Cough Correlates of Functional Swallow Outcomes in Atypical Parkinsonism

BACKGROUND

Swallow and cough impairments lead to aspiration and reduced clearance of aspirate material. Both behaviors are impaired in Parkinson's disease, but it is unknown whether a similar relationship of dysfunction exists in forms of atypical Parkinsonism (APD). Elucidating this association in APD may lead to early, comprehensive airway protection treatment.

OBJECTIVES

We tested the hypotheses that swallow deficits in APD are associated with impaired cough and that airway protective dysfunction is associated with longer disease duration.

METHODS

Swallowing difficulty was described by 11 participants with APD. Penetration-Aspiration Scale (PAS) and DIGEST scores for thin liquid trials were extracted from medical records of videofluoroscopic swallow study reports. Voluntary and capsaicin induced-reflex cough measures of flow, volume, and timing were analyzed.

RESULTS

While most participants did not have post-swallow residue, ~80% received abnormal PAS scores and reported swallowing difficulty. Those with abnormal PAS scores had lower voluntary cough expired volume (P = 0.037; mean rank difference = 5.0); lower reflex inspiratory flow rate (P = 0.034; mean rank difference = 5.5); and longer reflex expiratory flow rise time (P = 0.034; mean rank difference = 5.5). Higher PAS scores and reduced reflex cough volume acceleration were significantly correlated (r = -0.63; P = 0.04) and longer disease duration predicted larger voluntary cough expired volume (R2  = 0.72) and longer flow rise times (R2  = 0.47).

CONCLUSIONS

As swallow safety worsens, so might the ability to clear the airways with effective cough in in APD; particularly with longer disease duration. Assessing cough in conjunction with swallowing is important for informing airway protection treatment plans in APD.

Rehabilitating Cough Dysfunction in Parkinson's Disease: A Randomized Controlled Trial

BACKGROUND

Disorders of airway protection (cough and swallowing) are pervasive in Parkinson's disease (PD) resulting in a high incidence of aspiration pneumonia and death. However, there are no randomized controlled trials comparing strength and skill-based approaches to improve airway protection in PD.

OBJECTIVES

The aim of this study was to compare expiratory muscle strength training (EMST) and sensorimotor training for airway protection (smTAP) to improve cough-related outcomes in people with PD.

METHODS

Participants with PD and dysphagia were recruited for this prospective phase II randomized-blinded controlled clinical trial. Participants completed baseline assessment, 5 weeks of EMST or smTAP, and a post-training assessment. Primary outcome measures included maximum expiratory pressure (MEP) and voluntary cough peak expiratory flow rate (PEFR). Mixed effects models were used to assess the effects of EMST and smTAP on outcomes.

RESULTS

A total of 65 participants received either EMST (n = 34) or smTAP (n = 31). MEP improved from pre- to post-treatment for smTAP (P < 0.001, d = 0.19) and EMST (P < 0.001, d = 0.53). Voluntary PEFR increased from pre- to post-treatment for smTAP (P < 0.001, d = 0.19) and EMST (P < 0.001, d = 0.06). Moreover, reflex cough PEFR (P < 0.001, d = 0.64), reflex cough expired volume (P < 0.001, d = 0.74), and urge to cough (P = 0.018, OR = 2.70) improved for the smTAP group but not for the EMST group.

CONCLUSIONS

This clinical trial confirmed the efficacy of smTAP to improve reflex and voluntary cough function, above and beyond EMST, the current gold standard. © 2022 International Parkinson and Movement Disorder Society.

Voluntary Cough Testing as a Clinical Indicator of Airway Protection in Cervical Spinal Cord Injury

OBJECTIVE

Voluntary cough testing (VCT) may be useful for determining aspiration risk in neurogenic dysphagia; however, has yet to be investigated in traumatic cervical spinal cord injury (tCSCI). The study explored if VCT may elucidate swallowing safety and kinematics related to airway protection in tCSCI survivors.

METHODS

Ten inpatients, 13-73 days post-tCSCI (7 incomplete injuries), completed VCT and a modified barium swallowing study that was analyzed via the Penetration Aspiration Scale (PAS) and norm-referenced measures of swallowing events related to airway protection. Spearman rho correlations explored relations among cough airflow, median PAS, and airway protection. Mann-Whitney U tests explored group differences based on clinical airway invasion (PAS > 2) and receiver operating characteristic statistics probed the sensitivity/specificity of VCT measures.

RESULTS

Safe (PAS > 2) and unsafe swallowers differed by cough volume acceleration (CVA) for the total sample and by inspiratory duration for incomplete injuries (p = 0.03, r > 0.7). A cut-off value of 24.8 L/s for CVA predicted airway invasion (AUC = 0.917, p = 0.03) with sensitivity = 100%/specificity = 75%. CVA correlated with delayed laryngeal vestibule closure during swallowing for both the total sample and for incomplete injuries (r_s  > 0.6, p < 0.05). Blunted peak flow and prolonged cough phases were associated with disordered laryngeal kinematics and prolonged bolus transit during swallowing (p < 0.05).

CONCLUSIONS

Reduced CVA, blunted peak flow, and prolonged cough phases reflected PAS and disrupted mechanisms of airway protection in tCSCI survivors, demonstrating promise for VCT as a clinical assessment for post-tCSCI dysphagia.

LEVEL OF EVIDENCE

3 Laryngoscope, 2022.

Sensorimotor Cough Dysfunction Is Prevalent and Pervasive in Progressive Supranuclear Palsy

BACKGROUND

Pneumonia, a leading cause of death in progressive supranuclear palsy (PSP), results from progressive and pervasive deficits of airway protection, including both cough and swallowing dysfunction. Cough protects the airway by expelling aspirate and may be an important therapeutic target to protect against pneumonia in the presence of dysphagia. However, cough has not been objectively characterized in PSP or compared to other common forms of parkinsonism, such as Parkinson's disease (PD).

OBJECTIVE

The purpose of this study was to examine voluntary and reflex cough function in PSP, as compared to patients with PD matched for disease duration.

METHODS

Twenty-six patients with PSP and 26 with PD completed voluntary and reflex cough testing via spirometry. Linear mixed effects models examined comparisons between groups and within cough types across cough sensory and motor outcomes.

RESULTS

Patients with PSP demonstrated significantly reduced cough motor function compared to PD, specifically reduced peak expiratory flow rate (P < 0.001), cough expiratory volume (P < 0.001), and cough inspiratory volume (P = 0.008). Both groups showed similar reflex cough thresholds (P = 0.694), but PSP demonstrated an increased perception of cough stimuli (P = 0.041).

CONCLUSIONS

These findings suggest that sensorimotor cough dysfunction is prevalent in PSP, and cough motor deficits, in particular, are worse in PSP than in PD. These deficits likely contribute to the pathogenesis of pneumonia in PSP. Therefore, cough should be integrated into assessments of airway protection and considered as a therapeutic target to potentially reduce adverse health events and improve quality of life in this population. © 2021 International Parkinson and Movement Disorder Society.

Characteristics of impaired voluntary cough function in individuals with amyotrophic lateral sclerosis

OBJECTIVE

Although cough impairment (dystussia) is common in individuals with amyotrophic lateral sclerosis (ALS) and contributes to a reduced physiologic capacity to defend the airway, characteristics of dystussia have not yet been delineated. Therefore, we aimed to compare voluntary cough spirometry airflow patterns between individuals with ALS and healthy age and gender-matched controls.

METHODS

Thirty-two individuals with a diagnosis of probable-definite ALS (El-Escorial Criterion) and 29 healthy age and gender-matched controls underwent voluntary cough spirometry testing. Two blinded raters derived six objective voluntary cough airflow measures including: peak inspiratory phase duration, peak inspiratory flow rate, compression phase duration, peak expiratory rise time, peak expiratory flow rate, and cough volume acceleration. Independent samples t-tests with Cohen's d effect sizes were performed between Healthy versus ALS groups for cough metrics (alpha =0.05).

RESULTS

ALS individuals demonstrated prolonged inspiratory phase and expiratory phase rise time durations, reduced inspiratory and expiratory flow rates, and lower cough volume acceleration during voluntary cough production compared with healthy controls (p < 0.05). No differences in compression phase duration were observed (p > 0.05).

CONCLUSIONS

This study compared characteristics of voluntary cough airflow patterns of individuals with ALS to healthy-matched controls. Findings identified impairments in both inspiratory and expiratory voluntary cough airflow, resulting in slower, weaker, and thus less effectiveness voluntary cough production in ALS individuals. These data afford insight into the impaired physiology underlying inadequate airway clearance and secretion management in individuals with ALS.

Dysphagia, dystussia, and aspiration pneumonia in elderly people

Despite the development and wide distribution of guidelines for pneumonia, death from pneumonia is increasing due to population aging. Conventionally, aspiration pneumonia was mainly thought to be one of the infectious diseases. However, we have proven that chronic repeated aspiration of a small amount of sterile material can cause the usual type of aspiration pneumonia in mouse lung. Moreover, chronic repeated aspiration of small amounts induced chronic inflammation in both frail elderly people and mouse lung. These observations suggest the need for a paradigm shift of the treatment for pneumonia in the elderly. Since aspiration pneumonia is fundamentally based on dysphagia, we should shift the therapy for aspiration pneumonia from pathogen-oriented therapy to function-oriented therapy. Function-oriented therapy in aspiration pneumonia means therapy focusing on slowing or reversing the functional decline that occurs as part of the aging process, such as "dementia → dysphagia → dystussia → atussia → silent aspiration". Atussia is ultimate dysfunction of cough physiology, and aspiration with atussia is called silent aspiration, which leads to the development of life-threatening aspiration pneumonia. Research pursuing effective strategies to restore function in the elderly is warranted in order to decrease pneumonia deaths in elderly people.

Pharmacologic management of cough

This review is an update of recent advances in our understanding of cough suppressants and impairment of cough. Low-dose oral morphine has recently been shown to significantly suppress chronic cough, but the side effect profile of this opioid may limit its widespread utility. Several studies have demonstrated a dissociation between the efficacy of antitussives in some metrics of pathologic cough and their effects on cough sensitivity to inhaled irritants. The relevance of widely used inhaled irritants in understanding pathologic cough and its response to antitussives is questionable. A recent advance in the field is the identification and measurement of an index of sensation related to cough: the urge to cough. This measure highlights the potential involvement of suprapontine regions of the brain in the genesis and potential suppression of cough in the awake human. There are no new studies showing that mucolytic agents are of value as monotherapies for chronic cough. However, some of these drugs, presumably because of their antioxidant activity, may be of use as adjunct therapies or in selected patient populations. The term dystussia (impairment of cough) has been coined recently and represents a common and life-threatening problem in patients with neurologic disease. Dystussia is strongly associated with severe dysphagia and the occurrence of both indicates that the patient has a high risk for aspiration. No pharmacologic treatments ae available for dystussia, but scientists and clinicians with experience in studying chronic cough are well qualified to develop methodologies to address the problem of impaired cough.