White Paper by the European Society for Swallowing Disorders: Screening and Non-instrumental Assessment for Dysphagia in Adults.

This White Paper by the European Society for Swallowing Disorders (ESSD) reports on the current state of screening and non-instrumental assessment for dysphagia in adults. An overview is provided on the measures that are available, and how to select screening tools and assessments. Emphasis is placed on different types of screening, patient-reported measures, assessment of anatomy and physiology of the swallowing act, and clinical swallowing evaluation. Many screening and non-instrumental assessments are available for evaluating dysphagia in adults; however, their use may not be warranted due to poor diagnostic performance or lacking robust psychometric properties. This white paper provides recommendations on how to select best evidence-based screening tools and non-instrumental assessments for use in clinical practice targeting different constructs, target populations and respondents, based on criteria for diagnostic performance, psychometric properties (reliability, validity, and responsiveness), and feasibility. In addition, gaps in research that need to be addressed in future studies are discussed. The following recommendations are made: (1) discontinue the use of non-validated dysphagia screening tools and assessments; (2) implement screening using tools that have optimal diagnostic performance in selected populations that are at risk of dysphagia, such as stroke patients, frail older persons, patients with progressive neurological diseases, persons with cerebral palsy, and patients with head and neck cancer; (3) implement measures that demonstrate robust psychometric properties; and (4) provide quality training in dysphagia screening and assessment to all clinicians involved in the care and management of persons with dysphagia.

Buccofacial Apraxia, Oropharyngeal Dysphagia, and Dementia Severity in Community-Dwelling Elderly Patients.

Apraxia occurs frequently in patients with dementia. Buccofacial apraxia (BFA) characteristics have been less investigated than limb or speech apraxia. An association between BFA and oropharyngeal dysphagia (OD) in old patients with dementia has not yet been explored. We aimed to assess the prevalence of BFA in patients with dementia and evaluate the relationship between BFA, OD, and dementia. We have prospectively included 117 outpatients with dementia referred to a geriatric consultation. Oropharyngeal dysphagia was diagnosed using the volume viscosity swallowing test (V-VST). Buccofacial apraxia was evaluated by miming 7 meaningless gestures. A complementary geriatric assessment of 6-domains completed the evaluation. Buccofacial apraxia was present in 54 (48.6%) patients. Proxies reported OD more frequently in the group of patients with BFA compared to the group without (P = .04). Prevalence of OD assessed with the V-VST was similar between patients with and without apraxia (P = .9). Patients with BFA had a significant lower Mini-Mental State Examination suggesting a more severe cognitive decline (18.1 ± 4.5 vs 15.8 ± 5, P = .01), a lower activities of daily living relative to disabilities (5 ± 0.8 vs 4.3 ± 1.3, P = .001), and had a lower gait speed that indicated frailty (P = .03).In conclusion, our results indicate a relationship between BFA and severity of dementia, disability, and frailty with no significant association between BFA and OD.

ESSD Commentary on Dysphagia Management During COVID Pandemia.

Since the World Health Organization declared the COVID-19 pandemic a Global Public Health Emergency, experts in swallowing are seeking guidance on service delivery and clinical procedures. The European Society for Swallowing Disorders provides considerations to support experts in swallowing disorders in clinical practice. During the COVID-19 pandemic, assessment and treatment of patients with oropharyngeal dysphagia should be provided, while at the same time balancing risk of oropharyngeal complications with that of infection of patients and healthcare professionals involved in their management. Elective, non-urgent assessment may be temporarily postponed and patients are triaged to decide whether dysphagia assessment is necessary; instrumental assessment of swallowing is performed only if processing of the instruments can be guaranteed and clinical assessment has not provided enough diagnostic information for treatment prescription. Assessment and management of oropharyngeal dysphagia is a high-risk situation as it must be considered an aerosol-generating procedure. Personal protective equipment (PPE) should be used. Telepractice is encouraged and compensatory treatments are recommended.

Oropharyngeal dysphagia in children with multiple disabilities.

OBJECTIVE: This study aimed to investigate the prevalence of oropharyngeal dysphagia among institutionalised children with multiple disabilities, a topic with limited literature coverage. METHODS: The study employed a questionnaire, specifically the F-PEDI-EAT-10, to screen for dysphagia in children. Trained nurses administered the questionnaire to the participants. RESULTS: The study included 117 children with multiple disabilities (51.3 per cent boys and 48.7 per cent girls) with an average age of 14 ± 4.7 years. The questionnaire revealed that 53 per cent (n = 62) of the children had a positive score and, surprisingly, 29 per cent of them (n = 18) did not have a confirmed diagnosis of oropharyngeal dysphagia. Notably, children with a positive F-PEDI-EAT-10 score had a significantly higher prevalence of pneumopathy and undernutrition compared with those with a negative score. CONCLUSION: This study underscores the high prevalence of oropharyngeal dysphagia among children with multiple disabilities, a condition that is often underdiagnosed.

Feeding modality evolution in traumatic brain injury patients with severe alteration of consciousness: A observational study.

The aim of this study was to compare feeding modalities and the level of consciousness in patients with a severe brain injury during reeducation and rehabilitation. The clinical data of vegetative state or minimal conscious state due to severe traumatic brain injury hospitalized in a coma arousal unit were collected from 2012 to 2019. Feeding modalities were evaluated clinically and with functional endoscopy evaluation of swallowing or video fluoroscopy and functional oral intake scale. Evolution of consciousness was evaluated using Wessex Head Injury Matrix scale (WHIM). Comparison between WHIM score and feeding modalities were performed at admission and at discharge of the arousal unit. Of the 93 patients considered, 33 were included corresponding to inclusion criteria (traumatic brain injury, disorder of consciousness and age > 18 years). The mean age was 44.8 ±â€…16.8 years, and there were 6 females for 27 males. At admission, all patients were fed by gastrostomy (n = 25) or by nasogastric tube (n = 8) and 27 had a tracheostomy. At discharge, 10 patients keep an exclusive alimentation by gastrostomy (Group 1, G1) as 23 had exclusive oral feeding (Group 2, G2). The score of the WHIM at admission was identical in both groups (21.7 ±â€…10.9 (G1) vs. 21.0 ±â€…15.33 (G2) (ns)). At discharge, WHIM increased to 38.3 ±â€…15.4 in G1 and to 49.8 ±â€…9.7 in G2 (P < .05). WHIM score was significantly higher in G2 than in G1 (P < .05). There was a positive correlation between functional oral intake scale and WHIM at discharge. Our results demonstrated that recovery of oral feeding in patients with a severe traumatic brain injury appeared in those who had the better improvement of consciousness level.

Expert Consensus on Clinical Decision Making in the Disease Trajectory of Oropharyngeal Dysphagia in Adults: An International Delphi Study.

To date, no consensus exists on the complex clinical decision-making processes involved in oropharyngeal dysphagia, or swallowing disorders. This study aimed to develop an international consensus on a clinical decision tree for the disease trajectory of oropharyngeal dysphagia in adults, taking into account physiological impairments of swallowing, risk factors for the development of complications from oropharyngeal dysphagia, and prognostic factors for treatment outcomes. Using the Delphi technique, consensus was achieved among dysphagia experts across 31 countries, resulting in a total of 10 physiological impairments, 23 risk factors and 21 prognostic factors identified as relevant factors in the clinical decision-making process. Factors most contributing to the severity of oropharyngeal dysphagia were 'Aspiration', 'Incomplete ejection or failure to eject aspirated materials from the airways', 'Weak or absent cough', 'Choking' and 'Sensory deficits in the oropharynx'. To connect the existing theoretical framework to clinical practice, future research will develop the current findings by corroborating the domains based on relevant factors for clinical decision making and those that contribute to the severity of oropharyngeal dysphagia.

"Virtual" lesioning of the human oropharyngeal motor cortex: a videofluoroscopic study.

OBJECTIVE: To use focal cortical inhibition and create a "virtual" lesion in the oropharyngeal motor cortex in healthy subjects to determine whether this provokes swallowing dysfunction. DESIGN: Intervention study: before and after cortical stimulation. SETTING: Tertiary care center. PARTICIPANTS: Healthy adult volunteers (N=9; age range, 21-44y) participated in the study. INTERVENTIONS: Active or sham 1-Hz repetitive transcranial magnetic stimulation (rTMS) over the cortical sites in each hemisphere evoking the largest mylohyoid motor-evoked potentials (mMEPs) to single pulse transcranial magnetic stimulation. MAIN OUTCOME MEASURES: Videofluoroscopic assessment was performed before and 5, 30, and 60 minutes after rTMS. RESULTS: The motor threshold was 83%±10% for the hemisphere with the larger mMEP (dominant) and 92%±9% for the hemisphere with the smaller mMEP (nondominant). When rTMS was performed over the dominant hemisphere, there was a decrease in oral transit time (P=.05), an increase in swallow reaction time (P=.0001), but no change of pharyngeal transit time or laryngeal closure duration. When rTMS was performed on the nondominant hemisphere, there was also a decrease in oral transit time (P=.05), but no change in any of the other swallowing measures. Neither active intervention produced any signs of aspiration or penetration. Sham stimulation had no effect. CONCLUSIONS: Inhibiting the human oropharyngeal motor cortex using rTMS transiently modifies swallowing behavior in a way reminiscent to that seen in stroke patients.

SWALLOWING ACTIVATION USING SENSORY STIMULATION IN PATIENTS WITH SEVERE DISORDERS OF CONSCIOUSNESS.

Objective: Swallowing disorders are systematically present in patients with severe brain injury, disorders of consciousness, and subsequently poor quality of life. The study hypothesis was that taste and smell could improve swallowing function and quality of life in such patients, who are fed by gastrostomy tube. Methods: Eight patients with unresponsive wakefulness syndrome were included in this study. All patients had been in a stable state for at least 2 years, and the delay between the neurological event and the study was always more than 2 years. Strong tastes and smells were selected using the Pfister olfactory classification. Taste and smell stimulations were performed every weekday, Monday to Friday, for 1 week (5 sessions) by a speech and language therapist. Evaluation of swallowing was performed before the first session and after the fifth session, and included the number of spontaneous swallows during 10 min, the presence of drooling, and spontaneous tongue and velum mobility. Results: The number of spontaneous swallows at the initial evaluation was 6.8 ± 5.1 n/min. At the final evaluation there was a significant increase in the number of spontaneous swallows (9.1 ± 4.1 n/min, p < 0.01). Conclusion: This clinical observation has shown that taste and smell stimulations are relevant in clinical practice to improve spontaneous swallowing.

Can Swallowing Cerebral Neurophysiology Be Evaluated during Ecological Food Intake Conditions? A Systematic Literature Review.

Swallowing is a complex function that relies on both brainstem and cerebral control. Cerebral neurofunctional evaluations are mostly based on functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), performed with the individual laying down; which is a non-ecological/non-natural position for swallowing. According to the PRISMA guidelines, a review of the non-invasive non-radiating neurofunctional tools, other than fMRI and PET, was conducted to explore the cerebral activity in swallowing during natural food intake, in accordance with the PRISMA guidelines. Using Embase and PubMed, we included human studies focusing on neurofunctional imaging during an ecologic swallowing task. From 5948 unique records, we retained 43 original articles, reporting on three different techniques: electroencephalography (EEG), magnetoencephalography (MEG) and functional near infra-red spectroscopy (fNIRS). During swallowing, all three techniques showed activity of the pericentral cortex. Variations were associated with the modality of the swallowing process (volitional or non-volitional) and the substance used (mostly water and saliva). All techniques have been used in both healthy and pathological conditions to explore the precise time course, localization or network structure of the swallowing cerebral activity, sometimes even more precisely than fMRI. EEG and MEG are the most advanced and mastered techniques but fNIRS is the most ready-to-use and the most therapeutically promising. Ongoing development of these techniques will support and improve our future understanding of the cerebral control of swallowing.

Olfactory ensheathing cells in a rat model of laryngeal reinnervation.

OBJECTIVES: Olfactory ensheathing cells have been used successfully for recovery of nervous system lesions. The aim of our study was to determine whether olfactory ensheathing cells from the olfactory bulb or olfactory mucosa were able to improve functional recovery in a laryngeal reinnervation animal model. METHODS: Fifty-nine rats were divided into 6 groups. A group without nerve section (group 1; n=10) and a group without anastomosis (group 2; n=11) served as controls. Right vagus nerve section and immediate anastomosis (nonselective reinnervation) was performed in 4 other groups, as follows. In group 3 (n=10), there was selective reinnervation without any addition of substance; groups 4 (n=10), 5 (n=10), and 6 (n=8) received, on the section and anastomosis site, and at the same time, cultivated olfactory bulb, cultivated olfactory mucosa, and noncultivated olfactory mucosa from inbred rats, respectively. Three months later, videolaryngoscopy with vocal fold movement measurements, electromyography, and histologic examination were performed. RESULTS: The best right vocal fold angular movement (3.05 degrees +/- 1.14 degrees) was observed in group 5 with cultivated olfactory mucosa, versus group 3 (-0.28 degrees +/- 1.51 degrees; p = 0.06). The relative angular vocal fold movement was better in group 5 (p = 0.05). The mobility score was 0.6 +/- 0.27 for group 3 and 1.4 +/- 0.31 for group 5 (p = 0.07). Less synkinesis was observed in the reinnervated groups with cell addition, particularly with noncultivated olfactory mucosa (group 6; p = 0.05). CONCLUSIONS: Olfactory ensheathing cells obtained from olfactory mucosa cultures seem to improve functional laryngeal reinnervation in a rat model of nonselective vagus nerve section and anastomosis.

European Stroke Organisation and European Society for Swallowing Disorders guideline for the diagnosis and treatment of post-stroke dysphagia.

Post-stroke dysphagia (PSD) is present in more than 50% of acute stroke patients, increases the risk of complications, in particular aspiration pneumonia, malnutrition and dehydration, and is linked to poor outcome and mortality. The aim of this guideline is to assist all members of the multidisciplinary team in their management of patients with PSD. These guidelines were developed based on the European Stroke Organisation (ESO) standard operating procedure and followed the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. An interdisciplinary working group identified 20 relevant questions, performed systematic reviews and meta-analyses of the literature, assessed the quality of the available evidence and wrote evidence-based recommendations. Expert opinion was provided if not enough evidence was available to provide recommendations based on the GRADE approach. We found moderate quality of evidence to recommend dysphagia screening in all stroke patients to prevent post-stroke pneumonia and to early mortality and low quality of evidence to suggest dysphagia assessment in stroke patients having been identified at being at risk of PSD. We found low to moderate quality of evidence for a variety of treatment options to improve swallowing physiology and swallowing safety. These options include dietary interventions, behavioural swallowing treatment including acupuncture, nutritional interventions, oral health care, different pharmacological agents and different types of neurostimulation treatment. Some of the studied interventions also had an impact on other clinical endpoints such as feedings status or pneumonia. Overall, further randomized trials are needed to improve the quality of evidence for the treatment of PSD.

A lubrication analysis of pharyngeal peristalsis: application to flavour release.

After eating a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The aim of this article was to analyse the fluid mechanics of pharyngeal peristalsis and to develop a simple biomechanical model in order to understand the role of saliva and food bolus viscosity on the coating of pharyngeal mucosa. We began by analysing the physiology and the biomechanics of swallowing in order to determine relevant model assumptions. This analysis of the literature clarified the types of mechanical solicitations applied on the food bolus. Moreover, we showed that the pharyngeal peristalsis in the most occluded region is equivalent to a forward roll coating process, the originality of which is lubrication by a film of saliva. A model based on the lubrication theory for Newtonian liquids was developed in dimensionless form. The parametric study showed the strong influence of relative saliva thickness on the food bolus coating. A specific experimental device was designed that confirms the model predictions. Two sets of conditions that depend on the relative thickness of saliva were distinguished. The first is characterised by a relatively thin film of saliva: food bolus viscosity has a strong impact on mucosa coating. These phenomena are well represented by the model developed here. The second is obtained when the saliva film is relatively thick: hydrodynamic mixing with saliva, interdiffusion or instabilities may govern mucosa coating. Finally, these results were extrapolated to determine the influence of food bolus viscosity on the dynamic profile of flavour release according to physiological parameters.

Exhaled nitric oxide fractions are well correlated with clinical control in recurrent infantile wheeze treated with inhaled corticosteroids.

Fractional exhaled nitric oxide (FeNO) is a non-invasive marker of bronchial inflammation in asthma. However, the interest of FeNO measurement remained limited in infantile wheeze. The aim of this prospective study was to evaluate the feasibility and reproducibility of FeNO off-line measurement in very young children with recurrent wheeze and to assess whether clinical control of infantile wheeze correlates with FeNO levels. Two exhalation samples were collected in mylar balloon during quite tidal breathing. FeNO measurements were performed off-line by a NO analyzer. The participating patients were aged ≤36 months, wheezes had started before the age of 24 months, and they were receiving maintenance treatment with inhaled corticosteroids for at least 3 months duration. The studied population comprised of 40 uncontrolled infants with persistent wheezy respiratory symptoms, median age 14.5 months, and 40 with optimal controlled infantile wheeze, median age 14 months. The reproducibility was excellent (r = 0.95; p < 0.0001). There was a significant difference in FeNO levels between the groups of persistent wheeze and well-controlled infants: 19.8 (2.5-99.3) ppb vs. 7.7 (0.6-29.5) ppb, p < 0.0001. At a FeNO level >15 ppb, the predictive values for uncontrolled disease were as follows: positive predictive value = 65%, negative predictive value = 90%. FeN0 levels were not increased by atopy or passive tobacco. Off-line assessment of FeNO is feasible, reproducible, and well accepted in wheezy very young children. Optimal clinical control of infantile wheeze appeared to be associated with the control of bronchial inflammation when evaluated by FeNO measurements.

Sensory transcutaneous electrical stimulation improves post-stroke dysphagic patients.

Oropharyngeal dysphagia is frequent in stroke patients and increases mortality, mainly because of pulmonary complications. We hypothesized that sensitive transcutaneous electrical stimulation applied submentally during swallowing could help rehabilitate post-stroke oropharyngeal dysphagia by improving cortical sensory motor circuits. Eleven patients were recruited for the study (5 females, 68 ± 11 years). They all suffered from recent oropharyngeal dysphagia (>eight weeks) induced by a hemispheric (n = 7) or brainstem (n = 4) stroke, with pharyngeal residue and/or laryngeal aspiration diagnosed by videofluoroscopy. Submental electrical stimulations were performed for 1 h every day for 5 days (electrical trains: 5 s every minute, 80 Hz, under motor threshold). During the electrical stimulations, the patients were asked to swallow one teaspoon of paste or liquid. Swallowing was evaluated before and after the week of stimulations using a dysphagia handicap index questionnaire, videofluoroscopy, and cortical mapping of pharyngeal muscles. The results of the questionnaire showed that oropharyngeal dysphagia symptoms had improved (p < 0.05), while the videofluoroscopy measurements showed that laryngeal aspiration (p < 0.05) and pharyngeal residue (p < 0.05) had decreased and that swallowing reaction time (p < 0.05) had improved. In addition, oropharyngeal transit time, pharyngeal transit time, laryngeal closure duration, and cortical pharyngeal muscle mapping after the task had not changed. These results indicated that sensitive submental electrical stimulations during swallowing tasks could help to rehabilitate post-stroke swallowing dysphagia by improving swallowing coordination. Plasticity of the sensory swallowing cortex is suspected.

Effects of practice on a mechanical horse with an online feedback on performing a sitting postural coordination.

The present research aims at quantifying the impact of practicing a new coordination pattern with an online visual feedback on the postural coordination performed on a mechanical horse. Forty-four voluntary participants were recruited in this study. They were randomly assigned to four practice groups based on i) with or without feedback (i.e., group 1, control, did not receive the feedback; group 2, 3 and 4 received an online feedback during practice) and ii) the specific trunk/horse coordination to target during practice (group 1, target coordination = 180° (without feedback); group 2, target coordination = 0°; group 3, target coordination = 90°; group 4, target coordination = 180°). All participants performed pre-, practice, post- and retention sessions. The pre-, post- and retention sessions consisted of four trials, with one trial corresponding to one specific target coordination to maintain between their own oscillations and the horse oscillations (spontaneous, 0°, 90°, and 180°). The practice phase was composed of three different sessions during which participants received an online feedback about the coordination between their own oscillations and the horse oscillations. Results showed a significant change with practice in the trunk/horse coordination patterns which persisted even after one month (retention-test). However, all the groups did not show the same nature of change, evidenced by a high postural variability during post-test for 0° and 90° target coordination groups, in opposition to the 180° and spontaneous groups who showed a decrease in coordination variability for the 180° group. The coordination in anti-phase was characterized as spontaneously adopted by participants on the mechanical horse, explaining the ease of performing this coordination (compared to the 0° and 90° target coordination). The effect of online visual feedback appeared not only on the coordination pattern itself, but most importantly on its variability during practice, including concerning initially stable coordination patterns.

Effect of Mechanical Horse Practice as New Postural Training in Patients With Neurological Disorders: A Pilot Study.

Objective: From a dynamic system approach, this study evaluated the impact of a new training protocol using a mechanical horse on the postural coordination of brain-damaged patients. Methods: Eighteen volunteer brain-damaged patients (i.e., post-stroke or traumatic brain injury) were recruited and randomly divided into an experimental group (horse group; n = 10, conventional therapy associated with horse-riding exercise on the mechanical horse for 30 min, twice a week, for 12 weeks) and a control group (n = 8; conventional therapy without intervention on the mechanical horse). Postural coordination was evaluated during pre- and post-tests through discrete relative phase (DRP) computation: ϕHead-Horse, ϕTrunk-Horse. Results: A significant effect of used training has been showed, F (1, 15) = 16.6 (p < 0.05) for all patients, concerning the trunk/horse coordination. Conclusion: This pilot study results showed the impact of this new training method on the postural coordination of these patients. After 24 sessions, the coordination of the horse group patients differed from that of the control group, showing their ability to adapt to constraints and develop specific modes of postural coordination (trunk/horse antiphase) to optimize their posture.

Breathing pattern during sequential swallowing in healthy adult humans.

Sequential liquid swallowing is a common daily occurrence during which coordination of deglutition and breathing are highly regulated to avoid pulmonary aspiration and to maintain hematosis. We studied the effects of sequential water swallowing (SWS) at fixed swallowing rates and with regular succession of swallows on respiration in healthy subjects. Thirty-one normal adults (19 men, 12 women) with a mean age of 27.96 ± 3.68 yr were explored at rest and during SWS (at 12 and 24 swallows/min). Respiration was recorded by intranasal air pressure changes and timing of deglutition by an acoustic method. Oxygen saturation [arterial O2 saturation from pulse oximetry ( SpO2 )] was monitored with a finger probe. During SWS, we determined the respiratory phase (inspiration or expiration) before and after each ingestion cycle (IC; period of sustained apnea including 1 or more swallows). We also measured inspiratory time (TI), expiratory time (TE), respiratory cycle duration (TT), respiratory rate (RR) and SpO2 at rest and during SWS. We showed that respiration was interrupted by sequential swallows determining a succession of ICs that were often preceded and followed by expiration. During SWS, TI decreased and TE increased compared with rest ( P < 0.01). However, TT, RR, and SpO2 did not change. It seems that the preferential coupling of swallowing with expiration during SWS is favored by an increase in TE to ensure airway protection, although the repetitive swallows, RR, and SpO2 were not altered during SWS. These data may be useful to study the effects of aging and pathological conditions on swallowing and breathing coordination during SWS. NEW & NOTEWORTHY Sequential water swallowing induces ingestion cycles that are often preceded and followed by expiration. Moreover, inspiratory time decreases and expiratory time increases during sequential swallowing compared with rest without changes in ventilatory cycle duration, respiratory rate, and oxygen saturation.

Short-term training-dependent plasticity of the corticospinal diaphragm control in normal humans.

Mammalian ventilation is driven by automatic structures producing "metabolic" ventilation. Respiratory neuroplasticity can adapt this control to developmental, environmental, and disease-related changes. A corticospinal diaphragm pathway accounts for behavioural disruptions of metabolic ventilation. It should be sensitive to use-dependent short-term plasticity. However, the brainstem-generated permanent diaphragm activity could alter the learning-related corticospinal plasticity (metaplasticity). To test this hypothesis, eight healthy volunteers (six women, 21-25) were studied before and after having learnt to produce prominent diaphragm contractions during voluntary inspiratory manoeuvres. Diaphragm training resulted in (1) a decreased liminal stimulation intensities; (2) an increased number of responding sites on the diaphragm mapping with focal stimulation (5.1+/-3.3 versus 9+/-4.4, p=0.004 in relaxed conditions; 8.9+/-5 versus 15.3+/-4.5, p<0.0001, with underlying voluntary facilitation); (3) shortened motor evoked potentials latencies in response to non-focal stimulation (17.2+/-1.6 ms versus 16.2+/-1.4 ms, p=0.03 in relaxed conditions, and 16.8+/-1.1 ms versus 15.2+/-1.6 ms, p=0.003, with facilitation). These results are closely comparable with similar data in locomotor muscle. They provide a neurophysiological basis for the capacity of normal humans to rapidly acquire diaphragmatic skills.