The effects of aspirated thickened water on survival and pulmonary injury in a rabbit model.

OBJECTIVES/HYPOTHESIS: Liquid thickeners are one of the most frequently utilized treatment strategies for persons with oropharyngeal swallowing dysfunction. The effect of commercially available thickeners on lung injury is uncertain. The purpose of this study was to compare the effects of aspiration of water alone, xanthan gum (XG)-thickened water, and cornstarch (CS)-thickened water on survival and lung morphology in a rabbit model. STUDY DESIGN: Animal model. Prospective small animal clinical trial. METHODS: Adult New Zealand White rabbits (n = 24) were divided into three groups of eight rabbits. The groups underwent 3 consecutive days of 1.5 mL/kg intratracheal instillation of water (n = 8), XG-thickened water (n = 8), and CS-thickened water (n = 8). The animals were euthanized on day 4, and survival and pulmonary histopathology were compared between groups. RESULTS: In all, 12.5% of rabbits (n = 8) instilled with CS-thickened water survived until the endpoint of the study (day 4). All animals instilled with water (n = 8) or XG-thickened water (n = 8) survived. A mild increase in intra-alveolar hemorrhage was observed for the animals instilled with CS-thickened water compared to the other groups (P < .05). In the groups that survived to the endpoint of the study, instillation of water thickened with XG resulted in greater pulmonary inflammation, pulmonary interstitial congestion, and alveolar edema than water alone (P < .05). CONCLUSIONS: These data suggest that 3 consecutive days of 1.5 mg/kg of aspirated CS-thickened water are fatal, and that XG-thickened water is more injurious than aspirated water alone. Additional research is necessary to further delineate the dangers of aspirated thickened liquids. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:327-331, 2018.

Impact of expiratory strength training in amyotrophic lateral sclerosis.

INTRODUCTION: We evaluated the feasibility and impact of expiratory muscle strength training (EMST) on respiratory and bulbar function in persons with amyotrophic lateral sclerosis (ALS). METHODS: Twenty-five ALS patients participated in this delayed intervention open-label clinical trial. Following a lead-in period, patients completed a 5-week EMST protocol. Outcome measures included: maximum expiratory pressure (MEP); physiologic measures of swallow and cough; and penetration-aspiration scale (PAS) scores. RESULTS: Of participants who entered the active phase of the study (n = 15), EMST was well tolerated and led to significant increases in MEPs and maximum hyoid displacement during swallowing post-EMST (P < 0.05). No significant differences were observed for PAS scores or cough spirometry measures. CONCLUSIONS: EMST was feasible and well tolerated in this small cohort of ALS patients and led to improvements in expiratory force-generating pressures and swallow kinematics. Further investigation is warranted to confirm these preliminary findings. Muscle Nerve 54: 48-53, 2016.

Pharyngeal weakness and upper esophageal sphincter opening in patients with unilateral vocal fold immobility.

OBJECTIVES/HYPOTHESIS: To evaluate pharyngeal strength and upper esophageal sphincter opening in patients with unilateral vocal fold immobility (UVFI). STUDY DESIGN: Case control study. METHODS: Charts of individuals with UVFI who underwent a videofluoroscopic swallow study were reviewed. To exclude confounding variables associated with pharyngeal weakness, inclusion was limited to patients with iatrogenic and idiopathic UVFI. Data abstracted included patient demographics, etiology of UVFI, pharyngeal constriction ratio (PCR), and upper esophageal sphincter (UES) opening (UESmax). Data were compared to age/gender-matched controls with no history of dysphagia or UVFI. Discrete variables were analyzed using a chi-square test of independence, and an independent samples t test was used to compare the UVFI and control groups (P = 0.05). A one-way analysis of variance (ANOVA) was used to compare iatrogenic and idiopathic UVFI groups. RESULTS: The mean age of the cohort (n = 25) was 61 (±14 SD) years and 52% was female. The etiologies of UVFI were iatrogenic (n = 17) and idiopathic (n = 8). Thirty-eight percent of UVFI patients (n = 25) aspirated compared to 0% of controls (P < 0.05). The mean PCR for the UVFI group was 0.14 (±0.02) compared to 0.06 (±.01) for controls (P < 0.05). The mean UESmax for the UVFI group was 0.82 cm (±0.04) compared to 1.0 cm (±0.05) for controls (P > 0.05). CONCLUSION: Individuals with UVFI of iatrogenic and idiopathic etiologies with subjective dysphagia demonstrate objective evidence of pharyngeal weakness. The increased prevalence of aspiration in this population may not be solely the result of impaired airway protection.

Autologous myoblasts attenuate atrophy and improve tongue force in a denervated tongue model: a pilot study.

OBJECTIVES/HYPOTHESIS: Autologous muscle-derived stem cell (MdSC) therapy is a promising treatment to restore function. No group has evaluated MdSC therapy in a denervated tongue model. The purpose of this pilot investigation was to determine the extent of autologous MdSC survival, effects on tongue muscle atrophy, maximal contractile force, and lingual pressure in a denervated ovine tongue model. STUDY DESIGN: Pilot animal experiment. METHODS: Bilateral implantable cuff electrodes were placed around the hypoglossal nerves in two Dorper cross ewes. Tensometer and high-resolution manometry (HRM) testing were performed during supermaximum hypoglossal nerve stimulation to assess baseline tongue strength. Sternocleidomastoid muscle biopsies were acquired to create autologous MdSC cultures. At 1 month, 5 × 10(8) green fluorescent protein (GFP)-labeled autologous MdSCs were injected into the partially denervated tongue. Two-months postinjection, lingual tensometer testing, HRM, and postmortem histological assessment were performed. RESULTS: GFP+ myofibers were identified in denervated tongue specimens indicating MdSC survival. Muscle fiber diameter was larger in GFP+ fibers for both tongue specimens, suggesting attenuation of muscle atrophy. Myofiber diameter was larger in GFP+ myofibers than preinjury diameters, providing evidence of new muscle formation. These myogenic changes led to a 27% increase in maximal tongue contractile force and a 54% increase in maximum base of tongue pressure in one animal. CONCLUSIONS: Autologous MdSC therapy may be a viable treatment for the partially denervated tongue, with current findings demonstrating that injected MdSCs survived and fused with tongue myofibers, with a resultant increase in myofiber diameter and an increase in tongue strength. LEVEL OF EVIDENCE: N/A.

Neurophysiology and Clinical Implications of the Laryngeal Adductor Reflex.

The laryngeal adductor reflex (LAR) is an involuntary protective response to stimuli in the larynx. The superior laryngeal nerve (SLN) acts as the afferent limb and the recurrent laryngeal nerve (RLN) as the efferent limb of this reflex, which is modulated by the central nervous system. Perhaps the most clinically significant application of the LAR is its use in laryngopharyngeal (LP) sensory discrimination testing. Importantly, aberrations in the LAR may predict dysphagia or portend clinical phenotypes of chronic cough, vocal cord dysfunction or pediatric apneas. LP sensation is a potential target for interventions addressing the aforementioned conditions though currently remains an area of active investigation.