Do tight nosebands have an effect on the upper airways of horses?

BACKGROUND/OBJECTIVES: The public perception relating to the welfare of horses involved with equestrian sports is associated with training methods used and the presentation of horses at events. In this context, very tight nosebands, which are intended to prevent the horse from opening its mouth, also attract a lot of attention. Various studies have evaluated the impact of tight nosebands on stress parameters, whereas the effect of tight nosebands on upper airway function is unknown. Therefore, the aim of the study was to use overground endoscopy to evaluate changes in pharyngeal and laryngeal function when a tight noseband is fitted. Moreover, the ridden horse pain ethogram (RHpE) was applied to investigate signs of discomfort (Dyson et al., 2018). STUDY DESIGN: A randomized, blinded, and prospective study was performed. METHODS: Sixteen warmblood horses consisting of twelve mares and four geldings with a mean age of 11.63 ± 3.53 years were ridden on 2 consecutive days with either loose or tight nosebands (two fingers or no space between bridge of the nose and noseband, respectively) and inserted endoscope in a random order. Videos were taken in a riding arena during a standardized exercise protocol involving beginner level tasks for 30 min in all gaits. For video analysis, freeze frames were prepared and analyzed at the beginning of the expiration phase. Pharyngeal diameter was measured using the pharynx-epiglottis ratio. Other findings (swallowing, pharyngeal collapse, soft palate movements, and secretion) were also evaluated. Moreover, the RHpE was applied. Descriptive statistics and generalized linear mixed effects models were used. Results with a p-value < 0.05 were considered statistically significant. RESULTS: While the pharynx-epiglottis ratio did not change significantly in horses ridden with loose versus tight nosebands, there was an increase in mean grade and total counts of parameters assessed in the pharyngeal region, for example, grade of secretion (1.5 [±SD 0.89] vs. 3.13 [±SD 0.96]; p = 0.0001), axial deviation of the aryepiglottic folds (0.29 [±SD 0.73] vs. 1.33 [±SD 1.44]; p = 0.01), and pharyngeal collapse (0.69 [±SD 0.87] vs. 1.88 [±SD 1.54]; p = 0.005) in horses ridden with tight nosebands. There was no RHpE score above 8 indicating musculoskeletal pain, but the RHpE scores were significantly higher in horses ridden with tight nosebands (p < 0.001). MAIN LIMITATIONS: Video quality was limited when horses showed large amounts of secretion. Another limitation was the small number of horses. CONCLUSIONS: Results add to the evidence obtained in other studies that tight nosebands do not only cause adverse reactions based on the RHpE score such as head behind the vertical or intense staring but also contribute to changes in the pharyngeal region, such as increased secretion and collapse of pharyngeal structures. This may provide further support for future decisions regarding regulations on nosebands.

Recurrence plot embeddings as short segment nonlinear features for multimodal speaker identification using air, bone and throat microphones.

Speech is produced by a nonlinear, dynamical Vocal Tract (VT) system, and is transmitted through multiple (air, bone and skin conduction) modes, as captured by the air, bone and throat microphones respectively. Speaker specific characteristics that capture this nonlinearity are rarely used as stand-alone features for speaker modeling, and at best have been used in tandem with well known linear spectral features to produce tangible results. This paper proposes Recurrent Plot (RP) embeddings as stand-alone, non-linear speaker-discriminating features. Two datasets, the continuous multimodal TIMIT speech corpus and the consonant-vowel unimodal syllable dataset, are used in this study for conducting closed-set speaker identification experiments. Experiments with unimodal speaker recognition systems show that RP embeddings capture the nonlinear dynamics of the VT system which are unique to every speaker, in all the modes of speech. The Air (A), Bone (B) and Throat (T) microphone systems, trained purely on RP embeddings perform with an accuracy of 95.81%, 98.18% and 99.74%, respectively. Experiments using the joint feature space of combined RP embeddings for bimodal (A-T, A-B, B-T) and trimodal (A-B-T) systems show that the best trimodal system (99.84% accuracy) performs on par with trimodal systems using spectrogram (99.45%) and MFCC (99.98%). The 98.84% performance of the B-T bimodal system shows the efficacy of a speaker recognition system based entirely on alternate (bone and throat) speech, in the absence of the standard (air) speech. The results underscore the significance of the RP embedding, as a nonlinear feature representation of the dynamical VT system that can act independently for speaker recognition. It is envisaged that speech recognition too will benefit from this nonlinear feature.

Biomechanical increase in cervical esophageal wall tension during peristalsis.

During pharyngeal phase of swallowing, circumferential tension of the cervical esophagus (CTE) increases caused by a biomechanical process of laryngeal elevation pulling the cervical esophagus orad. The esophagus contracts longitudinally during esophageal peristalsis, therefore, we hypothesized that CTE increases during esophageal peristalsis by a biomechanical process. We investigated this hypothesis using 28 decerebrate cats instrumented with electromyographic (EMG) electrodes on the pharynx and esophagus, and esophageal manometry. We recorded CTE, distal esophageal longitudinal tension (DET), and orad laryngeal tension (OLT) using strain gauges. Peristalsis was stimulated by injecting saline into esophagus or nasopharynx. We investigated the effects of transecting the pharyngo-esophageal nerve (PEN), hypoglossal nerve (HG), or administering (10 mg/kg iv) hexamethonium (HEX). We found that the durations of CTE and DET increased and OLT decreased simultaneously during the total extent of esophageal peristalsis. CTE duration was highly correlated with DET but not esophageal EMG or manometry. The peak magnitudes of the DET and CTE were highly correlated. After HEX administration, peristalsis in the distal esophagus did not occur, and the duration of the CTE response decreased. PEN transection blocked the occurrence of cricopharyngeal or cervical esophageal response during peristalsis but had no significant effect on the CTE response. HG transection had no significant effect on CTE. We conclude that there is a significant CTE increase, independent of laryngeal elevation or esophageal muscle contraction, which occurs during esophageal peristalsis. This response is a biomechanical process caused by esophageal shortening that occurs during esophageal longitudinal contraction of esophageal peristalsis.NEW & NOTEWORTHY Circumferential tension of cervical esophagus (CTE) increases during esophageal peristalsis. CTE response is correlated with distal longitudinal tension on cervical esophagus during esophageal peristalsis but not laryngeal elevation or esophageal muscle contraction. CTE response is not blocked by transection of motor innervation of laryngeal elevating muscles or proximal esophagus but is temporally reduced after hexamethonium administration. We conclude that the CTE response is a biomechanical effect caused by longitudinal esophageal contraction during esophageal peristalsis.

Impact of palatopharyngeal sizes changing on pharyngeal airflow fluctuation and airway vibration in a pediatric airway.

Snoring is common in children and is associated with many adverse consequences. One must study the relationships between pharyngeal morphology and snoring physics to understand snoring progression. Although some model studies have provided fluid-structure interaction dynamic descriptions for the correlation between airway size and snoring physics, the descriptions still need to be further investigated in patient-specific airway models. Fluid-structure interaction studies using patient-specific airway structures complement the above model studies. Based on reported cephalometric measurement methods, this study quantified and preset the size of the palatopharynx airway in a patient-specific airway and investigated how the palatopharynx size affects the pharyngeal airflow fluctuation, soft palate vibration, and glossopharynx vibration with the help of a verified FSI method. The results showed that the stenosis anterior airway of the soft palate increased airway resistance and airway resistance fluctuations, which can lead to increased sleep effort and frequent snoring. Widening of the anterior airway can reduce airflow resistance and avoid obstructing the anterior airway by the soft palate vibration. The pharyngeal airflow resistance, mouth inflow proportion, and soft palate apex displacement have components at the same frequencies in all airway models, and the glossopharynx vibration and instantaneous inflow rate have components at the same frequencies, too. The mechanism of this same frequency fluctuation phenomenon can be explained by the fluid-structure interaction dynamics of an ideal coupled model consisting of a flexible plate model and a collapsible tube model. The results of this study demonstrate the potential of FSI in studying snoring physics and clarify to some degree the mechanism of airway morphology affecting airway vibration physics.

Deciphering the underlying mechanisms of the pharyngeal pumping motions in Caenorhabditis elegans.

The pharynx of the nematode Caenorhabditis elegans is a neuromuscular organ that exhibits typical pumping motions, which result in the intake of food particles from the environment. In-depth inspection reveals slightly different dynamics at the various pharyngeal areas, rather than synchronous pumping motions of the whole organ, which are important for its effective functioning. While the different pumping dynamics are well characterized, the underlying mechanisms that generate them are not known. In this study, the C. elegans pharynx was modeled in a bottom-up fashion, including all of the underlying biological processes that lead to, and including, its end function, food intake. The mathematical modeling of all processes allowed performing comprehensive, quantitative analyses of the system as a whole. Our analyses provided detailed explanations for the various pumping dynamics generated at the different pharyngeal areas; a fine-resolution description of muscle dynamics, both between and within different pharyngeal areas; a quantitative assessment of the values of many parameters of the system that are unavailable in the literature; and support for a functional role of the marginal cells, which are currently assumed to mainly have a structural role in the pharynx. In addition, our model predicted that in tiny organisms such as C. elegans, the generation of long-lasting action potentials must involve ions other than calcium. Our study exemplifies the power of mathematical models, which allow a more accurate, higher-resolution inspection of the studied system, and an easier and faster execution of in silico experiments than feasible in the lab.

A Review of In Vitro and In Silico Swallowing Simulators: Design and Applications.

Swallowing is a primary and complex behaviour that transports food and drink from the oral cavity, through the pharynx and oesophagus, into the stomach at an appropriate rate and speed. To understand this sophisticated behaviour, a tremendous amount of research has been carried out by utilising the in vivo approach, which is often challenging to perform, poses a risk to the subjects if interventions are undertaken and are seldom able to control for confounding factors. In contrast, in silico (computational) and in vitro (instrumental) methods offer an alternate insight into the process of the human swallowing system. However, the appropriateness of the design and application of these methods have not been formally evaluated. The purpose of this review is to investigate and evaluate the state of the art of in vitro and in silico swallowing simulators, focusing on the evaluation of their mechanical or computational designs in comparison to the corresponding swallowing mechanisms during various phases of swallowing (oral phase, pharyngeal phase and esophageal phase). Additionally, the potential of the simulators is also discussed in various areas of applications, including the study of swallowing impairments, swallowing medications, food process design and dysphagia management. We also address current limitations and recommendations for the future development of existing simulators.

[The upper airway in obstructive sleep apnea patients is pathological even when awake]. / Der obere Atemweg bei OSA-Patienten ist auch im Wachzustand pathologisch.

Obstructive sleep apnea (OSA) is characterized by partial or complete obstruction of the pharyngeal airway. Anatomical factors can be distinguished from non-anatomical factors. Age and obesity are the main risk factors for OSA; however, approximately 50% of patients are not obese. In older patients (>60 years), the importance of obesity decreases. There is an increased prevalence of OSA among patients with normal weight. The effects of chronic intermittent hypoxemia, low-grade inflammation, increased sympathetic tone and mechanical stress contribute to a transformation of muscle fibers in the upper airway, resulting in reduced muscle mass and strength. Less frequently encountered non-anatomical factors include decreased muscle tone, increased arousal threshold, and altered sensitivity of CO2 chemoreceptors.

The Cortical and Subcortical Neural Control of Swallowing: A Narrative Review.

Swallowing is a sophisticated process involving the precise and timely coordination of the central and peripheral nervous systems, along with the musculatures of the oral cavity, pharynx, and airway. The role of the infratentorial neural structure, including the swallowing central pattern generator and cranial nerve nuclei, has been described in greater detail compared with both the cortical and subcortical neural structures. Nonetheless, accumulated data from analysis of swallowing performance in patients with different neurological diseases and conditions, along with results from neurophysiological studies of normal swallowing have gradually enhanced understanding of the role of cortical and subcortical neural structures in swallowing, potentially leading to the development of treatment modalities for patients suffering from dysphagia. This review article summarizes findings about the role of both cortical and subcortical neural structures in swallowing based on results from neurophysiological studies and studies of various neurological diseases. In sum, cortical regions are mainly in charge of initiation and coordination of swallowing after receiving afferent information, while subcortical structures including basal ganglia and thalamus are responsible for movement control and regulation during swallowing through the cortico-basal ganglia-thalamo-cortical loop. This article also presents how cortical and subcortical neural structures interact with each other to generate the swallowing response. In addition, we provided the updated evidence about the clinical applications and efficacy of neuromodulation techniques, including both non-invasive brain stimulation and deep brain stimulation on dysphagia.

Oral Intake Difficulty and Aspiration Pneumonia Assessment Using High-Resolution Manometry.

OBJECTIVE: The sequential generation of swallowing pressure (SP) from the nasopharynx to the proximal esophagus is important for the bolus to pass from the oral cavity to the esophagus. The purpose of this study was to investigate the correlation of the SP sequence mode on high-resolution manometry (HRM) with oral intake difficulty and aspiration pneumonia. METHODS: Consecutive patients with dysphagia who were admitted to our dysphagia clinic between November 2016 and November 2020 were enrolled in this cross-sectional study. We classified the HRM pressure topography data according to the SP sequence mode into type A, normal; B, partially decreased; C, totally decreased; and D, sequence disappeared, and according to the upper esophageal sphincter (UES) during pharyngeal swallowing into type 1, flattening and 2, non-flattening. Clinical dysphagia severity was determined based on oral intake difficulty and aspiration pneumonia. RESULTS: In total, 202 patients with dysphagia (mean [standard deviation] age, 68.3 [14.5] years; 140 [69.8%] male) were enrolled. Type C (odds ratio [OR], 10.48; 95% confidence interval [CI], 2.89-51.45), type D (OR, 19.90; 95% CI, 4.18-122.35), and type 2 (OR, 6.36; 95% CI, 2.88-14.57) were significantly related to oral intake difficulty. Type C (OR, 3.23; 95% CI, 1.08-11.12) and type 2 (OR, 4.18; 95% CI, 1.95-9.15) were significantly associated with aspiration pneumonia. CONCLUSION: The failure of sequential generation of SP was associated with higher risk of oral intake difficulty and aspiration pneumonia. These assessments are useful in understanding the pathophysiology and severity of dysphagia and in selecting safety nutritional management methods. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:2127-2135, 2024.

Sex Differences in Velopharyngeal Anatomy of 9- and 10-Year-Old Children.

OBJECTIVE: Understanding the normal anatomy of velopharyngeal (VP) mechanism and the emergence of sexual dimorphism provides valuable insights into differences of VP anatomy among males and females. The purpose of this study is to examine sex differences in VP anatomy in a large data set of 3,248 9- and 10-year-old children. METHOD: Static three-dimensional magnetic resonance imaging was used to compare five VP characteristics including velar length, velar thickness, effective velar length, levator veli palatini muscle length, and pharyngeal depth between age-matched males (n = 1,670) and females (n = 1,578). Additionally, these dimensions were used to determine the VP ratio and effective VP ratio. RESULTS: Males showed significantly larger dimensions for all VP distances and significantly lower ratios of velar length and effective velar length to pharyngeal depth (p < .05). The magnitude of these effect sizes was small to medium, with Cohen's d values ranging from 0.12 to 0.63. Additionally, the VP ratio and effective VP ratio are lower among males compared to females (p < .05). CONCLUSIONS: Results suggest the presence of sexual dimorphism in the VP mechanism among 9- and 10-year-old children. These findings emphasize the necessity of using different normative data for males and females when making comparisons to patients with cleft palate.

Evaluation of pharyngeal airway space after orthodontic extraction treatment in class II malocclusion integrating with the subjective sleep quality assessment.

Orthodontic treatment with premolar extractions is typically used to relieve dental crowding and retract anterior teeth for lip profile improvement. The aim of the study is to compare the changes in regional pharyngeal airway space (PAS) after orthodontic treatment with Class II malocclusion and to identify the correlations between questionnaire results and PAS dimensions after orthodontic treatment. In this retrospective cohort study, 79 consecutive patients were divided into normodivergent nonextraction, normodivergent extraction, and hyperdivergent extraction groups. Serial lateral cephalograms were used to evaluate the patients' PASs and hyoid bone positions. The Pittsburgh Sleep Quality Index and STOP-Bang questionnaire were used for sleep quality evaluation and obstructive sleep apnea (OSA) risk assessment, respectively, after treatment. The greatest airway reduction was observed in hyperdivergent extraction group. However, the changes in PAS and hyoid positions did not differ significantly among three groups. According to questionnaire results, all three groups had high sleep quality and low risk of OSA, with no significant intergroup differences. Moreover, pretreatment-to-posttreatment changes in PAS were not correlated with sleep quality or risk of OSA. Orthodontic retraction with premolar extractions nither exhibit significant reduction in airway dimensions nor increase their risk of OSA.

The Evaluation of Benzodiazepine-induced Dysphagia Using High-resolution Manometry.

We evaluated the pathophysiology of dysphagia considered to be induced by benzodiazepine using high-resolution manometry (HRM). A 53-year-old man with Parkinson disease had had dysphagia for over 3 months. He had been taking several benzodiazepines for more than four years. Two weeks after discontinuation of the benzodiazepines, HRM revealed increased pharyngeal contractility and residual pressure at the upper esophageal sphincter. A video-fluoroscopic swallowing study showed improved pharyngeal bolus passage. Benzodiazepine-induced dysphagia may be due to the muscle relaxant effects on the swallowing muscles and attenuation of the barrier function which prevents reflux from the esophagus into the pharynx.

Evaluation of morphological features of palatopharyngeus insertion into the thyroid cartilage.

The attachment of the palatopharyngeus extended from the posterior end of the thyroid cartilage to the posterior margin of the inferior constrictor attachment that might contribute to successive swallowing movements. Laryngeal elevation is essential for proper swallowing and breathing. Recently, clinical research has demonstrated that the palatopharyngeus, a longitudinal muscle of the pharynx, is involved in the elevation of the larynx. However, the morphological relationship between the larynx and palatopharyngeus remains unclear. In the present study, we analyzed the attachment site and characteristics of the palatopharyngeus in the thyroid cartilage. We evaluated 14 halves of seven heads from Japanese cadavers (average age: 76.4 years); 12 halves, anatomically and two halves histologically. A part of the palatopharyngeus, which originated from the inferior aspect of the palatine aponeurosis, was attached to the inner and outer surfaces of the thyroid cartilage through collagen fibers. The attachment area extends from the posterior end of the thyroid cartilage to the posterior margin of the attachment site of the inferior constrictor. The palatopharyngeus may elevate the larynx with the suprahyoid muscles and contribute to successive movements of swallowing with surrounding muscles. Based on our findings and previous studies, palatopharyngeus with various muscle bundle directions may be essential for the coordination of continuous swallowing events.

Effects of carbonated beverages on sustained swallowing behavior changes in older inpatients.

Sensory stimulation, including stimulation with carbonated liquids, has been known to influence swallowing activity. The aim of this study is to determine the effect of sustained changes in the swallowing behavior of hospitalized patients without dysphagia using the cervical auscultatory recordings of swallowing sounds. The study participants were hospitalized older adults without dysphagia. The participants were asked to initially swallow water and then a carbonated beverage. The sustained effects of the carbonated beverage in relation to swallowing movements were evaluated by measuring the swallowing sounds at the following time periods: (1) immediately and (2) at 1 to 9 min with intervals of 2 min after swallowing the carbonated beverage. The swallowing sounds before and after swallowing the same volume of water were also measured and compared on a different day. Analysis was performed to calculate the time from a sound signal to the beginning of the swallowing sound. Significant shortening of the swallowing sound time of the late pharyngeal phase was observed up to 7 min after swallowing the carbonated beverage, except during the 3 min after swallowing. Shortening of the whole swallowing sound time was observed only immediately after swallowing the carbonated beverage. Regarding the shortening of the acoustic signal in the late pharyngeal period, the effect of cerebral excitability changes due to carbonic acid stimulation was considered.

Biomechanical effects of esophageal elongation on the circumferential tension of the cervical esophagus in vivo.

Evidence obtained ex vivo suggests that physical elongation of the esophagus increases esophageal circumferential stress-strain ratio, but it is unknown whether this biomechanical effect alters esophageal function in vivo. We investigated the effects of physical or physiological elongation of the cervical esophagus on basal and active circumferential tension in vivo. The esophagus was elongated, using 29 decerebrate cats, either physically by distal physical extension of the esophagus or physiologically by stimulating the hypoglossal nerve, which activates laryngeal elevating muscles that elongate the esophagus. Hyoid, pharyngeal, and esophageal muscles were instrumented with electromyogram (EMG) electrodes and/or strain gauge force transducers. Esophageal intraluminal manometry was also recorded. We found that physical or physiological elongation of the cervical esophagus increased esophageal circumferential basal as well as active tension initiated by electrical stimulation of the pharyngo-esophageal nerve or the esophageal muscle directly, but did not increase esophageal intraluminal pressure or EMG activity. The esophageal circumferential response to the esophago-esophageal contractile reflex was increased by distal physical elongation, but not orad physiological elongation. We conclude that physical or physiological elongation of the esophagus significantly increases esophageal circumferential basal and active tension without muscle activation. We hypothesize that this effect is caused by an increase in esophageal stress-strain ratio by a biomechanical process, which increases circumferential wall stiffness. The increase in esophageal circumferential stiffness increases passive tension and the effectiveness of active tension. This increase in cervical esophageal circumferential stiffness may alter esophageal function.NEW & NOTEWORTHY Physical or physiological esophageal elongation increases esophageal circumferential active or passive tension by a biomechanical process, which causes a decrease in esophageal circumferential elasticity. This increased stiffness of the esophageal wall likely promotes esophageal bolus flow during various esophageal functions.

Assessment of the Velopharyngeal Mechanism at Rest and During Speech in Children With 22q11.2DS: A Cross-Sectional Study.

OBJECTIVE: Velopharyngeal dysfunction (VPD) associated with 22q11.2 deletion syndrome (22q11.2DS) has a complex etiology. This study had 3 aims: (1) assess differences in velopharyngeal and levator muscle configuration during rest versus sustained speech production (2) compare differences in velopharyngeal changes between children with and without 22q11.2DS (3) examine the relationship between adenoid thickness, pharyngeal depth, and velopharyngeal changes. DESIGN: Cross-sectional. METHODS: A total of 22 participants, 11 with 22q11.2DS and 11 controls with normal speech and velopharyngeal anatomy (ages 4-12 years), underwent nonsedated MRI at rest and during sustained /i/. Differences in velar and levator muscle contraction across the 2 different conditions were analyzed, using matched paired t-tests. Mean differences across participant groups were examined. Correlation analyses were also conducted. RESULTS: When comparing differences between rest and sustained phoneme production (aim 1), significant (P < .05) differences were noted for all velar and levator muscle variables. For differences in velopharyngeal changes between children with and without 22q11.2DS (aim 2), VP ratio and effective VP ratio were noted to be significantly different. Pharyngeal depth and adenoid thickness were correlated with velar and levator muscle change measures and ratios (aim 3). CONCLUSION: Results from this study provide quantitative in vivo measurements of the contracted levator muscle and velum in young children with 22q11.2DS. Results demonstrated that VP ratio and EVP ratio are significantly different between children with and without 22q11.2DS and that pharyngeal depth is a strong clinical determinant of VPD in children with 22q11.2DS.

The Effect of Swallowing Cues in Healthy Individuals: An Exploratory Study.

The goal of this study was to determine whether providing verbal and visual cues about swallowing changes the timing of swallowing events, and whether this information interacts with bolus volume. 20 healthy adults swallowed 5 ml and 15 ml liquid barium mixed with orange juice under videofluoroscopy during 2 conditions: one condition absent swallowing-specific cues and one condition with verbal and visual input about the swallowing process. Outcome measures included the timing of 10 swallowing events and the number of swallows per bolus. As expected, volume had a significant effect on all outcome measures (p < 0.05). Three timing events differed by cueing condition: 1. swallowing reaction time was earlier for control (- 9.45 ms vs. - 2.01 ms, p = 0.033); 2. the time between initial hyoid movement and maximum hyoid elevation was longer for control (152.85 ms vs. 143.79 ms; p = 0.015); and 3. the onset of upper esophageal sphincter opening occurred later after bolus entry into the pharynx for the swallowing cues condition (111.9 ms vs. 103.31 ms; p = 0.017); however, effect sizes were small (< 0.2). There was a significant interaction between cue condition and bolus volume on swallowing frequency, such that the mean number of swallows of 15 ml boluses was slightly higher during the control condition than during the swallowing cues condition. There were no significant interactions on measures of timing, suggesting distinct mechanisms for the effect of bolus volume and cues on swallowing kinematics. Further research is needed to investigate the effects of different cue modalities and focus (internal vs. external) on swallowing physiology.

A biomechanical response of the esophagus participates in swallowing.

Evidence suggests that a biomechanical process participates in esophageal function, but no such function has yet been identified. We investigated the role of a biomechanical process during swallowing in 30 decerebrate cats instrumented using electromyogram (EMG) electrodes, strain gauge force transducers, and manometry. We found that the cervical esophagus has a short-lasting circumferential tension response during the pharyngeal phase of swallowing (CTPP), and a concomitant EMG response. The CTPP magnitude was correlated with magnitudes of contraction of the geniohyoideus, laryngeal elevation force, and esophageal orad elongation force. The magnitude of the CTPP was not correlated with the peak or area under the curve of the concomitant esophageal EMG response. Restricting laryngeal elevation by physical force or transecting the hypoglossal nerves decreased or eliminated the CTPP during swallowing. Elongation of the distal cervical esophagus increased basal circumferential cervical esophageal tension as well as the CTPP. Transecting the vagus or pharyngoesophageal nerves, or administering hexosamine intravenously, had no significant effect on CTPP. We conclude that CTPP is a response to esophageal elongation during laryngeal elevation during the pharyngeal phase of swallowing, which is not caused by muscle contraction or mediated by the nervous system. The CTPP may assist in the distal movement of boluses before activation of the esophageal phase of swallowing, and may serve to prevent esophagopharyngeal reflux. We hypothesize that the CTPP is a biomechanical decrease in elasticity of the circumferential connective tissue of the cervical esophagus caused by the stress of cervical esophageal elongation.NEW & NOTEWORTHY The pharyngeal phase of swallowing includes increased circumferential tension of the cervical esophagus during the pharyngeal phase of swallowing (CTPP). The CTPP is a biomechanical response caused by elongation of the esophagus during laryngeal elevation, and is not caused by muscle contraction or mediated by the nervous system. The CTPP may assist in the distal movement of boluses before activation of the esophageal phase of swallowing, and may serve to prevent esophagopharyngeal reflux.

Effects of the GABA(B) agonist baclofen on volitional swallowing in normal subjects.

The GABA(B) receptor agonist baclofen is known to suppress the rate of spontaneous swallowing but not pharyngeal muscle contraction. The extent to which baclofen may alter volitional swallowing is not currently known. We investigated the effects of baclofen in healthy subjects, hypothesizing that baclofen exposure would alter volume-regulation and/or piecemeal deglutition behaviors during volitional swallowing attempts. Pharyngeal high-resolution manometry impedance (P-HRM-I) protocol was used to assess swallowing function of 22 healthy adult volunteers (median 29 years) who were investigated on two occasions, receiving 40 mg baclofen (oral) 1 h before study, or placebo (randomized). Standard swallow function variables recommended by the pharyngeal HRM Working Group were derived for 5 ml, 10 ml, and 20 ml volumes of thin and extremely thick liquid challenges. Multiple swallow behaviors, comprising two swallows <5 s apart, were characterized. The spontaneous swallow rate was also determined. Baclofen exposure had no overall significant effect on swallow variables. Upper esophageal sphincter pressure was weaker during exposure to baclofen, during both the pre-deglutitive and post-deglutitive phases of the swallow (p < 0.05 during thick liquid swallows). Piecemeal swallows, where the bolus is separated in two potions, were significantly more common during 20 ml boluses (p = 0.002). Baclofen decreased the frequency of piecemeal deglutition overall. Baclofen has limited to no effect on volitional swallowing measures, however, does reduce the likelihood of initiation of piecemeal deglutition to large volume challenges.

Anatomy of the Pharynx and Cervical Esophagus.

The pharynx is a complex muscular structure allowing breathing, swallowing, as well speech through common airspace. The normal imaging appearance of the pharynx and cervical esophagus can be challenging given the numerous interleaved surrounding muscles and numerous connections. This article presents the imaging anatomy of the pharynx and cervical esophagus and also discusses the clinical relevance of selected anatomical structures that have important significance in disease development and extension.