Comprehensive Evaluation of Respiratory Impairment in Parkinson’s Disease

Parkinson’s Disease (PD), a progressive neurological disorder, affects an estimated 8.4 million people worldwide. While it is primarily associated with motor dysfunctions of bradykinesia, tremor and rigidity, respiratory disorders contribute significantly to morbidity and mortality. Despite its clinical relevance, respiratory impairments in PD are often under-diagnosed and under-treated, with the aetiology remaining inadequately understood. Understanding underlying mechanisms and evidence-based strategies to manage respiratory impairment/s is crucial to improve outcomes related to respiratory morbidity and mortality in PD. This research programme aims to comprehensively examine respiratory impairments in PD and their response to non-pharmacological interventions. A multiple methods approach was employed, including two systematic reviews and meta-analyses: (1) examining respiratory impairment/s in PD compared to healthy controls, and (2) examining the evidence supporting non-pharmacological interventions to improve respiratory impairment/s. A prospective cohort study was conducted to establish the presence of respiratory impairment/s in an Irish PD population and their responsiveness to an integrated community-based exercise programme. Finally, two exploratory case-controlled studies were undertaken: (1) examining breathing patterns and the presence of dyspnoea, and (2) specifically evaluating diaphragm muscle structure and function. Key findings indicate strong evidence of a restrictive pattern of respiratory dysfunction in PD, respiratory muscle weakness and impaired cough. Respiratory impairments exist even in early-stage PD, where individuals experience functional disability related to dyspnoea and altered breathing patterns compared to controls, providing evidence of impairment in central respiratory control. While diaphragm thickness and contractility appear to be maintained in early-stage PD, these outcomes, along with the observed slower speed of contraction during inspiration, warrant further investigation. Non-pharmacological interventions demonstrate efficacy to improve respiratory muscle strength and peak expiratory flow by meta-analysis and during an integrated community-based exercise programme, completed as part of this programme of research, where increased functional aerobic capacity was also noted. This thesis makes novel contributions to the literature on respiratory impairment in PD, emphasising clear impairments and the need for early respiratory assessment and integration of respiratory care into the holistic management of those with PD. Additionally, it provides a foundation for future research that addresses central and peripheral components of respiratory impairment in PD.