Multimodal Monitoring of Cardiovascular Responses to Postural Changes

Abstract

Background: In the poorly understood relationship between orthostatic hypotension and falls, next to blood pressure (BP), baroreflex sensitivity (BRS) and cerebral autoregulation (CAR) may be key measures. The posture-and movement dependency of orthostatic hypotension requires continuous and unobtrusive monitoring. This may be possible using simultaneous photoplethysmography (PPG), electrocardiography (ECG), and near-infrared spectroscopy (NIRS) signal recordings, from which pulse wave velocity (PWV; potentially useful for BP estimation), BRS and CAR can be derived. The PPG, NIRS and PWV signal correlation with BP and BRS/CAR reliability and validity need to be addressed. Methods: In 34 healthy adults (mean age 25 years, inter quartile range 22-45; 10 female), wrist and finger PPG, ECG, bifrontal NIRS (oxygenated and deoxygenated hemoglobin) and continuous BP were recorded during sit to stand and supine to stand movements. Sixteen participants performed slow and rapid supine to stand movements; eighteen other participants performed a 1-min squat movement. Pulse wave velocity (PWV) was defined as the inverse of the ECG R-peak to PPG pulse delay; PPG, NIRS and PWV signal correlation with BP as their Pearson correlations with mean arterial pressure (MAP) within 30 s after the postural changes; BRS as inter beat interval drop divided by systolic BP (SBP) drop during the postural changes; CAR as oxygenated hemoglobin drop divided by MAP drop. BRS and CAR were separately computed using measured and estimated (linear regression) BP. BRS/CAR reliability was defined by the intra class correlation between repeats of the same postural change; validity as the Pearson correlation between BRS/CAR values based on measured and estimated BP. Results: The highest correlation with MAP was found for finger PPG and oxygenated hemoglobin, ranging from 0.75-0.79 (sit to stand), 0.66-0.88 (supine to stand), and 0.82-0.94 (1-min squat). BRS and CAR reliability was highest during the different supine

Orthostatic blood pressure recovery associates with physical performance, frailty and number of falls in geriatric outpatients

“…The relatively weaker association in the 120 to 180-s interval with clinical outcome might indicate a compensation mechanism may play a role, though its nature is uncertain. Near-infrared spectroscopy measurements (NIRS) should be performed in future studies to quantify the brain oxygen concentration levels in the different time intervals and relate these to clinical outcome [ 38 – 40 ].…”

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation

“…These effects were observed in healthy young and older adults. Simultaneously, HHb increases after standing up and recovers to a value above baseline [15][16][17][18]. Within the first 30 s of standing, Pearson correlation coefficients between O 2 Hb and BP measured by volume-clamp photoplethysmography ranged from 0.66 to 0.94 depending on the type of postural change [17].…”

Functional Analysis of Continuous, High-Resolution Measures in Aging Research: A Demonstration Using Cerebral Oxygenation Data From the Irish Longitudinal Study on Aging

“…To ensure population representativeness, considering sample loss and non-attendance, weighting should be considered when the method is applied to specific outcome measures. Systems using NIRS can produce reliable estimates of CAR during orthostasis and have shown utility in clinical studies using head-up tilt testing (Bachus et al, 2018 ; Mol et al, 2020 ). There is a high correlation between CAR assessed using either TCD or NIRS (Zweifel et al, 2010 ).…”