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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Arjen Mol ()
Andrea Maier ()
Carel Meskers ()
Richard van Wezel ()

Abstract:
Background: Orthostatic hypotension (OH) is associated with poor physical performance, but this association is weak. This may be due to the involved compensatory physiological mechanisms, which are not fully captured by the onetime OH diagnosis as reflected by its poor reproducibility. Continuous, non-invasive, ambulatory assessment of blood pressure (BP), posture and activity of compensatory physiological mechanisms is needed to obtain insight in the relationship between posture, blood pressure and physical performance. Photoplethysmography (PPG) and near-infrared spectroscopy (NIRS) are measurement techniques reflecting systemic and cerebral circulation and suitable for continuous, non-invasive measurements. However, responses of these signals to postural changes in healthy adults must first be addressed to perform measurements in patients with OH. This study assessed signal sensitivity and reliability in healthy adults. Methods: PPG applied to the radial and digital artery of the left hand, bifrontal NIRS, continuous BP and ECG were measured in 34 healthy subjects (mean age 31.9 years, standard deviation 14.4). 16 were subject performed sit to stand (preferred speed), slow supine to stand (within 3 seconds) and rapid supine to stand (10 seconds) test conditions, while 18 performed sit to stand (preferred speed), supine to stand (preferred speed), head up tilt (15 seconds), Valsalva (15 seconds) and squat (1 minute) test conditions. Sensitivity was defined as the change of the signals during the test conditions relative to baseline variability. Test-retest reliability of the signals for each test condition was assessed and expressed using intraclass correlation coefficients. Results: The PPG and NIRS signals were sensitive to the test conditions. NIRS signals showed a large drop within 30 seconds, and a small drop between 30 and 180 seconds after standing up, both with a test-retest reliability ICCs > 0.8. Conclusion: PPG and NIRS measures were sensitive to postural change in healthy adults, indicating their potential value as a combined barocontrol monitor in older adults with orthostatic hypotension.