Investigation of triticeal cartilage anatomy in forensic autopsy cases.

PURPOSE: This study aims to determine the presence and morphology of triticeal cartilage (TrC) through autopsy cases and to examine its relationship with age, gender, and height, thus contributing to clinical practices and forensic perspective. MATERIALS AND METHODS:  Our study was conducted on a total of 84 autopsy cases between the ages of 20-90 years who came to Tokat Forensic Medicine Institute. The laryngeal region was palpated to determine whether TrC was present. The dimensions of the TrC and the length of the upper horn of thyroid cartilage (UHThC) were measured with precise digital calipers, and its weight was measured with an accurate digital scale. RESULTS: The presence of TrC was identified in 56% of the autopsy cases examined. The prevalence of TrC was higher in males (61.9%) than in females (23.1%). It was determined to be bilateral in 45% of the cases and unilateral in 11%. TrCs had a cylindrical shape in 68.2%, an oval shape in 25.8%, and a pyramidal shape in 5.8%. The average weight of TrC was 67.93 ± 33.91 mg on the right side and 72.67 ± 32.23 mg on the left. As the individual's height increased, the weight of TrC increased (p < 0.001). Additionally, there was a strong positive correlation between the lengths of TrC and UHThC and the individual's height (p < 0.001). CONCLUSION: TrC may be confused with UHThC fractures. Therefore, we believe that knowledge of the presence and morphology of TrC will contribute to clinical approaches and forensic cases, especially in relation to the neck region.

Comparison of the Conventional Downward and Modified Upward Laryngeal Handshake Techniques to Identify the Cricothyroid Membrane: A Randomized, Comparative Study.

BACKGROUND: Accurate identification of the cricothyroid membrane is crucial for successful cricothyroidotomy. The aim of this study was to compare the conventional downward and modified upward laryngeal handshake techniques in terms of accuracy to identify the cricothyroid membrane in nonobese female patients. METHODS: In 198 anesthetized female patients, the cricothyroid membrane was identified by either the conventional downward laryngeal handshake technique (n = 99) or the modified upward laryngeal handshake technique (n = 99). According to the conventional downward laryngeal handshake technique, the cricothyroid membrane was identified by palpating the neck downward from the greater cornu of the hyoid bone, thyroid laminae, and cricoid cartilage. According to the modified upward laryngeal handshake technique, the cricothyroid membrane was located by moving up from the sternal notch. The primary outcome was the accuracy of identifying the cricothyroid membrane. Secondary outcomes included the accuracy of midline identification and time taken to locate what participants believed to be the cricothyroid membrane. The primary and secondary outcomes according to the technique were analyzed using generalized estimating equations. RESULTS: The cricothyroid membrane could be identified more accurately by the modified upward laryngeal handshake technique than by the conventional downward technique (84% vs 56%, respectively; odds ratio [OR], 4.36; 95% confidence interval [CI], 2.13-8.93; P < .001). Identification of the midline was also more accurate by the modified laryngeal handshake than by the conventional technique (96% vs 83%, respectively; OR, 4.98; 95% CI, 1.65-15.01; P = .004). The time taken to identify the cricothyroid membrane was not different between the conventional and modified techniques (20.2 [16.2-26.6] seconds vs 19.0 [14.5-26.4] seconds, respectively; P = .83). CONCLUSIONS: The modified upward laryngeal handshake technique that involved tracing the trachea and laryngeal structures upward from the sternal notch was more accurate in identifying the cricothyroid membrane than the conventional downward technique in anesthetized female patients.

Emergency Front-of-Neck Airway Rescue Via the Cricothyroid Membrane: A High-Resolution Computed Tomography Study of Airway Anatomy in Adults.

BACKGROUND: Emergency front-of-neck airway rescue is recommended in a can't intubate, can't oxygenate clinical scenario. Cannula cricothyroidotomy has been reported as having a high failure rate. Our primary aim was to estimate the angle of the trachea in relation to the horizontal axis in a simulated emergency front-of-neck airway rescue position. Our secondary aims were to estimate the optimal cannula angle of approach and evaluate the anatomical relationship of the cricothyroid membrane (CTM) to adjacent structures. We also assessed whether the CTM lies above or below the neck midpoint, a point equidistant from the suprasternal notch (SSN), and the chin surface landmarks. All measurements were compared between the male and female subjects. METHODS: Subjects having elective computed tomography of their thorax were consented to have extension of the computed tomography to include their neck. A preliminary radiation dose and risk assessment deemed the additional radiation to be of very low risk (level IIa). Subjects were positioned supinely on the computed tomography table. Standard neck extension was achieved by placing a pillow under the scapulae and a rolled towel under the neck to simulate emergency front-of-neck airway rescue positioning. RESULTS: Fifty-two subjects were included in this study: 31 men and 21 women. The mean angle of the trachea in relation to the horizontal axis was 25.5° (95% confidence interval [CI], 21.8-29.1) in men and 14.0° (95% CI, 11.5-16.5) in women. The mean minimum angles required for hypothetical cannula cricothyroidotomy for men and women were 55.2° (95% CI, 51.8-58.7) and 50.5° (95% CI, 45.4-55.6), respectively. The CTM was located lower in the neck in men compared to women. The CTM was located below the neck midpoint in 30 of 30 (100%) male subjects and 11 of 20 (55%) female subjects (P < .001). CONCLUSIONS: The trachea angulates posteriorly in a simulated emergency front-of-neck airway rescue position in supine subjects and to a greater degree in men compared to women (P < .001). The minimum angle required for hypothetical cannula cricothyroidotomy was >45° in the majority (75%) of subjects studied. A steeper cannula angle of approach may be more reliable and warrants further clinical study. If airway anatomy is indistinct and performing a vertical scalpel cricothyroidotomy, consideration should be given to performing this incision lower in the neck in men compared to women.

Development and validation of a difficult laryngoscopy prediction model using machine learning of neck circumference and thyromental height.

BACKGROUND: Predicting difficult airway is challengeable in patients with limited airway evaluation. The aim of this study is to develop and validate a model that predicts difficult laryngoscopy by machine learning of neck circumference and thyromental height as predictors that can be used even for patients with limited airway evaluation. METHODS: Variables for prediction of difficulty laryngoscopy included age, sex, height, weight, body mass index, neck circumference, and thyromental distance. Difficult laryngoscopy was defined as Grade 3 and 4 by the Cormack-Lehane classification. The preanesthesia and anesthesia data of 1677 patients who had undergone general anesthesia at a single center were collected. The data set was randomly stratified into a training set (80%) and a test set (20%), with equal distribution of difficulty laryngoscopy. The training data sets were trained with five algorithms (logistic regression, multilayer perceptron, random forest, extreme gradient boosting, and light gradient boosting machine). The prediction models were validated through a test set. RESULTS: The model's performance using random forest was best (area under receiver operating characteristic curve = 0.79 [95% confidence interval: 0.72-0.86], area under precision-recall curve = 0.32 [95% confidence interval: 0.27-0.37]). CONCLUSIONS: Machine learning can predict difficult laryngoscopy through a combination of several predictors including neck circumference and thyromental height. The performance of the model can be improved with more data, a new variable and combination of models.

A proposal for needle projections in transcutaneous injection laryngoplasty using three-dimensionally reconstructed CT scans.

PURPOSE: This study aims to determine laryngeal dimension in relation to all three transcutaneous injection laryngoplasty (TIL) approaches (thyrohyoid, transthyroid and cricothyroid) using three-dimensionally reconstructed Computed Tomography (CT) scan and compare the measurements between sex, age group and ethnicity. METHODS: CT scans of the neck of two hundred patients were analysed by two groups of raters. For thyrohyoid approach, mean distance from the superior border of the thyroid cartilage to the laryngeal cavity (THd) and mean angle from the superior border of the thyroid cartilage to mid-true cords (THa) were measured. For transthyroid approach, mean distance from mid-thyroid cartilage to mid-true cords (TTd) and Hounsfield unit (HU) at mid-thyroid cartilage (TTc) were measured. For cricothyroid approach, mean distance from the inferior border of the thyroid cartilage to the laryngeal cavity (CTd) and mean angle from the inferior border of the thyroid cartilage to mid-true cords (CTa) were measured. RESULTS: There were statistically significant differences between males and females for all measurements except for CTa (p < 0.0001). No significant difference across age groups and ethnicities were found for all three approaches (p > 0.05). There was a significant fair positive correlation between age and TTc (p = 0.0002). For all measurements obtained, there were moderate to excellent inter-group consistency and intra-rater reliability. CONCLUSION: This study demonstrated a significant sex dimorphism that may influence the three TIL approaches except for needle angulation in the cricothyroid approach. The knowledge of laryngeal dimension is important to increase success in TIL procedure.

Nasolaryngeal Distances in the Adult Population and an Evaluation of Commercially Available Nasotracheal Tubes.

BACKGROUND: Preformed nasal endotracheal tubes (NETs) come with a predefined insertion depth due to their curved design. While size indication refers to internal diameter, there is a considerable variability in the corresponding lengths and proportions of same-sized tubes of different manufacturers which is probably based on the lack of data of nasolaryngeal distances (NLDs) in the adult population. Choosing the best-fitting NET is therefore difficult and carries the risk of endobronchial intubation or, on the contrary, cuff inflation at the vocal cord level. The aim of this study was to develop a prediction model for NLD and a selection guide to choose the appropriate NET based on a radiographic description of NLD in comparison to the measurements of available NETs of several manufacturers. METHODS: After institutional ethics board review, 388 computed tomography (CT) scan images of head, neck, and upper thorax in a heterogeneous adult cohort were included. Mean distances from the nares to the lower border of the thyroid cartilage were measured. NETs from different manufacturers were measured and compared to the NLD derived from the radiographic analysis. The patients' sex, body height, and weight were considered as possible covariates in quantile regression models for predicting the NLD. RESULTS: Data from 200 patients were analyzed. NLD was associated with sex, body height, and weight. A simple quantile regression model using the body height as the only covariate sufficed to achieve accurate predictions of NLD. Validation on independent test data showed that 92.8% of the NLD predictions were closer than ±20 mm to the observed NLD values. Measurements of equal-sized NETs varied considerably in outer diameter, proportion, the nasopharyngeal part, and guide marks. Length differences of the bend-to-cuff distance, containing the anatomically NLD, ranged between 218 and 270 mm at same sizes. CONCLUSIONS: A reliable prediction of NLD can be obtained simply by body height, using the formula (Equation is included in full-text article.). As manufacturers' tube lengths vary substantially, additional information about the bend-to-cuff distance as corresponding tube section would allow for more accurate tube selection.

Accuracy of pediatric cricothyroid membrane identification by digital palpation and implications for emergency front of neck access.

BACKGROUND: Emergency front of neck access in a "can't intubate can't oxygenate" scenario in pediatrics is rare. Ideally airway rescue would involve the presence of an ear, nose, and throat surgeon. If unavailable however, responsibility lies with the anesthesiologist and accurate identification of anterior neck structures is essential for success. AIM: We assessed anesthesiologists' accuracy in identification of the pediatric cricothyroid membrane by digital palpation in three predefined age groups (37 weeks to <1 year old, 1-8 years old, and 9-16 years old) and whether accuracy improved with repetition. We also investigated a novel hypothetical vertical skin incision strategy to successfully expose the cricothyroid membrane. METHODS: We asked anesthesiologists to identify the location of the cricothyroid membrane of anesthetized children in the extended neck position. Accuracy was defined as a mark made within the margins of the cricothyroid membrane using ultrasound as a reference standard. The position of the cricothyroid membrane relative to the neck midpoint, between the suprasternal notch and mentum, was defined for each child. Using this neck midpoint, we determined the hypothetical vertical skin incision lengths required to successfully expose the cricothyroid membrane ("midpoint incision"). RESULTS: Ninety-seven patients were included in this study. There were 14, 58, and 25 patients recruited across the three predefined groups. Accurate anesthesiologist identification of the location of the cricothyroid membrane occurred in 29.4%, 28.6%, and 38.2% of attempts, respectively. The majority of inaccurate assessments (64.1%) were below the cricothyroid membrane. There was no improvement in accuracy with repetition. Hypothetical "midpoint incision" lengths of 20, 30, and 35 mm were required. CONCLUSION: Significant anesthesiologist inaccuracy exists in locating the cricothyroid membrane in children of all ages. This has implications for the technical approach to emergency front of neck access and how we teach the management of "can't intubate can't oxygenate" in pediatric practice.

Experimental study of needle recording electrodes placed on the thyroid cartilage for neuromonitoring during thyroid surgery.

BACKGROUND: Needle electrodes placed on the thyroid cartilage (TC) are an alternative to endotracheal tube (ET) electrodes for assessing recurrent laryngeal nerve (RLN) function during thyroid surgery. Needle electrodes placed on the TC were evaluated in an experimental porcine model. METHODS: Continuous intraoperative neuromonitoring was used to record the electromyogram. Each TC side was delineated into nine areas to determine the optimal placement of the electrode, and needle electrode area, depth and orientation for optimal electromyographic (EMG) amplitudes were evaluated. RLN root locations were stimulated at four locations: vagus nerve distal to the neuromonitoring electrode, and most proximal, middle and laryngeal entry points of the nerve. A nerve retraction injury model was adapted to compare RLN monitoring by TC versus ET electrodes. RESULTS: An optimal site for placement of needle electrodes was identified, and electromyograms obtained from the various needle insertion depths and orientations were similar. Latencies recorded from the TC and ET electrodes were similar. The amplitude profile of TC electrodes responded earlier to RLN injury than that of ET electrodes. Amplitude and drop to loss of signal were also registered earlier. CONCLUSION: EMG amplitudes obtained using TC electrodes were higher, and identified RLN injury earlier than ET electrodes. Surgical relevance Needle electrodes placed on the thyroid cartilage (TC) are an alternative to endotracheal tube (ET) electrodes for assessing the function of the recurrent laryngeal nerve (RLN) in thyroid surgery. This study used an experimental porcine model to evaluate the use of needle electrodes inserted in the TC, compared with ET electrodes, for producing an electromyographic (EMG) profile of the RLN. Nine areas of the TC, with various needle insertion depths and orientations, were compared. Perichondral insertion into the avascular area of the TC was found to be safe. The EMG amplitude and latency features recorded via the TC and ET electrodes were compared, using both intermittent and continuous monitoring. Changes in EMG amplitudes in response to nerve traction injury were registered earlier with TC electrodes than with ET electrodes, and the amplitudes were higher and more stable. Latencies obtained via the TC and ET electrodes were similar. These results indicate that the development of a non-invasive monitoring electrode with improved function, easy placement and low cost is possible.

The effect of i-gel® insertion on the accuracy of cricothyroid membrane identification in adult females: a prospective observational study.

BACKGROUND: Identification of the cricothyroid membrane is frequently inaccurate in females because of less distinct anatomy compared with males. Supraglottic airway devices cause ventral displacement of the laryngeal structures. We investigated if this would impact on the accuracy of cricothyroid membrane identification using palpation. METHODS: We recruited 64 adult females who underwent assessment by volunteer participants with and without a sited i-gel® supraglottic airway device. The primary outcome was accuracy in identifying the cricothyroid membrane. Secondary outcomes included distance from participant estimate to actual cricothyroid membrane location and perceived difficulty using a visual analogue scale. Ultrasound images were analysed to determine the effect of the i-gel® on the anatomical structures relevant to cricothyroidotomy. RESULTS: The cricothyroid membrane was identified correctly in 42/64 subjects with the i-gel® in place (66%) vs 23/64 of controls (36%; P<0.001, mean difference 30%; 95% confidence interval, 12-47%). VAS (P<0.001) and distance to the cricothyroid membrane (P<0.001) decreased in the intervention group. Analysis of the ultrasound image series showed a reduction in the mean angle between the cricothyroid membrane and anterior wall of the trachea in the i-gel® group, because of the more ventral position of the cricoid cartilage compared with control images (166° vs 151°, P<0.001). CONCLUSIONS: The presence of the i-gel® improved accuracy of identifying the cricothyroid membrane using palpation in females. The cricoid cartilage was pushed ventrally by the i-gel® in the hypopharynx, creating a more palpable prominence. It may therefore be advantageous to retain a sited supraglottic airway, rather than remove it, before performing emergency cricothyroidotomy.

Common left carotid bifurcation at C7-Th1 level: a rare anatomical variant.

The left common carotid artery usually bifurcates to the internal and external carotids at or near the superior border of thyroid cartilage. In head and neck surgery, the common carotid arteries are important landmarks, defining the plane of dissection during radical neck surgeries. According to the literature, many variations exist regarding the carotid bifurcation. Anatomical knowledge of these variants is important for surgical approaches in the head and neck regions, to avoid devastating complications that may occur, mainly during anterior neck dissections. We report an interesting case of a 75-year-old male patient with low bifurcation of the left common carotid artery, accidentally found during a routine carotid Doppler ultrasonography. Bifurcation was located at the C7-Th1 intervertebral disc height, approximately 4 cm from the aortic arch.

Ultrasound Is Superior to Palpation in Identifying the Cricothyroid Membrane in Subjects with Poorly Defined Neck Landmarks: A Randomized Clinical Trial.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Success of a cricothyrotomy is dependent on accurate identification of the cricothyroid membrane. The objective of this study was to compare the accuracy of ultrasonography versus external palpation in localizing the cricothyroid membrane. METHODS: In total, 223 subjects with abnormal neck anatomy who were scheduled for neck computed-tomography scan at University Health Network hospitals in Toronto, Canada, were randomized into two groups: external palpation and ultrasound. The localization points of the cricothyroid membrane determined by ultrasonography or external palpation were compared to the reference midpoint (computed-tomography point) of the cricothyroid membrane by a radiologist who was blinded to group allocation. Primary outcome was the accuracy in identification of the cricothyroid membrane, which was measured by digital ruler in millimeters from the computed-tomography point to the ultrasound point or external-palpation point. Success was defined as the proportion of accurate attempts within a 5-mm distance from the computed-tomography point to the ultrasound point or external-palpation point. RESULTS: The percentage of accurate attempts was 10-fold greater in the ultrasound than external-palpation group (81% vs. 8%; 95% CI, 63.6 to 81.3%; P < 0.0001). The mean (SD) distance measured from the external-palpation to computed-tomography point was five-fold greater than the ultrasound to the computed-tomography point (16.6 ± 7.5 vs. 3.4 ± 3.3 mm; 95% CI, 11.67 to 14.70; P < 0.0001). Analysis demonstrated that the risk ratio of inaccurate localization of the cricothyroid membrane was 9.14-fold greater with the external palpation than with the ultrasound (P < 0.0001). There were no adverse events observed. CONCLUSIONS: In subjects with poorly defined neck landmarks, ultrasonography is more accurate than external palpation in localizing the cricothyroid membrane.

Relationship between severe obesity and depth to the cricothyroid membrane in third-trimester non-labouring parturients: a prospective observational study.

BACKGROUND: Severely obese parturients have increased 'cannot intubate, cannot oxygenate' risk during Caesarean section under general anaesthesia. Front-of-neck access (FONA) at the cricothyroid membrane (CTM) is definitive management; however, attempted FONA can fail. Point-of-care ultrasonography may provide useful information about CTM depth to aid FONA in obesity. This study determined the difference in CTM depth between severely obese and non-obese parturients, utilising ultrasonography. METHODS: In this prospective observational study, two anaesthetists performed airway ultrasonography on 15 severely obese (BMI >45 kg m-2) and 15 normal-weight (BMI ≤25 kg m-2) parturients in the third trimester, using the transverse and longitudinal planes, sniffing and extended head positions, and nil and firm transducer pressures. The primary outcome was CTM depth (millimetres) measured in the transverse plane with the head extended and nil transducer pressure. Secondary outcomes included CTM depth measurements using other factor configurations. Intra-class correlation coefficients assessed the inter-observer reliability. RESULTS: CTM depth measured in the transverse plane with head extended and nil transducer pressure was significantly greater in severely obese parturients, mean 18.0 mm (95% confidence interval 16.3-19.8), vs 10.6 mm (8.81-12.4) in non-obese (P<0.001); mean difference 7.4 mm (4.9-9.9; P<0.001). CTM depths were increased in the severely obese group regardless of scanning plane, head and neck position, or transducer pressure (all P<0.001). There was excellent inter-observer reliability. CONCLUSIONS: Cricothyroid membrane depth is significantly increased in severely obese vs normal-weight parturients independently of scanning plane, head and neck position, or transducer pressure.

Localisation of the cricothyroid membrane by digital palpation in the emergency department.

INTRODUCTION: A surgical approach to airway management may be essential in situations of difficult or failed airway, where immediate airway access is needed to provide oxygenation. However, the procedure is uncommonly performed and expertise among emergency clinicians may be limited. OBJECTIVES: The aim of this study was to assess the accuracy of cricothyroid membrane (CTM) identification by junior and senior emergency trainees by identification of surface anatomy landmarks. A secondary aim was to determine patient variables associated with accurate identification of CTM. METHODS: A prospective observational study was conducted in a tertiary emergency department in the Kingdom of Saudi Arabia. Saudi Emergency Medicine board trainees participated in the study. Data were also obtained on gender and body habitus of patients. Junior trainees attempted to locate the membrane by palpation and marked it with an ultraviolet mark (blinded) pen followed by senior trainees. A certified ultrasound physician, also blinded to the trainee attempts, marked the membrane within a 5 mm circumference using a different coloured ultraviolet pen and was used as the reference gold standard. RESULTS: There were 80 patients enrolled with junior and senior doctors assessing location for emergency cricothyrotomy. Proportion of correct localisation was 30% (95% CI 20% to 41%) among junior trainees and 33% (95% CI 22% to 44%) among seniors (P=0.73). Level of training, sex, height and weight of patients were not associated with success. CONCLUSIONS: Clinical localisation of CTM by emergency medicine trainees was poor even in non-stressful settings, and warrants further dedicated education and/or use of adjunct techniques.

Sonographic evaluation of the endochondral ossification process of the thyroid cartilage in children.

PURPOSE: To determine the sonographic appearances of the endochondral ossification process of the thyroid cartilage in children. METHODS: Thyroid cartilage sonography (US) of 420 children was performed with a high-resolution linear-array transducer. Right and left laminae of the thyroid cartilage, including the inferior horns, were examined. Ossification foci were evaluated for their presence, location, shape, size, echo pattern, and number. RESULTS: Four hundred nineteen children, 239 girls and 180 boys, were enrolled in the study with a mean age of 109.8 ± 60.7 months. Ossification foci were found in 167 children (39.9%). First ossification focus detection age was 72 months in girls and 79 months in boys. On both laminae, the most frequent appearance of the ossification focus was hypoechoic (right: 94.8%, left: 93.5%). Prevalence and number of ossification foci increased with age in each sex. The shape of the ossification foci in both laminae was generally nonexpansile (right: 92.9%, left: 93.5%). CONCLUSION: Endochondral ossification process of the thyroid cartilage begins in the first decade with extracellular matrix changes, which can be detected as hypoechoic foci by US. These foci can be expansile, and radiologists should be aware of this entity to avoid misdiagnosing them as abnormal masses.

Accuracy of identifying the cricothyroid membrane in children using palpation.

Accurate identification of the cricothyroid membrane (CTM) has paramount importance in the event of a 'cannot intubate, cannot oxygenate' scenario. We sought to determine the ability of anesthesiologists to correctly identify the CTM in obese and non-obese children. Anesthesiologists were asked to mark the entry point of the cricothyroidotomy device with an ultraviolet invisible pen on obese and non-obese (BMI < 95th percentile for age and sex) children aged 7-12 years. A correct estimation was defined as a mark made between the upper and lower borders of the CTM and within the 3-mm midline. Twenty anesthesiologists palpated 30 obese and 50 non-obese children. The CTM was accurately identified with digital palpation in a total 55% of children, and there were no differences inaccurate identification rates of the CTM between obese and non-obese children [57 vs. 54%, respectively; median difference 3%; 95% confidence interval (- 20 to 25%); p = 0.82]. Accuracy was not correlated with any demographic or morphometric features of the children. Percutaneous identification of the CTM in children aged 7-12 years was poor and not significantly different for obese and non-obese children. Pre-procedural ultrasonography may help to identify the landmarks for cricothyroidotomy.

Optimization of Ultrasound Transducer Positioning for Endotracheal Tube Placement Confirmation in Cadaveric Model.

OBJECTIVES: Sonography has been suggested as a possible means of endotracheal tube (ETT) placement confirmation. However, optimum ultrasound transducer placement has not been established. Using a cadaveric model, ETT placement by the sonographic appearance at the thyroid cartilage, cricoid cartilage, and suprasternal notch in the upper airway was assessed to determine which ultrasound transducer placement offered the most optimal images for ETT confirmation in the airway. METHODS: One provider intubated 5 cadavers, with the ultrasound transducer at each of the 3 levels, for a total of 30 intubations per specimen, while 2 providers assigned a visual score of 1 (subtle), 2 (clear), or 3 (pronounced) to each sonogram of the ETT in the airway. RESULTS: At the level of the thyroid cartilage, tracheal intubation was detected at a rate of 40%, with a median visualization scale of 1 (subtle movement). At the level of the cricoid cartilage, the visualization scale improved to a median of 2 (clear movement), with a 70% intubation detection rate. At the level of the suprasternal notch, 100% of the tracheal intubations were visualized on sonography, with a median score of 3 (pronounced movement). CONCLUSIONS: In comparing sonographic detection of ETT placement at 3 levels of the upper airway in a cadaveric model, our results clearly indicate that visualization was superior at the level of the suprasternal notch, with 100% of intubations detected with the best visualization scores.

A reassessment of cervical surface anatomy via CT scan in an adult population.

Surface landmarks in the neck are important for orientations of cervical glands, arteries, veins, nerves, and vertebrae. Recent research suggests some orientations are not correct. What are the cervical landmark orientations in the Chinese population? In this study, two essential cervical anatomy planes, the thyroid cartilage and C7 planes, were assessed in living adult Chinese subjects using computed tomography (CT), and the hyoid, carotid bifurcation, cricoid cartilage, thyroid arteries, and vertebral artery were simultaneously positioned. After excluding patients with distorting pathology, a total of 108 cervical CT scans were examined. The thyroid cartilage plane commonly passed through the C5 (in males) or C4 (in females) vertebral level. The carotid artery bifurcated most commonly at C3 (left) or C4 (right), more than 10 mm above the thyroid cartilage plane bilaterally in most cases. Orientation of the carotid bifurcation according to the body or greater horn of the hyoid was more accurate. The superior thyroid artery was found a finger-breadth below the thyroid cartilage plane, and the inferior thyroid artery in the C7 plane. The inferior border of the cricoid cartilage was most often at C7 (in males) or C6 (in females). The vertebral artery entered the C6 transverse foramen in more than 80% of scans. This reassessment of cervical surface anatomy using modern imaging tools in vivo provides both qualitative and quantitative information for surgeons in clinical practice. Clin. Anat. 30:330-335, 2017. © 2017 Wiley Periodicals, Inc.

Triticeal cartilage: the forgotten cartilage.

INTRODUCTION: The triticeal cartilage (TC) is a small cartilage found within the thyrohyoid membrane. The TC has a variable prevalence between and within individuals. It has been suggested that absence of a TC results from its failure to separate from the superior horn of the thyroid cartilage (SHTC) and that individuals without a TC will have a longer SHTC. This study aims to identify the prevalence of the TC and investigate the relationship between the length of the SHTC and presence of a TC. METHODS: Eighty seven adult cadavers underwent dissection. Data were collected on presence or absence of a TC and lengths of SHTC. RESULTS: A TC was identified in 28 cadavers (33%). In cadavers with a unilateral TC, there was no significant difference between the lengths of the SHTC on sides with a TC (1.6 mm, ±SEM 0.12 mm) to sides without a TC (1.7 mm, ±SEM 0.10 mm) (P = 0.47). In cadavers with no TCs, the length of the SHTCs (1.8 mm, ±SEM 0.04 mm) was significantly longer than the SHTCs of cadavers with a TC present bilaterally (1.4 mm, ±SEM 0.12 mm) (P = 0.02). CONCLUSIONS: A TC was found in 33% of cadavers. This study demonstrates a relationship between the presence of a TC and the length of the SHTC only in cadavers with a TC present or absent bilaterally.

The anterior commissure of the human larynx revisited.

BACKGROUND: The anterior commissure (AC) of the human larynx is usually understood as an area of the glottis anteriorly situated between the two vocal folds inserting to the thyroid cartilage (TC). The pattern of spread of AC carcinoma could hypothesize that AC could include other structures of the ventral larynx as developmental anatomy could demonstrate. METHODS: Ten adult larynx specimens from donation program cadavers and 15 selected fetal specimens (from 11 to 34 weeks of amenorrhoea) were studied using microdissection and histological serial sections stained with hematoxylin-eosin and reticuline. RESULTS: In adult specimens, internal perichondrium of the TC was easily detached from the entire lateral lamina but not from an intermediate lamina superiorly marked by the superior thyroid notch. On this median band of TC is inserted the ventral connective tissue of the three levels of the larynx: the ventral part of the vocal folds with the anterior macula flava, the Broyle's epiglottic ligament, and the subglottic part of the conoid ligament. In young fetuses (11-12 weeks), intermediate lamina of TC joined at the glottic level but not at the supraglottic level; in fetuses at 22-25 weeks, a meshwork of bundles of connective fibers inserted to the intermediate lamina of TC. In fetuses at 33-34 weeks, organization is practically identical to adult specimens. CONCLUSION: According to the adult anatomical features and the organogenesis, the AC of the human larynx could be anatomically defined ventrally as being made up of the intermediate lamina of TC beneath the superior thyroid notch and dorsally the ventral insertions of vocal folds with macula flava, supraglottic Broyle's ligament, and subglottic conoid ligament leading to a "developmental" AC definition which could better explain specific spreading of AC carcinoma.

Comparing success rates of anesthesia providers versus trauma surgeons in their use of palpation to identify the cricothyroid membrane in female subjects: a prospective observational study.

PURPOSE: The primary aim of this study was to compare the success rates of anesthesia providers vs trauma surgeons in their use of palpation to identify the cricothyroid membrane (CTM). The secondary aim was to explore whether prior training and experience performing surgical airways affected the success rates for identifying the CTM. METHODS: Four female adults participated in this prospective observational study. The participants had varying measurements of neck anatomy that were known or theorized to affect the accuracy of identifying the CTM location. For test purposes, the subjects were positioned with optimal neck extension via placement of a shoulder roll. Anesthesia providers (n = 57) and surgeons (n = 14) of various training levels and clinical experience marked the presumed CTM location on each subject. These palpation markings were then referenced against the ultrasound-confirmed CTM location, and the success rates for identifying the CTM were compared between groups. RESULTS: The overall success rate using palpation to identify the CTM was ≤ 50%, and there were no differences in success rates between the anesthesia providers and trauma surgeons (16% vs 26%, respectively; absolute difference, -10%; 95% confidence interval, -23 to 3; P = 0.15). Furthermore, there were no significant differences in the success rates for identifying the CTM based on either clinical experience or emergency surgical airway experience. CONCLUSION: The success rates for identifying the CTM using palpation were low and not significantly different for anesthesia providers and surgeons, collectively, as well as for the various levels of training. Anesthesiologists' ability to mark the CTM location correctly did not improve with years of experience.