Estimation of Muscle Activity Change under Different Bolus Conditions using Musculoskeletal Model of Swallowing.

Swallowing, deglutition, is realized by highly coordinated activities of many nerves and muscles, but it is hard to observe directly due to intracorporal movement, and there is a limitation to the number of muscles that can be percutaneously measured. In addition, since there are few studies on the mechanical analysis of the swallowing movement, the detailed muscle activity pattern during swallowing has not yet been clarified. To tackle this problem from the viewpoint of biomechanics, we have been developing the musculoskeletal model of swallowing which can estimate the activities of swallowing-related muscles based on the movements of hyoid bone and thyroid cartilage. In this paper, we analyzed the activities of swallowing-related muscles under two different bolus conditions: bolus of water and nectar thickened liquid to investigate the effect of physical property of bolus in the activities of swallowing-related muscles.

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.

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.

In vivo measurement of swallowing by monitoring thyroid cartilage movement in healthy subjects using thickened liquid samples and its comparison with sensory evaluation.

This research aimed to investigate the relationship between in vivo measurement of swallowing and sensory evaluation using thickened liquids as model foods. Healthy subjects (8 male and average 29.6-year old) participated in both tests, in which the subjects were asked to swallow the whole amount of sample (10 ml) at one time. In vivo measurement monitored thyroid cartilage movement during swallowing using a bendable pressure sensor synchronously with suprahyoid electromyography, whereas sensory evaluation measured perceived cohesiveness and adhesiveness on a visual analogue scale. Two variables from the pressure sensor analysis; activity of the thyroid cartilage and the maximum displacement of the thyroid cartilage were correlated negatively (p < .01) to perceived cohesiveness with high correlation coefficient (|r|> .9). Advantages of in vivo measurement over conventional shear rheology in assessing texture attributes perceived during swallowing were identified. PRACTICAL APPLICATIONS: This research provides food manufactures with knowledge on a novel objective method for texture measurement of fluid foods and beverages based on human physiology during swallowing. Variable from this method can work as a measure for texture design of food products to meet consumers' preference, particularly foods for dysphagia patients whose demand is increasing in this aged society although subjects of study should be expanded to these people in the future.

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.

Development and validation of a computational finite element model of the rabbit upper airway: simulations of mandibular advancement and tracheal displacement.

The mechanisms leading to upper airway (UA) collapse during sleep are complex and poorly understood. We previously developed an anesthetized rabbit model for studying UA physiology. On the basis of this body of physiological data, we aimed to develop and validate a two-dimensional (2D) computational finite element model (FEM) of the passive rabbit UA and peripharyngeal tissues. Model geometry was reconstructed from a midsagittal computed tomographic image of a representative New Zealand White rabbit, which included major soft (tongue, soft palate, constrictor muscles), cartilaginous (epiglottis, thyroid cartilage), and bony pharyngeal tissues (mandible, hard palate, hyoid bone). Other UA muscles were modeled as linear elastic connections. Initial boundary and contact definitions were defined from anatomy and material properties derived from the literature. Model parameters were optimized to physiological data sets associated with mandibular advancement (MA) and caudal tracheal displacement (TD), including hyoid displacement, which featured with both applied loads. The model was then validated against independent data sets involving combined MA and TD. Model outputs included UA lumen geometry, peripharyngeal tissue displacement, and stress and strain distributions. Simulated MA and TD resulted in UA enlargement and nonuniform increases in tissue displacement, and stress and strain. Model predictions closely agreed with experimental data for individually applied MA, TD, and their combination. We have developed and validated an FEM of the rabbit UA that predicts UA geometry and peripharyngeal tissue mechanical changes associated with interventions known to improve UA patency. The model has the potential to advance our understanding of UA physiology and peripharyngeal tissue mechanics.

Neural representation of swallowing is retained with age. A functional neuroimaging study validated by classical and Bayesian inference.

We investigated the neural representation of swallowing in two age groups for a total of 51 healthy participants (seniors: average age 64 years; young adults: average age 24 years) using high spatial resolution functional magnetic resonance imaging (fMRI). Two statistical comparisons (classical and Bayesian inference) revealed no significant differences between subject groups, apart from higher cortical activation for the seniors in the frontal pole 1 of Brodmann's Area 10 using Bayesian inference. Seniors vs. young participants showed longer reaction times and higher skin conductance response (SCR) during swallowing. We found a positive association of SCR and fMRI-activation only among seniors in areas processing sensorimotor performance, arousal and emotional perception. The results indicate that the highly automated swallowing network retains its functionality with age. However, seniors with higher SCR during swallowing appear to also engage areas involved in attention control and emotional regulation, possibly suggesting increased attention and emotional demands during task performance.

Aging-related changes in swallowing, and in the coordination of swallowing and respiration determined by novel non-invasive measurement techniques.

AIM: Previous studies have shown that the process of swallowing changes with aging, a phenomenon known as presbyphagia. These subtle and subclinical age-related changes make older adults more vulnerable to dysphagia during disease insults. However, there are limited studies of the swallowing process in older adults, because measurements are typically invasive or require exposure to X-rays. In the present study, we used integrated non-invasive measurements to determine aging-related changes of swallowing, and in the coordination of swallowing and respiration for a population of healthy participants. METHODS: The non-invasive system provided measurements of larynx movement with piezoelectric sensors, submental muscle activity with surface electromyography and respiration-swallowing coordination by measurement of nasal airflow. We recruited 112 healthy participants from the community, 35 in a young-age group (age 20-30 years), 38 in a middle-age group (age 31-50 years) and 39 in an old-age group (age 51-70 years). RESULTS: The oropharyngeal swallowing parameters of the old-age group had delayed onset latency and longer swallowing apnea duration relative to the other groups, and these differences were greater for larger boluses. The middle- and old-age groups had less expiratory-expiratory respiratory phase pattern than the young-age group. The probability of piecemeal deglutition was highest in the old-age group and lowest in the young-age group. These results show that the phases of oropharyngeal swallowing and the coordination of swallowing with respiration gradually change with aging. CONCLUSIONS: We used integrated non-invasive measurements to document age-related changes in swallowing, and in the coordination of swallowing and respiration in healthy adults.

Repair of cartilage defects in BMSCs via CDMP1 gene transfection.

This study aimed at investigating the ability of cartilage-derived morphogenetic protein 1 (CDMP1) gene-transfected bone marrow mesenchymal stem cells (BMSCs) loaded on the poly(lactic-co-glycolic acid) (PLGA) scaffold for the repair of laryngeal cartilage defects and make a preliminary assessment of its repair effect. The mRNA and protein expressions of hCDMP1 were detected by reverse transcriptase-polymerase chain reaction and Western blotting. The expression of type II collagen (Col II) and glycosaminoglycan (GAG) were detected by immunohistochemistry. The cytoskeletal culture systems before and after transfection were transplanted into the rabbit full-thickness defects of thyroid cartilage for observation of the repair of cartilage defects from general and histological aspects. The exogenous hCDMP1 gene could be successfully transplanted into BMSCs through adenovirus infection to obtain a stable expression. Compared with the control group, hCDMP1 gene-transfected BMSCs had enhanced secretory abilities of Col II, GAG, and other cartilage-specific matrices, with a trend of promoting cartilage differentiation. The transfected cytoskeletal complexes could more effectively repair laryngeal cartilage defects. hCDMP1 gene-transfected BMSCs/PLGA 3-D biological scaffold compounds transplanted into animal bodies could effectively repair laryngeal cartilage defects.

Effect of jaw thrust and cricoid pressure maneuvers on glottic visualization during GlideScope videolaryngoscopy.

PURPOSE: During performance of direct laryngoscopy in the difficult-to-visualize airway, several maneuvers have the potential to impact glottic visualization, including jaw thrust and cricoid pressure. The effect of these maneuvers on glottic visualization during videolaryngoscopy has not been studied. We evaluated the effect of jaw thrust and cricoid pressure maneuvers on both visualization of the glottis and the area of glottic opening visible during GlideScope-aided videolaryngoscopy. METHODS: One hundred patients were enrolled in this study. After induction of general anesthesia, videolaryngoscopy was followed by jaw thrust and cricoid pressure maneuvers performed in random order. Laryngeal anatomy was recorded continuously and was saved as digital images following the initial laryngoscopy and after each maneuver. Glottis grade [modified Cormack and Lehane (C&L)] was recorded, as was the total glottic area. RESULTS: There was improvement in glottis grade when utilizing jaw thrust maneuver in comparison to GlideScope videolaryngoscopy alone (31% improved, 4% worsened; P < 0.001). There was no difference in glottis grade when using the cricoid pressure maneuver in comparison with videolaryngoscopy alone (39% improved, 20% worsened; P = 0.19). Glottic opening area, however, was greater when utilizing the jaw thrust maneuver in comparison with videolaryngoscopy alone (P < 0.001), but smaller when utilizing the cricoid pressure maneuver in comparison with videolaryngoscopy alone (P < 0.001). CONCLUSIONS: The jaw thrust maneuver was superior to videolaryngoscopy alone in improving the modified C&L grade and the visualized glottic area; however, no significant improvement was noted with cricoid pressure. We therefore recommend the use of jaw thrust as a first-line maneuver to aid in glottic visualization and tracheal intubation during GlideScope videolaryngoscopy.

Analogy between laryngeal gesture in Mongolian Long Song and supracricoid partial laryngectomy.

This article reports the results of a multiparametrical analysis of Mongolian Long Song, characterised by multiple ornamentation and shows the similarities between the laryngeal behaviour observed during these ornamentations and the compensatory gesture produced by patients after supracricoid partial laryngectomy. This study includes (1) a physiological analysis of videofiberscopic laryngeal data from a healthy Mongolian singer and from three non-singer French-speaking clinical patients; and (2) an acoustical analysis (fundamental frequency and intensity). For the singer, the fiberoptic analysis showed two main laryngeal behaviours in producing ornamentations: (1) 'lyrical' vibratos mobilising the entire laryngeal block; (2) 'Mongolian' trills with essentially supraglottic movements, the arytenoids being mobilised independently of the rest of the laryngeal block. Patients demonstrated similar aryepiglottic trilling to fulfil a function of voicing. The acoustic analysis showed that the fundamental frequency and the intensity were in phase for vibrato, contrary to the 'Mongolian' trills which were in opposite phase, underlying a change of laryngeal vibratory mechanisms.

The role of the cricothyroid joint anatomy in cricothyroid approximation surgery.

OBJECTIVES/HYPOTHESIS: Cricothyroid approximation (CTA) surgery aims at raising the voice pitch in male-to-female transsexuals. However, 30% of the patients are not satisfied with the result. The purpose of our study was to examine the cricothyroid joint (CTJ) biomechanics and to analyze if (and how) the CTJ anatomy influences the movement of the cricoid and, consequently, the elongation of the vocal fold and the voice pitch after CTA. METHODS: Twenty-four cadaver larynges were examined with high-resolution computerized tomography and MIMICS three-dimensional imaging software (Materialise Interactive Medical Image Control System, Leuven, Belgium). After superimposing the two scans taken in "neutral" and in "CTA" positions, vector geometrical analysis was used to determine the effective rotation axis of the CTJ and to calculate the elongation of the vocal folds after CTA. RESULTS: Our results showed that the cricoid rotates around an axis, the position of which depends on the anatomical structure of the CTJ. Based on the location of this effective rotation axis, we could distinguish three groups. In group I (N=13), the rotation axis was located in the lower third; in group II (N=5), it was located in the middle third; and in group III (N=6), it was located in the upper third of the cricoid. The elongations of the vocal fold were 12%, 8%, and 3%, in groups I, II, and III, respectively. CONCLUSIONS: The anatomical structure of the CTJ influences directly (1) the position of the effective rotation axis and (2) the elongation of the vocal folds.

Variable application and misapplication of cricoid pressure.

BACKGROUND: In 1961, Sellick described a three-finger technique of cricoid pressure used to prevent gastric regurgitation during induction of anesthesia. The "Sellick maneuver" is now used worldwide. The authors have observed great variability in the application of cricoid pressure by health care providers and have suspected that misapplication occurs. The objectives of this observational study were to determine how many different techniques of cricoid pressure were being used and to identify the reasons for such variability of technique. METHODS: During a 30-month period, the authors observed 32 health care providers applying cricoid pressure at five hospitals. The technique and the professional degree of the person performing the maneuver were recorded. We also reviewed five national courses that provide airway management training to determine which technique of cricoid pressure was being taught. RESULTS: Ten different techniques of cricoid pressure were identified in 32 observations. We identified cases in which pressure was mistakenly applied to the thyroid cartilage and sternocleidomastoid muscles. The original three-finger Sellick technique was rarely used (3 of 32). A review of five national training courses revealed that none provide specific cricoid pressure training. CONCLUSION: This observational study demonstrates that there is great variability in the application of cricoid pressure, identifying 10 different techniques in 32 observations. Misapplication does occur with possible patient harm. We suggest four possible reasons for this variability of technique. The authors use the three-finger cricoid pressure technique as originally described by Sellick and thought that this technique is effective, easy to teach, and safely keeps the fingers in the midline of the cricoid cartilage.

Electroglottographic wavegrams: a technique for visualizing vocal fold dynamics noninvasively.

A method for analyzing and displaying electroglottographic (EGG) signals (and their first derivative, DEGG) is introduced: the electroglottographic wavegram ("wavegram" hereafter). To construct a wavegram, the time-varying fundamental frequency is measured and consecutive individual glottal cycles are identified. Each cycle is locally normalized in duration and amplitude, the signal values are encoded by color intensity and the cycles are concatenated to display the entire voice sample in a single image, similar as in sound spectrography. The wavegram provides an intuitive means for quickly assessing vocal fold contact phenomena and their variation over time. Variations in vocal fold contact appear here as a sequence of events rather than single phenomena, taking place over a certain period of time, and changing with pitch, loudness and register. Multiple DEGG peaks are revealed in wavegrams to behave systematically, indicating subtle changes of vocal fold oscillatory regime. As such, EGG wavegrams promise to reveal more information on vocal fold contacting and de-contacting events than previous methods.

The functional anatomy of the cricothyroid joint.

Postoperative long-term treatment problems of male-to-female transsexuals can be caused by the underestimated mobility of the cricothyroid joint. One hundred cadaveric larynges were analysed to reveal the morphological and functional anatomy of the CTJ focusing on possible horizontal and vertical gliding movements. Furthermore, the distance of the cricothyroid space for rotational movements was measured. The articular surface of the cricothyroid joint showed three different possibilities: a well-defined facet (Type 1 61%), no definable facet (Type 2 22%) or a flat surface with or without a tiny protuberance (Type 3 17%). Side different statements and intraindividual differences between male and female specimens were included. These different types affect horizontal and vertical gliding movements, besides rotational movements. The mobility between Type 1 and the others was highly significant (P < 0.001). Regarding different motions in the cricothyroid joint, rotational movements caused significant elongation of the vocal folds, which should be taken into consideration for phonosurgical methods.

Effects of digital vibrotactile speech feedback on overt stuttering frequency.

Fluency-enhancing speech feedback, originating from internally or externally generated sources via auditory or visual sensory modalities is not restricted to a specific sensory modality or signal origination. Research suggests that externally generated digital vibrotactile speech feedback serves as an effective fluency enhancer. The present purpose was to test the fluency-enhancing effects of self-generated digital vibrotactile speech feedback on stuttering frequency. Adults who stutter read passages aloud over the telephone, both with and without digital vibrotactile speech feedback. Digital vibrotactile speech feedback was operationally defined as feeling the vibrations of the thyroid cartilage with the thumb and index finger while speaking. Analysis indicated that self-generated digital vibrotactile speech feedback reduced overt stuttering frequency by an average of 72%. As the specific neural mechanisms associated with stuttering and fluency enhancement from tactile speech feedback remain unknown, theoretical implications and clinical applications were discussed.

The fate of chondrocytes during ageing of human thyroid cartilage.

Human laryngeal cartilages, especially thyroid cartilage, exhibit gender-specific ageing. In contrast to male thyroid cartilages, the ventral half of the female thyroid cartilage plate remains unmineralized until advanced age. In cartilage specimens from laryngectomies and autopsies, apoptosis was studied immunohistochemically and the oxidative mitochondrial enzyme nicotinamide adenine dinucleotide hydride tetrazolium reductase (NADH-TR) was localized histochemically. In addition, very fresh specimens from laryngectomies were fixed under addition of ruthenium hexamine trichloride or tannin to fixation solution to study cell organelles of chondrocytes by electron microscopic methods. In general, apoptotic chondrocytes decreased in thyroid cartilages of both genders, especially after the second decade. In the age group 41-60 years, thyroid cartilage from male specimens revealed a significantly higher percentage of apoptotic cells than did thyroid cartilage from women (P = 0.004), whereas in the age groups 0-20 years and 61-79 years no statistically significant gender difference was determined. In general, thyroid cartilage from women contained more living chondrocytes into advanced age than men. Chondrocytes adjacent to mineralized cartilage were partly positive for apoptosis and NADH-TR and partly negative. Apoptotic chondrocytes often were localized in areas of asbestoid fibres where vascularization and mineralization took place first. Electron microscopy revealed remnants of chondrocytes in asbestoid fibres. Taken together, it can be assumed that some chondrocytes in thyroid cartilage die by apoptosis and that these chondrocytes are characterized by absent reactivity for the mitochondrial enzyme NADH-TR. A possible influence of sexual hormones on apoptotic death of thyroid cartilage cells requires further elucidation.

Pitch synchronous changes of the anterior cricothyroid gap by using ultrasonography.

OBJECTIVES: The purpose of this study was to describe changes of the anterior cricothyroid space during respiration and phonation by using ultrasonography. Furthermore, to assess and correlate laryngeal dimensions in a large cohort of voice healthy men. STUDY DESIGN: Epidemiological study. METHODS: Ultrasound examinations of the laryngeal skeleton, as well as of the cricothyroid space were performed in 64 voice healthy, elderly male subjects. This was done during respiration, phonation in midrange, and high phonation. RESULTS: We could not find any significant correlation concerning lengths of the cricothyroid space when correlated with voice range, highest or lowest frequency. General anthropometric parameters such as body height, weight, or body mass index did not show any considerable correlation with dimensions of the laryngeal skeleton. CONCLUSION: Functionally orientated surgery of the larynx requires exact knowledge of the anatomy and landmarks of the laryngeal skeleton. Topographic relations and dimensions between the thyroid and cricoid cartilages play an important role in cricoid approximation.

The "BURP" maneuver worsens the glottic view when applied in combination with cricoid pressure.

PURPOSE: The purpose of this study was to determine if the application of a BURP maneuver to the cricoid cartilage would combine the benefits of both the BURP and the Sellick maneuvers, resulting in an improved glottic view and offer the potential of protection against passive gastric regurgitation. METHODS: This was a double-blind, prospective, randomized, crossover trial. Forty-three patients scheduled for elective surgery participated in this study. General anesthesia was induced using fentanyl, propofol and rocuronium. In a random sequence for each case and blinded to the laryngoscopist, one of three maneuvers was carried out. Direct vertical pressure, using 30 newtons, a BURP maneuver with cricoid pressure, or no pressure was applied to the cricoid and the laryngoscopic view was ascertained. A separate laryngoscopy was conducted for each maneuver and the views were graded as good (part of the glottis seen), poor (only the arytenoids were seen) or no view (only the epiglottis was seen). Endotracheal intubation was then performed in each case. RESULTS: The results showed that the combination of the BURP maneuver and cricoid pressure worsened the view obtained at laryngoscopy in 30% of cases (P = 0.007). Cricoid pressure alone worsened the view in 12.5% of cases (P = 0.279). No difference was seen in 65% of cases. All patients but one were intubated easily. CONCLUSION: There is no benefit to routinely applying a modified "BURP" maneuver to the cricoid cartilage during rapid sequence induction of anesthesia.