Striking a (vocal) chord: musical instruments as mnemonic devices when teaching the functional anatomy of the larynx.

Mnemonic devices are memory aids that make it easier to recall information and are widely used by students studying anatomy and physiology. Simple musical instruments and toys can serve as mnemonic devices for students learning the functional anatomy of the larynx: balloons can help learners understand and recall how sound is produced; tuning pegs can help learners understand how tension affects vocal pitch; fingers on a fretboard can help learners understand how pitch is further modulated; and a common coach's whistle can demonstrate how vocal volume is controlled. Using instruments and toys engages adult learners and helps them connect complex laryngeal anatomy with previous experiences.NEW & NOTEWORTHY Musical instruments and toys can be used as mnemonic devices to help students recall and understand the functional anatomy of voice production. The mnemonics can be implemented in a variety of classrooms and are flexible and engaging.

Homology and the evolution of vocal folds in the novel avian voice box.

The origin of novel traits, those that are not direct modifications of a pre-existing ancestral structure, remains a fundamental problem in evolutionary biology. For example, little is known about the evolutionary and developmental origins of the novel avian vocal organ, the syrinx. Located at the tracheobronchial junction, the syrinx is responsible for avian vocalization, but it is unclear whether avian vocal folds are homologous to the laryngeal vocal folds in other tetrapods or convergently evolved. Here, we identify a core developmental program involved in avian vocal fold formation and infer the morphology of the syrinx of the ancestor of modern birds. We find that this ancestral syrinx had paired sound sources induced by a conserved developmental pathway and show that shifts in these signals correlate with syringeal diversification. We show that, despite being derived from different developmental tissues, vocal folds in the syrinx and larynx have similar tissue composition and are established through a strikingly similar developmental program, indicating that co-option of an ancestral developmental program facilitated the origin of vocal folds in the avian syrinx.

Morphology and computed tomography of the larynx in the white-eared opossum (Didelphis albiventris).

The white-eared opossum (Didelphis albiventris) is a Neotropical marsupial that occurs in the Brazilian territory. The larynx is an important organ of vocalization in mammals, although, other laryngeal functions are more fundamental for survival of mammals than phonation. The anatomical knowledge of respiratory structures is pivotal for a better understanding of the species. Thus, this study aimed to examine the larynx of the white-eared opossum by gross anatomy, computed tomography and histological description. For this, 10 adult (six females and four males) white-eared opossums (D. albiventris) were used. The white-eared opossum larynx was formed by epiglottis, thyroid, cricoids and arytenoid cartilages and a corniculate process. There is a similarity between the larynx of this marsupial and those reported in other wild mammals, regarding the number of cartilages and their location. Histologically, the epiglottis consisted of elastic cartilage and thyroid, cricoid and arytenoid cartilages were composed of hyaline cartilage. The epiglottis protruded rostrally into the nasal part of the pharynx, above the soft palate, and this is probably a marsupial characteristic as the fact that the thyroid and cricoid cartilages were ventrally fused. The hyoid apparatus was similar to that of other animals, with the same bony constitution, but with a greatly reduced stylohyoid bone. Histologically, the larynx was similar to those of other species such as koala, armadillo, crab-eating foxes and giant anteaters. The knowledge of the larynx morphology is important for the anatomical features of the species and clinical and surgical procedures, such as endotracheal intubation.

Morphology of the syrinx of three species of birds from Brazilian cerrado (Psittacara leucophthalmus, Rhynchotus rufescens and Cariama cristata): Gross anatomy and light microscopy study.

The aim of this study was to describe the morphology of the trachea and syrinx at macroscopic and light microscopy levels of three species of birds from different orders that inhabit the Brazilian cerrado. For that, five adult specimens (three males and two females of each species) of white-eyed parakeet (Psittacara leucophthalmus), red-winged tinamou (Rhynchotus rufescens) and red-legged seriema (Cariama cristata) were used. The trachea and syrinx of the birds were collected and destined for anatomical and histological studies. The trachea of the studied birds presented an elongated path and originated in the larynx and extended caudally to the syrinx. No sexual dimorphism was observed in the syrinx of the studied species, probably because it is associated with their song, which is very similar between males and females of these species. The findings of this study allowed us to classify the syrinx as tracheal in the white-eyed parakeet and tracheobronchial in the red-winged tinamou and red-legged seriema. In general, the morphological features of the trachea and syrinx were similar to those described for other species of birds, such as the presence of intrinsic and extrinsic syringeal muscles, and the lateral and medial tympaniform membranes, which would represent important anatomical structures in sound production through vibration during expiration and eventual inspiration. The morphological structure of the syrinx in the three avian species of the Brazilian cerrado is consistent with the ability of these avian species to perform a potential vocalization, especially the red-legged seriema that emits characteristic sounds very loud and can carry several kilometres.

Amount and spatial arrangement of muscle fibers in the human laryngeal Musculus ventricularis.

Textbooks and atlases of human macroscopic and microscopic anatomy of the larynx generally provide, if at all, only sparse information on the laryngeal Musculus ventricularis. However, several studies indicate that this muscle takes over the function of vestibular (ventricular) fold phonation after denervation of the Musculus vocalis. In the present study, 29 laryngeal specimens were coronally dissected at different levels, i.e. the anterior (L1), middle (L2), and posterior third of the vestibular fold (L3), and they underwent histological analysis. In all specimens the vestibular folds of both hemi-larynxes contained striated muscle bundles in variable amounts, representing a ventricularis muscle. These muscle bundles obviously originated from the lateral (external) and thyroepiglottic part of the thyroarytenoid muscle and the aryepiglottic part of the oblique arytenoid muscle, as has been described by other authors. The areas of vestibular folds and their amounts of ventricularis muscle bundles were measured using image analysis software (imageJ) by manual tracing. The mean area of the vestibular folds of both hemi-larynxes was 27.9 mm2 (SD [standard deviation] ± 9.17), and the area occupied by fibers of the ventricularis muscle was 1.5 mm2 (SD ± 1.78). Statistical analysis comparing the areas of both hemi-larynxes and levels resulted in no significant differences, except for the levels 2 and 3. In level 2, significantly more muscle fibers (2.0 mm2 ; SD ± 2.21) were detectable within the vestibular fold than in level 3 (0.9 mm2 ; SD ± 1.43). Level 1 also contained more muscle fibers (1.1 mm2 ; SD ± 1.06) than level 3, however, without significance. In conclusion, the laryngeal ventricularis muscle is present in the majority of reported cases. Since the muscle is of clinical relevance, it should be included in anatomical textbooks by default.

Laryngeal Framework Surgical Anatomy: A Radiological Study.

PURPOSE: Awareness of variations in laryngeal anatomy among different age and gender groups is crucial during laryngeal framework surgery. The aim of this study is to demonstrate the relationship between gender and laryngeal radiologic morphometrics among different age groups and the applicability of important anatomical landmarks of laryngeal surgery. METHODS: Laryngeal images of 180 adult patients older than 18 years of age were obtained by computed tomography and assessed. A total of 11 measurements of important laryngeal landmarks were taken from the patients' computed tomography images. Results were subgrouped according to gender and age, and these groups were compared for each measurement. RESULTS: The majority of laryngeal measurements obtained in the study were higher in males than females, with the exception of the interlaminar angle. The mean interlaminar angle value was 88.27°± 14.99 for males and 103.04°± 14.81 for females (P <0.005). The distance from the anterior commissure to the inferior border of the thyroid cartilage was 10.46 ± 2.5 mm for males and 7.72 ± 1.9 mm for females. The anterior commissure locates slightly higher than the midpoint of the distance from the thyroid notch to the thyroid inferior border. The shortest distance between the muscular process of the arytenoid cartilage and the thyroid cartilage was found to be 9.60 ± 3.47 mm for males and 7.72 ± 2.33 mm for females (P <0.001). CONCLUSION: Observation of obvious diversities in the size and distance of the important laryngeal structures between the gender groups is an important factor to be considered for successful laryngeal framework surgery. Also, using the midpoint of the thyroid cartilage as a landmark for anterior commissure is a practical method during surgery, especially for thyroplasty.

Anatomy of the Larynx and Cervical Trachea.

The larynx serves as the gateway between the upper and lower respiratory tracts and is involved in the tasks of phonation, deglutition, and airway protection. Familiarity with the complex anatomy of the larynx is critical for detecting and characterizing disease in the region, especially in cancer staging. In this article, we review the anatomy of the larynx and cervical trachea, including an overview of their cartilages, supporting tissues, muscles, mucosal spaces, neurovascular supply, and lymphatics, followed by correlation to the clinically relevant anatomic sites of the larynx. Imaging techniques for evaluating the larynx and trachea will also be discussed briefly.

Evolutionary loss of complexity in human vocal anatomy as an adaptation for speech.

Human speech production obeys the same acoustic principles as vocal production in other animals but has distinctive features: A stable vocal source is filtered by rapidly changing formant frequencies. To understand speech evolution, we examined a wide range of primates, combining observations of phonation with mathematical modeling. We found that source stability relies upon simplifications in laryngeal anatomy, specifically the loss of air sacs and vocal membranes. We conclude that the evolutionary loss of vocal membranes allows human speech to mostly avoid the spontaneous nonlinear phenomena and acoustic chaos common in other primate vocalizations. This loss allows our larynx to produce stable, harmonic-rich phonation, ideally highlighting formant changes that convey most phonetic information. Paradoxically, the increased complexity of human spoken language thus followed simplification of our laryngeal anatomy.

The hyoid as a sound conducting apparatus in laryngeally echolocating bats.

The morphology of the stylohyal-tympanic bone articulation found in laryngeally echolocating bats is highly indicative of a function associated with signal production. One untested hypothesis is that this morphology allows the transfer of a sound signal from the larynx to the tympanic bones (auditory bulla) via the hyoid apparatus during signal production by the larynx. We used µCT data and finite element analysis to model the propagation of sound through the hyoid chain into the tympanic bones to test this hypothesis. We modeled sound pressure (dB) wave propagation from the basihyal to the tympanic bones, vibratory behavior (m) of the stylohyal-tympanic bone unit, and the stylohyal and tympanic bones when the stylohyal bone is allowed to pivot on the tympanic bone. Sound pressure wave propagation was modeled using the harmonic acoustics solver in ANSYS and vibratory behavior was modeled using coupled modal and harmonic response analyses in ANSYS. For both analyses (harmonic acoustics and harmonic response), the input excitation on the basihyal and thyrohyals was modeled as the estimated pressure (Pa) imposed by the collision of the vibrating thyroid cartilage of the larynx against these bones during signal production. Our models support the hypothesis that this stereotypical hyoid morphology found in laryngeally echolocating bats can transfer sound to the auditory bullae at an amplitude that is likely heard for the species Artibeus jamaicensis and Rhinolophus pusillus.

Implementation of a Low-Cost 3D-Printed Feline Larynx Model for Veterinary Students.

Endotracheal intubation (EI) in domestic cats is an important skill that veterinary students learn in order to perform anesthesia safely in this species. Implementing a 3D-printed larynx model (LaryngoCUBE) during the instruction process may improve student's learning of EI in felines. Twenty-two third-year students performed EI in cats with standard training (ST), and 16 students trained with the model (MT) the day before the laboratory. It was evaluated whether training with the model decreases the time and number of EI attempts, students' perceived difficulty performing EI using a visual analog score (VAS; 0 cm = very easy, 10 cm = extremely difficult; median [minimum-maximum]), and the incidence of failure to perform EI. The EI time on ST (58 [18-160] seconds) was longer, but not statistically different from MT (29 [13-120] seconds; p = .101). The number of EI attempts on ST (2 [1-3]) was higher than MT (1 [1-3]; p = .005). The VAS on the ST and MT were 4.5 (0.0-10.0) cm and 3.0 (0.2-10.0) cm, respectively (p = .029). The failure rate was 27% on the ST and 25% on the MT (p = 1.000). Students who practiced with a larynx model took fewer attempts to perform EI, tended to be faster, and found that EI was easier. However, the EI success rate in MT was not improved.

Anatomy of the respiratory system in the, "Portrait of a Musician" by Leonardo da Vinci.

The object of the research is the painting, Portrait of a Musician''. Upon closer examination of the painting, we discovered three details. Two have the shape of trachea and bronchi and the third a larynx. By moving the details through the program Paint X we got an image of the larynx, trachea and bronchi. The larynx is presented by thyroid and cricoid cartilage. The characteristic cartilaginous rings are distinguished on the trachea. The right and left main bronchi are also seen. In our opinion, Leonardo da Vinci reflected the elements of the respiratory system in the, Portrait of a Musician'', thus emphasizing the fact that the bronchi, trachea and larynx are involved in the production of sound.

Endoscopic and Computed Tomography Evaluation of Posterior Glottic Closure During Phonation.

OBJECTIVES/HYPOTHESIS: The anatomy of the posterior glottis, specifically the states of the posterior glottis during phonation, has not been thoroughly explored in laryngology. Conventional wisdom about the posterior glottis indicates that it tends to be completely closed in men but may be open in women. Furthermore, professional singers are expected to have a completely closed posterior glottis. The aim of this study was to investigate whether these generalizations are true by comparing rigid videolaryngostroboscopy results with high-resolution computed tomography (HRCT) and three-dimensional (3D) reconstruction findings. STUDY DESIGN: Prospective study. METHODS: Of the 90 volunteers (58 women, 32 men) examined, 48 were female professional singers, 10 were female nonsingers, 22 were male professional singers, and 10 were male nonsingers. Rigid videolaryngostroboscopy as well as HRCT scans were performed during singing at the average singing fundamental frequency. HRCT images of the larynx and air-column were 3D visualized using the software MIMICS®. The states of the posterior glottis were assessed in both examinations and compared among participants. RESULTS: The sensitivity of endoscopy was 67.5%. Complete closure of the posterior glottis was observed in 62.5% men and 52% women (P = .33). Complete closure of the posterior glottis was observed in 35% nonsingers and 61% professional singers (P = .036). CONCLUSIONS: The closure of the posterior glottis seen on videolaryngostroboscopy does not always correlate with actual closure. There seems to be no link between sex and complete closure of the glottis. However, there is strong evidence that posterior glottis closure can be influenced, to some degree, by vocal training. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:124-129, 2022.

Effects of Laryngeal Vibratory Asymmetry and Neuromuscular Compensation on Voice Quality.

INTRODUCTION: Vibratory asymmetry and neuromuscular compensation are often seen in laryngeal neuromuscular pathology. However, the ramifications of these findings on voice quality are unclear. This study investigated the effects of varying levels of vibratory asymmetry and neuromuscular compensation on cepstral peak prominence (CPP), an analog of voice quality. STUDY DESIGN: In vivo canine phonation model. METHODS: Varying degrees of vocal fold vibratory asymmetry were achieved by stimulating one recurrent laryngeal nerve (RLN) over 11 levels from threshold to maximal muscle activation. For each of these levels, phonation was induced at systematically varied combinations of neuromuscular compensation: three levels each of contralateral RLN stimulation (80%, 90%, and 100% of maximal), superior laryngeal nerve (SLN) activation (0%, 50%, and 100% of maximal), and airflow levels (500, 700, and 900 mL/s). Vocal fold symmetry was determined by assessing the opening phase of the vibratory cycle in high-speed video recordings. Voice quality was estimated acoustically by calculating CPP for each voice sample. RESULTS: Eight hundred twenty-two phonatory conditions with varying degrees of vibratory asymmetry were evaluated. CPP was highest at vibratory symmetry. Increasing levels of asymmetry resulted in significant decreases in CPP. CPP increased significantly with increasing contralateral RLN activation. CPP was significantly higher at 50% SLN activation than 0% or 100% SLN activation. CONCLUSION: Voice quality, as approximated by CPP, is best at vibratory symmetry and deteriorates with increasing degrees of asymmetry. Voice quality may be improved with neuromuscular compensation by increased adduction of the contralateral vocal fold or increased vocal fold tension at mid-levels of SLN activation. LEVEL OF EVIDENCE: NA, Basic Science Laryngoscope, 132:130-134, 2022.

Just Breathe: Tips and Highlights for Managing Pediatric Respiratory Distress and Failure.

Anatomically, the airway is ever changing in size, anteroposterior alignment, and point of most narrow dimension. Special considerations regarding obesity, chronic and acute illness, underlying developmental abnormalities, and age can all affect preparation and intervention toward securing a definitive airway. Mechanical ventilation strategies should focus on limiting peak inspiratory pressures and optimizing lung protective tidal volumes. Emergency physicians should work toward minimizing risk of peri-intubation hypoxemia and arrest. With review of anatomic and physiologic principles in the setting of a practical approach toward evaluating and managing distress and failure, emergency physicians can successfully manage critical pediatric airway encounters.

Echolocation in soft-furred tree mice.

Echolocation is the use of reflected sound to sense features of the environment. Here, we show that soft-furred tree mice (Typhlomys) echolocate based on multiple independent lines of evidence. Behavioral experiments show that these mice can locate and avoid obstacles in darkness using hearing and ultrasonic pulses. The proximal portion of their stylohyal bone fuses with the tympanic bone, a form previously only seen in laryngeally echolocating bats. Further, we found convergence of hearing-related genes across the genome and of the echolocation-related gene prestin between soft-furred tree mice and echolocating mammals. Together, our findings suggest that soft-furred tree mice are capable of echolocation, and thus are a new lineage of echolocating mammals.

Caracterización de estructuras anatómicas de la laringe por ultrasonografía / Characterization of anatomical structures of the larynx by ultrasonography

La laringe es un órgano impar situado en la línea mediana del cuello, compuesto por cartílagos, músculos y ligamentos. La TC y la RM se realizan como técnicas de imagen de primera elección en el estudio de la laringe, no obstante, no están exentas de limitaciones. La ecografía es un método accesible, de alta resolución y presenta una relativa buena visualización de las diferentes estructuras de la laringe. El objetivo del trabajo fue determinar las características de estructuras anatómicas de la laringe identificables ecográficamente. En este trabajo de carácter observacional descriptivo de corte transversal prospectivo se estudiaron 20 pacientes, sin patología laríngea con edades entre 20 y 35 años, ambos sexos. Se realizó ecografía laríngea utilizando transductor ecográfico Phillips® con sonda lineal de 4 a 12 MHz, preset de partes blandas.En todos los casos se pudo identificar y medir los cartílagos tiroides, cricoides y epiglotis; y en gran porcentaje de estos las cuerdas vocales, bandas ventriculares y comisura anterior. El cartílago aritenoides solo fue visible en un 85% de los casos.La ecografía se presenta como un método auxiliar útil en el estudio de la anatomía de la laringe, proponiendo el seguimiento y realización de estudios ulteriores que puedan complementar este estudio y su validez.

The larynx is an odd organ located in the midline of the neck, composed of cartilage, muscles and ligaments. CT and MRI are performed as first-choice imaging techniques in the larynx study; however, they are not without limitations. Ultrasound is an accessible, high-resolution method with a relatively good visualization of the different structures of the larynx. The objective of the work was to determine the characteristics of ultrasoundly identifiable larynx anatomical structures.In this prospective cross-sectional descriptive observational work, 20 patients were studied, without laryngeal pathology aged between 20 and 35 years, both sexes. Laryngeal ultrasound was performed using Phillips® ultrasound transducer with linear probe from 4 to 12 MHz, soft parts presetThyroid cartilage, cricoids and epiglotis could be identified and measured in all cases, and in a large percentage of these the vocal cords, ventricular bands and anterior corner. Aritenoid cartilage was only visible in 85% of cases.Ultrasound is presented as a useful auxiliary method in the study of the anatomy of the larynx, proposing the follow-up and conduct of further studies that may complement this study and its validity

Learning to Interpret Pediatric Vocal Fold Mobility: A Laryngeal Ultrasound Training Module.

OBJECTIVES/HYPOTHESIS: Vocal fold movement impairment (VFMI) in infants and children is most commonly evaluated by flexible nasolaryngoscopy (FNL). FNL in this population can be challenging due to movement, floppy supraglottic structures, or secretions. Laryngeal ultrasound (LUS) may be an alternative, less invasive means of evaluating VFMI that also decreases aerosolization during the COVID-19 pandemic. The primary objective was to examine LUS interpretation proficiency for VFMI via an educational module. A secondary outcome was to determine whether quantitative measurements increase interpretation accuracy. STUDY DESIGN: Prospective cohort trial. METHODS: Medical students, residents, fellows, faculty, and staff were recruited to complete the module, composed of a 13-minute teaching video followed by 20 cases. Participants determined both qualitatively (subjective assessment) and then quantitatively (through protractor measurements of the vocal fold to arytenoid angle) whether there was normal versus impaired vocal fold mobility. RESULTS: Thirty participants completed the LUS training module, and about one-third were otolaryngology residents. On average, each participant correctly identified 18 cases. The mean rank percent correct for quantitative measurements was significantly higher than that of qualitative interpretations (P < .0001). Measurements significantly caused participants to change their answer correctly compared to incorrectly (P < .0001). As the module progressed, there was no significant trend of more correct interpretations (P = .30). The sensitivity was higher for quantitative interpretations (89.0% vs. 87.3%) but specificity remained unchanged (92.6%). CONCLUSION: Quantitative measurements may increase LUS interpretation accuracy. There was not a specific number of cases interpreted to achieve learning proficiency. LUS is an easily learned method to evaluate for VFMI across all training levels. LEVEL OF EVIDENCE: 3 (local cohort study nonrandomized) Laryngoscope, 131:2545-2549, 2021.

Description and evolution of the larynx of the Physalaemus olfersii species group, with remarks on the laryngeal anatomy of the P. cuvieri clade (Amphibia: Anura: Leiuperinae).

The anuran larynx is an organ of great evolutionary interest because it impacts male reproductive success in courtships. However, little is known about the diversity of the larynx's anatomy, evolutionary history and systematics importance. Here, we describe and compare the anatomy of the larynx of 10 Physalaemus species of the P. cuvieri clade, focusing on the P. olfersii species group. We also reconstructed the ancestral states and tested the phylogenetic signal for the anatomical features. In all the species, the larynx has a general globular shape with the arytenoid cartilages covering almost its entire dorsal surface, while the anterior process of the cricoid cartilages covers most of the ventral surface. The size of the secondary fibrous mass, the thickness of the vocal membrane, and the attachment position of the vocal membrane's free edge considerably differ among the species. Moreover, only four species of a single clade in the P. olfersii species group have the primary fibrous mass well-developed with a suspended region in the dorsolateral passage. We found a significant phylogenetic signal for all these characters. Ancestral reconstructions pointed to reduction tendencies in the thickness of the vocal membrane and the size of the secondary fibrous mass, and a shift of the ventral attachment of the vocal membrane, increasing the angle of its free edge along the phylogeny. This latter trait can diagnose the entire Physalaemus olfersii group, which has the ventral ends of the arytenoids positioned posteriorly, giving this group the steepest angles for the vocal membrane's free edge in relation to the frontal plane. Based on our results, the larynges can contribute to the Physalaemus olfersii species group's systematics and could be elucidative to understand the evolution of the genus. High levels of anatomical and bioacoustical complexity and diversity observed in the group support the expected correlation between vocal anatomy and bioacoustical signal.

Anatomical In Vitro Investigations of the Pediatric Larynx: A Call for Manufacturer Redesign of Tracheal Tube Cuff Location and Perhaps a Call to Reconsider the Use of Uncuffed Tracheal Tubes.

BACKGROUND: Some in vivo studies question the traditional "funnel-shaped" infant larynx; further anatomic examinations were warranted. Examination of fixative free fresh autopsy laryngeal and upper tracheal specimens and multiple measurements was needed to determine consistency between current tracheal tube designs and anatomic observations. METHODS: Larynges from 19 males and 11 females (Caucasian term newborn to 126 months) were examined by the same forensic pathologist. Measurements included anterior/posterior (A/P) and transverse (T) diameters of the cricoid outlet (CO), interarytenoid diameter (IAD), cricothyroid membrane (CTM), distance from the vocal cords (VC) to CO (VC-CO), and calibration of the larynx lumen with uncuffed tracheal tubes as measuring rods. Assessment of "safe tracheal tube placement" was assessed using manufacturer recommended cuffed Microcuff (Kimberly-Clark, Koblenz, Germany) tubes. RESULTS: In 77% (95% confidence interval [CI], 58-90) of specimens, the proximal end of the cuff was within the CO and in 23% even with or close to the CO. The VC-CO varied from 9.1 to 13.17 mm in infants, 11.55 to 15.17 mm in toddlers, and 13.19 to 18.34 mm in children. The A-P/T ratio of the CO was nearly 0.99 in most larynges; the IAD was greater than CO in all specimens. The CTM could be minimally distended in all specimens. CONCLUSIONS: First, despite being marketed as a safer tracheal tube design, the proximal end of the Microcuff cuff rested within or close to the cricoid cartilage theoretically increasing potential cuff-induced injury when using the VC markings for positioning. Our data suggest that the optimal cuff free distance (VC-CO) would be ~13.5 mm for a Microcuff internal diameter (ID) size 3.0, ~15 mm for size 3.5, and ~16 to 19 mm for greater sizes.Second, the CO was virtually circular in all specimens, suggesting that appropriately sized uncuffed tubes should provide an adequate seal in most neonates and toddlers, thus avoiding the potential for cuff-related necrosis injury.Third, the IAD was always greater than CO confirming that the narrowest point of the infant larynx is the nondistensible cricoid cartilage and not the easily distended glottis.Fourth, appropriately sized Microcuff tubes with the cuff deflated completely filled the lumen of the CO and proximal trachea in all specimens. Our data suggest the need for all manufacturers to further evaluate tracheal tube cuff locations and lengths in relation to the VC safe insertion markings, particularly for neonates and toddlers.Fifth, the CTM is minimally distensible, thus having important implications for emergency surgical airway access with most currently available emergency airway devices.

Anterior neck soft tissue measurements on computed tomography to predict difficult laryngoscopy: a retrospective study.

Predicting difficult laryngoscopy is an essential component of the airway management. We aimed to evaluate the use of anterior neck soft tissue measurements on computed tomography for predicting difficult laryngoscopy and to present a clear measurement protocol. In this retrospective study, 281 adult patients whose tracheas were intubated using a direct laryngoscope for thyroidectomy were enrolled. On computed tomography, the distances from the midpoint of the thyrohyoid membrane to the closest concave point of the vallecular (membrane-to-vallecula distance; dMV), and to the most distant point of the epiglottis (membrane-to-epiglottis distance; dME) were measured, respectively. The extended distances straight to the skin anterior from the dMV and dME were called the skin-to-vallecula distance (dSV) and skin-to-epiglottis distance (dSE), respectively. Difficult laryngoscopy was defined by a Cormack-Lehane grade of > 2. Difficult laryngoscopy occurred in 40 (14%) cases. Among four indices, the dMV showed the highest prediction ability for difficult laryngoscopy with an area under the receiver operating characteristic curve of 0.884 (95% confidence interval 0.841-0.919, P < 0.001). The optimal dMV cut-off value for predicting difficult laryngoscopy was 2.33 cm (sensitivity 75.0%; specificity 93.8%). The current study provides novel evidence that increased dMV is a potential predictive indicator of difficult laryngoscopy.