Teresa Pitts

Aspiration and swallowing in Parkinson disease and rehabilitation with EMST: A randomized trial

Objective: Dysphagia is the main cause of aspiration pneumonia and death in Parkinson disease (PD) with no established restorative behavioral treatment to date. Reduced swallow safety may be related to decreased elevation and excursion of the hyolaryngeal complex. Increased submental muscle force generation has been associated with expiratory muscle strength training (EMST) and subsequent increases in hyolaryngeal complex movement provide a strong rationale for its use as a dysphagia treatment. The current studys objective was to test the treatment outcome of a 4-week device-driven EMST program on swallow safety and define the physiologic mechanisms through measures of swallow timing and hyoid displacement. Methods: This was a randomized, blinded, sham-controlled EMST trial performed at an academic center. Sixty participants with PD completed EMST, 4 weeks, 5 days per week, for 20 minutes per day, using a calibrated or sham, handheld device. Measures of swallow function including judgments of swallow safety (penetration–aspiration [PA] scale scores), swallow timing, and hyoid movement were made from videofluoroscopic images. Results: No pretreatment group differences existed. The active treatment (EMST) group demonstrated improved swallow safety compared to the sham group as evidenced by improved PA scores. The EMST group demonstrated improvement of hyolaryngeal function during swallowing, findings not evident for the sham group. Conclusions: EMST may be a restorative treatment for dysphagia in those with PD. The mechanism may be explained by improved hyolaryngeal complex movement. Classification of evidence: This intervention study provides Class I evidence that swallow safety as defined by PA score improved post EMST.

Impact of expiratory muscle strength training on voluntary cough and swallow function in Parkinson disease.

BACKGROUND Cough provides high expiratory airflows to aerosolize and remove material that cannot be adequately removed by ciliary action. Cough is particularly important for clearing foreign particles from the airway in those with dysphagia who may be at risk for penetration/aspiration (P/A). Expiratory muscle strength training (EMST) was tested to improve cough and swallow function. METHODS Ten male participants, diagnosed with Parkinson disease (PD), with videofluorographic evidence of penetration or with evidence for aspiration of material during swallow of a thin 30-mL bolus, completed 4 weeks of an EMST program to test the hypothesis that EMST would improve cough and/or swallow function. Measured parameters from an airflow waveform produced during voluntary cough, pre-EMST and post-EMST, included inspiration phase duration, compression phase duration (CPD), expiratory phase peak flow (EPPF), expiratory phase rise time (EPRT), and cough volume acceleration (VA) [ie, the EPPF/EPRT ratio]. The swallow outcome measure was the degree of P/A during the swallow task. RESULTS There was a significant decrease in the duration of the CPD and EPRT; the decrease in EPRT resulted in a significant increase in cough VA. Significant decreases in the P/A scores were found posttraining. CONCLUSIONS The results demonstrate that EMST is a viable treatment modality for a population of participants with PD at risk of aspiration.

Voluntary Cough Production and Swallow Dysfunction in Parkinson ’ s Disease

Cough is important for airway clearance, particularly if penetration/aspiration of foreign material occurs during swallow. Measures of voluntary cough production from ten male participants with stage II–III Parkinson’s disease (PD) who showed no videofluorographic evidence of penetration/aspiration (Group 1) were examined and compared with those of ten male participants with stage II–III PD who showed videofluorographic evidence of penetration/aspiration (Group 2). The degree of penetration/aspiration was expertly judged from the videofluorographic examinations of the participants’ sequential swallow of a thin, 30-cc bolus. Measured cough parameters included inspiratory phase duration, inspiratory peak flow, compression phase duration, expiratory peak flow, expiratory rise time, and cough volume acceleration. Results indicated significant group differences for the majority of cough measures, except for inspiratory phase duration and inspiratory peak flow. A modest relationship existed between voluntary cough parameters and penetration/aspiration scores. Decreased ability to adequately clear material from the airway with voluntary cough may exacerbate symptoms resulting from penetration/aspiration, particularly for those with neurodegenerative disease. Measurement of voluntary cough may be useful for the evaluation of airway clearance ability.

Respiratory strength training: concept and intervention outcomes.

Respiratory muscle strength training (RMST) focuses on increasing the force-generating capacity of the inspiratory and expiratory muscles. The choice of respiratory muscles that are targeted using RMST depends on the outcome desired. For example, if an individual has reduced inspiratory muscle strength due to a neurogenic injury and is unable to ventilate the lungs, then inspiratory muscle strength training may be the chosen rehabilitation target. On the other hand, if a professional voice user is complaining of difficulty generating adequate vocal loudness during song production and is suffering from laryngeal dysfunction, then an expiratory muscle strength training paradigm may be the chosen rehabilitation target. Our most recent work with RMST has focused on increasing expiratory muscle force generation for those with Parkinsons disease who have difficulty with breathing, swallowing, and cough production. This difficulty typically worsens as the disease progresses. Highlights of these outcomes are summarized in this article.

Using Voluntary Cough To Detect Penetration and Aspiration During Oropharyngeal Swallowing in Patients With Parkinson Disease

BACKGROUND Identification of people with Parkinson disease (PD) who are at risk for aspiration is important, especially because of the high prevalence of aspiration pneumonia. METHODS Fifty-eight consecutive patients (Hoehn and Yahr stage II-III; average age 72.3) were enrolled in the study. Measures of airflow during voluntary cough production and the degree of penetration/aspiration on a 3-oz oropharyngeal swallow task, derived from videofluorographic images, were examined. RESULTS To detect at-risk people (those with penetration and/or aspiration on the 3-oz swallow task), four objective measures of voluntary cough (compression phase duration [CPD], expiratory phase rise time [EPRT], expiratory phase peak flow [EPPF], and cough volume acceleration [CVA)]) were collected. CPD, EPRT, EPPF, and CVA measurements produced significant area under the curve (AUC) analyses and likelihood ratios equal to 0.83:2.72, 0.71:2.68, 0.69:1.75, and 0.78:18.42, respectively. CPD, EPRT, EPPF, and CVA measurements demonstrated sensitivities of 95.83%, 70.83%, 87.50%, and 84.53%, and specificities of 64.71%, 73.53%, 50.01%, and 97.06%, respectively. For detection of aspiration, EPPF was significantly associated with an AUC = 0.88 and with an EPPF < 5.24, which had a sensitivity of 57.15% and a specificity of 100%. CONCLUSIONS The data from this pilot study suggest that in patients with PD, objective airflow measures from voluntary cough production may identify at-risk penetrator/aspirators. To our knowledge, this is the first study to evaluate the discriminative ability of voluntary cough airflow characteristics to model airway compromise in people with PD.

Coordination of cough and swallow: a meta-behavioral response to aspiration.

Airway protections is the prevention and/or removal of material by behaviors such as cough and swallow. We hypothesized these behaviors are coordinated to respond to aspiration. Anesthetized animals were challenged with simulated aspiration that induced both coughing and swallowing. Electromyograms of upper airway and respiratory muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with rapid pharyngeal clearance. Phase restriction between cough and swallow was observed; swallow was restricted to the E2 phase of cough. These results support three main conclusions: 1) the cough and swallow pattern generators are tightly coordinated so as to generate a protective meta-behavior; 2) the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences; and 3) the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Blood pressure changes alter tracheobronchial cough: computational model of the respiratory-cough network and in vivo experiments in anesthetized cats

We tested the hypothesis, motivated in part by a coordinated computational cough network model, that alterations of mean systemic arterial blood pressure (BP) influence the excitability and motor pattern of cough. Model simulations predicted suppression of coughing by stimulation of arterial baroreceptors. In vivo experiments were conducted on anesthetized spontaneously breathing cats. Cough was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms (EMG) of inspiratory parasternal, expiratory abdominal, laryngeal posterior cricoarytenoid (PCA), and thyroarytenoid muscles along with esophageal pressure (EP) and BP were recorded. Transiently elevated BP significantly reduced cough number, cough-related inspiratory, and expiratory amplitudes of EP, peak parasternal and abdominal EMG, and maximum of PCA EMG during the expulsive phase of cough, and prolonged the cough inspiratory and expiratory phases as well as cough cycle duration compared with control coughs. Latencies from the beginning of stimulation to the onset of cough-related diaphragm and abdominal activities were increased. Increases in BP also elicited bradycardia and isocapnic bradypnea. Reductions in BP increased cough number; elevated inspiratory EP amplitude and parasternal, abdominal, and inspiratory PCA EMG amplitudes; decreased total cough cycle duration; shortened the durations of the cough expiratory phase and cough-related abdominal discharge; and shortened cough latency compared with control coughs. Reduced BP also produced tachycardia, tachypnea, and hypocapnic hyperventilation. These effects of BP on coughing likely originate from interactions between barosensitive and respiratory brainstem neuronal networks, particularly by modulation of respiratory neurons within multiple respiration/cough-related brainstem areas by baroreceptor input.

A Joint Computational Respiratory Neural Network-Biomechanical Model for Breathing and Airway Defensive Behaviors

Data-driven computational neural network models have been used to study mechanisms for generating the motor patterns for breathing and breathing related behaviors such as coughing. These models have commonly been evaluated in open loop conditions or with feedback of lung volume simply represented as a filtered version of phrenic motor output. Limitations of these approaches preclude assessment of the influence of mechanical properties of the musculoskeletal system and motivated development of a biomechanical model of the respiratory muscles, airway, and lungs using published measures from human subjects. Here we describe the model and some aspects of its behavior when linked to a computational brainstem respiratory network model for breathing and airway defensive behavior composed of discrete “integrate and fire” populations. The network incorporated multiple circuit paths and operations for tuning inspiratory drive suggested by prior work. Results from neuromechanical system simulations included generation of a eupneic-like breathing pattern and the observation that increased respiratory drive and operating volume result in higher peak flow rates during cough, even when the expiratory drive is unchanged, or when the expiratory abdominal pressure is unchanged. Sequential elimination of the model’s sources of inspiratory drive during cough also suggested a role for disinhibitory regulation via tonic expiratory neurons, a result that was subsequently supported by an analysis of in vivo data. Comparisons with antecedent models, discrepancies with experimental results, and some model limitations are noted.

Pathophysiology of Radiation-Induced Dysphagia in Head and Neck Cancer

Oncologic treatments, such as curative radiotherapy and chemoradiation, for head and neck cancer can cause long-term swallowing impairments (dysphagia) that negatively impact quality of life. Radiation-induced dysphagia comprised a broad spectrum of structural, mechanical, and neurologic deficits. An understanding of the biomolecular effects of radiation on the time course of wound healing and underlying morphological tissue responses that precede radiation damage will improve options available for dysphagia treatment. The goal of this review is to discuss the pathophysiology of radiation-induced injury and elucidate areas that need further exploration.

Co‐ordination of cough and swallow in vivo and in silico

Coughing and swallowing are airway‐protective behaviours. The pharyngeal phase of swallowing prevents aspiration of oral material (saliva, food and liquid) by epiglottal movement, laryngeal adduction and clearing of the mouth and pharynx. Coughing is an aspiration‐response behaviour that removes material from the airway. Co‐ordination of these behaviours is vital to protect the airway from further aspiration‐promoting events, such as a swallowing during the inspiratory phase of coughing. The operational characteristics, primary strategies and peripheral inputs that co‐ordinate coughing and swallowing are unknown. This lack of knowledge impedes understanding and treatment of deficits in airway protection, such as the co‐occurrence of dystussia and dysphagia common in Parkinsons and Alzheimers diseases, as well as stroke.