issues have arisen, including necessity, effectiveness in preventing aspiration, quantifying the cricoid force, and its reliability in certain clinical entities and in the presence of gastric tubes. Cricoid pressure-associated complications have also been alleged, such as airway obstruction leading to interference with manual ventilation, laryngeal visualization, tracheal intubation, placement of supraglottic devices, and relaxation of the lower esophageal sphincter. This review synthesizes available information to identify, address, and attempt to resolve the controversies related to cricoid pressure. The effective use of cricoid pressure requires that the applied force is sufficient to occlude the esophageal entrance while avoiding airway-related complications. Most of these complications are caused by excessive or inadequate force or by misapplication of cricoid pressure. Because a simple-to-use and reliable cricoid pressure device is not commercially available, regular training of personnel, using technology-enhanced cricoid pressure simulation, is required. The current status of cricoid pressure and objectives for future cricoid pressure-related research are also discussed.

The Cricoid Force Necessary to Occlude the Esophageal Entrance: Is There a Gender Difference?

BACKGROUND: We tested the hypothesis whether gender differences exist in the applied cricoid force necessary to prevent regurgitation. Real-time visual and dynamic means were used to assess the effectiveness of different applied cricoid forces in occluding the esophageal entrance in men (group 1) and in women (group 2). METHODS: In anesthetized and paralyzed patients, the glottis and esophageal entrance were visualized with a Glidescope video laryngoscope. Trained operators performed cricoid pressure (CP) and gastric tube insertion trials. Successful gastric tube insertion in the presence of CP was considered ineffective CP, whereas unsuccessful insertion was considered effective CP. The applied cricoid forces were measured with a novel instrument, the cricometer. The first patient in each group received 20 N. The applied cricoid force in successive patients was determined by the response of the previous patient within the same group, using the up-and-down sequential allocation technique. RESULTS: In the 30 men and 30 women who qualified for the study, the median cricoid force (cricoid force = 50) that occluded the esophageal entrance was 30.8 N (95% confidence interval = 28.15-33.5) in men, and 18.7 N in women (95% confidence interval = 17.1-20.3; P < .0001). Patency of the esophageal entrance was observed when CP was not applied and when inadequate forces that allowed successful esophageal cannulation were used. CONCLUSIONS: The current study provides evidence that the median force necessary to occlude the esophageal entrance to prevent regurgitation is less in women compared with men. Applying the appropriate cricoid force in women should also decrease airway-related problems that tend to occur with the use of excessive forces. The findings of the current study may only be applicable to patients with normal body habitus.

Relationship of the Cricothyroid Space with Vocal Range in Female Singers.

OBJECTIVES: This study aims to investigate the relationship between the anterior cricothyroid (CT) space at rest with vocal range in female singers. Potential associations with and between voice categories, age, ethnicity, anthropometric indices, neck dimensions, laryngeal dimensions, vocal data along with habitual speaking fundamental frequency were also explored. STUDY DESIGN: This is a cohort study. METHODS: Laryngeal dimensions anterior CT space and heights of the thyroid and cricoid cartilages were measured using ultrasound in 43 healthy, classically trained, female singers during quiet respiration. Voice categories (soprano and mezzo-soprano), age, ethnicity, weight, height, body mass index, neck circumference and length, anterior thyroid and cricoid cartilage heights, practice and performance vocal range, lowest and highest practice and performance notes along with habitual speaking fundamental frequency were collected. RESULTS: The main finding was that mezzo-sopranos have a significantly wider resting CT space than sopranos (11.6 mm versus 10.4 mm; P = 0.007). Mezzo-sopranos also had significantly lower "lowest and highest" performance notes than sopranos. There was no significant correlation between the magnitudes of the anterior CT space with vocal range. The participants with the narrowest and widest anterior CT space had similar vocal ranges. CONCLUSIONS: These results suggest that the CT space is not the major determinant of performance vocal range.

Ultrasound evaluation of the impact of cricoid pressure versus novel 'paralaryngeal pressure' on anteroposterior oesophageal diameter.

To assess the degree to which cricoid pressure (Sellick manoeuvre) actually compresses the oesophagus, we measured the effect of cricoid pressure and paralaryngeal pressure on the outer anteroposterior diameter of the upper oesophagus with ultrasound in 39 healthy volunteers. The mean (SD) outer anteroposterior oesophageal diameter was 0.77 (0.11) cm with no pressure, 0.79 (0.13) cm with the application of cricoid pressure of 30 N and 0.68 (0.12) cm with the application of paralaryngeal pressure of 30 N (p < 0.0001). If cricoid pressure does not reduce the anteroposterior diameter of the oesophagus, it is difficult or impossible to explain the efficacy of the Sellick manoeuvre. However, paralaryngeal pressure decreases this diameter and has the potential to occlude the upper oesophagus.

Cricoid pressure impedes tracheal intubation with the Pentax-AWS Airwayscope®: a prospective randomized trial.

BACKGROUND: It is unclear how cricoid pressure affects tracheal intubation with the Pentax-AWS Airwayscope(®) (AWS). We conducted a prospective randomized clinical trial in anaesthetized patients. METHODS: Sixty patients were allocated to either the cricoid pressure (CP) group (n=30) or the sham group (n=30). We compared the two groups with regard to intubation time, number of attempts required for insertion of the Intlock blade (disposable blade of the AWS) and tracheal intubation, percentage of glottic opening (POGO) score, and subjective difficulty of both laryngoscopy and passage of a tube through the glottis. RESULTS: Intubation time was significantly longer in the CP group (median 45[IQR40-59] s) than in the sham group (32[28-45] s) (P=0.003, 95% CI for median difference 5-24 s). The number required for insertion of the Intlock blade did not differ between the groups (P=0.08), but the number for tracheal intubation was significantly higher in the CP group (1 attempt in 14 patients, 2 in 7, 3 in 9) than in the sham group (1 attempt in 24 patients, 2 in 6; P=0.002). POGO score did not differ significantly between the groups (P=0.60), nor did the subjective difficulty of laryngoscopy (P=0.06). The visual analogue scale score for passage of a tube through the glottis was significantly higher in the CP group than in the sham group (P<0.001). CONCLUSIONS: Cricoid pressure impedes tracheal intubation using the AWS, and is associated with longer intubation time, which can be attributed to increased difficulty in the passage of a tube through the glottis. CLINICAL TRIAL REGISTRY NUMBER: UMIN000018209.

Cricothyroid Articulation in Elderly Japanese With Special Reference to Morphology of the Synovial and Capsular Tissues.

OBJECTIVE: The present study aimed to clarify individual variations in the cricothyroid joint (CT joint). METHODS: Using 30 specimens of the CT joint obtained from elderly donated cadavers, we examined the composite fibers of the capsular ligament as well as the morphology of the synovial tissue. RESULTS: The capsular ligament consistently contained abundant thick elastic fiber bundles on the anterior side of the joint (anterior band) and an elastic fiber-made mesh on the posterior side (posterior mesh). The synovial membrane, lined by synovial macrophages, was usually restricted to the recesses in the medial or inferior end of the joint cavity. Without the synovial lining, elastic fibers of the capsular ligament were subsequently detached, dispersed, and exposed to the joint cavity. We also observed a folded and thickened synovial membrane and a hypertrophic protrusion of the capsular ligament. In six specimens, the joint cavity was obliterated by debris of synovial folds and elastic fiber-rich tissues continuous with the usual capsular ligament. Notably, with the exception of two specimens, we did not find lymphocyte infiltration in the degenerative synovial tissue. DISCUSSION: We considered the CT joint degeneration to be a specific, silent form of osteoarthritis from the absence of lymphocyte infiltration. For high-pitched phonation, the elderly CT joint seemed to maintain its anterior gliding and rotation with the aid of elastic fiber-rich tissues compensating for the loss of congruity between the joint cartilage surfaces. Conversely, however, high-pitched phonation may accelerate obliteration of the joint.

The Effect of Cricoid Pressure on the Unstable Cervical Spine.

BACKGROUND: It has been proposed that cricoid pressure can exacerbate an unstable cervical injury and lead to neurologic deterioration. OBJECTIVE: We sought to examine the amount of motion cricoid pressure could cause at an unstable subaxial cervical spine injury, and whether posterior manual support is of any benefit. METHODS: Five fresh, whole cadavers had complete segmental instability at C5-C6 surgically created by a fellowship-trained spine surgeon. Cricoid pressure was applied to the anterior cricoid by an attending anesthesiologist. In addition, the effect of posterior cervical support was tested during the trials. The amount of angular and linear motion between C5 and C6 was measured using a Fastrak, three-dimensional, electromagnetic motion analysis device (Polhemus Inc., Colchester, VT). RESULTS: When cricoid pressure is applied, the largest angular motion was 3 degrees and occurred in flexion-extension at C5-C6. The largest linear displacement was 1.36 mm and was in anterior-posterior displacement of C5-C6. When manual posterior cervical support was applied, the flexion-extension was improved to less than half this value (1.43 degrees), and this reached statistical significance (p = 0.001). No other differences were observed to be significant in the other planes of motion with the applications of support. CONCLUSIONS: Based on the evidence presented, we believe that the application of cricoid pressure to a patient with a globally unstable subaxial cervical spine injury causes small displacements. There may be some benefit to the use of manual posterior cervical spine support for reducing motion at such an injured segment.