Measurement of respiratory-swallowing coordination using an oronasal facemask in healthy individuals.

Respiratory-swallowing coordination (RSC) is well established as an essential airway-protective mechanism. Previous studies have used nasal airflow and/or kinematic rib cage and abdominal measures to assess respiration surrounding swallowing, meaning that the direct influence of oral respiration on RSC remains unknown. This study used a partitioned oronasal facemask to compare respiratory phase patterns measured using isolated nasal airflow with those measured using combined oronasal airflow during non-ingestive and ingestive swallowing tasks. Twenty-four healthy individuals with no respiratory or swallowing disorders were assessed at rest and during cued dry, 10 mL water, continuous drinking and cracker swallowing tasks. Respiratory phase patterns were determined for discrete swallows using the nasal and combined oronasal channels separately. There was variable agreement between respiratory phase patterns according to the nasal and oronasal channels across swallowing conditions. The frequency of exhale-swallow-exhale, inhale-swallow-exhale and exhale-swallow-inhale patterns increased by 2%-3% each with the addition of oral flow data to nasal data, whereas the prevalence of inhale-swallow-inhale and ambiguous patterns decreased. This suggests that estimates of respiratory phase patterns are altered minimally by inclusion of oral respiratory estimates in a healthy sample. There were several additional findings of note, including lower within-participant, within-session trial consistency (test-retest reliability) than expected, suggesting high variability in respiratory phase patterns across trials. Additionally, data showed evidence of swallowing non-respiratory flow at the beginning and end of the respiratory-swallowing pause, moving in both inward and outward directions, potentially expanding current understanding of swallowing non-respiratory flow. Further in-depth physiological investigations are required to improve understanding of these findings.

The Influence of Cough Reflex Testing on Patient Management.

PURPOSE: Cough reflex testing (CRT) is an adjunct to the clinical swallowing evaluation (CSE), providing information on patients' risk of silent aspiration. CRT has been shown to influence diet recommendations, but in previous work, the many varied patient characteristics are not controlled. Therefore, the specific role of CRT results in these decisions remains unclear as this relationship has not been directly assessed. METHOD: An online survey was sent to speech language therapists working in dysphagia. Two patient cases were presented that differed only by the presence of risk factors for the development of aspiration pneumonia. For each patient case, there were three assessment scenarios: CSE information only, CSE information with a "pass" CRT result, and CSE information with a "fail" CRT result. Clinicians outlined their patient management plans for each of the six scenarios. RESULTS: Ninety-seven data sets were used in the final analysis. A "fail" result was found to lead to the most restrictive patient management. Decisions made when provided with only CSE information were very similar to decisions made for a CSE with a "pass" result. Aspiration pneumonia risk factors were shown to influence decision making, with the low-risk patient more likely to be recommended a less restrictive diet. CONCLUSIONS: When information was available regarding silent aspiration risk, clinicians factored the results into their decision making. However, in the absence of a CRT result, airway sensation was assumed to be intact in the absence of information. This finding warrants further investigation given the impact this assumption may have on a patient's pulmonary health.

Transcutaneous auricular vagus nerve stimulation alters cough sensitivity depending on stimulation parameters: potential implications for aspiration risk.

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) is considered a safe and promising tool for limb rehabilitation after stroke, but its effect on cough has never been studied. It is known that the ear and larynx share vagal afferent pathways, suggesting that stimulating the ear with taVNS might have effects on cough sensitivity. The specific stimulation parameters used can influence outcomes. Objective: To investigate the effect of various stimulation parameters on change in cough sensitivity, compared to the reference parameter of 25 Hz stimulation at the left concha (most commonly-used parameter for stroke rehabilitation). Design, setting, and participants: Randomized, single-blind, active-controlled, eight-period cross-over design conducted March to August 2022 at a New Zealand research laboratory with 16 healthy participants. Interventions: All participants underwent eight stimulation conditions which varied by stimulation side (right ear, left ear), zone (ear canal, concha), and frequency (25 Hz, 80 Hz). Main outcome measures: Change in natural and suppressed cough threshold (from baseline to after 10 min of stimulation) assessed using a citric acid cough reflex test. Results: When compared to the reference parameter of 25 Hz stimulation at the left concha, there was a reduction in natural cough threshold of -0.16 mol/L for 80 Hz stimulation at the left canal (p = 0.004), indicating increased sensitivity. For the outcome measure of suppressed cough threshold, there was no significant effect of any of the stimulation conditions compared to the active reference. Conclusion: Since stroke patients often have cough hyposensitivity with resulting high risk of silent aspiration, using 80 Hz taVNS at the left canal may be a better choice for future stroke rehabilitation studies than the commonly used 25 Hz taVNS at the left concha. Treatment parameters should be manipulated in future sham-controlled trials to maximize any potential treatment effect of taVNS in modulating cough sensitivity. Clinical trial registration: ACTRN12623000128695.

An Accurate Fiducial Marker for Aligning EMG signals with Swallow Onset.

Swallowing involves the precise coordination of a large number of muscles. This coordination can be quantified non-invasively by electromyographic (EMG) time-series analysis of swallowing events. The temporal alignment of swallow events is critical for defining coordination patterns. Here, a new framework was developed to use the acoustic signal associated with the opening of the Eustachian tube as a fiducial marker to align EMG signals with swallowing. To investigate its accuracy, manometry, audio from the Eustachian tube, and EMG were simultaneously recorded from two participants while performing different swallowing maneuvers. Eustachian tube opening consistently occurred alongside EMG activations and within 0.025 ± 0.022 s of the gold standard manometry-determined functional swallowing onset. A comparison with two traditional EMG alignment methods based on the integrated and rectified EMG signals was then performed over eight participants. Discrepancies of between 0.2 to 0.3 s were found between the initiation of swallowing and the onset or peak EMG activity. Eustachian tube opening served as a more accurate fiducial marker for temporal data alignment, compared to the traditional EMG alignment methods that were based on EMG parameters.Clinical Relevance- The proposed method will allow EMG recordings to be directly associated with the functional onset of swallowing. This provides a more accurate foundation for time-series analysis of muscle coordination and thus the identification of EMG biomarkers associated with healthy and dysphagic swallowing.

Non-invasive assessment of swallowing using flexible high-density electromyography arrays.

Swallowing is a vital function that serves to safely transport food and fluid to the stomach, while simultaneously protecting our airways. Evaluation of swallowing is important for the diagnosis and rehabilitation of individuals with dysphagia, a disorder of swallowing. Flexible high-density surface electromyography (HD sEMG) arrays were designed and fabricated to span the floor of mouth and neck muscles. These arrays were applied on 6 healthy participants over duplicate recording sessions. During each recording session, participants performed three different swallowing motor tasks. The HD sEMG signals were filtered and tasks extracted. For each task, the RMS amplitude was computed, visualized, and compared. Dynamic motor coordination was evident in the filtered signals traces, with different electrode locations showing unique temporal activations. The 2D topographical maps allowed the location of different RMS intensities to be visualized, revealing qualitatively similar patterns across participants and tasks. These motor task trends were also seen within RMS quantifications. The RMS metric across all participants identified significant differences between non-effortful 3 ml and effortful 3 ml swallow tasks ( p=0.006) and there was a minimal variation of 3.1±1.9 µV RMS for repeated recording sessions by each participant. The HD-sEMG array successfully recorded differences in muscle activations during swallowing and was able to discern between two different motor tasks. The arrays offers a spatially detailed non-invasive assessment of the neuromuscular performance of swallowing. Clinical Relevance- The utility of HD-sEMG arrays for evaluation of the muscles involved in swallowing could enable diagnosis and rehabilitation of individuals with dysphagia.

Effect of Topical Nasal Anesthetic on Comfort and Swallowing in High-Resolution Impedance Manometry.

OBJECTIVES/HYPOTHESIS: Use of topical nasal anesthetic (TNA) is common in high-resolution impedance manometry (HRIM). This study investigated the effect of TNA on swallowing and procedure tolerability during HRIM with a 4.2-mm catheter, a more commonly used catheter size with impedance capabilities. STUDY DESIGN: Randomised experimental study with blinding of participants. METHODS: Twenty healthy participants (mean age = 33 years, 16 female) were randomized to undergo HRIM using the ManoScan™ ESO Z 4.2-mm catheter twice, 1 week apart, under two conditions: with TNA (viscous lidocaine) and with placebo. Analyses included esophageal data of three saliva, three saline (5 mL), and three bread swallows (2 cm × 2 cm) performed while reclined 45°, and pharyngeal data under the same conditions while seated upright. Pharyngeal and upper esophageal sphincter (UES) HRIM parameters were analyzed using the Swallow Gateway analysis platform. Visual analogue scale (VAS) scores rating procedural comfort were analyzed. RESULTS: There were no significant physiological differences in pharyngeal and UES parameters between conditions. There were also no significant differences in VAS scores under placebo (mean = 54.8, standard deviation (SD) = 19.3) and TNA (mean = 60.0, SD = 21.9) (t[19] = -0.9, P = .4) conditions; however, there was a significant difference in the first versus second session (t[19]) = 5.1, P < .05). CONCLUSIONS: TNA did not improve comfort, but it also did not significantly affect swallowing behavior. There was, however, a practice effect regardless of TNA use with improved tolerance of the 4.2-mm catheter and likely more natural swallowing behavior during the second session of HRIM. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:2124-2131, 2022.

Effects of cerebellar transcranial direct current stimulation (tDCS) on motor skill learning in swallowing.

OBJECTIVE: This study evaluated the effects of cerebellar tDCS on motor learning for swallowing. METHODS: In a double-blind RCT, 39 healthy adults received either sham, anodal tDCS, or cathodal tDCS in two sessions on two consecutive days. Following 20 min cerebellar tDCS (2 mA) or sham, they underwent swallowing skill training that targeted control of timing and magnitude of submental muscle activation during swallowing. Linear mixed models were used to identify the effects of stimulation on timing and magnitude accuracy as measured by the change in task performance for each training session, and for skill retention on days 3 and 10 post-intervention. RESULTS: Only the sham group had a reduced temporal error from baseline to all following timepoints. When compared to error changes in the sham group, changes from baseline in temporal errors were higher at all timepoints post-intervention for the anodal group, and higher at both retention assessments for the cathodal group. Amplitude errors were smaller for all conditions at all timepoints post-intervention compared to baseline. CONCLUSIONS: Cerebellar tDCS was found to inhibit temporal aspects of motor skill learning in swallowing. For the tDCS parameters used in this study, there is no support for use of tDCS to facilitate swallowing rehabilitation. Trial Registry Number (https://www.anzctr.org.au/): ACTRN12615000451505.IMPLICATIONS FOR REHABILITATIONCerebellar tDCS, in combination with motor skill training, has been demonstrated to increase motor skill learning in healthy individuals and neurologically impaired patients.In this study, cerebellar tDCS applied prior to swallowing skill training adversely affected timing measures of submental muscle activation during swallowing.In contrast to published outcomes in the corticospinal literature, both anodal and cathodal tDCS resulted in a relative inhibitory effect on motor skill learning in swallowing when compared to the sham condition.Swallowing skill training without tDCS produced increased accuracy in outcomes.

Potential for Behavioural Pressure Modulation at the Upper Oesophageal Sphincter in Healthy Swallowing.

Supratentorial structures are known to be involved in the neural control of swallowing, thus the potential for volitional manipulation of pharyngeal swallowing is of rehabilitative interest. The extent of volitional control of the upper oesophageal sphincter (UOS) during swallowing remains unclear. Prior research has shown that the UOS opening duration can be volitionally prolonged during execution of the Mendelsohn manoeuvre, which does not change the UOS opening time in isolation but the swallowing response in its entirety. This study explored the capacity of healthy adults to increase the period of pressure drop in the region of the UOS (UOS-Pdrop) during swallowing, through volitional UOS pressure modulation in the absence of altered pharyngeal pressure. The period of UOS-Pdrop was used as a proxy of UOS opening duration that is associated with a pressure decrease at the region of the UOS. Six healthy adults were seen 45 min daily for 2 weeks and for one follow-up session. During training, high-resolution manometry contour plots were provided for visual biofeedback. Participants were asked to maximally prolong the blue period on the monitor (period of UOS-Pdrop) without altering swallowing biomechanics. Performance was assessed prior to training start and following training. There was evidence within the first session for task-specific volitional prolongation of the period of UOS-Pdrop during swallowing with biofeedback; however, performance was not enhanced with further training. This may suggest that the amount to which the period of UOS-Pdrop may be prolonged is restricted in healthy individuals. The findings of this study indicate a potential of healthy adults to volitionally prolong UOS opening duration as measured by the period of pressure drop at the region of the UOS. Further research is indicated to evaluate purposeful pressure modulation intra-swallow in patient populations with UOS dysfunction to clarify if the specificity of behavioural treatment may be increased.

Effect of Volitional Effort on Submental Surface Electromyographic Activity During Healthy Swallowing.

The effortful swallowing technique aims to compensate for or rehabilitate impaired swallowing by using maximal volitional effort to behaviorally modify aspects of swallowing physiology. Given that swallowing is a submaximal task, swallowing at submaximal levels has recently been suggested as a more task-specific therapeutic technique. The aim of this study was to investigate differences in muscle activity during minimum, regular, and maximum effort swallowing of different boluses and across different ages, with the goal of characterizing the task specificity of minimum effort and maximum effort swallowing. Forty-three healthy adults (22 female) representing four age groups (20-39, 40-59, 60-79, and 80 + years) participated in the study. They were verbally cued to swallow saliva and 5 mL water boluses using participant-determined minimum, regular, and maximum levels of effort, in randomized order. sEMG peak amplitude and duration of each swallow were measured. Linear mixed effects analyses demonstrated that compared to regular effort swallowing, maximum effort swallowing resulted in increased sEMG amplitude (p < .001) and prolonged duration (p < .001), while minimum effort swallowing resulted in decreased amplitude (p < .001) but no significant difference in duration (p = .06). These effects occurred regardless of age or bolus type. Differences in sEMG activity were smaller between regular and minimum effort swallowing than regular and maximum effort swallowing. Both increasing and decreasing volitional efforts during swallowing translate to significant modulation of muscle activity. However, regular swallowing is more similar to minimal effort swallowing. Results reinforce the concept of swallowing as a submaximal task, and provide insight into the development of sEMG biofeedback techniques for rehabilitation.

Ultrasound: Reliability of a Pocket-Sized System in the Assessment of Swallowing.

Purpose Ultrasound imaging offers a noninvasive adjunct to clinical swallowing assessment. Published reliability of sophisticated ultrasound systems is promising; however, no data exist for reliability using more affordable, pocket-sized devices. This study explored intrarater, interrater, and test-retest reliability of swallowing measures acquired with pocket-sized ultrasound technology. Method Five participants collected measures of swallowing from 20 healthy individuals using the Clarius ultrasound. Hyoid excursion and thyrohyoid approximation were derived during saliva, liquid, and puree swallowing. The cross-sectional area of the floor of mouth muscles and tongue thickness were obtained at rest. Measures were collected at two occasions minimum 11 days apart. Reliability was assessed for the entire process of data acquisition including scanning and online measurement, and for offline measurement of saved images. Results For most measures, reliability was poor (ICC [intraclass correlation coefficient] < .50) to moderate (ICC = .50-.75) for the entire process of data acquisition and poor to good (ICC > .75) when measuring saved images. Conclusion Further work is needed to elucidate whether our study findings apply to the Clarius system only or the data suggest a general limitation of pocket-sized ultrasound technology.

Ultrasound: Validity of a Pocket-Sized System in the Assessment of Swallowing.

Adequate hyoid and laryngeal displacement facilitate safe and efficient swallowing. Although videofluoroscopy is commonly used for assessment of this biomechanical event, ultrasound provides benefits as a radiation-free modality for this purpose. This study investigated validity of a pocket-sized ultrasound system (Clarius™) in the assessment of hyoid and laryngeal excursion. Hyoid excursion and thyrohyoid approximation were concurrently assessed in 20 healthy adults using ultrasound and videofluoroscopy during saliva, liquid, and puree swallowing. Correlation analyses were performed to evaluate validity. There was a strong and moderate positive association between ultrasound and videofluoroscopic measurements of hyoid excursion during dry and liquid swallowing, respectively. No evidence for a significant association was found for ultrasound and videofluoroscopic measurements of hyoid excursion for puree swallowing and of thyrohyoid approximation for any bolus type. Further work towards improved validity is necessary prior to clinical transfer of the pocket-sized Clarius™ system in clinical swallowing assessment.

Objective measurement of acoustic intensity of coughing for clearance of penetration and aspiration on video-fluoroscopy.

PURPOSE: This preliminary, exploratory study evaluated the acoustic intensity of effective and ineffective clearance of penetrated and aspirated material from the laryngeal vestibule in patients with dysphagia. METHOD: A lapel microphone was attached anterior to participants' tragus and recorded coughing in decibels during their videofluoroscopic swallowing studies (VFSS). RESULT: Eighty-eight patients were recruited. Thirteen patients, with visible airway invasion and coughing were included in the final analysis. No coughs were effective at expelling aspirated material from the airway (n = 10). Both effective (4/7) and ineffective (3/7) coughing to penetration were recorded. The mean acoustic intensity of effective coughing to penetration was -44.0 dBFS (decibel level relative to full scale) [SD = 7.3, 95% CI = -51.14, -36.86], and ineffective coughing to penetration was only marginally lower at -42.9 dBFS [SD = 2.0, 95% CI = -45.21, -40.59]. CONCLUSION: No coughs were effective at expelling aspirated material from the airway. Some coughs effectively expelled penetrated material from the airway. However, the relationship between acoustic intensity and cough effectiveness is unclear due to the limited number of observations. Given that perceptual evaluation of coughing is widely used in dysphagia clinical practice to determine cough effectiveness, this is an important area for future research.

Potential for Volitional Control of Resting Pressure at the Upper Oesophageal Sphincter in Healthy Individuals.

Resting pressure at the upper oesophageal sphincter (UOS) has been reported to be susceptible to factors such as emotional stress or respiration. This exploratory study investigated the potential for behavioural modulation of UOS resting pressure in healthy adults to increase our understanding of volitional control of UOS pressure, and the potential development of rehabilitation approaches. Six healthy adults were seen one hour daily for two weeks (10 days) and for one post-training session after a training break of two weeks. Manipulation of UOS resting pressure was practised during a protocol of alternating increased and decreased pressure. A high-resolution manometry contour plot was used as a biofeedback modality. Participants were asked to explore how to achieve warmer and cooler colours (pressure increase and decrease, respectively) at the UOS resting pressure band, without changing head position or manipulating activity of other muscles. Performance was analysed prior to training start and following daily training. Participants were able to increase resting pressure following one week of practice; however, there was no evidence for purposeful pressure decrease. The increased resting pressure achieved by participants indicates a capacity for purposeful pressure modulation given intensive biofeedback training. The lack of volitional reduction in pressure may be explained by sustained pressure generation due to the intrinsic muscular characteristics of the UOS and a flooring effect in healthy subjects, in whom physiology mandates a minimum degree of resting pressure to fulfil the barrier function. Distention caused by the presence of the intraluminal catheter cannot be ruled out.

Classification of Stroke Patients With Dysphagia Into Subgroups Based on Patterns of Submental Muscle Strength and Skill Impairment.

OBJECTIVES: To identify and characterize subgroups of stroke patients with clinical signs of dysphagia, based on swallowing-related strength and skill impairments of the submental muscle group. DESIGN: Prospective observational study. SETTING: Inpatient rehabilitation centers and community dwellings. PARTICIPANTS: Individuals (N=114), including stroke patients with dysphagia (n=55) and 2 control groups including myopathic patients with dysphagia (n=19) and healthy volunteers (n=40) were included in this study. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Novel clinical assessment of strength (force generation) and skill (spatial and temporal precision of muscle activation) of the submental muscle group during swallowing and nonswallowing behaviors, using surface electromyography and dynamometry. RESULTS: Hierarchical cluster analysis revealed 4 clusters, which could be broadly characterized as cluster 1: intact strength and skill, cluster 2: poor strength and poor nonswallowing skill, cluster 3: poor strength, and cluster 4: poor strength and poor swallowing skill. Membership in cluster was significantly associated with medical diagnosis (P<.001). The majority of healthy and myopathic participants were assigned to clusters 1 and 3, respectively, whereas stroke patients were found in all 4 clusters. Skill outcome measures were more predictive of cluster assignment than strength measures. CONCLUSIONS: Although healthy and myopathic participants demonstrated predominantly homogeneous swallowing patterns of submental muscle function within their etiology, several subgroups were identified within stroke, possibly reflecting different subtypes of swallowing function. Future research should focus on the nature and rehabilitation needs of these subtypes. Assessment of skill in swallowing may be an important but overlooked aspect of rehabilitation.

A Sensory Stimulation Protocol to Modulate Cough Sensitivity: A Randomized Controlled Trial Safety Study.

Purpose This study evaluated the safety and efficacy of a sensory stimulation protocol that was designed to modulate citric acid cough thresholds as a potential treatment for silent aspiration. Method Healthy adults (n = 24) were randomly assigned to one of three sensory stimulation groups: (a) high-intensity ultrasonically nebulized distilled water (UNDW) inhalations (1.6 ml/min); (b) low-intensity UNDW inhalations (0.5 ml/min); and (3) control, 0.9% saline inhalations (1.6 ml/min). Sensory stimulation was delivered once a day, for 4 consecutive days. Citric acid cough thresholds were determined at baseline, Day 3, and Day 5 to evaluate changes in cough sensitivity. Spirometry was undertaken before, during, and after each sensory stimulation session to monitor for bronchoconstriction. Results No participant showed evidence of bronchoconstriction during the sensory stimulation protocol. There was an interaction effect between day and group on suppressed cough thresholds, χ2(4) = 11.32, p = .02. When compared to the control group, there was a decrease in citric acid cough thresholds across Days 1-5 in the high-intensity (-1.8 doubling concentrations, 95% confidence interval [-2.88, -0.72], p = .01) and low-intensity (-1.3 doubling concentrations, 95% confidence interval [-2.4, -0.2], p = .03) UNDW inhalation groups, representing a sensitization effect of UNDW inhalations on cough sensitivity. Conclusions The UNDW sensory stimulation protocol was safe in healthy adults. The findings provide preliminary evidence that UNDW inhalations sensitize laryngeal afferents related to citric acid-induced cough induction. The therapeutic potential of the UNDW sensory stimulation protocol will be explored in patients with reduced cough sensitivity who are at risk of silent aspiration and aspiration pneumonia. Plain Language Summary This study explored the safety and efficacy of a sensory stimulation protocol that was designed to modulate cough sensitivity as a potential treatment for silent aspiration. The study revealed that inhalations of nebulized distilled water were safe and increased cough sensitivity, when compared to control saline inhalations.

Quantifying test-retest variability of natural and suppressed citric acid cough thresholds and urge to cough ratings.

INTRODUCTION: The citric acid cough reflex test (CRT) is used to quantify cough sensitivity and evaluate the effects of cough therapies and antitussive medications. This study quantifies the test-retest variability of natural and suppressed citric acid cough thresholds and urge to cough ratings in healthy individuals. METHODS: Healthy adults (n = 16) inhaled increasing concentrations of citric acid (0.01-3.2 mol/L) on three alternate days (1, 3, 5) until C2 cough thresholds (i.e. two consecutive coughs within 3 s) or the highest concentrations of citric acid was reached. Participants were instructed to "cough if you need to" in the natural cough condition, and "try not to cough" in the suppressed cough condition. Following each inhalation, participants were asked to rate their urge to cough (UTC) using a modified Borg Scale. RESULTS: Natural cough thresholds (NCTs) increased across days 1-3 (0.87 doubling concentrations, 95% CI, 0.28, 1.44, p = 0.004) and 1-5 (0.87 doubling concentrations, 95% CI, 0.33, 1.41, p = 0.004). Suppressed cough thresholds (SCTs) increased across days 1-5 (0.64 doubling concentrations per day, 95% CI, 0.03, 1.22, p = 0.04). After taking the effect of day into account, NCTs and SCTs varied within-participants by 0.75 (95% CI, 0.53, 0.93) and 0.78 (95% CI, 0.55,0.98) doubling concentrations respectively. UTC ratings at NCT, or SCT did not significantly increase across days 1-3 or 1-5. Sub-threshold (0.05 mol/L) UTC ratings increased across days 1-3 (-1.43 ratings per day, 95% CI, -2.31, -0.5, p = 0.005) and 1-5 (-1.71 ratings per day, 95% CI, -2.59, -0.79, p = 0.001). UTC ratings at NCT, SCT, and sub-threshold varied within-participants after taking into account the effect of day by 1.34 (95% CI, 1.03, 1.71), 1.47 (95% CI, 1.10, 1.91) and 1.20 (95% CI, 0.91, 1.50) ratings. CONCLUSIONS: Natural and suppressed cough thresholds and UTC ratings are subject to test-retest variability. These data are important for the use of citric acid CRT as an outcome measure in longitudinal cough research, as they facilitate interpretation of whether changes in citric acid cough thresholds across days reflect true changes in cough sensitivity, rather than an artefact of repeating the test.

A systematic review of methods of citric acid cough reflex testing.

INTRODUCTION: This systematic review summarises and appraises methods of citric acid cough reflex testing (CRT) documented in published literature. METHODS: Electronic databases, MEDLINE, EMBASE, CINAHL, PsychINFO, Scopus were searched up to and including 11th February 2018. Studies reporting a method of citric acid CRT, published in peer-reviewed journals in English or Spanish, were assessed for the inclusion criteria. Of the selected studies, information on the instrumentation and CRT protocol was extracted. RESULTS: A total of 129 studies were included. Instrumentation and protocols differed widely across studies. Reporting of methods of citric acid CRT was sub-standard, with many crucial methodological components omitted from published manuscripts, preventing their full replication. CONCLUSIONS: Considerable methodological variability exists for citric acid CRT in published literature. The findings suggest that caution is warranted in comparing citric acid cough thresholds across studies. Full replication of previously published methods of citric acid CRT is limited due to crucial elements of the citric acid CRT protocol being omitted from published manuscripts. These findings have implications on the use of citric acid CRT in clinical and pharmaceutical studies to evaluate the effects of antitussive medications and cough therapies.

Examination of swallowing maneuver training and transfer of practiced behaviors to laryngeal vestibule kinematics in functional swallowing of healthy adults.

Swallowing maneuvers are routinely trained in dysphagia rehabilitation with the assumption that practiced behaviors transfer to functional swallowing, however transfer is rarely examined in the deglutition literature. The goal of this study was to train the volitional laryngeal vestibule closure (vLVC) maneuver, which is a swallowing maneuver that targets prolonged laryngeal vestibule closure (LVC). In two different training experiments, 69 healthy adults underwent Long-hold (hold vLVC as long as possible) or Short-hold vLVC training (hold vLVC for 2s). Before and after vLVC training, natural swallows (swallowing without a therapeutic technique) were completed. The outcome variables included laryngeal vestibule closure reaction time and the duration of laryngeal vestibule closure. Results indicate that during both Long-hold and Short-hold vLVC trainings, vLVC swallows had faster laryngeal vestibule closure reaction times and longer durations of laryngeal vestibule closure than in pre-training 5ml liquid swallows. However, only faster laryngeal vestibule closure reaction times transferred to post-training 5ml liquid swallows (20-24% faster), but not prolonged durations of laryngeal vestibule closure. Our findings suggest that swallowing maneuver training has the potential to induce transfer of what was practiced to functional swallowing behavior, although not all practiced behaviors may generalize. These findings are significant for bolstering the effectiveness of dysphagia management in medical settings and should be tested in individuals with dysphagia.

Effects of chin-up posture on the sequence of swallowing events.

BACKGROUND: Chin-up posture is frequently used to manage oral dysphagia after head and neck cancer. This prospective study investigates the effects of chin-ups on the sequence of pharyngeal swallowing events. METHODS: Twelve healthy young adults performed 45 consecutive swallows of 5 mL water across 3 phases on videofluoroscopy: 5 swallows in the neutral head position; 30 swallows during chin-up posture; and 10 swallows in the neutral head position. Swallowing kinematic and bolus flow measures for 9 swallowing events were recorded. Linear trends were analyzed across 30 chin-up swallows; pairwise comparison was used to compare the 3 phases. RESULTS: Time to hyoid peak and laryngeal vestibule closure changed abruptly during chin-up swallowing compared to the initial neutral position. No measure changed across 30 chin-up swallows. Time of hyoid burst decreased upon returning to the neutral position. CONCLUSION: Our findings indicate that chin-up posture challenges the pharyngeal sequence of events for both swallowing kinematics and bolus flow. © 2017 Wiley Periodicals, Inc. Head Neck 39: 947-959, 2017.

The Relationship Between Submental Surface Electromyography and Hyo-Laryngeal Kinematic Measures of Mendelsohn Maneuver Duration.

PURPOSE: The Mendelsohn Maneuver (MM) is a commonly prescribed technique that is taught to individuals with dysphagia to improve swallowing ability. Due to cost and safety concerns associated with videofluoroscopy (VFS) use, submental surface electromyography (ssEMG) is commonly used in place of VFS to train the MM in clinical and research settings. However, it is unknown whether ssEMG accurately reflects the prolonged hyo-laryngeal movements required for execution of the MM. The primary goal of this study was to examine the relationship among ssEMG duration, duration of laryngeal vestibule closure, and duration of maximum hyoid elevation during MM performance. METHOD: Participants included healthy adults and patients with dysphagia due to stroke. All performed the MM during synchronous ssEMG and VFS recording. RESULTS: Significant correlations between ssEMG duration and VFS measures of hyo-laryngeal kinematic durations during MM performance ranged from very weak to moderate. None of the correlations in the group of stroke patients reached statistical significance. CONCLUSION: Clinicians and researchers should consider that the MM involves novel hyo-laryngeal kinematics that may be only moderately represented with ssEMG. Thus, there is a risk that these target therapeutic movements are not consistently being trained.