Mechanisms of airway protection dysfunction in Parkinson's disease

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Aspiration pneumonia (APn) occurs at a disproportionately high rate in patients with Parkinson's disease (PD) versus healthy age-matched older adults. This is of particular public health concern given that aspiration pneumonia infection is a leading cause of death in persons with PD. The development of APn is multifactorial with aspiration of material from disordered swallowing (dysphagia) without proper cough response being the main contributing factor. These findings reflect the fact that both swallowing and cough are sensorimotor behaviors, and thus require appropriate detection and scaling of a sensory stimulus in order to produce an appropriate motor response. The long-term goal of this research is to advance the management of airway protection deficits in patients with neurodegenerative disease in order to decrease morbidity and mortality due to aspiration related lung infection. The objective here, which is a critical step in pursuit of that goal, is to further specify the sensory mechanisms associated with airway protection disorders in order to advance the clinical management of these patients. In order to accomplish the objective of this application we have identified 3 aims: First, determine relationship(s) between airway somatosensation, reflex cough and swallowing function in people with PD, and how these relationships may change with disease progression, over time. Second, determine whether cortical processing of sensory information is associated with deficits in reflex cough sensitivity or swallowing function in people with PD, and third, to determine how the central neural filtering of airway sensory stimuli may relate to the development of airway protective disorders. We will accomplish these aims in 2 experimental studies. First, we will test the magnitude of respiratory resistive loads, in people with PD across a range of disease durations, and in a healthy control group. We will measure reflex cough, using a cough-inducing irritant (capsaicin), and swallowing function. We will perform these tests at 3 time-points, spaced 10-14 months apart, in order to determine the relationships between respiratory sensation, cough sensitivity and effectiveness, and swallowing function, and how they change with advancing disease duration. Next we will perform electroencephalographic recordings time-locked to paired respiratory stimuli to determine cortical processing of airway sensory information. We will measure the amplitude and latency of the sensory evoked potential peaks, and compute ratios of peak amplitude between the first and second paired stimulus in order to determine the degree of sensory gating. The realization of the proposed aims and studies is significant because it is a necessary step in our program of research that is expected to lead to earlier, more accurate identification, as well as targeted interventions for airway protection deficits in PD. Completion of this research is systematically important for our goal of maintaining adequate airway protective function in PD patients; the results are expected to directly impact reductions in health care costs, morbidity, and mortality related to airway protection deficits.