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Session: Wearable
Session starts: Friday 27 January, 11:30
Presentation starts: 12:15
Room: Room 531

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Marjolein Klop (Department of Biophysics, Donders Institute for Brain, Cognition and Behaviour, Radboud University)
Rianne de Heus (Department of Geriatric Medicine, Radboudumc)
Andrea Maier (Yong Loo Lin School of Medicine, National University of Singapore)
Carel Meskers (Department of Rehabilitation Medicine, Amsterdam UMC)
Jurgen Claassen (Department of Geriatric Medicine, Radboudumc)
Richard van Wezel (Department of Biophysics, Donders Institute for Brain, Cognition and Behaviour, Radboud University)

Abstract:
Background: Orthostatic hypotension (OH) is highly prevalent in older adults. OH is defined as a blood pressure (BP) drop ≥20 mmHg systolic and/or 10 mmHg diastolic, within 3 minutes after standing. OH is associated with symptoms like dizziness, falls, lower physical and cognitive function, cardiovascular disease and mortality. Currently, OH is diagnosed with single-time-point cuff BP measurements that are not representative for the repeated posture changes that occur in life. These drawbacks may be overcome by use of a non-invasive wearable near-infrared spectroscopy (NIRS) device that uses near-infrared light to measure cerebral oxygenation continuously for longer periods of time. Aim: To validate cerebral oxygenation measured with NIRS as a proxy for BP changes during and after standing up. Methods: Cross-sectional study, including 11 younger (18-35 years) and 30 older adults (≥65 years) with normal and impaired BP responses upon standing. They performed different postural changes, while BP (volume-clamp photoplethysmography) and cerebral oxygenation were measured continuously. Correlations between BP and cerebral oxygenation curves were calculated within participants (based on curve dynamics) and between participants (based on curve characteristics, like maximum drop amplitude and recovery values). Results: Within participants, BP correlated best with oxygenated hemoglobin (O2Hb), but only showed good correlations in the initial 30s after standing up. During baseline and after 30s, all correlations were poor. Characteristics derived from BP and O2Hb measurements correlated poorly, but did show associations in a multilevel linear regression analysis. Conclusion: NIRS-measured O2Hb can capture dynamic BP changes: when BP increased, O2Hb increased as well. However, more complex models are needed for absolute BP estimations, as a larger BP drop did not necessarily result in a larger O2Hb decrease. Individual characteristics might explain these findings.