Access Type
Open Access Embargo
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Electrical and Computer Engineering
First Advisor
Amar S. Basu
Abstract
ABSTRACT VALIDATION OF ORTHOSTATIC VITAL SIGNS MEASURED USING A WEARABLE SENSOR by ZIAD ABDELWARET ELHAJJAJI December 2024 Advisor: Dr. Amar Basu Major: Computer Engineering Degree: Doctor of Philosophy
Orthostatic hypotension (OH), a prevalent condition affecting nearly 30% of older adults, is characterized by a drop in blood pressure and cerebral blood flow upon standing, leading to increased fall risk and other health complications. Standard methods for monitoring OH, such as blood pressure (BP) cuffs, are inadequate as they fail to capture the initial orthostatic hypotension (IOH) and other rapid hemodynamic changes during orthostasis. More sophisticated techniques like continuous BP monitoring or cerebral blood flow velocity (CBFV) are expensive and often impractical for routine clinical use or home monitoring. As result OH is often underdiagnosed and poorly managed. This dissertation introduces a novel approach to OH monitoring using TRACE, a wireless earlobe sensor. TRACE offers a unique approach by directly measuring cephalic (head) blood volume, enabling the derivation of a novel biometric called orthostatic hypovolemia (OHV). OHV quantifies the reduction in cephalic blood volume upon standing, which may be directly correlated with dizziness and other presyncope symptoms. TRACE also captures changes in heart rate and motion indicating when a stand up occurred. A signal processing algorithm employing a Savitzky-Golay filter algorithm achieves a 99% success rate in extracting these metrics from TRACE data. This research derived and evaluated several biometrics: 1) OHV1: reflects the immediate loss of cephalic (head) blood volume immediately upon standing and is potentially indicative of IOH; 2) OHV2: reflects the steady state deficit in cephalic blood volume after the body achieves homeostasis upon standing; 3) POT (postural orthostatic tachycardia): the increase in heart rate upon standing, which reflects the ability of the autonomic system to compensate for orthostatic stresses; 4) OPVR1 (Orthostatic Pulse Volume Reduction 1): Immediate change in pulse volume reduction upon standing; 5) OPVR2 (Orthostatic Pulse Volume Reduction 2): Change in pulse volume reduction after initial orthostatic adjustment; 6) PAR1 (Pulse Amplitude Ratio 1): Immediate change in pulse amplitude ratio upon standing; and 7) PAR2 (Pulse Amplitude Ratio 2): Change in pulse amplitude ratio after initial orthostatic adjustment. A proof-of-concept study on 101 older adults demonstrated the effectiveness of these metrics. Participants wore the TRACE device during postural transitions and self-reported orthostatic symptoms. Significant differences were found between individuals with and without symptoms across all metrics: observed for OHV1 (p-value = 0.0002), OHV2 (p-value = 0.0219) and POT (p-value = 1.2 × 10⁻⁶), OPVR1 (p-value = 0.001), OPVR2 (p-value = 0.00003), PAR1 (p-value = 0.00031), and PAR2 (p-value = 0.00026). Combining the metrics in a logistic regression model achieved 90% sensitivity and 81% specificity in predicting symptomatic and asymptomatic individuals. To our knowledge, this is the first report demonstrating that a wearable device can predict orthostatic symptoms. These findings highlight the potential of TRACE to aid clinicians and patients in the diagnosis and evidence-based management of orthostatic disorders, including orthostatic hypotension and dysautonomia. The wearable form factor opens the possibility of doing such diagnosis and management in a home setting or other remote monitoring scenarios.
Recommended Citation
Elhajjaji, Ziad Abdelwaret, "Validation Of Orthostatic Vital Signs Measured Using A Wearable Sensor" (2024). Wayne State University Dissertations. 4179.
https://digitalcommons.wayne.edu/oa_dissertations/4179