Effects of laryngeal restriction on pharyngeal peristalsis and biomechanics: Clinical implications

Relationship between Swallowing Pressure and Saliva Residue on Endoscopic Evaluation in Pharyngeal Dysphagia

OBJECTIVE

In pharyngeal dysphagia, poor pharyngeal contraction and upper esophageal sphincter (UES) dysfunction result in post-swallow saliva residue (SR). This study aimed to clarify the relationship between swallowing pressure and SR in the valleculae and piriform sinuses on flexible endoscopic evaluation of swallowing (FEES).

METHODS

Pharyngeal dysphagia patients with Wallenberg syndrome were included. Amounts of post-swallow SR in the valleculae and piriform sinuses were classified into four grades using SR scores based on FEES. The Hyodo score was also calculated to evaluate swallowing function. High-resolution manometric data in the nasopharyngeal, oropharyngeal, hypopharyngeal, oro-hypopharyngeal, and UES zones on swallowing were obtained for comparison with SR and Hyodo scores.

RESULTS

Of the 31 recruited, data from 26 patients who successfully underwent FEES and manometry were analyzed. Vallecular SR scores were strongly negatively correlated with a maximum pressure of the oropharynx (r = -0.52, p = 0.006), distal contractile integrals (DCI) of the oropharynx (r = -0.52, p = 0.007), and DCI of the oro-hypopharynx (r = -0.55, p = 0.004). Hyodo scores for parameters 1 and 4 (corresponding to salivary pooling and pharyngeal clearance, respectively) were strongly negatively correlated with a maximum hypopharyngeal pressure (r = -0.57, p = 0.002) and strongly positively correlated with peristaltic velocity (r = 0.53, p = 0.007), respectively. SR scores and Hyodo scores related to SR were not correlated with pressure data of the UES.

CONCLUSION

Manometric analysis of our SR scoring method using FEES revealed that a higher amount of SR in the valleculae, but not in the piriform sinuses, is associated with weaker pharyngeal pressure in pharyngeal dysphagia, especially at the oropharyngeal level.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:3519-3526, 2024.

Objective Tinnitus of Nasopharyngeal Origin

We report a rare case of objective tinnitus induced by nasopharyngeal muscle constriction. A 49-year-old female patient presented at the clinic with unintentional sounds coming from the nasal cavity while talking or swallowing, which were similar to the lip-smacking sound. Physical examination revealed a hypertrophic posterior nasopharyngeal wall and torus tubarius at rest. With voluntary effort, the posterior pharyngeal wall protruded prominently and collided with the torus tubarius on either side, generating a sound when they were separated. Botox injection was recommended but the patient refused. The diagnosis and treatment of objective tinnitus are well established, but in some cases, it may occur under unexpected conditions. We report a novel type of objective tinnitus. A thorough physical examination for tinnitus could reveal the cause.

Swallowing biomechanics in tracheostomised critically ill patients compared to age- and gender-matched healthy controls

Objective

The mechanistic effects of a tracheostomy on swallowing are unclear. Pharyngeal high-resolution manometry with impedance (P-HRM-I) is a novel swallow assessment tool providing quantifiable metrics. This study aimed to characterise swallowing biomechanics in tracheostomised critically ill (non-neurological) patients.

Design

Cohort study.

Setting

Australian tertiary hospital intensive care unit.

Participants

Tracheostomised adults, planned for decannulation.

Main outcome measures

Swallowing assessment using P-HRM-I, compared to healthy age- and gender-matched controls.

Results

In this tracheostomised cohort (n = 10), the Swallow Risk Index, a global measure of swallow function, was significantly elevated (p < 0.001). At the upper oesophageal sphincter (UOS), hypopharyngeal intrabolus pressure and UOS integrated relaxation pressure were significantly elevated (control 0.65 mmHg [-1.02, 2.33] v tracheostomy 13.7 mmHg [10.4, 16.9], P < 0.001; control -4.28 mmHg [-5.87, 2.69] v tracheostomy 12.2 mmHg [8.83, 15.6], P < 0.001, respectively). Furthermore, UOS opening extent and relaxation time were reduced (control 4.83 mS [4.60, 5.07] v tracheostomy 4.33 mS [3.97, 4.69], P = 0.002; control 0.52 s [0.49, 0.55] v tracheostomy 0.41 s [0.37, 0.45], P < 0.001, respectively). Total pharyngeal contractility (PhCI) measuring pharyngeal pressure generation was significantly elevated (control 199.5 mmHg cm.s [177.4, 221.6] v tracheostomy 326.5 mmHg cm.s [253.3, 399.7]; P = 0.001).

Conclusion

In a critically ill tracheostomised cohort, UOS dysfunction was the prevalent biomechanical feature, with elevated pharyngeal pressures. Pharyngeal weakness is not contributing to dysphagia in this cohort. Instead, elevated pharyngeal pressures may represent a compensatory mechanism to overcome the UOS dysfunction. Further studies to extend these findings may inform the development of timely and targeted rehabilitation.

Accuracy of High-Resolution Pharyngeal Manometry Metrics for Predicting Aspiration and Residue in Oropharyngeal Dysphagia Patients with Poor Pharyngeal Contractility

Several physiological metrics can be derived from pharyngeal high-resolution impedance manometry (HRPM), but their clinical relevance has not been well established. We investigated the diagnostic performance of these metrics in relation to videofluoroscopic (VFS) assessment of aspiration and residue in patients with oropharyngeal dysphagia. We analyzed 263 swallows from 72 adult patients (22-91 years) with diverse medical conditions. Metrics of contractility, upper esophageal sphincter (UES) opening and relaxation, flow timing, intrabolus distension pressure, and a global Swallow Risk Index (SRI) were derived from pressure-impedance recordings using pressure-flow analysis. VFS data were independently scored for airway invasion and pharyngeal residue using the Penetration-Aspiration Scale and the Normalized Residue Ratio Scale, respectively. We performed multivariate logistic regression analyses to determine the relationship of HRPM metrics with radiological outcomes and receiver-operating characteristic (ROC) analysis to evaluate their diagnostic accuracy. We identified aspiration in 25% and pharyngeal residue in 84% of the swallows. Aspiration was independently associated with hypopharyngeal peak pressure < 65 mmHg (HypoPeakP) [adjusted odds ratio (OR) 5.27; 95% Confidence Interval (CI) (0.99-28.1); p = 0.051], SRI > 15 [OR 4.37; 95% CI (1.87-10.2); p < 0.001] and proximal esophageal contractile integral (PCI) < 55 mmHg·cm·s [OR 2.30; 95% CI (1.07-4.96); p = 0.034]. Pyriform sinus residue was independently predicted by HypoPeakP < 65 mmHg [OR 7.32; 95% CI (1.93-27.7); p = 0.003], UES integrated relaxation pressure (UES-IRP) > 3 mmHg [OR 2.96; 95% CI (1.49-5.88); p = 0.002], and SRI > 15 [OR 2.17; 95% CI (1.04-4.51); p = 0.039]. Area under ROC curve (AUC) values for individual HRPM metrics ranged from 0.59 to 0.74. Optimal cut-off values were identified. This study demonstrates the diagnostic value of certain proposed and adjunct HRPM metrics for identifying signs of unsafe and inefficient bolus transport in patients with oropharyngeal dysphagia.

The Upper Esophageal Sphincter Distensibility Index Measured Using Functional Lumen Imaging Probe Identifies Defective Barrier Function of the Upper Esophageal Sphincter

Background/Aims

The mechanism via which supra-esophageal symptoms are generated is unclear. We assessed upper esophageal sphincter (UES) function in novel fashion using functional lumen imaging probe (FLIP) topography. We hypothesize that symptoms related to aspiration of esophageal contents may be associated with a more distensible UES.

Methods

FLIP and reflux symptom index score data from patients undergoing diagnostic evaluation for an esophageal complaint over a 10-month period were analyzed retrospectively. UES distensibility on FLIP was studied at 40-70 mL volumes with in-depth analysis at 50 and 60 mL. Symptoms were compared between patients with low, middle, and high UES-distensibility index (UES-DI). Receiver-operating characteristic analysis was performed to determine associations between the UES-DI and individual reflux symptom index symptom item scores.

Results

One hundred and eleven subjects were included. Overall, the associations between UES-DI and symptoms that could be related to supra-esophageal aspiration were strongest at the 50 mL FLIP volume. Choking item score was highest in the high UES-DI group (2.8) vs 1.4 (P < 0.001) in the middle UES-DI and 1.1 (P = 0.004) in the low UES-DI groups. Similarly, the cough item score was highest in the high UES-DI group (2.7) vs 1.5 (P = 0.009) and 0.9 (P = 0.002) groups.

Conclusion

A higher UES-DI measures defective barrier function which could may be the main pathophysiology that generates supra-esophageal symptoms.

Variables influencing manometric parameters of deglutitive and non-deglutitive upper esophageal sphincter: A study of 89 asymptomatic participants

BACKGROUND

High-resolution manometry overcomes limitations imposed by axial and radial asymmetry as well as swallow and respiration-induced movement of the upper esophageal sphincter (UES), allowing for its reliable use in evaluation of dysphagic and reflux patients. The aim of this study was to determine normative values and their variability across position, sex, age, height, weight, BMI, and volume for clinically relevant deglutitive and non-deglutitive UES parameters.

METHODS

We studied 89 asymptomatic volunteers age 19-90 years, (45 female) during 3-10 repetitions of dry, 5 and 10 ml water swallows at 30-s intervals using high-resolution manometry.

KEY RESULTS

Upper esophageal sphincter high-pressure zone was longer in men than women and in supine than upright position. UES basal contractile integral and mean basal pressure were higher in supine compared to upright; higher in men than women, inversely correlated with age, correlated positively with height and with weight in the supine position only. UES relaxation duration was longer in upright than in supine position but not affected by age, sex, height, weight, or BMI. It was longer with 5 and 10 ml compared with dry swallows. UES minimum/nadir relaxation and mean relaxation pressures were lower in upright than supine position, increased with increase in age and were higher in men than women.

CONCLUSIONS AND INFERENCES

Position, sex, age, height, weight, and volume affect some deglutitive and non-deglutitve UES manometric parameters. BMI does not affect the studied manometric parameters. These effects should be taken into consideration in clinical evaluation of UES.

Effects of oral screen exercise on orofacial and pharyngeal activity: An exploratory study using videofluoroscopy and surface electromyography in healthy adults

Objective

The oral screen is a device commonly used for treatment of orofacial disorders. The objective of this exploratory study was to examine the effect of oral screen exercise on the muscle activity in the lips, submental complex, masseter muscle, and kinematic activity of the tongue base, soft palate, pharynx, and larynx in healthy adults. This was compared with the kinematic activity during a dry swallow. It was hypothesized that not only the lip musculature but also other structures in the oral and pharyngeal cavities are activated while using an oral screen device.

Method

Ten healthy subjects used an oral screen during examination with videofluoroscopy and surface electromyography (EMG). Three different instructions for oral screen application and a dry swallow were examined.

Results

The lip muscles showed the highest activity during oral screen exercise. The other muscle groups were activated to a lesser degree. The pattern of activation differed between individuals. Compared with a dry swallow, the range of motion of the tongue base, posterior pharyngeal wall, and the larynx was significantly smaller during oral screen activation. No major differences were found between three different instructions.

Conclusion

This study indicates that the lips and submental complex and, to a lesser degree, oral, pharyngeal, and laryngeal structures are activated with the oral screen, but the pattern of activation varied between individuals. In comparison to the activity during a dry swallow, range of motion during oral screen exercise is small.

Analysis of Factors That Influence the Prognosis of Swallowing Function Rehabilitation Therapy in Patients with Dysphagia After Medullary Infarction

PURPOSE

This study investigated the factors that influence the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction.

PATIENTS AND METHODS

This retrospective study was conducted using the clinical data of 51 patients who were diagnosed with dysphagia after medullary infarction and hospitalized at our institution between January 2019 and January 2021. As per the water swallow test (WST) grade at 1 month after rehabilitation treatment, patients were classified into the good prognosis group and the poor prognosis group. Univariate analysis as well as univariate and multivariate logistic regression analysis were used to analyze factors that influence the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction. Receiver operating characteristic (ROC) curves were then used to test the predictive ability of the significant parameters to predict the prognosis of the rehabilitation therapy in these patients.

RESULTS

Univariate analysis and univariate logistic regression analysis showed that previous stroke (odds ratio [OR] = 1.361), dysarthria (OR = 3.771), disease course (OR = 1.112), National Institutes of Health Stroke Scale (NIHSS) score at admission (OR = 2.596), and infarct site (OR = 11.071) were all significantly correlated with the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction (P < 0.05). Multivariate logistic regression analysis showed that dysarthria (OR = 5.519, 95% confidence interval (CI) 1.413-21.566), infarct site (OR = 18.634, 95% CI 1.696-204.73), and the NIHSS score (OR = 1.001, 95% CI 1.536-4.820) were independent influencing factors of the prognosis of swallowing function rehabilitation therapy in these patients. The ROC curve showed that the area under the curve for the combined prediction of the three indicators was 0.943.

CONCLUSION

The NIHSS score, dysarthria, and infarct site are independent influencing factors for the prognosis of swallowing function rehabilitation therapy in patients with dysphagia after medullary infarction.

Differences in fatigability of muscles involved in fecal continence: Potential clinical ramifications

INTRODUCTION

Fatigue of the anal sphincter complex has been demonstrated using high-resolution anorectal manometry (HRAM). However, the fatigability of individual muscles such as the external anal sphincter (EAS) and puborectalis muscles (PRM) has not been described. Vaginal manometry has been used to study contractile activity of the PRM. By applying both modalities, we attempted to differentiate the fatigability between the PRM and the EAS under different exercise conditions.

METHODS

We studied two groups: group 1, 12 healthy women (21 ± 2.7 years) with HRAM and group 2, 10 healthy (20 ± 3 years) women with vaginal manometry. All subjects performed 40 repetitive contractions with and without an intra-anal resistive load. In group 1, areas under the curve (AUC) of the anal canal high-pressure zone (HPZ) including the caudal and rostral halves were compared. In group 2, the maximum and mean pressures of the vaginal HPZ were compared.

RESULTS

The AUC decreased significantly only after repetitive contractions against a resistive load (462 ± 129 vs. 390 ± 131 mmHg-cm, p = 0.02), indicating fatigue. The caudal half (EAS) decreased significantly after contractions against a load (288 ± 75 vs. 239 ± 82 mmHg-cm, p = 0.02), while the rostral half (PRM) did not. The vaginal pressures (PRM) also decreased only after repetitive contractions against a load (maximum pressures, 358 ± 171 vs. 239 ± 109 mmHg, p = 0.02).

CONCLUSIONS

The EAS and PRM both exhibit fatigue with contractions only against a resistive load. These findings may guide the development of appropriate exercise regimens to target specific muscles involved in fecal continence.

Fatigability of the external anal sphincter muscles using a novel strength training resistance exercise device

Exercises involving pelvic floor muscles including repetitive voluntary contractions of external anal sphincter (EAS) musculature have been used to improve fecal incontinence. Muscle fatigue is a prerequisite for successful strength training. However, muscle fatigue induced by these exercises has not been systematically studied. We aimed to assess the fatigability of EAS muscles during various exercise methods. Twelve nulliparous (21 ± 2.7 yr) women were studied. We evaluated fatigue during 40 repetitive 3-s contractions and 30-s long squeeze contractions both with and without an intra-anal compressible resistant load. The sequence of exercises was randomized. This load was provided by the continence muscles Resistance Exerciser Device. Anal canal pressures were recorded by high-resolution manometry. Exercise against a resistive load showed significant decrease in anal contractile integral (CI) and maximum squeeze pressure during repetitive short squeeze contractions compared with exercise without a load. Linear regression analysis showed a significant negative correlation between anal CI and successive contraction against load, suggesting "fatigue." Similar findings were observed for maximum squeeze pressure (slope with load = -4.2, P = 0.0003, vs. without load = -0.9, P = 0.3). Long squeeze contraction against a load was also more susceptible to fatigue than without a load (P < 0.0001). In conclusion, repetitive contractions against a compressible load induce fatigue and thus have the potential to strengthen the anal sphincter contractile function than contractions without a load. Fatigue rate in long squeeze contraction exercises with a load is significantly faster than that without a load, also indicating greater effectiveness in inducing muscle fatigue.NEW & NOTEWORTHY Fecal incontinence is a distressing disorder with a mainstay of treatment being pelvic floor muscle exercises. However, none of these exercises has proven occurrence of fatigability, which is an important prerequisite for successful muscle strengthening in rehabilitative exercises. In this study, we proved that we can fatigue the external anal sphincter muscles more efficiently by providing a resistive load during anal repetitive short squeeze contractions and long squeeze contraction exercise.

Effect of Dysphagia Rehabilitation Using Kinesiology Taping on Oropharyngeal Muscle Hypertrophy in Post-Stroke Patients: A Double Blind Randomized Placebo-Controlled Trial

Background: It has recently been shown that suprahyoid muscle exercise using kinesiology taping (KT) increases the activation of the suprahyoid muscle in healthy adults, suggesting a potential therapeutic clinical exercise for dysphagia rehabilitation. This study investigated the effect of dysphagia rehabilitation using KT in stroke patients with dysphagia. Methods: Thirty subjects in South Korea were enrolled in this prospective placebo-controlled double-blind study. Participants were randomly assigned to the experimental and sham groups. In the experimental group, the tape was attached to the hyolaryngeal complex, pulled downward with approximately 70% tension, and then attached to the sternum and the clavicle bilaterally. In the sham group, the tape was applied similarly but without the tension. Both groups performed voluntary swallowing 50 times (10 times swallowing per set, times 5 sets) a day for 4 weeks with KT applied. Outcome measures were assessed using portable ultrasound equipment. The parameter measured was the change in thickness of the tongue muscle, mylohyoid muscle, and the anterior belly of the digastric muscle. Results: The experimental group showed statistically significant changes in the thickness of the tongue muscle, mylohyoid muscle, and anterior belly of the digastric muscle than the sham group (p = 0.007, 0.002, and 0.001). Conclusion: Dysphagia rehabilitation using KT is a technique that may promote oropharyngeal muscle thickness in patients with dysphagia after stroke.

Swallow strength training exercise for elderly: A health maintenance need

BACKGROUND

Recent studies have shown high prevalence of oropharyngeal dysphagia associated with frailty- and age-related muscle weakness. Strength training exercises have been advocated for locomotive health maintenance in the elderly and have shown positive outcomes. As muscles involved in oropharyngeal phase of swallowing are also comprised of striated muscles, the aim of this study was to determine biomechanical effect of a novel resistance exercise program, Swallowing Against Laryngeal Restriction (SALR), on pharyngeal phase swallowing in the healthy elderly.

METHODS

A total of 28 volunteers (75 + 7 years; 17 females) with no complaint of dysphagia were studied using video fluoroscopy before and after 6 weeks of the swallow strength training exercise. Eighteen of these volunteers also underwent high-resolution pharyngeal manometry non-concurrent with fluoroscopy. Ten additional volunteers (81 + 6 years; 9 females) were studied by videofluoroscopy before and after 6 weeks of a sham exercise.

KEY RESULTS

Swallow resistance exercise but not the sham exercise resulted in a significant increase in maximum upper esophageal sphincter opening (P < .01), superior and anterior laryngeal excursion (P < .01) as well as posterior pharyngeal wall thickness (P < .01). Resistance exercise but not sham exercise also resulted in a significant increase in deglutitive pharyngeal contractile integral (P < .01).

CONCLUSIONS & INFERENCES

Strength training of muscles involved in the pharyngeal phase of swallowing using the swallowing against laryngeal restriction technique is feasible and significantly improves key physiologic features of the pharyngeal phase of swallowing. These findings provide the basis for consideration of developing an exercise-based swallow health maintenance program for the elderly swallow health maintenance program for the elderly.

Defining pharyngeal contractile integral during high-resolution manometry in neonates: a neuromotor marker of pharyngeal vigor

BACKGROUND

Pharyngeal contractility is critical for safe bolus propulsion. Pharyngeal contractile vigor can be measured by Pharyngeal Contractile Integral (PhCI): product of mean pharyngeal contractile amplitude, length, and duration. We characterized PhCI in neonates and examined the hypothesis that PhCI differs with mode of stimulation.

METHODS

Nineteen neonates born at 38.6 (34-41) weeks gestation were evaluated at 42.9 (40.4-44.0) weeks postmenstrual age using high-resolution manometry (HRM). PhCI was calculated using: (a) Conventional and (b) Automated Swallow Detection algorithm (ASDA) methods. Contractility metrics of all pharyngeal regions were examined using mixed statistical models during spontaneous and adaptive state (pharyngeal and oral stimulus) swallowing.

RESULTS

PhCI of oral stimuli swallows were distinct from pharyngeal stimuli and spontaneous swallows (P < 0.05). Correlation between conventional and ASDA methods was high (P < 0.001). PhCI increased with swallows for pharyngeal stimulation (P < 0.05) but remained stable for swallows with oral stimulation. PhCI differed between proximal and distal pharynx (P < 0.001).

CONCLUSIONS

PhCI is a novel reliable metric capable of distinguishing (1) proximal and distal pharyngeal activity, (2) effects of oral and pharyngeal stimulation, and (3) effects of prolonged stimulation. Changes in pharyngeal contractility with maturation, disease, and therapies can be examined with PhCI.

Characterization of pharyngeal peristaltic pressure variability during volitional swallowing in healthy individuals

BACKGROUND

Recent technological advances incorporated in high resolution manometry have justifiably heightened interest in manometric evaluation of the pharynx. Despite this interest, from both physiologic and clinical perspective there remain a number of unanswered questions regarding the magnitude of variability of pharyngeal pressure phenomena. Therefore, the aim of the present study was to characterize in healthy individuals the inter-subject and recording-site specific variability of pharyngeal peristaltic pressure phenomena.

METHODS

We studied 32 healthy subjects (age: 21-83 years,20 under 35 years) during dry,5 and 10 mL water swallows ×3. Pharyngeal peristaltic pressures were recorded using a high resolution (HR) manometric system and a catheter assembly with 36 circumferential sensors spaced at 1 cm intervals positioned trans-nasally to traverse the pharynx, UES and proximal esophagus.

KEY RESULTS

Both site-specific pressure data and the Pharyngeal contractile integral (PhCI) showed wide dispersion ranging between values under 50 mm Hg to over 300 mm Hg and 100-600 mm Hg/cm/s,respectively. There was also wide range of dispersion of data for both the standard deviations and the coefficient of variation for all sites (P=.001). The coefficient of variation for PhCI ranged between 0.02 and 0.25 representing data dispersion of 2-25 percent of the mean among subjects (P=.001). Position, age and volume of swallowed fluid did not influence the magnitude of variability.

CONCLUSIONS

Deglutitive Pharyngeal peristalsis generates pressures with significant degree of site-related and inter-subject variability. This variability is not influenced by age, position and volume of swallowed fluid.

Pharyngeal peristaltic pressure variability, operational range, and functional reserve

The present understanding of pharyngeal motor function remains incomplete. Among the remaining gaps of knowledge in this regard is the magnitude of variability of pharyngeal peristaltic pressure amplitude. Although variability can pose difficulty in interpretation of manometric findings, its magnitude can inform the operational range and reserve of the pharyngeal contractile function. We aimed to define the intra- and intersubject and intersession variability of select pharyngeal manometric parameters and, using this information, determine the number of swallow repetitions for acquiring reliable pharyngeal manometric data. We recorded pharyngeal peristalsis in 10 healthy subjects (age: 50 ± 25 yr, 5 women) by high-resolution manometry during two separate sessions of 20 sequences of 0.5-ml water swallows. Two-way ANOVA showed significant variation in the mean peak peristaltic pressure value across sites (P < 0.0001) as well as within the data at each site (P < 0.0001). Similarly, the pharyngeal contractile integral exhibited significant inter- (P = 0.003) and intrasubject (P < 0.001) variability. The Shapiro-Wilk normality test showed mixed results, in that some sites showed normally distributed data, whereas others did not. A robust Monte Carlo simulation showed that the nominal sample size was different for various tested metrics. For a power of 0.8, commonly accepted as an adequate threshold for acceptable statistical power, the optimal sample size for various peristaltic parameters ranged between 3 and 15. There is significant intra- and intersubject variability in site-specific and integrated parameters of pharyngeal peristalsis. The observed variance indicates a significant operational range and reserve in pharyngeal contractile function while necessitating parameter-specific sample size for reliable results.NEW & NOTEWORTHY Intra- and intersubject variability are significant and different at various sites within the contractile pharynx. In addition, significant swallow-to-swallow and subject-to-subject variability exists in pharyngeal contractile integral. The range of intrasubject variability indicates the existence of broad operational range and reserve. Lastly, our variability studies informed Monte Carlo and power analyses, yielding estimates of sample size that would ensure accurate representation of pressure metric variability.