An observational study in Swallowing, sponsored by Hopital Forcilles. Active, not recruiting at 1 site in France. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-23.
Sponsored by Hopital Forcilles · Observational
Ultrasound applied to the upper aerodigestive tract for the assessment of swallowing disorders has been the subject of numerous publications in recent years. Changes in the range of motion or muscular characteristics of the structures involved in swallowing are associated with the presence of swallowing disorders. However, current assessment remains limited to morphological parameters at rest, whereas the combined analysis of measurements at rest and during contraction is a recognised indicator of muscle activity and recruitment capacity in other areas (diaphragm, pelvic floor).
For the anterior bellies of the digastric muscles, which are central to hyo-laryngeal kinematics during swallowing, the conventional transverse ultrasound approach yields a non-interpretability rate of approximately 30% at rest and exceeding 50% during dynamic assessment, along with insufficient reproducibility. These limitations prevent reliable access to functional muscle parameters such as thickness variation during contraction and pennation angle.
This single-centre, cross-over study aims to evaluate whether a proposed new ultrasound approach (NAEP), based on a longitudinal (sagittal) probe positioning, achieves a significantly higher rate of interpretable measurements compared to the conventional approach. The study enrolls 35 healthy volunteers and 35 patients with dysphagia. Both approaches are applied during the same session for each participant, across four swallowing conditions (dry swallow, 5, 10, and 20 mL water boluses). Secondary objectives include assessment of intra- and inter-rater reliability of the NAEP, analysis of the impact of bolus volume on muscle contraction and hyoid movement, and comparison of morphometric parameters between healthy subjects and dysphagic patients.
Background and technical information :
Ultrasound assessment of the anterior bellies of the digastric muscles (ABDM) has historically relied on a transverse (cross-sectional) approach placing the probe in the submental region. This conventional approach (CA) yields a non-interpretability rate of approximately 30% at rest and exceeding 50% during dynamic swallowing assessment, with poor reproducibility, preventing reliable access to functional muscle parameters such as thickness variation during contraction or pennation angle.
The proposed new ultrasound approach (NAEP) involves repositioning the probe to obtain a longitudinal (sagittal) section of the ABDM by rotating the probe 90° from the cross-sectional plane and applying a lateral displacement to align the muscle fibres along their axis. This approach is hypothesised to improve image interpretability and provide access to the pennation angle, a parameter not measurable with the CA.
All examinations are performed using a Sonoscape Expert 2 ultrasound scanner (7-10 MHz high-frequency linear probe), with the participant seated.
Study procedures Healthy volunteers: Each participant undergoes a single-session ultrasound assessment (≤45 minutes total) including image acquisition during four swallowing conditions - dry swallow and 5, 10, and 20 mL water boluses - in a randomised order (block randomisation, n=4). Both the NAEP and CA are applied to each condition, with the order of approaches also randomised at the subject level. Each bolus volume is assessed once per approach.
To assess reproducibility, a second complete examination is performed by a second independent operator (inter-rater reliability) and repeated by the first operator (intra-rater reliability), each separated by a standardised 5-minute interval.
Subjects with dysphagia: Ultrasound acquisition (NAEP and CA) is performed simultaneously during the clinically-indicated Volume-Viscosity Swallow Test (V-VST), following the standard V-VST volume sequence (non-randomised). No additional bolus volumes are administered beyond those clinically validated during the V-VST. The examination may be interrupted at any time based on clinical signs (coughing, wet voice, desaturation). The number of volumes assessed may therefore vary across subjects and will be systematically documented. Ultrasound image analysis is conducted offline, after the clinical assessment.
Parameters recorded
For each swallowing condition and each approach:
ABDM thickness at rest and during contraction (mm) Hyoid bone cranio-caudal displacement (mm) Pennation angle of the ABDM (NAEP only, when obtainable) An image is classified as interpretable if both superficial and deep muscular fasciae of the ABDM are identifiable over ≥50% of the visualised muscle length and allow reliable caliper placement for thickness measurement at rest and during contraction.
Blinded independent review All images are reviewed by a third independent assessor blinded to the primary operator's classifications, to assess inter-rater agreement on interpretability (Cohen's Kappa coefficient) and to conduct a pre-specified sensitivity analysis of the primary endpoint.
Statistical analysis The primary analysis uses a mixed-effects logistic regression model with feasibility (interpretable: yes/no, per swallow) as the dependent variable, approach (NAEP vs. CA), bolus volume, group (healthy/dysphagic), and order of administration as fixed effects, and a random subject intercept to account for repeated measures. The primary result is the odds ratio for the NAEP effect with 95% CI.
A supplementary analysis applies McNemar's test on subject-level overall feasibility (threshold: ≥75% interpretable swallows).
Secondary analyses include: ICC (two-way mixed model) for intra- and inter-rater reliability; linear mixed-effects models for the impact of bolus volume on ABDM thickness variation (Δ%) and hyoid displacement; Pearson/Spearman correlations between muscle parameters and hyoid movement; and between-group comparisons (healthy vs. dysphagic) using t-tests or Mann-Whitney tests with adjusted regression models.
The significance threshold is set at α=0.05 (two-sided) for the primary objective and α=0.01 for confirmatory secondary objectives.
710 studies on the registry are indexed under Deglutition Disorders; 219 are open to participants now.
This study's planned enrollment of 70 is below the median of 97 across 207 observational studies indexed under Deglutition Disorders.
Browse Deglutition Disorders studies →Hopital Forcilles is the lead sponsor of 11 studies on the registry; 4 are open to participants now.
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Two populations are recruited at Hôpital Forcilles (Férolles-Attilly, France):
For healthy volunteers:
For subjects with swallowing disorder
Exclusion Criteria:
For healthy volunteers :
For Subjects with swallowing disorders
Adults without history of swallowing disorders, recruited voluntarily among hospital staff. Each participant undergoes ultrasound assessment of the anterior bellies of the digastric muscles using both the NAEP and the conventional approach, during four swallowing conditions (dry swallow, 5, 10, and 20 mL), in a randomised order. Reproducibility assessment (intra- and inter-rater) is performed in this group only.
Hospitalised subjects with a clinically indicated swallowing assessment. Ultrasound acquisition (NAEP and conventional approach) is performed simultaneously during the standard Volume-Viscosity Swallow Test (V-VST). No additional bolus volumes are administered beyond those clinically validated during the V-VST. The number of volumes assessed may vary according to clinical tolerance and is systematically documented.
The primary objective of this study is to evaluate the rate of interpretable ultrasound measurements (feasibility) of the anterior bellies of the digastric muscles obtained using a new ultrasound approach employing a longitudinal section
For each swallowing condition (dry swallow, 5 mL, 10 mL, and 20 mL water bolus), an ultrasound image is classified as interpretable if both superficial and deep muscular fasciae of the anterior belly of the digastric muscle are identifiable over at least 50% of the visualised muscle length, allowing reliable caliper placement for thickness measurement at rest and during contraction. Images not meeting these criteria are classified as non-interpretable. The feasibility rate is expressed as the proportion of interpretable images per swallow (with 95% CI) for each approach (NAEP and conventional approach), and compared using a mixed-effects logistic regression model adjusted for bolus volume, group, and order of administration. A higher proportion indicates better feasibility.
Time frame: Day 1
Intraclass Correlation Coefficient (ICC) for NAEP measurements of anterior belly of digastric muscle thickness
Relative reliability of ultrasound thickness measurements of the anterior bellies of the digastric muscles obtained using the NAEP, assessed at rest and during contraction. Intra-rater reliability is evaluated by repeating the full examination twice by the same operator, separated by a 5-minute interval. Inter-rater reliability is assessed by two independent operators performing the examination successively, also separated by a 5-minute interval. Results are expressed as ICC (two-way mixed model) with 95% CI. ICC ≥ 0.75 is considered good reliability.
Time frame: Day 1
Change in anterior belly of digastric muscle thickness according to swallowed bolus volume
The relative change in muscle thickness (Δ thickness) is calculated for each swallowing condition as: \[(thickness during contraction - thickness at rest) / thickness at rest\] × 100. The impact of bolus volume (dry swallow, 5 mL, 10 mL, 20 mL) on Δ thickness is analysed using a linear mixed-effects model with random subject intercept, adjusted for sex, height, and BMI. Post-hoc comparisons between consecutive volumes are performed with Bonferroni correction. A linear trend test assesses the dose-response relationship.
Time frame: Day 1
Hyoid bone displacement according to swallowed bolus volume
Hyoid bone movement is defined as the maximum displacement (mm) from rest to peak position during swallowing, measured by ultrasound for each bolus condition (dry swallow, 5 mL, 10 mL, 20 mL). The impact of bolus volume is analysed using a linear mixed-effects model with random subject intercept, adjusted for sex, height, and BMI, with post-hoc Bonferroni-corrected comparisons between consecutive volumes.
Time frame: Day 1
Rate of interpretable images for pennation angle measurement of the anterior bellies of the digastric muscles using the NAEP
The pennation angle of the anterior bellies of the digastric muscles is only measurable using the NAEP (longitudinal approach) and is not applicable with the conventional transverse approach. Feasibility is defined as the proportion of swallowing conditions yielding an image of sufficient quality to allow reliable measurement of the pennation angle. Results are expressed as a proportion with 95% CI.
Time frame: Day 1
Correlation between change in anterior belly of digastric muscle thickness and hyoid bone displacement during swallowing
The association between relative change in ABDM thickness (Δ thickness, %) and cranio-caudal hyoid bone displacement (mm) is analysed using a linear mixed-effects model with random subject intercept, adjusted for bolus volume and ultrasound approach. The regression coefficient β quantifies the increase in hyoid movement per 1% increase in Δ thickness. An interaction term (Δ thickness × volume) tests whether this relationship varies across bolus volumes.
Time frame: Day 1
Correlation between change in pennation angle of the anterior bellies of the digastric muscles and hyoid bone displacement during swallowing
The association between variation in the ABDM pennation angle between rest and contraction during swallowing and cranio-caudal hyoid bone displacement (mm) is analysed using a linear mixed-effects model with random subject intercept, adjusted for bolus volume. This analysis is performed exclusively for NAEP measurements and is conditional on a pennation angle feasibility rate of ≥70%.
Time frame: Day 1
Comparison of ultrasound morphometric parameters of the anterior bellies of the digastric muscles between healthy volunteers and patients with dysphagia
The following parameters are compared between the two groups for swallowing conditions common to both populations (dry swallow and 5 mL): rate of interpretable images per approach, resting ABDM thickness (mm), relative change in ABDM thickness during contraction (Δ%), and cranio-caudal hyoid bone displacement (mm). Between-group comparisons use Student's t-test or Mann-Whitney test depending on normality (Shapiro-Wilk), with effect sizes (Cohen's d or rank r) and 95% CI. Adjusted regression models control for age, sex, and BMI. Given the sample size of the dysphagia group (n=35) and the exploratory nature of this analysis, results are interpreted as hypothesis-generating.
Time frame: Day 1
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