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 ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n=6, 3</tex> 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 ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p < 0.05</tex> ) in the PD+OH group compared to the PD group. Further, the change in PPG amplitude was significantly correlated ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r=0.83,\ p < 0.05</tex> ) 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.