Evaluating Orthostatic Responses with Wearable Chest-based Photoplethysmography in Patients with Parkinson's Disease

Orthostatic hypotension (OH) is a hallmark manifestation of cardiovascular autonomic dysfunction in Parkinson's disease ( PD). Following an orthostatic stressor, OH in PD is characterized by impaired baroreflex and vasomotor function, resulting in a pathological fall in blood pressure (BP). The morbidity associated with cardiovascular autonomic dysfunction, in conjunction with the current limitations of methods for assessing OH, presents a challenging clinical and technological problem. Wearable cardiovascular sensing holds promise for improving detection and management of OH. In this study, participants with PD ( n=6, 3 with OH) underwent an orthostatic challenge wearing a chest patch capturing electrocardiogram ( ECG) and photoplethysmogram (PPG) signals alongside reference beat-to-beat BP. From supine to standing, PPG amplitude decreased significantly more (p<0.05) in the PD+OH group compared to the PD group. Further, the change in PPG amplitude was significantly correlated (r=0.83, p<0.05) to the change in pulse pressure (PP) during the orthostatic challenge. These findings suggest that sternal PPG amplitude is a potential discriminative marker of OH and may enable noninvasive detection of OH episodes, allowing for earlier diagnoses and more optimal management of cardiovascular autonomic health.