Novel orthostatic vital signs measured by an earlobe wearable device

Project Summary
Orthostatic disorders, including orthostatic hypotension (OH), disproportionately affect older adults, presenting
in 30% of older adults and up to 70% of nursing home residents. As OH is a major risk factor for syncope, falls,
and cognitive decline, medical agencies stress the public health need for monitoring orthostatic vital signs
(OVS) in at-risk individuals. This proposal investigates an NIA award-winning wearable device called TRACE,
which addresses fundamental limitations of the current clinical standard, the blood pressure (BP) cuff: 1) The
BP cuff measures central BP, but it is known that the root cause of orthostatic symptoms is a lack of blood flow
to the head. TRACE’s unique blood volume-based metrics are predictive of orthostatic symptoms, whereas BP
is not. 2) BP cuffs cannot capture the rapid hemodynamics of the initial orthostasis response (first 10-30
seconds), a predictive marker for adverse outcomes. Continuous BP and transcranial Doppler (TCD) can
capture these dynamics, but their cost make them impractical for routine monitoring. TRACE offers real-time
monitoring in a low cost wearable. 3) TRACE offers multiple metrics to aid clinicians in a specific diagnosis.
Our long-term goal is to address the underdiagnosis and mismanagement of orthostatic disorders using the
TRACE remote OVS monitoring platform. The objective of this application is to validate TRACE’s 4 novel
orthostatic metrics against the gold standard of perfusion measurement, TCD. Our central hypothesis is that
normalized metrics will match their counterpart TCD metrics, and both will be more predictive of self-reported
OH symptoms than the BP cuff. The team includes PI Prof. Amar Basu, an electrical/biomedical engineer who
developed TRACE and has >15 years of experience in wearable sensors; Dr. Joseph Miller, an emergency
medicine physician with expertise in orthostatic measurements by transcranial Doppler; and Dr. Paul Kilgore,
an expert in clinical study design. Henry Ford Hospital and the Wayne State Integrative Biosciences Center will
provide participant recruitment and facilities. Aim 1 will evaluate TRACE’s 4 orthostatic metrics that quantify
relative physiologic changes during orthostasis. Their robustness to confounding factors will be evaluated in 25
older adults by measuring the agreement between two TRACE sensors, one on each earlobe, during active
stand tests. Aim 2 will compare TRACE blood volume metrics with TCD perfusion metrics. We will perform tilt
table and active stand tests in 100 older adults, monitoring simultaneously with TRACE, TCD, BP, and
continuous BP. Aim 2 will test our central hypothesis described above. The proposed work could have a
transformative impact in managing incurable orthostatic disorders like Neurogenic OH. TRACE brings
perfusion-based metrics in a wearable form factor that can assess orthostatic metrics every time an individual
stands. Temporally rich information can empower clinicians and patients to understand the effect of triggers
(large meals, poor hydration), and the efficacy of interventions (crossing legs, compression stockings),
improving patient outcomes.

Grant Number: 1R21AG088945-01A1
NIH Institute/Center: NIH
Principal Investigator: Amar Basu